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Articles from 2007 In October

Canadian Counts Slip Further

Canada's quarterly Hog Statistics report was released yesterday by Statistics Canada. The report showed a continuing decline in hog numbers, especially in the market hog categories.

Canada's inventory of pigs weighing over 20 kg (44 lb.) was 7.6% smaller on Oct. 1, 2007 compared to one year earlier. The reduction reflects higher exports of feeder pigs to the United States, which are up 7.2%, year-to-date.

Canada's breeding herd continues to shrink and was 1.4% lower than one year ago. That number is a slightly larger decline than the last quarterly report (see Figure 1), but reflects the economic pressure that has come to bear on Canadian producers. This marks the 10th straight quarter in which the Canadian herd has declined relative to one year earlier. The herd, now numbering 1.56 million head, is the smallest it's been since October 2002, and it is 4.5% smaller than it was at its peak in January 2005.

The decline of Canadian breeding hog numbers, when combined with growth in the United States, leaves the Canadian-U.S. herd 0.6% larger than it was last fall. That is about the same rate that the combined herds have grown for the past seven quarters.

The economic pressure in Canada has increased during October and is likely to get more intense. The Canadian dollar is beyond par with the U.S. dollar and has gained over 35% in value over the past five years. That gain has caused Canadian hog and pork prices to steadily erode relative to U.S. prices. We have to remember that in the North American pork market, the United States is the dog and Canada is the tail when it comes to hog prices. When stated in the same currency, prices move together, but the exchange rate is the translator that has changed dramatically.

On the other side of the ledger, only about half of Canadian costs are directly tied to the U.S. dollar. That half of costs has gone down but the other half has remained high, putting Canadian producers in a very bad cost-price squeeze. The real trouble arises when you factor in higher wheat and barley prices, which have caused the dollar-denominated costs (that should have fallen) to go up as well for producers who use those grains as feed. It is not a good situation for the Prairie Provinces, most notably Alberta, which saw the largest breeding herd reduction excluding the Maritime Provinces.

I expect more reductions in Canada and I fear that they may be very severe before this is over.

A Bit of Good News
Although many of you will see this as rather perverse -- things aren't as bad as they should be, or at least as they could be. Many of you will not like that statement, so I ask you to write it off to economist pin-headedness. Let me explain.

Look at this week's Price and Production tables (below). U.S. hog slaughter for the week that ended Oct. 20 was nearly 6% larger than one year ago. Combined Canadian-U.S. slaughter was 5% larger. The same percentages apply to pork production since weights were quite close to year-ago levels. The normal relationship between percentage price change and percentage quantity change is -3:1. I would probably use -4:1 at present, since we are so close to slaughter capacity in the United States.

That relationship would suggest hog prices 15-20% lower than one year ago. Canadian prices are indeed that much lower, but that decline is largely due to a Canadian dollar that is 16% stronger than last year! U.S. prices are down only 6 to 8%. That says that live hog demand is very good due to, I'm quite confident, stronger domestic pork demand, higher export values (and, quite possibly, higher volume in recent weeks) and, surprisingly tight packer margins (see Figure 2).

Perhaps "tight" is not the correct descriptor for last week's margin but "tighter than they should be with 2.3 million-plus hogs every week" would certainly be appropriate. In spite of those slaughter levels, packers are still competing for hogs. Packers' net margins are probably pretty good since this level of throughput would divide fixed and sunk costs over many, many pounds and leave them just about as low on a per unit basis as they could possibly be. One caveat is that these computations use "net" prices, which are being helped mightily by the Other Formula prices that we discussed last week. Margins on hogs purchased on the spot market (i.e. negotiated prices) are considerably better.

And finally -- the hero in this whole mess may just be chicken. I know it is hard to admit that, but chicken part prices are still double-digits above last year in spite of production that is now consistently running 2-3% higher. Let's hope that continues. We still need all the help we can get!

Click to view graphs.

Steve R. Meyer, Ph.D.
Paragon Economics, Inc.

Cash Hog Prices Show Resiliency

If there is anything more remarkable than the weekly slaughter runs we have seen thus far in October (in case you missed it, we set another record last week at 2.353 million head), it has been the fact that cash hog prices have held their own. If you had told me (or anyone else for that matter) last summer that we would see this level of slaughter in October, I would have told you I was concerned, but that slaughter wouldn't get that big, especially that early. If you had told me that slaughter would indeed get this big this early, and that negotiated net hog prices would still be nearly $58, I would have inquired about your inhaling habits!

Figure 1 shows negotiated net prices on a weekly basis. The decline in hog prices two weeks ago was definitely no fun for those selling on that pricing method. But slaughtering 2.321 million head two weeks ago and 2.353 million head last week hasn't triggered an unmitigated disaster. Further, Thursday's price was higher than last week's average, and this week's estimated federally inspected (FI) slaughter is 5,000 head more than last week's pace through Thursday.

The cutout value has fallen as well but it remains above $60/cwt. Again, this is not a bad showing for these kinds of supply levels. Hams are still the only cut that is under heavy pricing pressure. Think of where we would be had ham shipments to Mexico during the summer just matched those of 2006.

None of this means that I'm not concerned and I'm skipping along singing, "Don't Worry, Be Happy" to pork producers. This fall could still be very tough on the bottom line, cash reserves and/or operating loan balances. On average, FI hog slaughter levels out for the remainder of October and into November before spiking about 5% in early December to handle the hogs not slaughtered during the Thanksgiving holiday.

It will be very difficult to push 5% (about 100,000 head) more through U.S. packing plants given the fact that last Saturday's run was 243,000 head. But U.S. packers processed 300,000-plus on a Saturday in 2003 and 2005 and almost did it last year. Oh yes -- and it happened twice in 1998. Ugh.

Pork Demand Holds Prices Together
Why have things held together? Demand. Domestic pork demand is 1.9% higher than last year through August, and export value is higher even though export quantity is still slightly lower than last year (see last week's North American Preview for details). Whether those numbers are going to be large enough to soak up continued high production remains to be seen, but they have done well so far. One packer told me last Friday that they were remarkably "clean" (meaning they had most of the week's production sold) going into the weekend considering the number of hogs they had handled the past two weeks. I hope that trend continues.

