Daily and between-milking variations and repeatabilities in milk yield, somatic cell count, fat, and protein of dairy ewes

Abstract

A total of 801 test day records were obtained consecutively over 3 days from a.m. and p.m. milkings of 267 Churra ewes belonging to two commercial dairy flocks, one machine milked and the other hand milked. The daily intervals between milkings were 14 and 10 h in both flocks during midlactation (76.2 ± 0.9 days postpartum). There were significant effects of flock, sampling day, milking time, and parity for most variables. SCC, log-transformed SCC, and fat and protein contents for the p.m. milking were higher than for the a.m. milkings. These differences are probably connected with a concentration effect owing to the lower milk yield in p.m. milking. Lowest values were always for first lactation. Daily and between-milking repeatabilities were high for yield (0.53–0.85), protein (0.61–0.78), and log SCC (0.54–0.65), but lower for fat (0.27–0.45) particularly in the machine-milked flock. Small daily variations and high repeatabilities between milkings of milk yield, log SCC, and protein makes periodic samplings possible for only one of the milkings and the use of correction factors to quantify daily total tests. Simplification of sampling procedures for fat content does not seem advisable.