Genetic analysis of feed conversion efficiency in relation to daily gain in Magra lambs under arid climatic...

The present study investigated feed efficiency in Magra lambs using average daily gain (ADG) and Kleiber ratio (KR). The data generated for 22 years (1998 to 2019) on Magra lambs maintained at ICAR-Central Sheep and Wool Research Institute, Arid Region Campus (ICAR-CSWRI, ARC), Rajasthan, India, were used for analysis on ADG and KR using a linear mixed model methodology incorporating sire as a random effect and year of birth, sex of lamb, inbreeding level, dam's age at lambing and dam's weight at lambing as fixed covariates. For ADG in body weight during 0-3 (ADG1), 3-6 (ADG2) and 6-12 (ADG3) months of age, the overall least-squares means were observed as 143.95 ± 0.70, 81.18 ± 0.79 and 30.05 ± 0.54 g/day, respectively. Corresponding KR1, KR2 and KR3 were observed to be 17.76 ± 0.04, 7.65 ± 0.07 and 2.83 ± 0.04, respectively. Results revealed 23.05, 73.18, 8 and 38.39 per cent improvements in the ADG1, ADG3, KR1 and KR3 across the study period. This is also reflected in the significant impact of sire, birth year, sex and dam's weight at lambing as covariate on all ADGs and KRs. The study revealed the non-significant effect of inbreeding level on all ADG and KR except ADG1. The heritability estimates using the Bayesian approach for ADG and corresponding KR ranged from 0.35 (KR1) to 0.17 (ADG3). The estimates of genetic and phenotypic correlations among the traits ranged between - 0.51 (KR1-KR3) to 0.97 (ADG1-KR1) and - 0.49 (ADG1-KR2) to 0.95 (ADG1-KR1), respectively. The low-to-moderate estimates of heritability and the high and positive genetic correlations among the traits in the study were suggestive of the potential for genetic improvement in Magra sheep under selection. Overall, the observed phenotypic improvements, moderate heritability estimates and favourable genetic correlations indicate the potential for genetic improvement of growth and feed efficiency traits in Magra sheep under the existing selection program. However, regular monitoring of post-weaning ADG and KR is necessary, and factors affecting growth rate must be monitored to attain better future growth rates.