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Understanding Why Sows Are Culled

Sow culling rates have a direct correlation to the economic efficiency of a breeding herd.

Some sows are culled voluntarily in an effort to improve overall herd performance. These sows may have weaned small litters, savaged their pigs or had a poor disposition.

Other sows are culled involuntarily. These sows may have failed to breed, failed to conceive after two estrous cycles or simply died.

Most recordkeeping programs offer mechanisms to record the reason(s) why individual sows are culled.

Cull Sow Study

In an attempt to more specifically identify the reasons sows are culled, Iowa State University researchers, with funding from the National Pork Board, investigated the physical and reproductive conditions of 3,158 cull sows delivered to midwestern sow harvest plants.

Two plants were chosen because they harvest sows considered representative of the range of sows — thin or “boner” sows to well-conditioned or “fancy” sows — culled from North American sow herds.

Body condition, feet and legs, shoulders, teeth, respiratory system, digestive and reproductive tracts were visually evaluated for the presence (or absence) of lesions and abnormal conditions in the sows.

A National Swine Improvement Federation certified Real-Time ultrasound technician measured backfat, loineye area and loin muscle depth from a cross-sectional image taken at the 10th rib of sows prior to slaughter. A visual assessment of body condition was made immediately postmortem, evaluating each sow's condition and scoring them on a 1 (thin) to 5 (fat) scale, much as a producer would do as sows reenter the gestation barn.

Front feet, rear feet and dewclaw condition were evaluated and recorded by a trained technician. Both hooves (toes) and dewclaws were evaluated for various abnormalities, including sidewall lesions, cracks in the white line and toes, cracks in the soft heel of the toe, abscesses, cuts, abrasions and bruising. Overgrown and missing toes and/or dewclaws were also recorded.

Shoulders were evaluated for the presence of lesions in the form of abscesses, abrasions and wounds. Shoulder lesions were categorized as follows:

  • No lesion;

  • Abscess (open or closed);

  • Abrasion; or

  • Wound (open wound/healing open wound).

Teeth were evaluated and recorded by a trained technician. Top and bottom teeth were counted and scored for severity of wear as follows:

  • Minimum wear — sharp points present on molars and incisors;

  • Moderate wear — points on molars and incisors present but smooth; and

  • Severe wear — no points present on molars and incisors.

Harvest plant personnel removed all thoracic and abdominal viscera, including the respiratory, reproductive and digestive organs from the carcass. Immediately after removal from the carcass, U.S. Department of Agriculture personnel and a veterinarian visually inspected the viscera.

From the macroscopic appearance of the ovaries, the sows were classified as normal, cystic or acyclic (non-cyclic). Pregnancy status was determined and fetal tissues (if present) were classified as normal, decomposing or mummified.

The research veterinarian visually evaluated the thoracic and abdominal cavity and organs for clinical signs of disease. The presence or absence of peritonitis, pleural adhesions, and pneumonia were recorded. If pneumonia was visually diagnosed, an estimate of the percentage of lung involvement was made. Lesions other than those previously mentioned were noted when visually present.

Early Findings

Preliminary evaluation of the data is underway. The most common, observable disorders among harvested cull sows were rear and front pad lesions, found in 67.5% and 32.9% of sows, respectively (Table 1).

Rear pad lesions were associated with body condition scores (BCS). As BCS increased, sows had more rear pad lesions. One possible explanation is that as BCS increases, sow weight generally increases. This added weight might increase pressure and thereby cause damage to the rear pad.

The second most common observable disorder was front and rear cracked hooves, found in 22.6% and 18.1% of sows, respectively.

Again, both front and rear cracked hooves were associated with BCS. But in this case, the incidence of cracked hooves increased as sow body condition became poorer (thinner).

Previous research has shown flooring type influences the presence of cracked hooves. Sows housed in confinement housing (stalls, tethers) with partially slotted flooring generally had fewer cracked hooves when compared to sows housed in loose housing systems with partially slotted concrete flooring. The same study reported that sows housed in a loose housing arrangement that included deep bedding were associated with minimal claw lesions.