Cashing in on Futures Prices
Producers should note that the quotes for negotiated prices, whether on the daily purchase reports or the prior day slaughter reports, will not be a perfect barometer of producer revenues and profits this year. The prices of hogs sold on Other Market Formulas (virtually all cash delivery contracts tied to futures market prices) are running as much as $10/cwt. carcass above the negotiated price. It certainly appears that a number of you did indeed price hogs during last summer's futures rally. Good for you!

And there are many, many more hogs that have been hedged by producers instead of contracted through packers. Those premium prices will not show up in a price report, since the producer will simply sell the hogs at the negotiated or some formula-based price, and then capture the extra profit from the future market when they lift hedges this fall. Good for you, too!

Futures May Provide Profits in '08
Which brings us to the futures market now and what it means relative to fundamental supply and demand. Figure 2 shows a summary of price forecasts by four analysts or analysis groups based on the September Hogs and Pigs Report. Note that all of us actually forecast a different price series, but you can use the annual averages for 2006 to see the "normal" differences that exist in these prices.

Regardless of differences, one thing is clear: none of us believe that current fundamental supply and demand will result in hog prices anywhere near what Chicago Mercantile Exchange Lean Hogs Futures are offering for next year. That doesn't mean the futures are wrong. I don't like to bet against many, many people using real money. But the fact is that futures prices are offering positive margins for much of next year if you have costs in the high $40s on a live weight basis or mid $60s on a carcass weight basis. Perhaps more important, they are offering only small losses in Q1 and Q4 of 2008 and those quarters appear quite problematic at present.

Click to view graphs.

Steve R. Meyer, Ph.D.
Paragon Economics, Inc.

Don’t Forget Your Flu Shot

All hog farm workers should get a flu shot in October or November in anticipation of this year’s flu season.

“Producers and hog farm workers can reduce the risk of getting sick and bringing the flu to the farm by getting a flu shot,” says Liz Wagstrom, DVM, assistant vice president of Science and Technology for the National Pork Board.

“The flu shot contains two type-A viruses that we want to prevent from spreading between people and pigs,” she points out. “The vaccine also has a type-B virus in the mix, but this type of virus is not of concern to the health of our pigs. Humans will develop antibodies against the flu virus two weeks after taking the flu shot.”

The flu shot is available as an injection or in a nasal spray. “The Centers for Disease Control and Prevention (CDC) recommends that pregnant women not get the nasal vaccine,” she notes.

Wagstrom recommends the following additional practices to reduce infection of pigs with human influenza viruses:

  • Modifying sick leave policies to encourage workers to stay away from the farm if they are suffering. “Virus shedding is at its peak when the clinical illness is most severe, but can last as long as the symptoms do and that is from three to seven days,” she says.
  • Ensuring good building ventilation and good hygiene will also reduce transmission of the flu viruses. “To prevent pigs and humans from other species’ influenza viruses, producers also should look at bird-proofing their buildings, protecting feed from birds and enforcing biosecurity practices, such as the use of farm-specific clothing and footwear,” she says.
  • Chlorinating the water used on the farm is a good idea, especially if it is surface or pond water.

“The CDC has great information about the flu shot, who should get it and who should not. I’d recommend that everybody visit their Web site ( for more information,” adds Wagstrom.

The Pork Board has a fact sheet on influenza: “Influenza: Pigs, People and Public Health,” available at

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Wet Weather Raises Fears Of Mycotoxin in Corn

Continued rain throughout the Upper Midwest following this summer’s drought has heightened fears that harvested corn could contain mycotoxins which may prove harmful to pigs and people alike.

“What we are seeing and hearing is that molds and mycotoxins are going to be two to three times higher than average due to all the moisture in the field.

“In some areas, the problems are even worse where it has been exceedingly wet or where much of the corn is down due to wind and storms. These fields will take a long time to dry, which will further contribute to mold growth,” reports Mark Boggess, director of Science and Technology for the National Pork Board.

Worst areas of concern are in Minnesota and northern Iowa, but there are also areas of concern for southwest Iowa, western Nebraska and northern Missouri, which “are drowning in moisture right now,” and have been unable to finish their corn harvest, he notes.

Also, ethanol production concentrates mycotoxins in distiller’s dried grains with solubles (DDGS) by a factor of three. If feeding DDGS, make sure the corn used and DDGS product both have been adequately screened for mycotoxins, urges Boggess.

Some agronomists are suggesting that people combining and working in fields with significant mold should wear masks to protect against floating aerosol mycotoxins, because many are actually carcinogenic, he warns.

For pigs, problems with moldy corn “can produce horror stories” due to the mycotoxins themselves as well as palability problems that can lead to poor-doing hogs, emaciation and sometimes even death, as well as reproductive problems.

As always, pork producers should work with their mills to ensure corn and feed are aggressively tested for mycotoxins. This year looks to be one of the worst in recent memory, says Boggess.

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Proper AI techniques, semen handling

The first and overriding principle of artificial insemination in swine is — if a sow is in standing heat, she can be bred; if she is not in standing heat, do not attempt to breed her.

This key to maximizing fertility rates in the breeding herd requires a solid understanding of AI basics, timing of insemination, use of lubricants, boar usage, overbreeding and nine key semen-handling principles.

Artificial insemination

For all of the years that AI has been practiced in the pork industry, we must always remind the inexperienced technicians of the standing heat principle. All other techniques and timing of insemination revolve around this core principle.

In sow farms served by our swine veterinary practice, I like to teach technicians to work with the basic nature of the animals.

With natural service, the timing is easier. The sow won't let the boar stay mounted if she is not in heat. The problem with natural service, however, is that we don't know the quality of each boar's semen.

If we could use the same concept in checking for standing heat that the boar would normally use, we would have a big advantage, because with AI we know the semen quality has been checked before a sow is inseminated.


In most cases, one insemination/day is adequate. Try to set up a schedule that ensures repeat inseminations will occur less than 24 hours apart.

For example, breed sows scheduled for a second service before the first-service sows each day. If doing a third-service mating, complete those before the second service, or 12 hours following the second mating.

During the insemination process, make sure the sow or gilt is properly stimulated, which means having a boar present. For all of the hands-free devices and labor-saving innovations, the presence of the boar is still needed to stimulate the uterus to draw the semen up into the uterine horns.

