Genetic Resources for Efficient Meat Production in Sheep. Growth and Carcass Characteristics of Ram Lambs of Seven Breeds

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Abstract
Growth and carcass characteristics of straightbred ram lambs of seven breeds were compared as part of a study of genetic resources for efficient meat production in sheep. Breeds represented were Suffolk, Hampshire, Polled Dorset, Rambouillet, Targhee, Corriedale and Coarse Wool. Body weights were obtained at birth and weaning (at 8 to 12 or 10 to 14 weeks) and at 4- or 2-week intervals to slaughter at 20 to 24 or 24 to 28 weeks of age. Carcass data were obtained for 610 of the 860 spring lambs weighed in 1969 and 1970. Lambs were fed from weaning to 22 or 26 weeks in drylot on a mixed ration; TDN and crude protein in dry matter were 74.4% and 12.3%, respectively, in 1969, 72.6% and 13.5% in 1970. Growth data were adjusted for important effects of variation in season of birth, type of birth and rearing, age of dam and of lamb. Body weights at 24 and 26 weeks and all carcass data also were adjusted to mean 22 week weight for all rams of the same breed. Live weights at 22 and 26 weeks averaged 44 and 51 kg in 1969, but 51 and 61 in 1970. Differences in relative growth among breeds were large and rather consistent from birth to 26 weeks. Relative to the general mean, Suffolks were 108% in weight at birth, 111% at 10 weeks and 115% thereafter; Dorsets were 85% at all ages; Coarse Wool, Targhee, Rambouillet and Hampshire lambs were grouped between 100 and 102% except that at weaning the first three were 106 to 102% and Hampshires were 96%; Corriedales were 104% at birth but only 95% at weaning and later. Corresponding breed ranking for estimated weight of trimmed retail or of boneless major cuts at same age was Suffolk 119%, Hampshire 104%, Coarse Wool 102%, Targhee 99%, Rambouillet 97%, Dorset 90% and Corriedale 89%. Suffolk and Hampshire gained most and Targhee, Rambouillet and Corriedale least in absolute yields between 22 and 26 weeks of age, but breeds were similar in % gain. Hampshires, Suffolks and Dorsets excelled other breeds by nearly two-thirds of a U.S.D.A. carcass grade in both general and conformation scores. At both ages, Dorsets excelled Hampshires, Suffolks and Rambouillet slightly and other breeds even more in yield grade and in estimated percent of trimmed and of boneless cuts; Dorset and Rambouillet had least rib and kidney fat. Rib eye area was largest in Suffolks, followed by Hampshire and Dorset, but did not increase from 22 to 26 weeks except in Suffolk (+2.2 cm2) and Coarse Wool (+1.0 cm2) lambs. Holding ram lambs on feed 4 weeks beyond 22 weeks increased live weight about 19%, carcass weight 23%, estimated weight of trimmed cuts 18% and of boneless major cuts 21%; however, these gains may be largely in fat deposits since rib eye area changed little in most breeds. Copyright © 1972. American Society of Animal Science . Copyright 1972 by American Society of Animal Science.

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