Factors affecting individual lactation curve shape in Italian river buffaloes

Lactation curves for milk yield of 3860 Italian river buffaloes were modelled with the Wilmink function. For this species, a wide range of goodness of fit indicates much variation of shapes among animals. Moreover, about 30% of individual curves showed the atypical shape, i.e., characterised by the absence of the lactation peak. The presence of atypical curves may seriously bias results of analysis based on comparison between individual parameter values. Factors affecting the occurrence of atypical curves were investigated by a logistic regression model. Biological and environmental factors (age at calving and calving season, herd) and, mainly, the structure of data analysed (distance of the first recorded test from parturition) were significantly related to the probability of having an atypical shape.