For the sperm, the uterus is a battlefield, so it's vital to help as many as possible to survive. They don't complete the journey on their own. They need a strong, powerful current pulling them up into the uterine horns. This cannot be accomplished well without good, face-to-face exposure of the boar with the sow.

Boar usage

Normally, I do not recommend the use of cleanup boars. However, I do recommend allowing every boar (vasectomized or intact) to breed a sow once a week. Allowing boars to breed regularly will make them much more useful and they will do a better job of stimulation.

Let boars breed cull sows or first-service matings. Keep a record for each boar to ensure they have this opportunity.


For twice-a-day services, make sure you allow six hours or more between inseminations. This includes weekend matings.

If this can't be done, practice once-a-day inseminations and make sure to keep the service interval under 24 hours.

With the rather hostile environment in the uterus, the immune system invades rapidly after insemination. It takes time for things to simmer down before the time is right to inseminate females with another dose of semen.


I've seen quite a few disasters with lubricants. Lubricants have no antibiotics, so contamination of the containers is common. Generally, a smaller package size for lubricants works best. Buying in bulk may save money, but the extra cost of using smaller packages is easily overcome with the reduced risk.

Remember, the lubricant travels all the way to the cervix just as the catheter does.

In addition, there are differences in the osmolarity or concentration of the solution, the pH or measure of acidity.

I like to use an AI lubricant that is backed by research, such as AiGel from ReproQuest LLC, located in Fitchburg, Wis. Contact the company by phone 877-270-1250, fax 608-270-1240 or email for general information, or email for sales information.

Nine semen-handling principles

Here are some guidelines for handling semen:

  1. Ensure semen is fully cooled before packaging and before leaving the boar stud.

  2. Ensure semen temperature is controlled during transport with cool (not frozen) gel packs or cooling units. Vehicle transport won't provide any effective cooling because the semen is bundled up and conductive cooling happens slowly.

  3. Store semen in the cooling unit immediately after arrival at the farm. Do not let it sit out on the counter. It is surprising how often this happens. If you can't provide storage upon arrival, buy another cooling unit so the delivery person can store it directly when he/she arrives.

  4. Track high/low temperatures daily. Rotate semen daily to resuspend the sperm.

  5. Twice-a-week delivery should ensure that all semen is used within five days of collection. With delivery three times a week, semen should be used within four days of collection. And with daily delivery, semen should be used by Day 2. Check orders frequently to make sure this process is being followed.

  6. Set the cooling unit at the same temperature the boar stud uses to cool semen (normally 61°F.). If you don't know what that temperature is — ask.

  7. Check on-farm semen motility or activity using a microscope. I have seen many situations where the boar stud discovered a bad batch of semen, called the farm, and the farm had already used all of the semen. Remember, the boar studs check semen quality once a day. If you bred all of your sows before the boar stud conducted their tests, and found that a batch had gone bad, you're going to have to rebreed those females or you're in trouble.

    Contact the boar stud on the proper procedure to check motility, because there is a huge difference among different semen extenders. One isn't necessarily better than another; they just affect the sperm differently. With Beltsville thawing solution (BTS) extender, for example, the sperm will be moving rapidly. With HEPES-based extenders, the sperm will not be moving rapidly. With TRIS-based extenders, you need to look at the sperm within 15 seconds before they stick to the glass slide and give the false impression that they are not moving. With HEPES-based extenders and BSA, the sperm look best after one minute.

    Regardless of extender, the semen should be warmed for a couple of minutes prior to evaluation. An alternative is to use a slide warmer and allow the droplet to warm on the slide before putting the cover slip on and evaluating the sample.

  8. Take semen to the barn in a cooler with gel packs from the cooling unit (not frozen packs). Only take what you'll use in an hour. Do not return doses to the cooling unit.

  9. Make sure you are not using semen before the boar stud has provided polymerase chain reaction test results for porcine reproductive and respiratory syndrome. If this isn't possible, testing for PRRS virus by PCR loses most of its value. Normally, this means you'll be using semen starting the day after collection. There should be no loss in production with Day 1 semen vs. Day 0 semen. In fact, semen quality may be better because the extender has had time to stabilize the sperm and the antibiotics have had time to work.

Fertility Revisited

One of the successes in pig production has been an almost continuous increase in sow herd productivity. Sow herds have continued to increase the number of pigs produced per inventoried female per week.

Figure 1 on page 8 shows the trends seen in the industry, as portrayed through the PigChamp benchmarking program, depicting pigs weaned/mated female/year.

There have been improvements in the productivity of the North American swine herd, but the past few years have seen some flattening out of those improvements.

Nonetheless, the improvements have ensured that adequate pigs are available within most systems, at least on average.

Quantity to Quality Shift

The concerns about the sow herd have turned from a simple measure of the total pigs produced, to measuring the quality of the individual pigs and the flow of pigs out of a sow reproductive unit.

As we look at reproduction as a discipline to ensure a quality product, and an efficient utilization of the overall pork chain, we can identify several opportunities for improvement.

The sow unit must be a supporting enterprise for the entire pork chain system. Unfortunately, in many cases, we have not adequately focused on the need for high-quality productivity from the sow unit. Grow-out facilities are often a captive client of the sow unit, and inadequate communication and sharing of records occur in many situations.

Weaning Age Debate

As we look more closely at the need for coordination, various sow output parameters are being revisited. The most publicized choice in this discussion is weaning age.

Though it can be argued that increasing the weaning age decreases the productivity of the sow herd in some cases, in most cases that increased cost to the sow herd is recouped through increased performance of progeny downstream.

Figure 1 shows such a relationship, illustrating that the likelihood of success in the nursery is directly related to the weight and age of pigs at weaning. This balancing of costs and benefits can only be made when projects are correctly evaluated. Costs are not a problem, but benefits need to be captured downstream.

Seasonal Variation

It is not only the quality of pigs that should be evaluated, but the problems in seasonal variation. Figure 2 helps identify seasonal variation in output as a major problem in the American swine herd.

The amount of seasonality in weaned pig production leads to inefficient use of facilities, both in growing out pigs and at slaughter. Even worse, the seasonal supply is put against a retail pork demand that is relatively static. That's why we see seasonal price variation that can be as high as 25%.

