Characterization of the lactation curve in Murciano-Granadina dairy goats

The lactation curve of Murciano-Granadina goats was studied by using records collected between 2004 and 2010 under its Official Dairy Recording program, which includes three milking control programs (Granada, Almeria and Cordoba). A total of 518,557 test-day records corresponding to 69,330 lactations by 38,039 does in 130 herds were included in the analyses. Different mathematical models were fitted, and average curves for region of production, parity, kidding season and type of kidding were estimated. A quadratic spline function gave the best fitting performance and provided a good description of the Murciano-Granadina lactation curve. All the factors studied affected both the scale of the lactation curve and its shape, with more distinct curves in first lactations, goats kidding in the summer and those producing singletons. When compared with later parities, first-parity does had a lower initial level of production, later and lower peak yield, and a smaller decline in milk production after the peak. Goats kidding in the Summer had a steep increase in milk yield up to the peak, which occurred earlier and with a higher yield than in other seasons, but seasonal effects differed slightly among regions. The lactation curve was flatter and with a later peak in goats producing single kids, and a steeper increase in yield up to the peak was observed as the number of kids increased.