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

Abstract

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