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Articles from 2004 In December

Mandatory Price Reporting Extended

Congress has passed legislation extending the mandatory price reporting provision for one year. The extension expires Sept. 30, 2005.

“While pork producers are pleased by this action, we call on members of Congress to take the lead in the reauthorization of this important tool which helps producers make knowledge-based decisions and to have a better understanding of the marketplace,” says Keith Berry, Greencastle, IN, producer and president of the National Pork Producers Council.

Today, 53% of hogs sold in the U.S. are priced using this system. “By using this tool, producers are able to obtain more transparent and timely market information on pricing, contracting for purchase and supply and demand conditions for hogs,” Berry says.

Pork Board Sets Budget

The National Pork Board's budget of $53.7 million for 2005 includes the first major change in the pork industry's consumer marketing program since the “Pork. The Other White Meat” campaign was launched in 1986.

The new budget also includes $12 million that goes to state pork producer organizations for local pork checkoff programs.

The budget request now goes to the U.S. Department of Agriculture for final approval.

Pork producers have enjoyed profitable hog prices throughout much of 2004, thanks to strong consumer demand domestically and internationally, and higher pork prices at wholesale and retail, even in the face of record pork production.

“This has been a remarkable year for pork demand,” says Dave Culbertson, Geneseo, IL, pork producer and president of the Pork Board. “With production running at near-record levels, we wouldn't have guessed that pork prices would remain so strong. We're pleased that consumers are finding reasons to put more pork on their plates.”

The robust market has also generated $10 million more than budget expectations from the pork checkoff, which is tied to a percentage of hog sales. The funds will help support industry programs in promotion, research and consumer education.

“As a result, we're seeing new ideas, including the launch in March 2005 of a bold new marketing initiative to build on the phenomenal success of our ‘Other White Meat’ campaign,” adds Danita Rodibaugh, Rensselaer, IN, pork producer and chairman of the board's Budget Committee.

The 2005 budget also supports both new and existing environmental, animal health and welfare programs, and educational materials to pork producers.

Key issues identified by the board for 2005 include:

  • Increasing pork demand;

  • Improving the consumer's pork eating experience;

  • Developing new industry leaders;

  • Implementing an issues-management process;

  • Establishing industry standards in environmental and animal health areas; and

  • Improving the pork industry's image in local communities.

The budget also provides support to the national effort to map the swine genome.

product news

Compost Spreader

The new V-bottom composter spreader from Mohrlang Mfg., Inc., can be truck, Gator or trailer mounted. It is available in 15, 18 and 20-ft. lengths and features variable speed control. The spreader has a 36-in. hydraulic drive gear reduction floor chain, which is heavy duty D88. It also features 27-in., high-speed spinners with adjustable spinner location to optimize broadcasting. The 40-in. rear gate is roller guided and electric linear actuator controlled. The spreader box has a 3/4-in. plastic floor.
(Circle Reply Card No. 101)

Auto-Sort Software

Farmweld, Inc., introduces a Web browser-based, subscriber service called eBarn. The service enables swine producers and other authorized individuals, such as employees or consultants, to obtain performance management reports generated by Fast II (Farmweld Automatic Sorting Technology) from any online computer. The service provides detailed reports, including a histogram showing distribution of pig weights, five-day tactical summaries and 30-day summaries that display scale activity. It also provides average weights plus temperature and water usage; active sort summaries that show weight averages for high and low pig groups; inventory reports that keep managers up to date on the number of pigs moved in to the facility; the number that died or sold and other events; and a scale report that indicates activity on the scale to help analyze barn activity and pig training. The eBarn data is updated continuously — within 24 hours of real time with an automated connection.
(Circle Reply Card No. 102)