There is a very strong case to be made that the major disease problem in the American swine herd is actually seasonal infertility. No other condition leads to such a variation in supply, nor to such an effect upon prices.

As we have looked more closely at the problem of seasonal infertility, we have found that two broad mechanisms should be considered.

First, the worst seasonal infertility occurs in herds that have marginal fertility during the winter. In other words, if proper methodologies and management are not utilized during the winter breeding period, the sow herd is exposed to a higher risk of fertility problems during the summer.

This scenario suggests that control of seasonal infertility is within our reach using methodologies already available. It should also be emphasized that the first and major mechanism of seasonal infertility is reflected through reduced farrowing rates and smaller litter sizes (Figure 3, page 10).

The second broad mechanism of seasonal infertility is the response to this so-called “disease.”

As seasonal infertility progresses through the summer, sow herd size will increase. As pregnancy rates drop, more sows are retained and the proportion of open sows increases.

Complicating matters further, seasonal infertility appears to end quite quickly, the proportion of sows successfully bred increases, and, subsequently, the result is overproduction of the sow herd.

This cyclical under- and over-production of the sow herd leads to variation in weaning weight and variation in grow-out performance.

As previously suggested, Figure 1 shows the relationship between weaning weight and the likelihood that a pig will be produced at an adequate weight.

Pig weight has often been measured as an average, but it is the distribution of weights, and the existence of low-weight pigs in particular, that leads to problems in the nursery. Much of the mortality problems and issues of slow growth are concentrated in these pigs.

Though weaning weight is a major predictor of subsequent performance, factors such as the manipulation of litter size and its impact on weaning weight have not been taken into account.

With lower weights, the likelihood that a weaned piglet carries a pathogen is a major concern. Factors such as parity, weaning weight, season, and of course, disease status of the sow herd, are all major concerns.

In addition, the proportion of gilts in a farrowing group has been found to be a predictor of disease outbreaks. Minimizing culling rates has often been argued on the basis of sow herd performance.

Perhaps an even greater emphasis should be placed on the quality of the progeny. Many cases have shown where stopping the introduction of gilts sometime before a planned depopulation has reduced the amount of disease in the nursery.

Moreover, culling is detrimental unless it is focused on older sows. Culling rates should be minimized, but the focus should be on reducing the culling of sows with less than three parities. This approach improves reproductive and progeny performance.

In some ways, the savvy production unit can be considered an input supplier to the pork chain that can be treated similar to a feedmill. It must provide a high-quality product, and it must have adequate capacity to meet the requirements of downstage production.

Unfortunately, the value of a unit's output is such that even if it overproduces, that product is put into the pork chain.

Stable production of robust progeny that do not transfer pathogens is our aim. It should also be our focus in measurement and optimization.

Health Problems That Affect Fertility

Breeding-herd efficiency requires good fertility. Expected performance in the United States is to have conception rates of 92-94% and farrowing rates of 88-90%. Anything less than these standards indicates a problem with fertility and reproductive performance within the breeding herd.

There are a number of potential factors, both infectious and non-infectious, that can affect fertility.

Health problems can result in lower fertility, leading to common symptoms including anaestrous (poorer cycling), decreased ovulation rates and embryo survivability, increased number of sows that recycle, and mummies and abortions. These symptoms are due to the following pathogens:

  • Viral agents:
    • Porcine parvovirus (PPV), porcine reproductive and respiratory syndrome (PRRS), swine influenza virus (SIV), porcine circovirus type 2 (PCV2), adenovirus and enterovirus.

  • Bacterial agents:
    • Brucellosis;
    • Leptospirosis;
    • Erysipelas;
    • Bacterial discharges (E. coli and Actinobacillus rossii);
    • Bacterial contamination of semen.
  • Parasitical agents:
    • Eperythrozoonosis.
  • Nutritional deficiency or toxicity:
    • Choline deficiency;
    • Pantothenic acid deficiency;
    • Riboflavin deficiency;
    • Vitamin B12 deficiency;
    • Zinc deficiency;
    • Selenium toxicity;
    • Mycotoxins (contamination in the field, bin or system).
  • Management:
    • Animal density too tight;

    • Chronic environmental and housing stressors;

    • Poor stockmanship and handling (moving animals poorly or moving animals prior to 30 days of pregnancy);

    • Poor heat detection and artificial insemination techniques.

This list demonstrates many possible causes for infertility. A good diagnostic plan is essential to determine the cause of the problem. Sometimes infertility problems are a combination of multiple factors, making it an even greater challenge to specifically diagnose the exact cause.

Good breeding herd and herd history records are essential to demonstrate the problem. Recording significant events in the herd history is also important. Laboratory diagnostics on fetuses from aborted litters can be helpful, but many times unrewarding. Serology can help confirm or rule out specific pathogens, as can a full diagnostic workup including nasal swabs in the case of SIV, and postmortem examinations to evaluate the entire system.

Viral Pathogens

Routine vaccination programs include PPV, multiple species of leptospira and erysipelas. Many farms also vaccinate for swine influenza virus. However, with the ever-changing flu virus, it is difficult to ensure complete protection. The best procedure for SIV is to use a vaccine that contains multiple isolates from the farm or of recently circulating local strains.

PRRS certainly can be a very big concern with infertility; one of the most common signs is abortion. Farms have used a variety of means to control this disease, including eradication procedures to eliminate the virus from their herds.

One of the first methods used was depopulation and repopulation. The most common method has been the use of herd closure. The greatest success has been achieved in herds that have been able to close for at least 220 days, with no outside introductions into the herd once all animals in the herd have been exposed to the virus.

The use of direct PRRS viral exposure to negative replacement gilts and the sow herd has helped to standardize this process, but many herds have been cleaned up simply with closure. If direct virus exposure is used, and staged gilts are exposed at the time of closure, there is little effect on the number of animals produced during the exposure.

One challenge with herd closure is aging parity distribution, which needs attention once the herd is reopened. The herd's age distribution going into the closure is an important consideration.

Other methods for PRRS control are continued introduction of gilts that are negative and exposed with direct virus exposure during their isolation period. This has worked well in hog-dense areas where the likelihood of the herd remaining negative is low.

