Location: Dale Bumpers Small Farms Research CenterTitle: Genetic parameters for fecal egg count and body weight in Katahdin lambs
|NGERE, LAURETTA - Oak Ridge Institute For Science And Education (ORISE)|
|NOTTER, DAVID - Virginia Tech|
|MORGAN, JAMES - Katahdin Hair Sheep International|
|MILLER, JAMES - Louisiana State University|
Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 11/15/2016
Publication Date: 2/4/2017
Citation: Ngere, L., Burke, J.M., Notter, D.R., Morgan, J.L., Miller, J.E. 2017. Genetic parameters for fecal egg count and body weight in Katahdin lambs. Journal of Animal Science. 95 (E-Suppl.1). 1.
Technical Abstract: The objective of this study was to estimate genetic parameters for fecal egg count at weaning (WFEC) and post weaning (PWFEC), and weights at birth (BW), weaning (WW) and post weaning (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 – 2015. Animal models were investigated using ASReml statistical package. The significance of the inclusion of random effects was tested using the Log Likelihood ratio test. Fixed effects were dam age, type of birth and rearing, management group (defined by sex, site and birth year), and age of lamb in days, at 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. While maternal effect was significant (P < 0.01) for all body weights, it was very low for fecal egg count and its inclusion in the model was not significant based on likelihood ratio test. 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. Weaning fecal egg count heritability was 0.24 and post weaning heritability was 0.26. Preliminary analyses obtained higher estimates of heritability for fecal egg count when less restrictive management groups were used. 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 for WWEC and PWWEC were 0.80 and 0.31; BW and WW were 0.66 and 0.47; BW and PWW were 0.44 and 0.38; WW and PWW were 0.89 and 0.82, respectively. This study reveals an influence of maternal effects on body weights of Katahdin lambs and the inclusion of both permanent and temporary maternal environmental effects may lead to better genetic estimates and selection decisions. The low correlations between body weights and fecal egg counts indicate that selection for parasite resistance may not affect performance in body weights.