Genetic Evaluation Of Growth Performance Of Farmbred Nilagiri And Sandyno Sheep
KrishiKosh
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Title |
Genetic Evaluation Of Growth Performance Of Farmbred Nilagiri And Sandyno Sheep
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Creator |
Venkataramanan, R.
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Contributor |
Subramanian, A.
Sivaselvam, S.N. Sivakumar, T. Sreekumar, C. |
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Subject |
Sheep
Nilagiri Sandyno Growth Genetic parameters |
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Description |
Nilagiri and Sandyno sheep were evaluated for growth performance. Data on pedigree information for 48 years (1965-2012) and growth for 21 years (1992- 2012), collected from records maintained at the Sheep Breeding Research Station, Sandynallah, The Nilgiris were utilised for the study. The different growth traits studied were body weights at birth (BW), weaning (WW), 6-months (6W), 9- months (9W), 12-months (YW) and 18-months (18W) of age and absolute growth rate (AGR), relative growth rate (RGR) and Kleiber ratio (KR) estimated on a daily basis at different age intervals from birth to 12 months. The various traits were analysed using least-squares method for effect of breed, contemporary groups of year-season, sex, type of birth, age of dam at lambing and inbreeding. The inbreeding parameters calculated were Wright’s Inbreeding coefficient and equivalent inbreeding coefficient. (Co)Variance components were estimated through restricted maximum likelihood technique (REML) using an Animal model. The fixed effects found to be significant from the least-squares analyses were fitted for each trait. The mean BW, WW, 6W, 9W, 12W and 18W for Nilagiri and Sandyno sheep were 2.29, 9.47, 13.10, 15.99, 19.22 and 24.45 kg and 2.57, 10.24, 14.46, 17.55, 21.00 and 27.49 kg respectively. The pre- and post-weaning (3-12 m) AGR in Nilagiri sheep were 79.76 and 36.00 g, respectively and corresponding values in Sandyno sheep were 85.15 and 38.92 g. The mean generation interval (GI), inbreeding coefficient (F), proportion of population inbred, equivalent no. of generations (EqGi), equivalent inbreeding coefficient (EF) and effective population size (Ne) for Nilagiri sheep were 3.36 years, 2.17 per cent, 100 per cent, 3.75, 2.05 per cent and 90.34 respectively. The corresponding values for Sandyno sheep were 3.73 years, 0.83 per cent, 95 per cent, 2.52, 0.90 per cent and 134.86 respectively. EF was found to correct for inbreeding coefficient in the Sandyno population, in which ancestral knowledge was comparatively less. The regression of most of the traits on F and EF were negative. In Nilagiri sheep, significant effects of F was observed for WW (-0.048 kg), YW (-0.062 kg), pre-weaning AGR (-0.470 kg) and pre-weaning KR (- 0.029). In addition to these traits 6W (-0.031 kg), 9W (-0.046 kg) and 18W (- 0.076 g) were found to be influenced by EF. In Sandyno sheep, YW(-0.100 g) and post-weaning AGR (3-12 m) with a regression of -0.263 g were influenced by F, while EF had significant influence on YW (-0.098), post-weaning AGR for the periods from 6 to 9 m (-0.420g) and 3-12 m (-0.273g). Post-weaning KR for the same periods were also affected by EF in Sandyno sheep, with regression values of -0.039 and -0.016 respectively. The direct heritability for BW, WW, 6W, 9W, YW and 18W estimated from the best model in Nilagiri sheep were 0.140, 0.130, 0.074, 0.168, 0.129 and 0.166 respectively. In Sandyno sheep, the respective values were 0.147, 0.114, 0.098, 0.141, 0.144 and 0.115. Maternal genetic influence was important up to 9W in Nilagiri sheep. In Sandyno sheep, in addition to the other traits, 18W was also affected. The genetic correlations among body weight traits were positive and high, and higher than the phenotypic correlations. Genetic correlations between most of the body weight traits and pre-weaning AGR, RGR and KR were high and positive. Early body weights had negative or positive, negligible genetic correlation with post-weaning AGR and RGR. Correlated responses to selection were higher in body weight traits, when selection was based on 9W and 6W in Nilagiri and Sandyno sheep respectively. The direct genetic trends for BW, WW, 6W, 9W, YW and 18W were 0.000, 0.011, 0.006, 0.016, 0.011 and 0.015 respectively in Nilagiri sheep and for Sandyno sheep, the values were 0.001, 0.013, 0.011, 0.017, 0.017 and 0.022 respectively. In general, the moderate values for heritability, positive genetic correlations and positive genetic trends for different growth traits are indicative of good scope for genetic improvement. The BLUP estimates of breeding value showed an accuracy of selection almost equal to unity and could be effective in ranking of superior animals. The individual inbreeding coefficient also must be considered, when ranking is based on breeding values. The traits with best correlated responses identified through this study could be explored. Especially 9W even though available at a later age, could be added as a last stage selection criterion for better responses in other economically important body weights. In Sandyno, 6W could be continued as an effective means to bring about overall improvement in growth. |
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Date |
2016-05-23T17:04:55Z
2016-05-23T17:04:55Z 2013 |
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Type |
Thesis
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Identifier |
http://krishikosh.egranth.ac.in/handle/1/66238
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Language |
en
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Format |
application/pdf
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Publisher |
Tamil Nadu Veterinary and Animal Sciences University
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