Bulk Feed Transport

Sudenga Industries, Inc., introduces the new Max-Flow model to its line of bulk feed transports. Engineered to efficiently handle bulky feeds with a tendency to bridge, the Max-Flow bulk feed transport features an unload system design which promotes consistent, trouble-free loading, even in feeds that have byproducts with poor flowability characteristics. The Max-Flow's unique unload system eliminates the standard “inverted V” to provide an unobstructed path to the unload auger located beneath each feed compartment. Specially designed, 17-in.-wide horizontal gates open from the center and are engineered to function easily under load. Rack and pinion gears on each gate ensure equal tracking. The Max-Flow model is available for straight trucks to 20 tons in Standard or EZ Fill aluminum or steel body configurations.
(Circle Reply Card No. 103)

Pressure Washer

Landa announces a new line of portable, hot water pressure washers capable of supporting two spray wands that clean with a high-pressure spray heated to 200 ∞F. The six SLT models deliver cleaning power of 5.2 to 7.8 gal./minute (gpm) and 3,000 to 3,200 psi. An insulated, high-capacity, shut-off spray gun is fitted with a swivel crimp to prevent hose tangles. The stainless steel, variable pressure wand makes it easy to adjust the water pressure while cleaning. The SLT also features a large-volume heating coil, consisting of 300 ft. of cold-rolled, 3/4-in. Schedule 80 steel pipe. The coil is covered by stainless steel upper wrap, and the water is heated using a burner fueled by diesel or heating oil. The large, metal fuel tanks offer hours of uninterrupted operation.
(Circle Reply Card No. 104)

Manure Digester

Write-A-Way introduces the CompoStore, a manure digester that dissolves solids, digests fiber and prepares manure for soil application. The product is formulated from all-natural ingredients, including Yucca extracts, bacteria cultures and enzymes that work in harmony to accelerate decomposition and control odor. CompoStore is safe and 100% biodegradable. There are no ingredients that will irritate skin nor corrode metal, concrete or plastic. CompoStore is available in both dry and liquid formulas.
(Circle Reply Card No. 105)

Magnetic Hitch Locator

White Company's Magnetic Hitch Locator makes lining up a trailer hitch and hitch ball easy. The locator consists of a set of reflector globes attached to masts that extend up to 60 in. The masts attach to the bumper and hitch by strong magnets and the globes extend above or outside the vehicle bed, allowing the driver to see the two globes touch, meaning the hitch ball and trailer are aligned. The Magnetic Hitch Locator is the only hitch alignment guide that works on all vehicles, including rear-view and side-view mirrored vehicles.
(Circle Reply Card No. 106)

Send product news submissions to Dale Miller, Editor (952) 851-4661;

2004 Swine Research Review

Manure/Odor Control

Test of Farrowing Environments Reveals No Clear-Cut Winner

Growing concerns over odor and gas levels being released from pig production units has led agricultural engineers across the U.S. to test a variety of facilities to determine actual air emission rates.

In doing so, engineers are accumulating data on emission rates for gases (ammonia and hydrogen sulfide), particulate matter (dust) and odor concentrations, to determine their impact on existing and potential state and federal regulations and public nuisance concerns.

Studies at the University of Minnesota West Central Research and Outreach Center near Morris, MN, compared a deep-bedded “Swedish” style farrowing facility and a conventional-crated farrowing facility.

Hydrogen sulfide and odor levels were highest from the conventional deep-pit barn. Ammonia emissions recorded were higher from the deep-bedded barn during the summer farrowing, but ammonia levels were otherwise similar to the deep-pit barn in other months.

Particulate matter and odor emissions were higher for the conventional, deep-pitted farrowing barn.

The “Swedish” farrowing barn was built in 2002 and includes three farrowing rooms (eight sows/room) with a 33-sq.-ft. solid floor that is heavily bedded. At the start of farrowing, solid partitions that form 6×8-ft. cubicles are placed along the outside walls for use by sows and piglets, as desired. PVC pipes are placed at the bottom of cubicle doors to keep piglets inside for the first 10 days after farrowing.

After 10 days, the cubicle partitions are removed and sows and pigs are permitted to commingle at will.

The conventional farrowing facility was built in the 1970s and features two rows of eight crates. An 8-ft.-deep manure pit is pumped once a year.

