Effects of breed and milking frequency on udder histological structures in dairy goats

Abstract

Tissue percentages (secretory, connective, ductal and vascular tissues) and the number and size of the alveoli in the udders of three dairy goat breeds under two milking frequencies (once- vs. twice-daily milking) were studied. Nine dairy goats, three of each breed studied (Majorera, Tinerfena and Palmera), were milked during 6 weeks beginning at the tenth week of lactation. The right udder half was milked twice daily, and the left udder half was milked once daily. Moreover, during the experimental period, morphological udder data, milk yield, milk fractioning and milk composition were recorded. The goats were sacrificed and two samples for each gland were taken for the histological study. The statistical analyses revealed that the histological parameters were not influenced by the milking frequency, and that the breed determines different percentage of tissue components. Correlations between morphological parameters of the udder and milk-yielding parameters were high and determined the greater importance of the globosity and the structure of the udder in the milk production. Furthermore, it was determined that the percentage of secretory tissue in the mammary parenchyma has no correlation with the milk yield parameters in different high-production dairy breeds. Histological parameters (secretory and connective tissues) only have an impact in the milk fractions.