Analysis of environmental effects on test day milk yields of Sarda dairy ewes

Temporal evolution of Sarda ewes milk production was analyzed with mixed li near models and factor analysis to investigate environmental effects on the shape of lactation curves and on milk yields during different lactation st ages. Parity, year of production, level of altitude, and flock within altit ude affected milk, yield, whereas the effect of type of lambing was not sig nificant. Lactation curves pertaining to the three altitudes were clearly d ifferent. Factor analysis suggested an independence among yields recorded d uring different phases of lactation and a specific behavior of (co)variance s structure among test day yields obtained in mountains compared with hills and plains.