001 Genetic Parameters for Fecal Egg Count and Body Weight in Katahdin Lambs

• Published in: Journal of animal science 2016-12, Vol.95 (suppl_1), p.01-01
• Main Authors: Ngere, L., Burke, J. M., Notter, D. R., Morgan, J., Miller, J. E.
• Format: Article
• Language: English
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/ssasas2017.001

Abstract The objective of this study was to estimate genetic parameters for fecal egg count at weaning (WFEC) and postweaning (PWFEC), and weights at birth (BW), weaning (WW) and postweaning (PWW) in Katahdin lambs by investigating direct additive, maternal additive, maternal permanent environmental and maternal temporary environmental (litter) effects. WFEC (n = 2,537), PWFEC (n = 3,478), BW (n = 12,869), WW (n = 10,961) and PWW (n = 7,812) records of 12,869 Katahdin lambs were available for this study. These records, from 13 different flocks, were collected between 1998 and 2015. Animal models were investigated using the ASReml statistical package. The significance of inclusion of random effects was tested using the Likelihood ratio tests. Fixed effects were dam age, type of birth and rearing, and management group (defined by sex, site and birth year). Lamb age in days at the time of measurement was fitted as a covariate. Litter was a significant (P < 0.01) random effect for BW and WW but not for the other traits. Maternal effects were significant (P < 0.01) for all body weights, but were very small and not significant for fecal egg counts. Depending on the model used, heritability estimates ranged from 0.18 to 0.50 for BW, 0.15 to 0.40 for WW, and 0.16 to 0.40 for PWW. Heritability estimates were 0.24 for WFEC and 0.26 for PWFEC. Preliminary analyses, with less restrictive management groupings, gave higher estimates of heritability for fecal egg count. Bi-variate analyses revealed very low genetic (-0.06 to 0.16) and phenotypic (-0.09 to 0.08) correlations between weights and fecal egg counts. Genetic and phenotypic correlations were, respectively, 0.80 and 0.31 for WWEC and PWWEC; 0.66 and 0.47 for BW and WW; 0.44 and 0.38 for BW and PWW; and 0.89 and 0.82 for WW and PWW. This study revealed an influence of maternal effects on body weights of Katahdin lambs; the inclusion of both permanent and temporary maternal environmental effects may lead to better estimates of breeding values and selection decisions. The low correlations between body weights and fecal egg counts indicate that selection for parasite resistance may not affect genetic potentials for growth.