Estimation of Individual and Maternal Heterosis, Repeatability and Heritability for Ewe Productivity and its Components in Suffolk and Targhee Sheep

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Abstract
The objectives of this study were to estimate individual and maternal heterosis, repeatability and heritability for ewe productivity and its components in Suffolk and Targhee sheep and to predict the productivity of various mating systems from the performance of breeds and crosses in the study. Suffolks from the North Dakota Experiment Station at Fargo (NDS), Targhees from the Ohio Experiment Station at Wooster (OT) and Suffolks and Targhees (ILS and ILT, respectively) from the University of Illinois Dixon Springs Agricultural Center (DSAC) were assembled at DSAC over a 3-yr period (1959 to 1961) by sampling the respective populations. Reciprocal matings were made between ILS and OT and between ILT and NDS to obtain F1 females. These F1 ewes were back-crossed to a ram from the breed-station flock of the F1 ewe's dam. Records from 747 purebred or crossbred ewes, 150 sires of ewes and 143 service sires over a 7-yr period were included in the data set. Individual heterosis estimates were fertility, .6%; prolificacy, 3.3%; lamb survival, 6.9%; 90-d weight, 2.8% and ewe productivity, 13.8%. Maternal heterosis estimates were fertility, 2.6%; prolificacy, 6.6%; lamb survival, 1.4%; 90-d weight, 5.4% and ewe productivity, 10.1%. Repeatability estimates were fertility, .11; prolificacy, .11; lamb survival, .18; 90-d weight, .24 and ewe productivity, .15. Heritability estimates were fertility, .07; prolificacy and lamb survival, inestimable; 90-d weight, .07 and ewe productivity, .10. Simulated mating systems that produced F1 terminal market lambs were calculated to produce 12.8% more weight of marketable lamb at weaning than mating systems that produced only purebred lambs, and mating systems that produced back-cross terminal market lambs from F1 ewes produced 25.1% and 10.9% more weight of marketable lamb at weaning than mating systems that produced purebred lambs only or F1 terminal market lambs, respectively. Copyright © 1989. American Society of Animal Science . Copyright 1989 by American Society of Animal Science

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