RESTRICTED SELECTION INDEXES TO INCREASE MARKETING BODY WEIGHT WITH MINIMUM CHANGE IN MATURITY WEIGHT IN EGYPTIAN BARKI SHEEP | ||
| Journal of Animal and Poultry Production | ||
| Article 6, Volume 33, Issue 1, January 2008, Pages 129-136 PDF (508.87 K) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/jappmu.2008.217711 | ||
| Author | ||
| A. R. Shemeis, | ||
| Dept. of Animal Production, Fac. of Agric., Ain Shams Univ., Shoubra Al-Kheima, 11241 Cairo, Egypt | ||
| Abstract | ||
| Age-weight data of 1150 Barki sheep (600 females and 550 males) progeny of 60 sires and 850 dams were fitted to Brody growth function to estimate body weight at maturing. Genetic and phenotypic parameters for body weights at birth (W0), weaning (W04), 8-month (W08), yearling (W12) and maturity (WM) were estimated using a multi-trait animal model including the fixed effects of sex of lamb, year of birth and age of dam and the random effects of direct genetics. The estimated parameters were used to construct seven selection indexes aiming to improve marketing body weights W08 and W12 , representing the aggregate genotype, with minimum changes in WM. From the standpoint of accuracy, the full index (I1 = 2.69 W0 - 0.977 W04 + 0.909 W08 + 0.433 W12)had the highest correlation with the true breeding value (rTI = 0.74) followed by late selection (rTI = 0.56 to 0.62) then early selection (rTI = 0.26 to 0.33). Use of I1 should result in developing sheep with W0 (0.14 kg), W04 (0.51 kg), W08 (1.72 kg) and W12 (2.08 kg), provided an increase of 1.36 kg in WM would be accepted. If not, two restricted selection indexes were recommended viz., I(WM) and I(W0). The index I(WM) = -2.508 W0 -0.228 W04 +0.396 W08 + 0.020 W12, would reduce the expected increase to zero in WM and to essentially zero in W0, but at the cost of reducing selection accuracy excessively (rTI = 0.30) and limiting improvement in marketing weights (0.67 and 0.87 kg). The index I1(W0) = -2.764 W0 - 0.391 W04 + 0.477 W08 + 0.342 W12, representing a good compromise, would lead to only 0.55 kg increase in WM and zero increase in W0 together with more acceptable improvement in marketing weights (1.18 and 1.48 kg). | ||
| Keywords | ||
| Barki sheep; marketing body weight; mature body weight; genetic parameters; selection indexes | ||
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