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However, based on litter size (LS) records of FecL L non-carrier ewes, the segregation of a second prolificacy major mutation was suspected in this population. In the Noire du Velay (NV) sheep population, a recent genetic study has evidenced the segregation of such a mutation named FecL L. The search for the genetic determinism of prolificacy variability in sheep has evidenced several major mutations in genes playing a crucial role in the control of ovulation rate.
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Selection on growth variables seems promising (in Texel more than SBF), but high genetic correlations between variables may restrict the possibilities to change the growth curve shape. The linear model had a lower average R 2 than any of the nonlinear models (0.92). In both breeds, all nonlinear models fitted the data well, with an average coefficient of determination (R 2) of >0.98. Biologically relevant variables were estimated for each lamb from modified versions of the logistic, Gompertz, Richards, and exponential models, and from linear regression.
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Live BW records (n = 7559) from 240 Texel and 231 Scottish Blackface (SBF) lambs weighed at 2-wk intervals were modeled. This study compared the use of various models to describe growth in lambs of 2 contrasting breeds from birth to slaughter.