EVALUATION OF DIRECT AND MATERNAL (CO) VARIANCE COMPONENTS AND HERITABILITIES FOR SOME BODY WEIGHTS AND GROWTH TRAITS IN BARKI SHEEP | ||||
| Egyptian Journal of Sheep and Goats Sciences | ||||
| Article 3, Volume 9, Issue 1, April 2014, Page 1-10 PDF (255.57 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/ejsgs.2014.26752 | ||||
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| Authors | ||||
| El-Wakil, Salwa I.; S. M. A. Gad | ||||
| Animal and Poultry Breeding Dept., Desert Research Centre, ElMatareya, Cairo, Egypt. | ||||
| Abstract | ||||
| ABSTRACT The present study was conducted to investigate the importance of maternal effects on some body weights and growth traits in Barki sheep. Body weight records and pedigree information of 3189 lambs progenies of 186 sires were taken from the Barki sheep flock of the Desert Research Centre maintained at two research stations; Ras Elhekma (from 1963 to 1972) and Maryout (from 1973 to 2004). The present study dealt with body weights at birth, BW, weaning, 120 days, WW and yearling, 360 days, YW as well as average daily gain from birth to weaning, DGBW and from weaning to yearling, DGWY. (Co) variance components and the corresponding genetic parameters were estimated by fitting a series of six animal models using the MTDFREML program. These models included the significant fixed effects together with the animal, sire and dam as random effects. Such models were fitted for each studied trait and differed in ignoring or including various random effects. Log-likelihood ratio tests were conducted to determine the most suitable model for the studied traits. Results indicated that the animal model which includes only direct genetic effect was the most appropriate one. Direct heritability estimates ranged from 0.10 to 0.36 for BW, 0.13 to 0.30 for WW, 0.07 to 0.23 for YW, 0.13 to 0.26 for DGBW and 0.08 to 0.10 for DGWY. The corresponding values for maternal heritability ranged from 0.18 to 0.20, 0.12 to 0.19, 0.12 to 0.19, 0.10 to 0.17 and 0.01 to 0.07, respectively. It is obvious that maternal influences were generally higher for BW, WW and YW than the respective direct ones. The direct and maternal environmental components tended to increase as age advanced from birth to yearling. The correlation between direct and maternal genetic effect ranged from 0.07 to 0.35 for the studied traits except for DGWY (-0.72). Although total direct components has a major contribution (82%) to the phenotypic variance, total maternal components controls the remainder of about 20% and being relatively constant at that level to the yearling stage which imply the importance of maternal influences on growth traits of Barki sheep. The impact of maternal effects on BW appeared to be mainly genetic and tended to decline as age advanced. The current investigation advocates that selection process should account for both direct and maternal genetic effects to increase the accuracy of genetic evaluation and enhance the genetic gain for growth traits in Barki sheep. | ||||
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