Vaccination for PRRS is another option and has worked well for some herds.

Biosecurity for all herds is very important due to the fact that most new PRRS strains that gain entrance into a herd will result in the expression of clinical signs.

Darwin Reicks, DVM, of the Swine Veterinary Center, Scott Dee, DVM, University of Minnesota, and Andrea Pitkin, freshman veterinary student at the University of Minnesota, have all demonstrated that 95 DOP filters are an effective barrier for virus entry into herds (pictured on page 50).

The use of air filtration in boar studs has been an effective barrier to PRRS virus, based on field reports the last couple of years. One sow herd has been built with air filtration units using the 95 DOP filters in a pig-dense area, and so far the results have been promising.

PCV2 can also be a concern for reproductive health since it has been demonstrated to be present in herds with fertility problems in sows. Vaccination is becoming very common in developing gilts. At this time, no vaccine has been cleared for use in sow herds, although many herds have been vaccinated with commercial vaccines.

SIV has been a real problem in some herds. The virus continues to change over time, and new strains are circulating in the swine population. This can result in sows running very high fevers and becoming infertile with more recycles, abortions etc. Treating sows with aspirin in the water and Flunixin meglumine (Banamine from Schering-Plough Animal Health) injections will help to control the fever while the herd is breaking. Commercial vaccines are available, but make sure the strains identified on the farm are included in the vaccine. Work with your veterinarian on the products to use.

Water and feed-grade medications, such as tetracyclines, can be used to treat secondary bacterial infections due to the SIV virus infection.

The diagram above (Table 1) demonstrates an example of a vaccination schedule, detailing the type of products to use and timing of vaccinations, as well as a weekly organizer of activities.

Bacterial Pathogens

Common bacterial infections that lead to infertility include erysipelas, salmonella and ileitis. When these conditions are present, animals will become clinically sick and fertility will drop. Treating these infections and vaccinating are often the best ways to prevent these problems.

Erysipelas treatment with injectable penicillin, boostering vaccination (make sure to use an extended duration product) and using tetracycline in the feed are ways to control this problem.

Salmonella can be treated with ceftiofur sodium (Naxcel Sterile Powder or Excenel from Pfizer Animal Health), along with vaccination and tetracycline in the feed.

Ileitis can be treated with injections of tylosin (Tylan, now a generic drug), or lincomycin (Lincocin from Pfizer Animal Health), vaccination (Enterisol Ileitis from Boehringer Ingelheim Vetmedica, Inc.) and water medication of tylosin, lincomycin or tiamulin (Denagard from Novartis Animal Health).

Bacterial Discharges

Discharges caused by bacterial infections can be a problem in herds and tend to occur more in the summer because environmental conditions are conducive for growth of these organisms. This coincides with seasonal infertility.

Whenever you see bacterial discharges, review the breeding technique to ensure sows aren't being serviced too late in the heat cycle, when they are more prone to contamination. Their systems change from estrogen control to progesterone control during that time.

Also, review the breeding process to ensure pipettes are being handled properly and lubricants haven't become contaminated.

Another possibility for bacterial infection is poor technique when assisting sows at farrowing. This contamination and infection often doesn't show up until breeding. Review farrowing procedures to make sure this isn't a problem. Tetracycline can be used in the feed to help treat these problems.

Prevent these management problems by making sure sows are in good standing heat when bred. Keep the environment and equipment as clean as possible.

Bacterial contamination of semen can destroy semen in storage. If problems are suspected, check with your boar stud to see if they are routinely culturing semen samples and testing processing methods. Stored semen can also be cultured to check for problems. The shorter the storage time, the less likely semen will be damaged even if contaminated.

Review age of semen and delivery schedule and adjust ordering schedule to ensure semen is as fresh as possible.

Eperythrozoonosis can still be an infertility problem, although it is less of a concern today and not commonly diagnosed. Most herds have eradicated external parasites, which helped to spread this agent within herds.

Any pathogen that can produce an elevated body temperature can produce infertility. A good example is SIV, which causes high fevers resulting in infertility. A number of pathogens can result in fevers. Occurrence will vary with the herd's health and vaccination status.

Internal Gilt Replacements

Due to concerns with the introduction of new pathogens, such as PRRS and PCV2, some herds have turned to raising their own replacement gilts on site. This can be done by herd closure or by greatly reducing the number of introductions of grandparent gilts brought on-site. The only introduction to the fully closed herds would be semen, which is the safest form of internal multiplication.

With this approach, it is very important that the proper matings occur. Using a genetic improvement plan is important, as well as making sure that the semen used to develop replacements is the proper semen to maintain a high genetic value. It is important to monitor the estimated breeding values (EBV) of the boars used to produce the next generation of replacement gilts. If the genetics are not properly managed, this can potentially result in bigger costs to the herd than disease.

Tagging replacement gilts at birth will ensure that only the correct gilts are considered as replacements. Figure that roughly 60% of replacement female candidates will meet selection criteria. Grandparent females should represent approximately 10% of the sow herd.

Environmental Factors

Environmental conditions are another factor. Higher barn temperatures can definitely impact fertility with increased returns both at regular and irregular time frames. The use of cool cells has greatly reduced the impact of high temperatures. Some boar studs are using air conditioning along with filtration to control temperature.

In tunnel-ventilated barns, especially in late summer and fall, days are shorter and nighttime temperatures begin to drop. If the ceiling inlets are not reopened in time, the cool cell end of the barn can drop to very cool temperatures because the controllers read the average temperature of the barn. They continue to get cooler on the cool cell end because the curtain opens and lets 50°F air in and the fan end of the barn just gets warmer.

This situation sets up a repeating cycle unless the ceiling inlets are opened on the fan end of the barn to allow some attic air in to balance out the temperatures. This chilling at the cool cell end of the barn results in stress, and can cause the animals to develop any number of diseases, and they are therefore more likely to show infertility problems.

There is also debate about the use of timed lighting, but the cost of running lights and timers for 16 hours is not that high, so most lighting systems attempt to mimic the longest day. A guide to the amount of light needed is if you can read the paper, you have enough.

Seasonal Problems

Entering the fall, most producers focus on the seasonal effects on fertility. In the northern hemisphere, seasonal infertility is associated with sows bred from July through September. This seasonal infertility results in fewer sows farrowed and fewer pigs born in early winter — November through January.

