Dh. Beermann et al., IMPACT OF COMPOSITION MANIPULATION ON LEAN LAMB PRODUCTION IN THE UNITED-STATES, Journal of animal science, 73(8), 1995, pp. 2493-2502
At present less than 30% of the market lambs slaughtered in the United
States meet the requirements for leanness and muscling as specified i
n the ''Certified Fresh American Lamb'' program established in 1990 by
the American Sheep Industry Association (ASI). Carcass composition of
slaughter lambs is determined by stage of growth relative to mature s
ize, genotype, sex, and matching dietary nutriment to nutrient require
ments for lean tissue growth. On the average, current production strat
egies produce carcasses that contain excessive amounts of fat, impedin
g optimized efficiency at all levels of production. Use of large-matur
e-size terminal sires, feeding rumen-escape dietary protein, feeding i
ntact males, and slaughtering at appropriate weights all improve compo
sition of gain. Improvements of 10 to 20% in rates of gain and efficie
ncy of nutrient use and similar reductions in feed cost can be achieve
d with each of these management strategies. Results from several exper
iments demonstrate that these effects are additive and provide a measu
re of the true genetic capacity for protein accretion rate in growing
lambs. Adoption of these management strategies will allow lambs to be
slaughtered at a younger age, which may improve meat quality and concu
rrently reduce the amount of nitrogen waste returned to the environmen
t. Potential for further manipulation of composition exists through mo
re accurately defining nutrient requirements of growing lambs and thro
ugh use of metabolism modifiers. Maintaining a competitive, profitable
, and sustainable sheep industry depends on continued improvement of p
roduction efficiency, preferably in systems with high reproductive rat
es.