For the study, data was collected from October 2003 to June 2004, spanning four farrowing cycles and covering all seasons. Ammonia and hydrogen sulfide levels were monitored continuously in both buildings. A 24-hour particulate matter sample was collected weekly, while an odor sample was taken once during each farrowing cycle.

The daily mean values for ammonia and hydrogen sulfide emissions for the November farrowing period for the deep-bedded barn and the deep-pit barn are shown in Figures 1 and 2, respectively.

Figures 3 and 4 show measurements recorded for the June farrowing period for the deep-bedded barn and deep-pit barn, respectively.

Overall, for the summer farrowing cycle, ammonia emissions were about two times greater in the deep-bedded barn than the deep-pit barn on an animal unit (AU) basis. One AU equals 1,100 lb.

But during the other seasons' ammonia emission rates were found to be quite similar for the two barns; the lowest emission rates occurred in winter.

Hydrogen sulfide emissions were very low in the bedded barn, while gas levels from the deep-pit barn were highest during the summer farrowing period. Around 80% of the hydrogen sulfide gas exhausted from the deep-pit barn exited via the pit fans, with the rest going out the sidewall fans.

Particulate matter emissions were lowest in winter and spring farrowings and were found to be slightly higher in the deep-pit barn.

Odor discharges were very low from the deep-bedded facility, averaging 85% less than the deep-pit barn.

The cost-benefit analysis of this information is difficult to evaluate, but could be sizable if limits on certain emissions are implemented.

Researcher: Larry D. Jacobson, University of Minnesota; phone Jacobson at (612) 625-8288; fax (612) 624-3005; or e-mail

Click to view graphs.

NPPC Files Request To End Canadian Subsidies

The National Pork Producers Council (NPPC) has filed a letter with U.S. federal officials asking that the Canadian government end subsidies to its hog farmers.

The Nov. 19 letter to the U.S. Trade Representative, Secretary of Agriculture and Secretary of Commerce seeks a bilateral agreement between the two countries “that will end the substantial payouts being given to Canadian hog farmers. This agreement would take the Canadian government out of the hog market and restore free trade to the marketplace,” says Jon Caspers, immediate past president of the NPPC.

This action follows NPPC's filing of countervailing and antidumping duty petitions on imports of Canadian live hogs. The Commerce Department has provisionally placed antidumping duties of 14% on live hog imports from Canada. The duty is to be paid by the importer of record.

Caspers says information released by the Canadian government (Figure 1) shows that in 1999, Canadian hog farmers had a net income of $44,000 Canadian on a per-farm basis. Of that amount, $43,000 was linked to government program payments. In 2002, Canadian hog farmers netted an average of $46,000; more than half, or $25,000, was linked to program payments, he adds. One Canadian dollar equaled about 84¢ U.S. at press time.

Parasites: An Overlooked Problem

In a world where we deal with big-picture items that affect swine health, nutrition, welfare and other areas, we sometimes forget about the basics that need to be attended to every day.

One of those potentially forgotten areas is parasite control. Parasites in swine are often silent thieves with no obvious signs of health effect or financial loss. But parasites can also be not-so-silent thieves.

Case Study No. 1

We were called to a farm where finishing pigs were experiencing diarrhea problems. Pigs were finished outside.

This group of pigs had been placed for about a month. The majority showed signs of diarrhea. Many had blood in the feces. Approximately 10% of the group were showing signs of slow growth. The list of health issues that we ruled out included ileitis, swine dysentery and whipworms.

On postmortem examination, there were no respiratory lesions and no evidence of liver scars, and the intestines looked normal except for the colon and cecum, which were lined with what looked like “hair.” This hair was actually attached whipworms.

The group was dewormed with a parasiticide that controlled whipworms. The pigs responded well and had no subsequent concerns.

Case Study No. 2

We were called to a 600-head finishing farm with a history of skin lesions in pigs about 40 days after purchase. About 30% of the group showed some skin thickening in the shoulder area and crusting around and in the ears. The pigs were very restless. At any one time, about 5% of the group could be seen scratching on the gating or with their hind legs.