This trend has a well-established pattern, which is even reflected in the market price of hogs slaughtered in the May through July period. Understanding this pattern is important, because many times this may be the most or only profitable time of the year. If producers prepare for this pattern, they can capitalize on it.

It is believed that warm summer temperatures and changes in the photoperiod (amount of daylight) cause this seasonal infertility. Diseases only compound and potentially magnify this problem.

One other concern is the money producers spend on diagnostics for this seasonal problem, which may not have anything to do with a pathogen. The challenge for veterinarians and producers alike is not to let a health problem go undiagnosed, thinking it will get better later in the fall.

Expect to see a 2-5% decrease in breeding performance due to seasonal infertility if temperatures are controlled with some form of evaporative cooling. If rates exceed that range, there are most likely other problems in the herd. Watch for longer wean-to-first-service intervals, an increase in irregular recycles, more not-in-pig sows and more pseudopregnancies.

False Pregnancies

Pseudopregnancy is one of the most frustrating types of infertility. The definition of pseudopregnancy is the functional corpus luteums (structures on the ovary that form after the egg ovulates and produce progesterone to maintain pregnancy) are maintained beyond expected luteolysis (the process of breaking down the corpus luteums either to come back into heat or at farrowing in the absence of viable fetuses).

There are two types of pseudopregnancies — a short and a long form. The short form may be as little as three days in an extended return to heat cycle. These are often undiagnosed and may be interpreted as an abnormal recycle. The long form is greater than 50 days and commonly diagnosed. Most of these sows visibly appear to be pregnant, and the pseudopregnancy may not be apparent until the sow has gone through an extended gestation period and accumulated many nonproductive days.

If a nonproductive sow day costs $1.50/day, and a sow goes 114 days before detection, these losses can cost $171/sow in direct cost. The lost opportunity of another litter of pigs in that week of production at 10 pigs weaned/litter at a value of $30/pig adds another $300 loss.

Some of these sows have udder development and have even raised nurse pigs without farrowing any piglets themselves.

How does this happen?

The sows really were pregnant, but the fetuses were lost some time between Day 11 and 35 of pregnancy. This makes diagnosing this problem very difficult, because by the time the sows are identified, it is well after the cause. Anything that can affect the fetuses in this time frame — including viral diseases such as PPV, PRRS and SIV — may have caused the losses.

Zearalenone toxicity (a mycotoxin) is another cause, and can develop as both the short and long forms. Zearalenone acts like estrogen and can lead to pseudopregnancy if cycling animals are exposed at Days 11-12 of their cycle. If the source of zearalenone is present for more than 8-9 days during this period, it can lead to a long pseudopregnancy.

Very often sows visibly appear pregnant and will even develop an udder; however, at the time of their normal 114-day gestation period, these signs will disappear and the sow will look open. If these sows are moved back to the breeding area, they will cycle and come back into heat, typically in 5-7 days. The best way to diagnose these sows is with repeated real-time ultrasounds.

Sow Nutrition

When diets are properly formulated, there should be no concerns about nutrient shortages or toxicities that could result in infertility. Test the diet periodically to ensure standard inclusion rates have been met and formulations match what sows are actually getting.

Keep an eye on the age of vitamin ingredients (no more than 90 days); this is the key to making sure what is still active.


The best means to manage seasonal infertility is to compensate for it in the number of females serviced. However, this doesn't help if it results in more crowding and stress, which can also lead to lower fertility rates.

There are many reasons for infertility. A good vaccination protocol to prevent the common infectious agents that can cause infertility is the backbone of prevention.

Having a good biosecurity program is essential to disease control. Providing a good-quality environment will help to reduce the impact of seasonal infertility.

A good recordkeeping program can be a great help in diagnosing fertility problems in a breeding herd.

Table 1. Vaccination Schedule1
Animal Timing Product4 Method of Administration Withdrawal, days
New gilts and vasectomized boars In week post-arrival/at selection Ileitis
Autogenous SIV2
Porcine circovirus type 2
2-weeks post-arrival/at selection Swine influenza virus (SIV)
Autogenous SIV
Last week before entry into herd Dewormer Oral 5
Gilts Entry into main herd IM 21
Vasectomized boars Every 6 months
Every 3 months
Swine influenza virus
Gilts prefarrowing 6 weeks prefarrowing Feedback Oral 0
5 weeks prefarrowing Rotavirus-clostridium perfringens-type C-E. coli
Swine influenza virus (SIV)
Autogenous SIV


4 weeks prefarrowing Feedback Oral 0
3 weeks prefarrowing Feedback IM
1 week prefarrowing Dewormer Oral 21
Sows prefarrowing 6 weeks prefarrowing Feedback Oral 0
5 weeks prefarrowing Feedback
Autogenous SIV
Swine influenza virus (SIV)
4 weeks prefarrowing Feedback Oral 0
3 weeks prefarrowing Feedback
Rotavirus-clostridium perfringens-type C-E. coli


1 week prefarrowing Dewormer Oral 21
Piglets Day 1 Fortified iron (200 mg) IM 30
1Herd is negative for porcine reproductive and respiratory syndrome and Mycoplasmal pneumoni.
2SIV refers to swine influenza virus.
3IM refers to intramuscular (injection).
4Dosage per label instructions.

Designs to Reduce Seasonal Effects On Reproduction

When you see the term “seasonal infertility,” do you ever wonder which season of the year is causing the problem?

In my opinion, the term should be replaced with a better description of the problem, such as “summer infertility” or “fall infertility.”

Summer infertility clearly identifies that reproductive problems are occurring during the summer months. Summer infertility covers a wide spectrum of problems, including anestrus in gilts and sows, estrous detection problems, decreases in conception rate, decreases in embryonic survival and decreases in fertility of boars.

Fall infertility clearly identifies that reproductive problems are occurring during the autumn months.

The severity of summer and fall infertility varies from farm-to-farm, region-to-region and year-to-year. In the end, what we are most interested in is maximizing fertility and breeding herd reproductive performance regardless of season or location.

