Genetic analysis of reproductive traits of Sahiwal cattle

Abstract

Data on first lactation reproduction traits of Sahiwal cattle maintained at an organized herd of the institute over a period of 29 years (1988–2016) were analyzed in the present study. Effect of various genetic and non–genetic factors on first lactation reproduction traits in addition to their genetic control was assessed by using mixed model least–square analysis. The overall least–square means for first lactation reproduction traits, viz. age at first service (AFS), age at first calving (AFC), number of services per conception (NSC), conception rate (CR), gestation period (GP), calving to first insemination interval (CFI), service period (SP), calving interval (CI) and pregnancy rate (PR) were 784.84±8.03 days, 1116.18±10.38 days, 1.86±0.11, 0.97±0.06, 287.73±0.60, 84.75±5.01, 119.86±8.31, 420.53±3.33 days and 0.27±0.02, respectively. Analysis of variance revealed that random effect of sire had non– significant influence on all the considered traits in present study. Period of birth significantly influenced AFS and AFC. Differences were statistically significant for effect of period of calving on NSC; season of calving on NSC, CR and PR; age group on NSC and CR. The effect of lactation length used as co–variable had significant influence on CFI, SP and PR. Service period as co–variable significantly affected CI. The magnitudes of heritability estimates were low to medium varying from 0.09 to 0.27 for different reproduction traits indicating large role of environment and management for improvement of these traits.

Bayesian approach for assessment of co-variances and genetic parameters of economically important traits in Sahiwal cattle

“…Posterior mean of permanent environmental (above diagonal) and residual correlations (below diagonal) along with posterior standard deviation for different performance traits in Sahiwal cattle LMY, LL, PY, DPY, DP GP, CFI, DO and CI as 1935.13 kg, 2022.49 kg, 277.90 days, 12.62 kg, 43.90 days, 137.13 days, 286.82 days, 85.62 days, 134.22 days and 425.42 days, respectively in Sahiwal cattle.Means observed for different traits were in concordance with the results of earlier studies(Ratwan et al 2018a(Ratwan et al , 2019a(Ratwan et al , 2020b(Ratwan et al , 2021. Period of calving had signi cant (p < 0.01) in uence on all considered traits except DPY and GP.…”

“…A multi-trait model includes all the information available on animals and thereby increases the precision of estimating genetic parameters (Pollak et al 1983). Earlier, researchers used maximum likelihood approaches in Sahiwal cattle to assess genetic parameters of performance traits (Rehman et al 2008;Ratwan et al 2018a;2019a;a). Additionally, researchers have estimated heritability, repeatability and genetic associations between production and fertility traits in dairy animals using Bayesian and restricted maximum likelihood methods (Kumar et al 2016;Ratwan et al 2018b;2019b;Worku et al 2021;.…”

Computation of Heritability for Production and Reproduction Traits in Frieswal Cattle under Field Progeny Testing

“…Guo et al [22], Ben et al [9] and Zhu et al [62] have reported similar heritability estimates in Holstein Friesian cattle. Ratwan et al [47] reported a higher estimate in Sahiwal and Lomole [36] reported a slightly higher estimate in Sahiwal cattle than the present study. Zhu et al [62] reported a lower estimate in Holstein Friesian cattle than in the presentstudy.…”

“…Heritability estimate for the gestation period was found to be relatively low compared to production traits, indicating that genetic factors play a smaller role in determining the length of pregnancy.Management practices such as nutrition and health care may have a more substantial impact on the gestation period compared to genetic selection.The heritability estimate of the gestation period in the present study was in agreement with the reports of Al-Samarai et al [2], Das et al [13] and Kumar et al [27] in Holstein Friesian and crossbred cattle, respectively. Ratwan et al [47] also reported a similar estimate in Sahiwal cattle. Selvan et al [50], Lomole [36] and Ratwan et al [48] reported a lower estimate in Sahiwal cattle than the present study.…”