Skin scraping for mange was not attempted due to the difficulty in getting a positive result in spite of positive signs of skin lesions. The group was fed a mange control product for seven days. The skin lesions resolved nicely.

Case Study No. 3

We were called to a 600-head, farrow-to-finish farm with a history of chronic respiratory disease in finishing pigs.

Postmortem examinations were done on two finishing pigs. Both livers in these pigs were nearly white with ascarid (roundworms) migration liver scars.

The normal life cycle of ascarids involves the eggs being eaten, then burrowing through the liver and the lungs. The pig then coughs them up, only to be swallowed and grown into egg-laying adult worms.

This farm was already deworming sows and pigs — but it was not being done at the correct times. Their process was to deworm sows twice per year as an entire herd program and deworm pigs in the nursery.

Since an ascarid can go from an egg that is eaten to an egg-laying adult worm in 6-8 weeks, the farm needed to adjust the timing of the deworming program.

We have changed to deworming sows as they enter the farrowing crate. Feces are scraped behind the sows for 48 hours after the dewormer is administered. The theory here is to provide “clean” pigs going into the nursery. Before the worm eggs can become egg-laying adults, the pigs are weaned and have moved into the nursery.

Since most of the modern nurseries have raised flooring, the amount of fecal-oral contamination is limited and so is the exposure to worms. Therefore, the pigs entering and leaving the nursery should have very few, if any, worms.

In the new program, no nursery deworming is done. From the postmortems that were conducted, it was known that the finishers were contaminated with ascarid eggs.

We chose to begin with a two-step deworming program in the finisher. Forty days after the pigs are placed in the finisher, the first deworming is done. This allows the pigs to go around like little vacuum cleaners picking up ascarid eggs.

The process of deworming kills the adult worms before they are old enough to lay eggs. The groups were all dewormed a second time in 40 days to again decrease the numbers of eggs in the environment. This was done for two turns of the finisher. The second round of deworming was phased out in the third turn of pigs.

We continue to monitor this farm intermittently with fecal examinations. The fecal exams have been negative to date. At a cost of slightly more money per head, this farm has gone from terrible to good internal parasite control.


The industry has excellent deworming and mange control products that will effectively control internal and external parasites. Contact your veterinarian for assistance in choosing the correct product and the strategic time for its use.

2004 Swine Research Review


Boosting Lysine Levels Spurs Gilt Development When Given PG600

Ensuring that developing gilts have adequate lysine:metabolizable energy levels improves body growth, muscle and reproductive response when gilts are given PG600.

University of Illinois researchers studied three diets with different amino acid levels to determine whether diet could affect the introduction of replacement gilts into the breeding herd.

The one-year study involved PIC C-22 terminal line gilts at the University of Illinois swine research center.

The diets were formulated for two phases — from 100 to 145 days of age and for over 145 days of age. The diets provided high, medium or low standardized digestible lysine:metabolizable energy.

Gilts were housed and fed individually in an environmentally controlled area. Feed was restricted to match the amount required for gilts from the genetic line to maximize growth when group-housed. Feeding was adjusted so that total daily energy intake was equalized across treatments.

Gilts were weighed weekly and body composition determined at 115, 145 and 175 days of age. Blood was collected and tested for insulin at Day 145.

At 175 days of age, gilts were injected with PG600 (Intervet Inc.). During this time, gilts were exposed to a mature boar and checked for estrus once daily using fenceline contact for seven days. Reproductive tracts were collected 20 days after PG600 injection and assessed for ovarian structures.

The experiment showed that the high and medium diets increased body weight by Week 8, and that average gilt body weight remained above those gilts from the low diet until the end of the study (Table 1).

Insulin and backfat were not influenced by diet; however, loineye area was increased by diet from the onset of the trial (Table 1).

As Table 2 illustrates, the expression of estrus increased as the lysine ratio increased, while other measures of estrus were unaffected.

Also, the percentage of gilts ovulating remained unchanged between treatments and exceeded 85%, and there was no effect on the number of corpora lutea (Table 2).