The incidence of overgrown toes and/or dewclaws on the rear feet of all sows evaluated was higher than expected (21.1%). Additionally, the incidence of overgrown rear toes and/or dewclaws increased as BCS decreased. Whether this is attributable to some genetic, nutritional, environmental or some unknown factor is not clear.

Previous reports have indicated that pigs housed on plastic slats had a greater prevalence of overgrown toes when compared to pigs housed on concrete slats. This may be attributable to decreased wear on plastic compared to concrete floor surfaces.

Yet another study reported that gilts reared on higher feeding levels had longer dewclaws later in life. This indicates a farm nutritional component to the formation of overgrown dewclaws.

Toe lesions were more frequently observed on the rear toes when compared to the front toes. One possible explanation may be uniformity of toe size. It has been demonstrated that front toes are more uniform in size than the rear toes. Furthermore, toe lesions are known to increase as the difference in size between the medial and lateral toes becomes larger.

Housing conditions may also have an impact. Toes on the rear feet of sows housed in crates may experience wetter conditions when compared to the front feet because of urination.

The presence of severe teeth wear was found in 42.5% of sows. However, neither minimum, moderate, nor severe teeth wear scores and teeth numbers were associated with BCS.

The occurrence of shoulder abrasions was recorded in 12.5% of sows. The incidence of shoulder abrasions increased as the BCS decreased. Of the sows with a BCS of 1, 21.6% had shoulder abrasions. By comparison, only 3.9% of sows with a BCS of 4 or 5 had shoulder abrasions.

Shoulder lesions commonly occur during lactation, because sows spend a greater percentage of the time lying on their side. Good lactation management and improved body condition prior to farrowing can reduce the risk of shoulder lesions.

The presence of pneumonic lesions was found in 9.7% of sows. The majority of these pneumonia lesions had less than 10% of lung involvement.

The incidence of pneumonia lesions increased as BCS decreased among the sows evaluated. This study was designed to detect an association between BCS and pneumonia lesions, but couldn't determine if the pneumonia led to poor condition or, conversely, poor condition led to greater susceptibility to pneumonia.

The presence of acyclic ovaries was identified in 9% of sows. The incidence of acyclic ovaries increased as BCS decreased.

Previous reports have demonstrated that acyclic ovaries were associated with protein loss. Because protein loss was unknown in this study (sows were not evaluated at the farm), it is not clear if it contributed to the incidence of acyclic ovaries.

What Have We Learned?

The current study suggests that cull sows evaluated at U.S. harvest facilities have a relatively high presence of foot disorders. Additionally, these cull sows had shoulder, teeth, respiratory and reproductive lesions.

Reproductive failure is the most commonly cited reason for culling, but the question remains: “Why are sows with normal ovaries culled for reproductive reasons?”

The incidence of reproductive tract problems was substantially less than the percentage of sows culled for reproductive failure by commercial recordkeeping services.

It is important to distinguish between gross lesions and functionality. It is possible that sows with ovaries that appear grossly normal still fail to exhibit behavioral estrus reliably. If ovaries appear functional on gross examination, environmental factors on the farm would more likely explain poor reproductive performance by these sows.

Table 1. The Incidence of Abnormalities Among Sows Evaluated at Two U.S. Cull Sow Harvest Facilities
Trait Frequency or Count (n=) Incidence, %
Front feet, n= 3,1171
Heel lesions 1,024 32.9
Cracked hooves 703 22.6
Digital overgrowth 109 3.5
Abscesses 20 0.6
Missing dewclaws 4 0.1
Hind feet, n= 3,058
Heel lesions 2,064 67.5
Digital overgrowth 644 21.1
Cracked hooves 552 18.1
Missing dew claws 152 5.0
Abscesses 134 4.4
Ovaries, n= 3,062
Acyclic 277 9.0
Cystic 192 6.3
Fetuses, n= 3,070
Pregnant 180 5.9
Normal 157 5.1
Mummified 15 0.5
Decomposed 8 0.3
Disease processes, n= 3,083
Pneumonia 1- 10%2 153 5.0
Pneumonia >10%3 145 4.7
Pleural adhesion 174 5.6
Peritonitis 54 1.7
Detritus 11 0.4
Shoulder lesions, n= 3,146
Abrasions 394 12.5
Open 150 4.8
Abscesses 12 0.4
1n= number of sows with recorded data
25.0% of sows had pneumonia with 1-10% lung involvement.
34.7% of sows had pneumonia with >10% lung involvement.

