Ashish Chauhan

The objective of the study was to estimate genetic parameters of the growth traits under Bayesian inference in Harnali sheep. The information of pedigree and targeted traits of 2404 Harnali animals born to 159 sires and 695 dams was collected for the period from 1998 to 2021. The growth traits included weight at birth (BWT), 3 (WWT), 6 (6WT) and 12 (YWT) months of age. The genetic evaluation was carried out using six univariate animal models comprising direct and maternal effects using THRGIBBS1F90 and POSTGIBBSF90 programs. The fixed factors adjusted in the analysis were period of birth, sex of lamb and dam's weight at lambing. Bayesian estimates of direct heritability under best model for BWT, WWT, 6WT and YWT traits were 0.16 ± 0.04, 0.10 ± 0.04, 0.18 ± 0.04, and 0.05 ± 0.03, respectively. The significant maternal influences observed for BWT and WWT traits with 9% and 8% contribution to total phenotypic variances, respectively. Additionally, maternal permanent environmental influences were observed to BWT (4%) and YWT trait (3%). The genetic and phenotypic correlations among studied traits were high and positive. The genetic changes were positive and significant for WWT only. It was concluded that the weight at 6 months of age can be continued as selection criterion for further genetic improvement through selection. Also, maternal effects should be considered in breeding programme for enhancing early growth performance in Harnali sheep.

The present study evaluated maternal and additive influences that contribute to phenotypic variation in various growth traits in Munjal sheep. The targeted traits that pertained to 2278 records of 706 lambs were birth weight (BWT), weaning weight (WT3), 6-month body weight (WT6), 12-month body weight (WT12), average daily gain (ADG1: 0–3 months; ADG2: 3–6 months, ADG3: 6–12 months of age) and their corresponding Kleiber ratios designated as KR1, KR2 and KR3. The direct heritability estimates for BWT, WT3, WT6, WT12, ADG1, ADG2, ADG3, KR1, KR2 and KR3 under animal models were 0.20 ± 0.08, 0.28 ± 0.08, 0.17 ± 0.07, 0.47 ± 0.09, 0.33 ± 0.08, 0.09 ± 0.06, 0.36 ± 0.10, 0.33 ± 0.08, 0.09 ± 0.06 and 0.32 ± 0.10, respectively. The estimates of maternal genetic effects contributed significantly and were 8% and 7% for BWT and WT3 traits, respectively, which highlighted the considerable role of maternal effects on early growth traits. Genetic and phenotypic correlations ranged from moderate to high between weaning and post-weaning traits. It was concluded that early selection that considered additive as well as maternal effects at weaning age may be delivered to the desired genetic progress in Munjal sheep.

Lamb survival is a critical aspect in the sheep industry as it increases the chances of economic gain in the flock. The objective of the current study was to assess the incidence of lamb mortality in Harnali sheep and to estimate maternal and additive genetic effects of lamb survival using the data of 2057 lambs born to 134 sires and 623 dams for the period of 20 years (2001–2020). The genetic evaluation was carried out using threshold animal models comprising direct and maternal effects using THRGIBBS1F90 and POSTGIBBSF90 programs. Cumulative mortality (95% CI (confidence interval)) for the S1 (lambs which died up to weaning age), S2 (lambs which died from birth to 6 months of age) and S3 (lambs which died from birth to 12 months of birth) groups was 8.41 (7.21–9.61), 14.10 (12.59–15.60) and 17.70 (16.05–19.34) %, respectively. The logistic regression analysis revealed significant (p < 0.05) influences of non‐genetic factors and indicated that the female lambs, heavier dam and higher birth weight of lamb were associated with better survival as compared to their counterparts. The estimates of direct additive heritability for S1, S2 and S3 were 0.04 ± 0.01, 0.07 ± 0.03 and 0.11 ± 0.04, respectively. In addition to this, significant influences of the maternal permanent environmental effects were observed for lamb survival up to weaning as well as six months of age. Thus, the present findings suggest that lamb survival could be improved through better management practices but consideration of maternal permanent environmental effects is important for initial survival of the lamb.

Summary: The present work evaluated animal models comprising direct and maternal effects to estimate (co)variance components and genetic parameters of growth rates and Kleiber ratio in Harnali sheep. The information on pedigree and targeted traits of 1862 lambs born to 144 sires and 591 dams was collected for the period from 1998 to 2018. The traits studied were average daily gain from birth to 3 months of age (ADG₁), 3 months to 6 months of age (ADG₂), and 6 months to 12 months of age (ADG₃) and their corresponding Kleiber ratios as KR₁, KR₂ and KR_3, respectively. The statistical methods included the general linear model for analyzing the effects of fixed factors and animal models for deriving variance components for targeted traits. According to best model evaluated on the basis of likelihood ratio test, the estimated direct heritability was low in magnitude and ranged from 0.04 to 0.14. Direct heritability estimates for ADG₁, ADG₂, ADG₃, KR₁, KR₂ and KR₃ were 0.06, 0.14, 0.05, 0.04, 0.11 and 0.05, respectively. The maternal genetic effects contributed (4–7%) significantly for ADG₁, KR₁ and KR₂ traits. The genetic correlations ranged from −0.35 ± 0.11 (ADG₁-KR₂) to 0.98 ± 0.01 (ADG₂-KR₂ and ADG₃-KR₃) and phenotypic correlations ranged from −0.36 ± 0.02 to 0.98 ± 0.01 for ADG₁-KR₂ and ADG₂-KR₂, respectively. The significant maternal effects along with low levels of direct effects for average daily gain and Kleiber ratio at different age group should be considered while setting selection and managerial strategies to achieve anticipated growth rates in Harnali sheep.