Relation of Birth Weight to Death Losses and to Certain Productive Characters of Fall-Born Lambs

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Abstract
Analyses were made on birth weight and death losses of 2,368 fall-born lambs. Type of birth and system of mating affected significantly both birth weight and death losses. Twin lambs weighed 1.6 Ib. less and had a 9.2% higher death loss than those born as singles. As a group, crossbred lambs (Rambouillet ewes bred to Hampshire, Suffolk, Dorset and Columbia rams) weighed 0.6 Ib. more and had 3.7% less death losses than straight Rambouillet lambs. Only Dorset sired lambs were smaller than Rambouillet. Death losses were closely related to birth weight. Losses ranged from a high of 65.3% for lambs weighing less than 4 Ib. to a low of 6.4% for lambs weighing 10 to 11 Ib. Above this weight losses tended to increase slightly. In this fall lambing flock 84.3% of the lambs weighed less than 10 Ib. Birth weight was also correlated with post-weaning gains or 120-day weight. Through the combined influence on death losses and post-weaning gains, it was estimated that an increase of 6.8 Ib. in 120-day weight was associated with each 1 Ib. increase in birth weight. Both birth weight and rate of gain to 120-day weight were significantly negatively related to fiber diameter of the yearling fleece. Birth weight was shown to have a significant positive correlation with clean fleece weight. This would indicate that adverse prenatal environment could permanently affect the wool production potential of sheep. Rate of gain from birth to 120 days was not significantly correlated 2 with clean wool production. Copyright © 1964. American Society of Animal Science . Copyright 1964 by American Society of Animal Science

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