Pork Exports Continue to Rock!

U.S. pork exports have begun 2006 just where they left off in 2005: up, up, up!

Data released by USDA on Thursday shows total U.S. exports for February were 23% higher than last year. That increase comes on the heels of a 20% increase in January and leaves year-to-date exports up 21% vs. the same time period in 2005. See Figure 1 for a year-over-year comparison of the monthly data.

What makes this performance quite remarkable is that exports in February to Japan and Canada, our first- and third-largest pork export buyers, were lower by 10% and 3%, respectively. This marks the third straight month that pork shipments to Japan have been lower than one-year-earlier and year-to-date exports, now trailing 2005 by 7%.

The big story is robust export growth to Mexico -- now up 37% for the year, following an increase of 44% in February. In addition, shipments to Russia more than tripled in February, while those to Hong Kong/China were 41% larger. Exports to Taiwan nearly doubled in February.

The combination of robust exports and imports that are quite close to year-ago levels leaves U.S. net pork exports near a record high (see Figure 2). Last month's net exports of 175.346 million lb. are second only to April 2005, when the figure hit 176.367 million lb.

The February 2006 figure represents 10.7% of total U.S. production during February. Had that product been placed on the U.S. market, it would have driven prices down by 40% or so. Exports are extremely valuable to this industry!

Chicken Exports Up, Too
Probably the most important piece of news in the export report, though, was the surprisingly high level of U.S. chicken exports in February (see Figure 3). Many market observers had expected U.S. exports to be lower due to difficulties in shipping products to Eastern Europe in the wake of avian influenza outbreaks that had sickened a large number of people and killed a few. But these data indicate otherwise.

February exports were 15.4% larger than one year ago. Shipments to Russia were 89% higher, and those to Eastern Europe were 54% larger.

From the viewpoint of a jaded economist, this means only one thing: People will buy cheaper product regardless of the other issues at stake. Perhaps that statement would be more accurate by beginning it with the qualifier "some," but the effect of lower prices has obviously overshadowed some negative sentiments.

So larger chicken exports are good news, right? Not necessarily. While it is good to get the product shipped elsewhere, that means that we now have to find another explanation for extremely low domestic prices. These export data, when combined with domestic production and freezer inventories through March 1, mean that domestic chicken availability/disappearance for February 2006 is only 0.3% higher than it was one year ago. Had exports been lower, the quantity available to U.S. consumers would have been higher and possibly could have explained low chicken prices.

We do not measure consumption of any meat directly. We just use a balance sheet (Beginning inventory + Production + Imports - Exports - Ending inventory) to determine the total amount that disappears during any given time period. Then, when we compute per capita consumption, we make the heroic assumption that all of that is consumed by humans. We simply have no data from which to draw any other conclusions.

Given that limitation, the February chicken data suggest that domestic consumption was about equal to last year, while domestic wholesale chicken prices were anywhere from 10% (for whole birds) to 40% (for some parts) lower than last year. Therefore, those are not supply-induced price declines -- they would suggest very soft chicken demand.

I'm not sure how to handle that because it has hardly ever happened during my professional lifetime. It could be good if consumers turn to pork and beef. It could be bad if it is a symptom of a broader decline in meat demand. It may just mean that U.S. consumers are reacting to day after day of avian influenza gloom and doom in a more emotional manner than I had expected.

It certainly suggests that chicken companies will have to reduce output, perhaps dramatically, in order to help chicken prices. There has been little news of such cuts, but perhaps these data will drive the real world home to decision makers.

Though times are harder than they have been for the past couple of years, remember this weekend that they are not near as hard as they have been, and they are not even comparable to the conditions faced by many in this world. This weekend symbolizes untold blessings and hope for us Christians. Whether you agree with our view or not, take a few minutes to reflect this weekend. I think you'll be better for it, and the real importance of things like chicken exports will likely pale a bit. Happy Easter!




