Showing 2 results for Genetic Trend
M. Sargolzaei, M. A. Edriss,
Volume 8, Issue 1 (4-2004)
Abstract
In this study, 14322 growth trait records of 2387 sheep bred and reared in the Rearing and Breeding Station of Bakhtiari Sheep during 1989-1997 were used to estimate the phenotypic, genetic, and environmental trends for some of the growth traits using Animal Model for lambs, rams, and ewes. The genetic trend of birth weight, weaning weight, six month's weight, daily gain from birth to weaning, daily gain from weaning to six month and daily gain from birth to six month were 12.2 (+2.9), 19.6 (+5.5), 28.7 (+8.7), .15(+0.04), 0.06 (+0.05) and 0.014 (+0.04) gr. for ewes as an indicator of genetic level of the herd respectively. Also, average of the genetic change rate per year for rams and lambs were calculated. Overall, the maximum progress rate was for six-month body weight (28.7 gr. per year) and the next was weaning weight (19.6 gr. per year). The results for lambs and rams also showed that these traits had the same rank for the genetic progress. The progress could be due to direct selection for these traits in the selection index criterion although there were negative phenotypic and environmental trends during the study years. Negative phenotypic and environmental trends could be due to bad environmental conditions, especially to nutrition of the sheep in an unsuitable (drought) climate during the study years. .
M. Vatankhah, M. A. Talebi, M. A. Edris,
Volume 11, Issue 41 (10-2007)
Abstract
In this study 5025 records from the Lori-Bakhtiari sheep stud were used to predict phenotypic, genetic and environmental change in ewe traits from 1989 to 2004. Best linear unbiased prediction (BLUP) of breeding values were estimated by Drivative Free Restricted Maximum Likelihood (DFREML) procedure using single and multi-trait animal model. Phenotypic, genetic and environmental trends were calculated by regressing of the average phenotypic values, predicted breeding values and environmental values in the year of ewe birth respectively. The estimated phenotypic trends were –0.1223 kg for ewe body weight, -0.0415 kg for greasy fleece weight, 0.6639% for conception rate, 0.0003 for number of lambs born per ewe lambing, 0.0094 for number of lambs weaned per ewe lambing, 0.0380 kg for total birth weight per ewe exposed and 0.4227 kg for total weaning weight per ewe exposed. The estimated genetic trends were 0.0603 kg, -0.0004 kg, 0.0183%, -0.0012, -0.0007, 0.0030 kg and 0.0211 kg from single trait analysis and 0.0549 kg, -0.0006 kg, 0.0089%, -0.0008, -0.0008, 0.0030 kg and 0.0230 kg respectively from multi-trait analysis. The estimated phenotypic and environmental trends were significant but genetic trends were not significant (P<0.05) for often traits.
