ASSESSMENT OF REPRODUCTIVE AND LIFETIME FITNESS TRAITS IN CHOKLA SHEEP
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Date
2017
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Rajasthan University of Veterinary and Animal Sciences, Bikaner
Abstract
The data for the present investigation were collected from the 1172 records of the Chokla sheep maintained under the Network Project on Sheep Improvement, presently located at the Arid Region Campus of Central sheep and Wool Research Institute (CSWRI), Bikaner, Rajasthan.
The reproductive traits were analysed as age at first service (AFS; 572.39 ± 6.59 days), weight at first service (WFS; 25.16 ± 0.16 kg), age at first successful service (ASS; 635.71 ± 9.36 days), weight at first successful service (WSS; 25.85 ± 0.16 kg), age at first lambing (AFL; 773 ± 8.77 days), ewe’s weight at lambing (WL; 28.61 ± 0.21 kg), lambing interval (LI; 371 ± 6.875 days), service period (SP; 228.31 ± 6.62 days) and gestation period (GP; 152.11 ± 0.11 days).
Using LSMLMW procedure, the reproductive traits were analysed for the effect of non-genetic factors viz. period of birth of ewe, season of birth of ewes, inbreeding and ewe’s weight at birth. Sire of ewe was considered as random genetic effect. Additionally, WFS, AFS, WSS, ASS and WL were considered as covariates for the analysis of AFS, WFS, ASS, WSS and AFL, respectively. Period of birth and sire of ewe significantly influenced all the reproductive traits except LI and SP. Season of birth of ewe had a significant influence on AFL. Ewe’s weight at birth had a significant influence on AFS, WFS, ASS, WSS, AFL and WL. Inbreeding coefficient had no significant influence on any trait. AFS, WFS, ASS, WSS and AFL were highly significantly influenced by their respective covariates.
For the fitness traits, the records for 661 ewes with 3 or more lambings were collected. The study analysed total lambs born (TLB; 4.60 ± 0.92 lambs), total female lambs born (TFLB; 2.42 ± 0.90 lambs), total lambs weaned (TLW;4.01 ± 0.09 lambs), total female lambs weaned (TFLW; 2.08 ± 0.88 lambs), selective value or the female lambs reaching 12 months of age per ewe (SV; 1.50 ± 0.078 lambs), total birth weight of lambs (TLBW; 13.43 ± 0.29 kg), total weaning weight of lambs (TLWW; 55.079 ± 1.477 kg), total adult weight of lambs (TLAW; 72.54 ± 2.65 kg), mean birth weight of lambs (MLBW; 2.81 ± 0.02 kg), mean weaning weight of lambs (MLWW; 13.57 ± 0.12 kg) and mean adult weight of lambs (MLAW; 27.05 ± 0.21 kg) per ewe over its lifetime. The fitness traits were examined for effect of period and season of birth of ewe and inbreeding coefficient. The period of birth of ewe had a highly significant influence on all the lifetime fitness traits. MLWW and MLAW were also highly significantly influenced by the season of birth of ewe.
The heritability estimates for reproductive and fitness traits, through REML procedures, were low to moderate. The maternal direct and permanent effects were meagre for all the traits.
The genotypic correlations of WFS and WSS with AFS, ASS, IL and SP were high and negative, ranging from - 0.420 to - 0.906. High and positive genetic correlation was present among age traits, among weight traits and between IL and SP, ranging from 0.644 to 1.00. The genotypic correlations among other reproductive traits were low. TLB, TFLB, TLW, TFLW, SV, TLBW, TLWW and TLAW had moderate-high genotypic correlations among them, ranging from -0.380 to 1.00. The mean weight traits had low-moderate genotypic correlations with the rest of the lifetime fitness traits.
The phenotypic correlations between age and weight traits were moderatehigh and negative. The phenotypic correlations among age traits, among weight traits and between IL and SP were high and positive. The phenotypic correlations among TLB, TFLB, TLW, TFLW, SV, TLBW, TLWW and TLAW were high and positive. These lifetime fitness traits had low-moderate phenotypic correlations with the mean weight traits.
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