Overall, this experiment indicated that increasing the lysine-to-energy ratio during gilt development impacts body weight, loin muscle area and estrus expression.

But diet enhancement had little effect on other body measures and ovulation characteristics.

The response to PG600 in this study reflected a high level of gilt fertility, with an average of 80% estrus expression, 89% ovulation and 19 eggs ovulated.

Study results cannot be extrapolated to predict the impact of increased amino acid levels on long-term gilt reproductive performance, researchers said.

Table 1. Impact of Dietary Lysine Levels on Reproductive Responses to PG600
Item High Medium Low
Number 34 36 36
Week 0 weight (lb.) 109.3 108.7 110.2
Week 5 weight (lb.) 174 176.7 169.6
Week 10 weight (lb.) 251.2 253.7 230.3
Insulin (IU/ml.)* 6.9 8.2 8.6
Backfat Day 100 (in.) 0.45 0.46 0.46
Loineye Area Day 115 (sq. in.) 4.2 4 3.9
Backfat Day 145 (in.) 0.5 0.52 0.52
Loineye Area Day 145 (sq. in.) 5.82 5.7 5.1
Backfat Day 175 (in.) 0.64 0.63 0.66
Loineye Area Day 175 (sq. in.) 7.3 6.83 6.32
*IU = International Units

Researchers: R. Knox, K. Soltwedel, J. Pettigrew, K. Farris, M. Hon, S. Breen, A. Jackson, S. Bensen and M. Ellis, University of Illinois. Contact Knox by phone (217) 244-5177; fax (217) 333-8286; or e-mail

Table 2. Estrus Expression in Response to Increases in Lysine Ratio
Item High Medium Low
Estrus in 7 days (%) 90.9 83 72.2
PG600 to estrus (hours) 118 116 108
Duration of estrus (hours) 47 56 52
Ovulating (%) 91.9 89.5 86.4
Number of corpora lutea 16.4 18.5 21.4

What a Year!

Pork producers welcomed excellent profits, fabulous demand here and abroad, all in the face of near-record levels of production in 2004.

Everyone seems to be looking around, quietly asking: “How long do you think this will last?”

Most of the hog economics gurus seem pretty comfortable predicting reasonable profits well into 2005. But as 2004 fades, there are ample issues and concerns that will spill into 2005.

Congress' unCOOL Move

Congress' rejection of a voluntary country-of-origin labeling program for pork and other meats, fruits and vegetables was decidedly un-cool. For the life of me, I can't understand why a program, which COOL zealots so adamantly profess to be good and beneficial to all, needs a government mandate. Certainly, if the rewards of COOL exist, they will surface under a voluntary program — and at a fraction of the cost.

If the cost estimate near $3.9 billion for the first year alone is even remotely close, I would argue there are far more urgent needs in the pork industry. For starters, I'd notch out a healthy chunk for research to solve the porcine reproductive and respiratory syndrome (PRRS) virus conundrum.

In late October, the National Pseudorabies Control Board announced that all 50 states are now free of pseudorabies in commercial swine for the first time in history. Hallelujah! If the U.S. remains free of infection for the next 12 months, we will be declared, “officially free” of the disease. Having wrestled this often-elusive foe into submission, now would be a good time to redouble our efforts to beat back PRRS.

BSE Flashback

While writing this column, news of inconclusive tests for bovine spongiform encephalopathy (BSE) in a cow were being forwarded to the National Veterinary Services Laboratory in Ames, IA. The news came like a flashback to Dec. 23, 2003, when the first case of BSE in the U.S. was confirmed. Thankfully, the suspect cow was confirmed negative and the U.S. livestock industry breathed a collective sigh of relief.

The upside of the BSE situation is we've learned a great deal about disease surveillance, testing, and the impact of disease on our export markets.

Then There's the Checkoff

The Supreme Court's decision on the beef checkoff case, scheduled to go before the Justices on Dec. 8, will have far-reaching effects on the structure of pork industry governance and pork positioning in years to come. A final ruling is expected early in 2005.

