The effects of weather on milk production in dairy sheep vary by month of lambing and lactation phase

Abstract

A total number of 609 bulk-tank milk controls on a dairy sheep farm in Spain were used to determine how weather affects milk production in sheep, related to lambing period and lactation phase. Data from individuals were assigned to one of five lactation periods based on the timing of lambing: FEB (n=124); APR (n=141); JUL (n=114); SEP (n=102), and NOV (n=128). Milk yield per ewe per day was calculated as total milk volume/number of ewes milked. Lactation was divided into three phases: Early-lactation (from lambing to month 2), Mid-lactation (from month 3 to 7), and Late-lactation (month 8). Milk yield per ewe was higher (P<0.01) in SEP than in FEB, APR, or NOV; production peaked in JUL and was lowest in FEB. In lactations initiated in JUL and SEP, milk yield per ewe per day was higher (P<0.05) in early lactation than it was in the other lambing periods; however, in APR and SEP, per ewe production was highest (<0.01) in mid-lactation. Milk yield in each of the five lambing periods was significantly (P=0.001) associated with several meteorological variables, and the strongest (R2=0.732) was with solar radiation and minimum temperature in the APR lactation period. In all lactation periods, the relationship between milk yield and weather differed among the three phases of lactation. In conclusion, the effects of meteorological conditions on milk yield in sheep cannot be understood without assessing production among milking periods in the same year and the phases of lactation, especially if milking periods are long.