Production Management Featured Articles
The Challenge of the Lightweight Pig
By Dr Morgan Morrow, Swine Veterinary Specialist, North Carolina State University - Lightweight pigs are a major problem in assembling slaughter loads. The problem begins at birth because, as England showed in 1974, piglets born lightweight will be weaned lightweight. Further, lightweight weanlings remain small and are a significant contributor to the variation in slaughter weight, as other studies have established.
 Dr Morgan Morrow Swine Veterinary Specialist |
Given the economic incentives to produce and deliver similarly sized "cookie-cutter" pigs to slaughter, various techniques have been pursued to improve the profitability of lightweight pigs. Some have concluded it is cheaper to euthanize them as soon as they are identified; others have advocated special treatment, including penning by size, special accommodation, and special diets, even liquid diets.
The importance of product uniformity is illustrated by producers' responses to the USDA's National Animal Health Monitoring System (NAHMS) survey, which examined how pork producers sold their finished hogs as part of the Swine 1995 study. The survey showed that 64.2 percent of operations in the United States always assembled a "uniform group based on weight." Also, 61.8 percent never sold "all animals in pen or building," further illustrating the objective of providing what the packer wants.
Like most complex problems, there is unlikely to be one solution. The optimal approach will vary by farm and the particular mix of genetics, nutrition, and overall stockmanship.
Selecting individual pigs for special treatment is not hard: one simply picks the lightest ones. The difficulty lies in determining the total number, butthat is usually decided by the housing limitations of the farm. The real difficulty is deciding which ones to euthanize because, on an individual pig basis, there is no room for error.
Advantages of culling the lightweights include:
- Increased floor space for the remaining pigs.
- A market for the lightweights, such as the barbecue market in the Southeast.
- An increase in the throughput (turns) for the building.
- A decrease in the risk of disease transmission.
- The antibiotic residue problem is avoided.
- No need for special housing or handling.
- No mixing problems postaccumulation.
- No marketing problems.
- No cull trucks picking up lightweights from multiple farms.
The need to do something is compelling: A recent study by Azain, Jones, and Glaze (1998) at the University of Georgia demonstrated that lighter pigs at day 14 were also lighter at birth and lighter at weaning (28 days). Then they found that the growth rate of the heavier pigs was greater than that of the lighter ones. The difference in growth rate was greatest between birth and 14 days, with the lighter pigs growing at only 45 percent of the rate of the heavier (122 vs. 223 gm/day).
Their efforts to assist the lighter pigs were unrewarding: Although piglets fed a liquid milk replacer had greater growth and greater dry matter intake, the benefit was not sustained through day 14 of the study. They were able to improve 21 day weights in pigs weaned at 7 days fed liquid diets to day 21 (Azain et al 1994). However, they stated that the obstacle preventing the use of liquid diets is in a feasible means to automate and mixing and dispensing of milk replacer and cleaning the equipment.
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Figure 2 illustrates the average weights by pen when the pigs are sorted by weight. Average pen weights are more predictable. For a pen averaging 10 pounds at entry, the exit range will be 21 to 34 pounds. Remember, these are the results for one farm and may not apply to the pigs on all farms.
In the field, producers have had success in minimizing lightweights by feeding Paylean (ractopamine hydrochloride by Elanco) in the period before slaughter. Paylean is approved at a feeding rate of 4.5 to 18 grams per ton (5-20 ppm) for pigs in the range of from 150 to 240 pounds live weight, that is, during the last 90 pounds of live weight gain before slaughter. Paylean can increase the rate and efficiency of muscle tissue growth and give lightweights an extra 2 pounds at slaughter; thus, fewer penalties are levied for pigs outside the packer's matrix.
Producers in the field also have been able to reduce the mean percentage of lightweight pigs to 3.1 percent, compared to 9.6 percent, by injecting 900 milligrams of lincomycin intramuscularly for 3 consecutive days, a practice stemming from the work reported by Connor (2000).
To help determine if producers need to do anything special on their farms, we recommend that they measure the growth rate and fate of lightweight pigs entering the facility. Producers should tag and weigh the lightest 5 percent of pigs at entry and when they are shipped. If a pig dies, the date and its death weight also should be recorded. Producers are likely to find that lightweight pigs have a high mortality or are sold as lightweights. These data will help you decide whether more pigs should be euthanized or just be given special weight-gain treatment.
References
Azain, M. J., R. A. Arentson, T. Tomkins, and J. S. Sowinski. 1994. The effect of pelleted or liquid diets on performance of pigs weaned at 7 to 10 days of age. J. Anim. Sci. 72(Suppl 1):215.
Azain, M. J., R. Jones, and T. Glaze. 1988. Management of lightweight pigs. University of Georgia, annual report, pp. 164-167.
Connor, J. 2000. Evaluation of the effect of the intramuscular injection of Lincomix 300 (lincomycin) for three consecutive days in lightweight pigs at 150-180 pounds on the percentage of lightweight pigs marketed (recent research reports). Allen D. Leman Swine Conference proceedings, p. 47.
Deen, J., and R. Desrosiers. 1995. The utility of lightweight pigs. North Carolina Healthy Hogs Seminar, p. 39.
England, D. C. 1974. Husbandry components in prenatal and
perinatal development in swine. J. Anim. Sci. 38:1045.
Source: North Carolina State University Swine Extension - July 2001