Factors Influencing Fertility

Many scientific studies and articles on seasonal infertility in pigs have described the symptoms and the relationship of ambient temperature, photoperiod and nutrition to reproductive performance of gilts, sows and boars.

However, a large volume of scientific literature does not exist on the design and management of swine breeding-gestation facilities to eliminate summer infertility.

Although ambient temperature and photoperiod are thought to be the two major factors influencing lower reproductive performance during the summer and fall, many other factors contribute directly or indirectly to the effect of temperature and photoperiod on reproduction.

Other factors that can influence reproductive performance of sows and gilts during the summer include:

  • Skills of the workforce;

  • Design, maintenance and management of the ventilation and cooling systems of the breeding-gestation building;

  • Functionality of floor plan design to enhance accomplishments of work tasks by employees;

  • Design, ease of functioning and maintenance of equipment;

  • Lactation feed intake; and

  • Management procedures for performing estrus detection and mating activities.

Tasks conducted in marginally acceptable working environments are most likely accomplished in a marginal manner. I am not aware of a swine breeding facility that absolutely eliminates summer infertility.


The intensity and duration of photoperiod in a breeding-gestation facility is not clearly defined.

A study in France used two light regimens that mimicked spring daylight (a gradual increase in daylight from 12 hours up to 16 hours/day; “long” days) or autumn daylight (a gradual decrease in daylight from 12 hours down to 8 hours/day; “short” days) during gestation of first-parity sows (Figure 1 on page 28).

During lactation and postweaning, the long-day group was maintained at 16 hours of light, and the short-day group was maintained at 8 hours of light. Age at weaning was 20.6 ± 1.1 days.

The effect of photoperiod on reproductive performance is also indicated in Table 1 on page 28. The percentage of sows in estrus within 10 days after weaning was higher for sows exposed to short days than for sows exposed to long days.

In sows that farrowed in January, the wean-to-estrus interval was less for sows exposed to short days (5.2 ± 0.3 days) compared to sows exposed to long days (7.0 ± 0.7 days).

However, the wean-to-estrus interval for sows farrowed in July was no different for sows exposed to either short (10.4 ± 2.3 days) or long days (12.6 ± 3.2 days).

Therefore, this data suggests that under high-ambient temperatures, the duration of photoperiod (short or long) does not restore a good wean-to-estrus interval in first-parity sows. The light level for a breeding and gestation facility is indicated in Table 2 on page 29.

Ambient Temperature

High-ambient temperatures seem to have a stronger impact on summer infertility than either long or short light duration. Research in Australia found that when the average daily maximum temperature exceeded 89.6° F during the week of service, there was an increase in the number of sows returning to service (Table 3 on page 30). The number of sows returning to estrus after mating appeared to start increasing when the average daily maximum temperature was in the range of 82.4 to 89.4° F.

Bred females should be kept in a cool environment (85° F or less) during the first 30 days and the last two weeks of gestation. To prevent an increase in stillbirths, keeping sows cool the last 14 days of gestation is critical. Therefore, because a gestation facility houses sows in various stages of gestation, the entire facility needs to be kept cool.

Tunnel Ventilation

Although tunnel ventilation with evaporative pads is widely used to help cool breeding-gestation facilities, scientifically controlled studies have not been published to document the effect of tunnel ventilation on reproductive performance.

In general, the exhaust fans on tunnel-ventilated buildings are placed at one end of the building, and air is brought in from the opposite end of the building. If possible, air inlets should be located on the wall opposite the fans.

Air will not turn 90-degree corners unless forced. If air enters from the sidewall on the opposite end from the ventilation fans, it will generate airflow across the building rather than along the length of it. This perpendicular airflow will eventually turn and move endwise to the exhaust fans, but it will also leave a dead air zone along the sidewall containing the inlet panel. A dead air zone might also occur in the center portion of the building on the opposite end of the ventilation fans.

A weakness of the tunnel ventilation system is a difference in air quality from one end of the building to the other. The true effect of tunnel ventilation on animal comfort, health and performance from one end of the building to the other has not been documented.

Air movement and cooling through the animal zone in crated buildings is a concern. A high-velocity layer of air will be flowing above the crates, but air speed in the space actually occupied by the sow will be far less than the design speed.

Evaporative Pads

Evaporative cooling uses heat in the air to evaporate water, thereby reducing the air temperature. The disadvantage of this system is that it increases the humidity in the building.

Evaporative pad cooling systems work better in geographic areas that have humidity levels less than 80%. In some areas of the United States, the relative humidity is high during the morning hours; however, by the afternoon, the relative humidity is low. This process occurs because sunlight removes the relative humidity when the temperature gets warmer.

The pad is sized to optimize the evaporation and static pressure loss across the pad. The area of the pad is generally between 3 and 5 sq. ft./1,000 cfm drawn through the system. The wetting of the pad should start at 75 to 78° F. The pad should be allowed to dry before switching off the airflow. This procedure will dry the pad and prolong its life.

Scientific literature could not be located that compared the impact of an evaporative pad cooling system with ventilation systems using fans and sprinklers on reproductive performance.

Fans and Sprinklers

Pigs do not sweat. Therefore, evaporation of water from the skin of pigs plays a major role in cooling gestating sows. The key to cooling sows with fans and sprinklers is to thoroughly wet the animals and then let them evaporate dry. This process is called intermittent sprinkling and cooling. The type of flooring can influence the duration of sprinkling. It is important to let the floor surface dry to prevent foot problems.

Heat-Checking Procedure

It is well known that the characteristics of an excellent heat-check boar are sight, sound and smell. The smell of a boar is a key factor in stimulating sows to express the standing response.

A high ventilation rate is utilized during the summer months to enhance cooling of the sows. However, these high ventilation rates are most likely moving the boar odor quickly toward the ventilation fans as the heat-check boar moves down the alley.

The quick removal of boar odor can create two problems. First, if the airflow is moving toward the rear of the boar, the boar odor received by the sow next to the boar might be minimal. And, if the airflow is moving toward the head of the boar, the sows farther down the row may become stimulated before the boar arrives.

If estrous sows are being inseminated at the time of estrous detection, some of the sows farther down the row may be refractory to boar stimuli by the time the boar gets to their stall. Some sows will only stand for 5-10 minutes after responding to boar stimuli (Figure 2 on page 30).

