Direct and maternal variance components and genetic parameters for average daily body weight gain and Kleiber ratios in Nellore sheep

Abstract

The objective of the present study was to estimate variance components and genetic parameters for average daily gain from birth to weaning (ADGa), birth to 6 months (ADGb) and 3 to 6 months (ADGc) and corresponding Kleiber ratios (Ka, Kb, and Kc) in Nellore sheep. Data were collected from the records maintained at Livestock Research Station, Palamaner, for analysis and the data spread from 1993 to 2016 (23 years). Lambing year, sex of lamb, season of lambing, and parity of dam were included in the model as fixed effects, and ewe weight was kept as a covariate. Six animal models were fitted with various combinations of direct and maternal genetic effects using restricted maximum likelihood procedure. The Akaike's information criterion was employed to determine the best model for each trait. Direct heritability estimates obtained in the study for ADGa, ADGb, ADGc, Ka, Kb, and Kc were 0.37, 0.41, 0.34, 0.48, 0.46, and 0.37, respectively, and their corresponding maternal heritabilities ranged from 0.11, 0.21, 0.11, 0.24, 0.22, and 0.11, respectively. (Co)variance among the direct and maternal effects were found to be negative in all the traits. Direct genetic correlations among the studied traits were positive with few exceptions, and they ranged from - 0.03 (Ka-Kc) to 0.99 (ADGa-Ka); similarly, the phenotypic correlations ranged from low to high - 0.18 (ADGa-Kc and Ka-Kc) to 0.95 (ADGa-Ka). These results indicated the importance of maternal effects in affecting the growth rate and efficiency of feed utilization traits and also suggested the possibility of moderate genetic progress for these traits through selection.

Estimates of (co)variance components and genetic parameters for pre-weaning body weight traits and Kleiber ratio in Sangsari sheep breed

“…Likewise, the direct heritability estimate of PWDG (0.15) in the current study was in accordance with the estimated values reported by Mandal et al (2015), Jafari et al (2014) and Sallam et al (2019) in Muzaffarnagari, Makuie and Barki sheep, respectively. However, these results were incompatible with those obtained by Lalit et al (2016) in Harnali (0.40), Illa et al (2019) in Nellore (0.37) and Latifi and Mohammadi (2019) in Afhshari (0.37) sheep, who reported higher values. Other authors have also reported lower values for the mentioned trait compared to those estimated in the present study (Boujenane and Diallo 2017;Gholizadeh and Ghafouri-Kesbi 2017;Bangar et al 2018).…”

“…The moderate estimates of heritability for BW and WW in our study show that these traits have moderately heritable variation. Therefore, genetic gain in these traits may result from selection designs (Illa et al 2019).…”

Evaluation of models for estimation of genetic parameters for post-weaning body measurements and their association with yearling weight in Nellore sheep

“…In Nellore sheep, the genetic parameters and (co)variance components for body weight, average daily gain and Kleiber ratio's at different ages were estimated using animal model, direct genetic and maternal effects on the traits were evaluated, genetic diversity and effects of inbreeding on growth traits in Nellore sheep were also assessed in this sheep [10,11]. Rajkumar et al [12] studied the effect of management system (semi-intensive vs intensive) on the slaughter age with respect to carcass characteristics and other related traits.…”

Evaluation of models for estimation of genetic parameters for post-weaning body measurements and their association with yearling weight in Nellore sheep

“…In Nellore sheep, the genetic parameters and (co)variance components for body weight, average daily gain and Kleiber ratio's at different ages were estimated using animal model, direct genetic and maternal effects on the traits were evaluated, genetic diversity and effects of inbreeding on growth traits in Nellore sheep were also assessed in this sheep [10][11]. Raj kumar et al [12] studied the effect of management system (semi-intensive vs intensive) on the slaughter age with respect to carcass characteristics and other related traits.…”