NCSU Extension Swine Husbandry
A more printable version of Swine News in Adobe Acrobat.
July, 2000 . Volume 24, Number 6
THE CHALLENGE OF THE LIGHTWEIGHT PIG
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.
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.
Additional advantages for euthanizing
the lightweights include:
• 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.
For weaner pigs, Deen and Desrosiers
(1995) established that beginning weight is the
best predictor of end weight. Figure 1 illustrates
that incoming lightweight pigs will exit at a lighter
weight as well. The middle bar shows the average, and
the outside bars show the expected weight range for
95 percent of pigs at a specific entry weight. For instance, a pig entering at 10 pounds is expected
to exit at between 18 and 40 pounds.
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.
—Morgan Morrow
2001 N.C. PERFORMANCE MARKET HOG SHOW
The annual N.C. Performance Market Hog
Show at the N.C. State Fair in October combines fun and
fellowship with an excellent educational
opportunity. Pigs that are nominated, ear-tagged, and
weighed on-test by July 20 may be exhibited in the performance market hog classes at the fair,
where they will be evaluated, both live and on the
rail. Anyone interested in nominating pigs for the
2001 event should contact his or her County
Extension livestock agent on or before July 13.
For the live competition, the judge is provided
with the average daily gain of each animal, which he
uses along with visual appraisal, to determine a
ranking. On the rail, the pork carcasses are evaluated for
fat depth, loin muscle area, carcass length, loin
muscle color, loin muscle marbling, loin firmness,
and carcass weight. These measures are combined to predict the pounds of lean gain per day
on-test, which is used for the final ranking.
In today's pork industry, the amount and quality
of carcass information collected on the pigs in
this program can be very valuable.
—Todd See
Frank Hollowell
Breeder
Address
Breeds
Bob Ivey*
314 N.C. 111 S, Goldsboro 27530
L, D, H, Y, CW, X
Wesley Looper*
4695 Petra Mill Rd., Granite Falls 28630
L, D, H, Y, X
Thad Sharp, Jr., & Sons
5171 N.C. 581 Hwy., Sims 2788030
D, Y, X
Tommy Spruill
Rt. 1, Box 149, Columbia 27925
L, X
Swan Acre Farm
1060 Main Street, Swan Quarter 27885
X
Thomas Farms
8251 Oxford Rd., Timberlake 27583
X
UCPRS (Swine Dev. Center)
Rt. 2, Box 400, Rocky Mount 27801
X
*Real-Time Ultrasound
David Lee
Last modified July 10, 2001.