The overseers of pork checkoff funds, the National Pork Board, are not sitting on their collective hands, however. Plans are underway to roll out a brand new extension of the highly successful Pork — The Other White Meat campaign early next year.

On a Positive Note

One of the most unique and gratifying stories to cross my desk this year was a Kansas City Star article entitled: “Students Can Swap Pigskin for Sheepskin.”

No, it is not a story about football scholarships. It's much better.

The article explained how a private university in southeastern Missouri, Lindenwood University, tapped into the age-old bartering concept for the betterment of cash-strapped students. The “Pork for Tuition” program is aimed at helping rural families defray the cost of a college education.

Having demonstrated a student's financial need, family farmers are cleared to deliver hogs to a designated USDA-approved processing facility. The school pays the processing fees and in return receives roasts, sausages and burgers for preparation in the student cafeteria.

To meet Lindenwood U's annual tuition of $11,200, participants must deliver market animals to cover just 20% of the tab. At recent hog prices, 15-20 market weight hogs would cover a student's tuition for a year. Room-and-board is $6,600/year, but students can work off up to $1,800 (10 hr./week) through on-campus jobs.

“I don't want anybody dropping out of school because of money,” stated Lindenwood President Dennis Spellman in the Kansas City Star article. He launched the bartering program in 2000 and, to date, nearly two dozen students have taken advantage of the program.

Can We Stand Prosperity?

When the hog market has been good for a spell, pork industry economists are fond of saying: “Pork producers just can't stand too much prosperity.”

The not-so-hidden message — when profitability returns, producers often turn to expansion. Wouldn't it be great to prove them wrong this time? Slow, controlled growth to meet real demand makes sense. Let's shoot for that.

Serve pork this Christmas and often in the new year. Best wishes to you and yours for a strong and profitable pork industry in 2005.

2004 Swine Research Review

Herd Health and Management

Immune Tools Measure Pig Disease, Vaccine Responses

U.S. Department of Agriculture (USDA) scientists at the Beltsville, MD, Agricultural Research Center (BARC), working with University of Illinois (UI) researchers, have tested new tools for measuring pig immune responses to vaccination or infection with porcine reproductive and respiratory syndrome (PRRS) virus and with the foodborne parasite Toxoplasma gondii (Tg).

The pig has immediate, non-specific or innate responses to infection and vaccination. But for long-term recovery and prevention of new infections, specific immunity is required. This involves activation of the immune system, resulting in complex interactions of immune cells and hormone-like proteins called cytokines.

Previous studies at BARC have shown that infection or vaccination with Tg leads to strong T cell-mediated responses, termed T helper 1 (Th1) responses, producing immune-stimulating proteins, or cytokines, including interferon-gamma (IFNG).

For this study, BARC and UI researchers asked if vaccination with PRRS modified live virus (MLV) leads to effective Th1 responses in 6-week-old Yorkshire x Landrace crossbred pigs. Detailed immune responses were monitored in groups of nine pigs.

UI scientists showed that the anti-PRRS virus peripheral blood cell IFNG immune response was slow in developing. An MLV booster vaccination was given eight weeks after initial vaccination and immunity response was maximized 10-13 weeks after vaccination.

In contrast, for Tg, BARC scientists showed much faster IFNG responses over a 2- to 10-day period, with pigs recovering from Tg-induced clinical symptoms within two weeks.

BARC scientists asked whether differences in protective immunity for PRRS infections could be attributed to immune factors. They used differential immune gene expression tools to measure the levels of 24 different immune gene products by real-time molecular assays on blood lymphocytes or cells related to immunity.

Gene expression data showed that pigs vaccinated with PRRS MLV had a very slow and weak immune response, with low levels of IFNG mRNA (ribonucleic acid) developing only at five weeks after vaccination. The related interleukin-12 showed no increases.

When the immune-stimulating innate markers were examined, it was clear that they had actually decreased, rather than increased. Levels of interferon-alpha (IFNA), a major innate immune marker, were down, as were levels of interleukin-8.

Thus, there was a lack of early immune activation with PRRS vaccination.

