Heterosis for Ewe Lamb Productivity

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Abstract
Ewes of all possible reciprocal crosses were compared to contemporary straightbreds for production as ewe lambs. Breeds were the Hampshire, Suffolk and Willamette (a strain of 50% Columbia, 25% Border Cheviot and 25% Dorset Horn ancestry). The ewes had been reared to weaning on dryland hill pastures or on irrigated valley pastures. Hill pasture ewes were 1 kg heavier than irrigated pasture ewes at the beginning of mating. Heterosis percentages for fertility and prolificacy were 25 and 10%, respectively. Heterosis for weight of lamb weaned per ewe lambing and per ewe joined averaged 14 and 30%, respectively. Most crossbred groups exceeded the better parent breed for lamb production. Heterosis percentages for lamb survival to weaning and for average weaning weight were −5 and 8%, respectively. Of the total crossbred advantage for weight of lamb weaned per ewe joined, 58% was attributable to heterosis for fertility, 23% to heterosis for prolificacy, 0% to heterosis for lamb survival and 19% to maternal heterosis effects on lamb weaning weight. Copyright © 1976. American Society of Animal Science . Copyright 1976 by American Society of Animal Science.

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