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Steve R. Meyer, Ph.D.
Paragon Economics, Inc.
e-mail: [email protected]

Hog Futures Slide As Competing Meats Grow

First, a correction is in order to last week's North American Preview. While actual federally inspected (FI) hog slaughter during March of this year was 3.5% larger than last year, I made a critical omission in my year-over-year comparisons: adjusting for a holiday last year. Easter 2005 fell during March. That didn't cause an entire lost day as would Thanksgiving or Christmas, but it did cause short days on March 25 and 28. Adjusting for those short days leaves March 2006 slaughter 1.6% larger than a comparable March 2005 slaughter (23 full weekdays and four Saturdays), and that number is very close to the March Hogs and Pigs Report over-180 lb. estimate of +1.7%.

After a positive Monday on Chicago Mercantile Exchange (CME) Lean Hogs futures, this week has seen a continued decline in CME Lean Hogs futures, with April making four consecutive contract life lows, and both June and July breaking support at $65. The August, October and December contracts are now nearing support lines at $62.50, $53.50 and $51.20, respectively. Should those be broken, the next support for August would be at $60, and the next objective for October and December would be contract life lows near $50, made either on or just after the contracts came on the board.

The meat complex got a bit of help from lower cattle weights last week, and those declines are expected to continue as the market sees the effects of the recent large snowstorm in the Northern Plains. Federally inspected cattle slaughter through Thursday was still nearly 5% larger than last year, so beef production rolls along.

And chicken production for the week that ended March 25 was 10% larger than last year. Goldkist CEO John Bekkers told a March 14 conference held by Stephens, Inc. that the current financial situation for chicken producers is worse than in 2002 and 2003 due to low white meat prices. He said that Goldkist had made some cutbacks amounting to about 3.25% of production. These followed, though, a statement during his prepared remarks that "We have a very disciplined strategic plan that we continue to execute without regard to what's happening in the market." In other words -- Damn the Torpedoes. Total broiler egg sets for the week ending April 1 were 0.5% higher than one year ago. That increase is smaller than in previous weeks, but the year-to-date total is still 0.75% larger than last year.

Growth in the Pork Sector
Amid all of this, there will also be more growth in the U.S. pork industry. Veteran pork sector banker Lee Fuchs, now with Farm Credit Services of Missouri, told the National Pork Board's Pork Management Conference this week that he knows of 140,000 more sows that will be in production by mid-2007. I have seen similar lists that did not have quite that many sows, but I think Lee has a better view of a broader market area than do the authors of the other lists I have seen. That increase would represent 2.6% more growth and bring the two-year total to 4%.

The question of productivity gains remains unanswered at this time. Recall the graph in Figure 1 that shows the historic positive relationship between sow herd change and productivity. I have added an observation for Q1-2007 based on Lee's growth prediction.

Hog Expansion Like No Other
It is difficult to predict how these relationships might play out for this hog cycle. First, note that this "expansion" is like no other. Since the high point of liquidation of the last cycle (Q1-2003 at -3.3%), we have seen only five positive quarters out of 12. It normally takes about five quarters to get back to positive, and then we stay there for a while. This thing is slow.

Second, the magnitude of productivity gains is definitely slowing. The rapid growth of the '90s was driven by new technology, structural change and better management systems. The rate of change for all three of those variables has now declined as the law of diminishing marginal returns comes to bear. There just aren't as many places to make easy improvements. Add in a few porcine reproductive and respiratory syndrome (PRRS) (and now postweaning multisystemic wasting syndrome or porcine circovirus-Type 2) outbreaks, and we just aren't jacking up the efficiency like we were.

That is not to say that efficiency will not grow. Litter size set a new December-February record. That's the 10th-consecutive quarterly record. The new serum treatment for PRRS is having some success. The new circovirus vaccine is being used in Canada on an experimental basis. New hog buildings are still clean and productive, and there will be less trial-and-error in managing these new buildings since they are mainly being built or managed by entities already familiar with how to run a hog farm.