In many infections, innate cytokine stimulation is essential for speedy and effective anti-viral immune responses. The range of innate and acquired immune markers activated is critical to the level of pig response to infection.

This technology will now serve to help design better immune and vaccine approaches for prevention and control of PRRS, which the National Pork Board says costs the pork industry an estimated $600 million annually.

Additionally, BARC scientists have expanded the number of immune genes they can measure. Now more than 250 genes can be measured to assess the effect of therapeutic treatments and nutrition on infectious and metabolic diseases and vaccinations.

Researchers: Robert J. Husmann, Gabriela Calzada-Nova, William M. Schnitzlein and Federico A. Zuckermann, University of Illinois; Harry Dawson and Joseph F. Urban Jr. of the Nutrient Requirements and Functions Laboratory, Beltsville Human Nutrition Research Center, BARC, and Atabak Royaee and Joan Lunney, Animal Parasitic Diseases Laboratory, Animal and Natural Resources Institute, BARC. Contact Lunney at (301) 504-9368 or

2004 Swine Research Review

Herd Health and Management

Weaning Age, Lighting Impact Gains, Immunity

The duration of lighting and the age at which pigs are weaned can influence their immune system and weight gains, according to preliminary studies at the University of Illinois.

In short, pigs that were weaned at 28 days of age and maintained on 16 hours of light from weaning until 10 weeks of age were the heaviest in the study. They gained at least 7.7 lb. more than their counterparts provided only eight hours of light.

For the study, piglets were weaned at either 14, 21 or 28 days of age, and were moved to a standard nursery and kept on either eight or 16 hours of light until 10 weeks of age. Blood samples were drawn and analyzed to assess the impact of weaning age and light exposure on the immune system.

The combined effect of weaning age and light exposure are depicted in Figure 1. Pigs weaned in all three age groups and exposed to 16 hours of light were the heaviest. Pigs weaned at 21 days of age gained the least amount of weight of those groups exposed to 16 hours of light.

Figure 2 shows body weight at 10 weeks of age and exposure to different lighting treatments. Pigs exposed to 16 hours of light gained much more weight during the study regardless of weaning age. Pigs weaned at 14 days of age and exposed to 16 hours of light gained more weight than all of their counterparts exposed to eight hours of light.

The lightest-weight pigs in the study were those weaned at 14 days of age and exposed to only eight hours of light.

Without the controlled lighting experiment, weaning age dictates immunity. Maternal antibodies appear to be higher in 14-day-old vs. 28-day-old weaned pigs. Cell-mediated immune levels independent of maternal antibodies appear to be higher in older-weaned pigs.

The ability of “natural killer cells” to protect against infection is shown (Figure 3) to be much higher in pigs weaned at an older age (21 and 28 days old) compared to those weaned younger (14 days). Natural killer cells are a type of immune cell that eliminates or attacks viruses and cancerous cells.

Weaning age and the amount of lighting that young pigs are exposed to jointly affects immune response up to 10 weeks of age. The ability of B-lymphocytes to increase was most stimulated by eight hours of light in 28-day-old weaned pigs (Figure 4). B-cells are white blood cells that include elements related to immunity.

Also, by eight weeks of age, pigs weaned at 14 days of age and exposed to only eight hours of light had higher B-cell responses than 14-day-old weaned pigs exposed to 16 hours of light.

In contrast, 28-day-old weaned pigs maintained on 16 hours of light recorded higher total lymphocyte numbers than their eight-hour counterparts, despite having lower B-cell proliferation.

From these trials, it becomes apparent that age of weaning and amount of light exposure can influence different aspects of the immune system in different ways.

For instance, it may be possible to use photoperiod to enhance immunity during times of stress and to improve performance at a particular stage of production.

What remains is to determine the impact of photoperiod manipulation for immune stimulation during production challenges.

Researchers: Janeen L. Salak-Johnson and Sherrie Neikamp, University of Illinois. Contact Salak-Johnson by phone (217) 333-0069; fax (217) 333-8286; or e-mail

Click to view graphs.