Lamb Weights in Some Pure Breeds and Crosses

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Abstract
Birth weight, weaning weight, and gain from birth to weaning, were studied on Hampshire, Shropshire, Southdown and Merino breeds of sheep and their crosses and on the Columbia-Southdale strain of sheep at Beltsville, Maryland. Totals of 4331 lambs born and 3423 lambs weaned from 1952–1961 were included. Breed, breed cross, years, sex, type of birth and rearing and age of dam all had significant effects on weight at birth and weaning and gain from birth to weaning. In addition, days growth from birth to weaning, date of birth, and birth weight had significant effects on the latter two traits. Least squares means for both birth weight and weaning weight ranked breeds in the same order, with Hampshires highest, followed by Columbia-Southdale, Shropshires, Merinos and South-downs. Two-breed cross offspring tended to rank in the same order for all three traits as the purebred lambs from the dam's breed. The offspring also tended to rank in the order of the sire's breed within a dam's breed, but there were some exceptions. Trends were less apparent with 3- and 4-breed crosses. Cross-bred rams mated to purebred ewes excelled over purebred rams, but not over purebred rams when mated to crossbred ewes. Advantages of all crossbred lambs over purebred lambs involving the same breeds were 7 lb. for weaning weight, 0.63 lb. for birth weight and 6.5 lb. gain from birth to weaning. Cross-breds always excelled over comparable averages for purebreds for each trait. The average gains in weaning weight over the purebreds were 5.2 lb. for 2-breed crosses, 9.5 lb. for 3-breed crosses, and 10.4 lb. for 4-breed crosses. Copyright © 1964. American Society of Animal Science . Copyright 1964 by American Society of Animal Science

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