Submitted to: World Congress of Genetics Applied in Livestock Production
Publication Type: Proceedings
Publication Acceptance Date: 3/13/2002
Publication Date: 8/19/2002
Citation: Robison, O.W., Pala, A., Leymaster, K.A., Mccraw, R.L., Young, L.D. 2002. Genetic parameters in 6-month breeding systems. Proceedings of the 7th World Congress of Genetics Applied in Livestock Production. CD-ROM Communication No. 02-43. Montpellier, France. Interpretive Summary: The effectiveness of selecting for increased productivity of sheep in 6-month breeding schedules is uncertain. Development of effective selection procedures requires estimates of genetic influences on traits that determine productivity. Data collected on four breeds of sheep under three different 6-month breeding schedules were analyzed to provide estimates of genetic parameters. Sufficient genetic variation exists to increase productivity by selecting for performance under 6-month breeding schedules.
Technical Abstract: Genetic parameters were estimated using animal models in populations of Dorset, Finnsheep, Composite I (50% Finnsheep, 25% Dorset, and 25% Rambouillet) and Composite II (50% Finnsheep, 25% Suffolk, and 25% Targhee). Estimates of heritability for conception rate ranged from 0.17 (Dorset) to 0.27 (Composite I). Heritabilities for litter weaning weight were similar across breeds and ranged from 0.31 to 0.36. Overall heritabilities for litter weaning weight, weaning weight, conception rate and litter size were 0.33, 0.64, 0.24 and 0.16, respectively. Overall Spearman rank-order correlations of litter weaning weight with conception rate or litter size ranged from 0.81 to 0.88. Genetic correlations between dry and lactating ewes for conception rate and litter size were small (0.009 and 0.108, respectively). Selection should be practiced among lactating animals for conception rate and litter size.