Lactation Curve of Local Goat, Pure Breds and Crosses in Southern Tunisia

The gamma function was used to fit lactation curve of local goat, pure breds and crosses under southern Tunisian conditions. Data of 16 years of 993 adult dairy milk goats was analyzed to adjust individual milking curve per genetic group. Gamma models parameters were estimated by non linear regression iterative proceure. The local goat lactation curve was fitted after 16 iterations with a value of 0.22 as the residual means squares (RMS). The fastest convergence was led for Murciana with only 10 iterations. The most accurate assessment is registered for the local goat and F2 Alpinexlocal curves when the RMS reaches 0.22. Among pure breeds, the Alpine had the highest production at peak with 1.9 kg day(-1). Within crossed genotypes, the peak of production was 3.66 kg for F2 Alpinexlocal. The starting production, the milking peak and date, the persistence coefficient illustrated differences between studied genotypes. Lactation curve shape and parameters highlighted milking differences and merits of studied genotypes and offer precious tools to optimise the local goat crossbreeding regarding the improvement objectives.