Due to these two situations, it is best to have highly trained and dedicated workers heat-checking and inseminating females early in the morning (Figure 3). The workers might also want to consider using a boar stink stick to supplement the boar odor. The boar stink stick is a 1 in.-diameter PVC pipe with rags attached to one end. The rags are soaked with preputial fluids, saliva and a small amount of boar urine. Depending on the level of use, the stick is recharged once or twice daily.

Group Housing in Gestation

We do not know if heat stress will have a more detrimental effect on reproductive performance when sows are housed in groups compared to individual crates.

The floor plan design and group management will have important effects on reproductive performance. The term “group housing” needs to be clearly defined. If group housing means that the sows are housed in groups all of the time except during farrowing, reproductive performance will most likely be influenced by heat stress.

In addition to heat stress, other stressors (mixing of bred sows, bouts of fighting, inadequate feed intake, etc.) will have detrimental effects on reproductive performance.

In short, the breeding-gestation facility needs to be designed and managed so that the sows are not mixed during the first 30 days of gestation. The combination of heat stress and fighting will increase the body temperature of sows compared to heat stress alone.

If group housing means that the sows are housed in groups after 35 to 42 days of gestation, the detrimental effects of mixing and fighting on reproduction would be prevented. However, it is important to remember that high-ambient temperatures will still have detrimental effects on conception rate, farrowing rate and litter size on sows housed in individual stalls during this critical period.

Operations that house sows in individual stalls from weaning to 42 days after mating have an established area that is used specifically for breeding and the first part of gestation. Sometimes this area is a specific building or area within a building.

Compared to housing breeding and gestating sows in a “snake” system (filling rows of gestation stalls in sequence), the use of a specific breeding and early gestation area provides an opportunity to focus on a means to enhance the cooling of sows. Depending on the current cooling system, enhancement factors might include the addition of an intermittent sprinkling system or adding fans to improve airflow.

Replacement Gilts

Replacement gilts play a key role in reaching breeding targets during the hot months. Heat stress does lower the proportion of gilts reaching puberty, reduces ovulation rate, and reduces the proportion of gilts expressing second estrus.

Although photoperiod might be a concern, many scientific studies used boar exposure to detect estrus when evaluating the effects of photoperiod on puberty attainment. Thus, the true effect of photoperiod has not been established.

Table 4 on page 32 indicates the proportion of gilts reaching puberty is greatest when gilts are exposed to mature boars, regardless of whether duration of daylight is increasing or decreasing.

Instead of maintaining gilts under long photoperiod, it is most economical to maintain developing gilts under cool, white, fluorescent light (270 to 500 lux) for 10 to 12 hours/day. The light is measured at the eye level of a standing pig. The light should be measured at several locations throughout the building.

Because replacement gilts play a key role in keeping the farrowing facility full, pork producers need to seriously consider establishing an effective gilt development unit. A gilt development unit should implement a strict selection program to identify 75-80% of the most fertile gilts, minimize non-productive days, and breed the gilts at second or third estrus when weighing 300 to 330 lb.

This unit should be designed to reduce heat stress on gilts and enhance estrous detection, especially during the hot months.

To enhance and simplify the detection of estrus in replacement gilts, the facility should be designed to individually house the mature heat-check boars in one area. This design should help concentrate boar odor.

Gilts should be moved to heat-check pens located in front of the boar stalls. With the appropriate floor plan, the boar stalls can be designed so the boars can face either direction in the stall.

This design allows the heat-check pen to be established on either end of the boar stall (Figure 3). The boar stalls are 24-30 in. wide × 6-8 ft. long × 46 in. high. The boar stalls have boar-secure latches at both ends. Nipple drinkers are available on either end of the stalls.

This effective boar stimulation system was designed by the Swine Research & Technology Centre at the University of Alberta.

Table 1. Influence of a Step-wise Photoperiod on Reproductive Performance
Item Replication 1 Replication 2
Month bred September March
Temperature during gestation, °F 64.4 to 68.0 68.0 to 100.4
Month farrowed January July
Temperature in farrowing facility, °F 68.0 to 77.0 77.0 to 95.0
Photoperiod,a days Long days Short days Long days Short days
Cycling by day 10, % 53 92b 14 32b
Wean-to-estrus interval, days 7.0 5.2b 12.6 10.4
aBetween 14 and 105 days of gestation, light duration was either increased or decreased to mimic those occurring during spring (long days) or autumn (short days). Figure 1 indicates the two light regimens. The intensity of light at the level of the animal's eye ranged between 150 to 250 lux.
bValues for short days were significantly different (P < .05) from long days.
Source: J. Anim. Sci. 72:1461-1466, 1994.
Table 2. Light Level for Breeding and Gestation Facilities
Level of illumination, foot-candlesa Watts per square foot of floor area
Standard cool white fluorescent Standard incandescent Compact fluorescentb
40 watts 100 watts 150 watts 20 watts 23 watts
15 0.42 1.72 1.50 0.42 0.37
aUnit of illumination equal to one lumen per square foot.
bRetrofit bulbs.
Source: MWPS-43, Swine Breeding and Gestation Facilities Handbook
Table 3. Incidence and Distribution of Returns to Service of Sows Related to the Average Maximum Temperature During the Week of Mating
Temperature range, °F Weeks per year Total services Return to service after mating, %
68.0° to 75.0° 7.78 1,116 12.2
75.2° to 82.2° 15.09 2,584 11.4
82.4° to 89.4° 13.11 2,392 14.4
89.6° 16.02 2,919 19.7
Source: Australian J. Exp. Agric. & Anim. Husb. 18:698-701, 1978.
Table 4. Proportion of Gilts Reaching Puberty When the Duration of Daylight is Increasing or Decreasing
Duration of daylight is increasing Duration of daylight is decreasing
Study Boar exposurea No boar exposure Boar exposurea No boar exposure
1 74.0 13.9 89.4 52.6
2 72.4
3 79.0
aAge of gilts at initiation of boar exposure was 165 to 173 days.
bNumbers in parentheses are average age at puberty in days.
Source: Anim. Reprod. Sci. 24:323-333, 1991; Anim. Reprod. Sci. 23:135-144, 1990; J. Anim. Sci. 57:1235-1242, 1983.