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Jannoune A.,National Association for Sheep and Goat | Boujenane I.,Hassan II Institute of Agronomy and Veterinary Medicine | Falaki M.,National School of Agriculture, Meknes | Derqaoui L.,Hassan II Institute of Agronomy and Veterinary Medicine
Small Ruminant Research | Year: 2015

Genetic parameters and breeding values for live weight from birth to weaning (85 days) of Sardi sheep were estimated using random regression (RR) and multi-trait (MT) animal models. A longitudinal data set for live weight of 44,509 lamb progeny of 605 sires and 18,569 dams were used to describe variance components along growth curve trajectory using RR model. This data set was collected in 89 flocks between 2001 and 2012, with a total of 45,941 animals in the pedigree. Eleven RR models were compared based on the log likelihood and Akaike information criterion. The model with the best fit was found to include quadratic Legendre polynomials for direct and maternal genetic effects and direct permanent environment effects and a linear polynomial for maternal permanent environment effects, including covariance between direct and maternal genetic effects and a heterogeneous residual variance. Direct and maternal heritabilities were 0.11 and 0.03, respectively, at the first day of age, and 0.37 and 0.10, respectively, at 85 days of age. The increase of heritability and genetic variance indicated that there was a large potential for selection of Sardi sheep and suggested that selection during the study period would be more effective if it was done on weaning weight. The low genetic correlation between early weight and weaning weight suggests that these traits are controlled by different genes. Genetic parameters obtained at the selected ages (i.e. 10, 30, 70 days) using MT and RR models were generally similar, but the two methods produced different ranking of genetic merit. This study has demonstrated the possibility of applying RR model for routine genetic evaluation of Sardi sheep. © 2015 Elsevier B.V.. Source


Jannoune A.,National Association for Sheep and Goat | Boujenane I.,Hassan II Institute of Agronomy and Veterinary Medicine | Falaki M.,National School of Agriculture, Meknes | Derqaoui L.,Hassan II Institute of Agronomy and Veterinary Medicine
Small Ruminant Research | Year: 2015

Lamb survival in Timahdite sheep was analyzed using survival records from 79,565 lambs born between 2001 and 2012 in 37 flocks in the breeding program of National Association of Sheep and Goats (ANOC) in Morocco. Traits analyzed were lamb survival from birth to 10 (S10), 30 (S30), and 70 days of age (S70) and to weaning age (SW). The corresponding averages of survival were 97, 96, 90, and 86%, respectively. Hazard ratios obtained by the Cox model showed that male lambs, twin-born lambs and winter-born lambs were less likely to survive than female lambs, single-born lambs and autumn-born lambs, respectively. The heritability estimates obtained using the logistic and probit scales were low to moderate (0.01-0.18), while they were low (0.01-0.08) using the complementary log-log scale. Phenotypic and genetic correlations between lamb survival traits varied from 0.10 to 0.82 and from 0.09 to 0.90, respectively. The phenotypic correlations between lamb survival traits and average daily gains (ADG) between the last two weights above mortality were low and they increase from -0.02 for S10 to 0.24 for SW. At the genetic level, a negative correlation but weak was recorded between ADG and S10 (-0.19). ADG was slightly correlated with S30 (rg=0.08) and S70 (rg=0.24) and moderately correlated with SW (rg=0.41). Annual genetic change for lamb survival, expressed relatively to overall means, amounted to +0.0014, -0.0105, and -0.0176% per annum from birth to 30 days, to 70 days and to weaning age, respectively. The results of this study suggest that to improving survival, it is necessary to combine the direct selection and improvement of breeding conditions of lambs. © 2015 Elsevier B.V. All rights reserved. Source

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