Impact of parity and litter size on dairy traits in Istrian ewes

The aim of the study was to determine the influence of parity and litter size on dairy traits in Istrian ewes. The following traits were analysed: lactation milk yield, daily milk yield, fat yield, fat content, protein yield, protein content, lactose yield, and lactose content. Lactation records (n = 6,481) collected on 2,786 ewes were analyzed using a statistical model adjusted for unbalanced data structure accounting for all the available sources of phenotypic variability. Parity had a statistically significant effect on all the investigated traits (P<0.01, P<0.001). Lactation milk yield, daily milk yield, protein yield, and lactose yield peaked in 3rd , fat yield, fat content, and protein content in 4th, and lactose content in 2nd lactation. Litter size had a significant effect on all the investigated traits (P<0.01, P<0.001) except the fat content (P<0.05). Multiple litters led to higher yields of milk and all the examined dry matter components. The results of the study should contribute to better understanding of the phenotypic variability of some economically very important dairy traits in ewes.