Estimates of Phenotypic and Genetic Parameters for Traits of Reproductive Efficiency in Kajli Sheep in Punjab, Pakistan
Estimates of Phenotypic and Genetic Parameters for Traits of Reproductive Efficiency in Kajli Sheep in Punjab, Pakistan
Asad Ali1*, Khalid Javed1, Imran Zahoor1, Khalid Mahmood Anjum2, Numan Sharif1, Imtiaz Ahmad3 and Aftab Hussain Aftab3
ABSTRACT
The objectives of this study were to evaluate non-genetic and genetic effects as well as heritabilities and repeatabilities for seven reproductive traits using phenotypic records from an experimental Kajli flock in Punjab, Pakistan. Phenotypic data comprised 2501 records of litter size at birth (LSB), cumulative litter weight at birth (LWB), and mean litter weight at birth/ lamb born (LMWB), 1657 records of litter size at weaning (LSW), cumulative litter weight at weaning (LWW), and mean litter weight at weaning/ lamb weaned (LMWW), and 1674 records of lambing interval (LI) from Kajli sheep housed at the Livestock experiment station Khushab from 2007 to 2018. Least squares procedures (SAS, 9.1) were used to assess the effect year of service (YOS), season of service (SOS), parity of dam, and breeding ram on the expression of all reproductive traits. A derivative free REML algorithm was used to estimate heritabilities and repeatabilities with software WOMBAT®. The overall least squares means ± standard error for LSB, LWB, LMWB, LSW, LWW, LMWW and LI were 1.19±0.03, 5.75±0.17 kg, 4.88±0.06 kg, 1.17±0.05, 20.77±0.91 kg, 17.87±0.57 kg, 330.69±20.48 days, respectively. The YOS had significant (p≤0.01) impact on LSB, LWB, LMWB, LWW and LMWW. However, SOS did not affect any reproductive trait except for LI (p≤0.01). Parity significantly affected LMWB (p<0.05) as well as LSB, LWB, LSW and LWW (p≤0.01), but not LMWW and LI. Breeding ram influenced LSB, LSW and LWW significantly (p≤0.01). Genetic parameter estimates were very low due to large values of environmental variances for all reproductive traits. Estimates of heritability were low for all traits (0.08±0.05, 0.01±0.02, 0.02±0.02, 0.01±0.01, 0.04±0.03, 0.07±0.05 for LSB, LWB, LMWB, LSW, LWW and LMWW, respectively). The heritability for LI was zero. Repeatability estimates were also low for all traits (0.09±0.05, 0.02±0.02, 0.06±0.03, 0.02±0.01, 0.04±0.02, 0.09±0.06, 0.01±0.01 for LSB, LWB, LMWB, LSW, LWW, LMWW and LI, respectively). Regression of estimated breeding values for all reproductive traits on year of breeding yielded no significant genetic trends during the 12 years of the study.
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