Gauging the Impact of Future Production
Let's consider how much larger production could be by the end of 2007: Pencil in that 2.6% breeding herd growth. Add in 2-3% productivity growth and another 1% for higher weights (only very high corn prices will prevent that) and you get 5.5 to 6.5% higher pork production. Even another 20% increase in exports will account for only 2.5% of that, leaving 2-3% more for U.S. consumers to consume.

By the way, Lee's topic at the conference was "Preparing for the Downturn."




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Steve R. Meyer, Ph.D.
Paragon Economics, Inc.
e-mail: [email protected]

Large Chicken, Beef Stocks Dampen Pork Price Prospects

Iowa State University costs and returns estimates show 26 consecutive, profitable months -- and yet the U.S. pork sector is growing only marginally as of March 1. Of course, that is the good news from Friday's USDA Quarterly Hogs and Pigs Reports. All of the key numbers from this report (which appear in Table 1) differ from pre-report estimates by a relatively small amount -- small enough that Chicago Mercantile Exchange (CME) Lean Hogs futures prices should not move dramatically on Monday.

The only numbers that differed from pre-report estimates by more than 1% were the inventories of pigs weighing under 180 lb. and the number of farrowings during the December-February quarter. All of those numbers were smaller than expected and thus would be bullish, if anything, for Lean Hogs futures.

The U.S. breeding herd grew by 84,000 head or 1.4% from last March, while the inventory of market hogs rose by only 0.6% from last year. Both of those numbers would indicate manageable supplies for the rest of this year and, thus, would be encouraging for hog prices if it were not for large current and potential supplies of chicken and beef.

Record Pork Production Slated for 2006
Producers should always keep in mind that the price strength during 2004 and 2005 happened in spite of the fact that production was higher both years (see Figure 1). In fact, both slaughter and production were higher in both 2004 and 2005 -- and production has now set a record for five years. The March inventory estimates indicate that 2006 will be more of the same. X and Y in Figure 1 indicate annual commercial slaughter and production forecasts of 104.75 million head and 2.111 billion pounds.

The question is whether demand can recover enough to overcome this year's production increase. That will be difficult with chicken prices at extremely low levels and cattle prices falling into the low $80s. Low prices of competing goods cause the demand for any product to fall.

Those slaughter and production estimates are conservative since we still don't have a good handle on the effect of Canada's corn import duty on the number of pigs that will be imported this year.

Confounding the effort to predict imports is the fact that we can't easily make year-over-year comparisons because one year ago the U.S. import duties on Canadian pigs kept those numbers artificially low. Suffice it to say that feeder pig imports have increased substantially over the past two months, and there could be a jump in market hog imports beginning in May because Canadian exporters can get corn duties rebated if hogs fed U.S. corn are exported.

Prices Still Profitable Through the Third Quarter
Weekly slaughter for the remainder of 2006 should be very close to that of 2005 given these inventory estimates, with only the fourth quarter exceeding last year by any marked amount -- about 1.5%. That adds to my feeling that the fourth quarter will see prices below breakeven, and that prices will remain profitable through the third quarter. Yes, less profitable than last year, but still profitable.

Crop Planting Projections Surprising
It's hard to believe but Friday's Prospective Plantings report may be as important to pork producers -- mainly because it was such a surprise. Acres planted to corn are predicted to be 5% lower than last year, while soybean acres are predicted to be 7% larger.

That caused new crop corn to set new contract life highs on Friday, and sets the stage for some active acreage-buying by new crop corn futures over the next few weeks. I'm not too excited about buying corn futures at contract life highs, but this situation could get explosive if planting troubles or a dry summer comes.

If the growing season is good, corn will be cheaper this fall than futures now predict -- perhaps much cheaper. Producers need to consider their corn needs and devise a strategy to control corn prices for the remainder of 2006 and into 2007. Out-of-the money calls would be one way to put a lid on corn costs.




Click to view graphs.

Steve R. Meyer, Ph.D.
Paragon Economics, Inc.
e-mail: [email protected]