The yield and composition of the milk of Finnish Landrace × Blackface ewes: II. Ewes and lambs grazed on pasture

SUMMARY The milk production of 14 Finnish Landrace × Blackface ewes suckling either single, twin or triplet lambs was recorded while they were wholly maintained on a high-quality grazed pasture. Intravenous administration of oxytocin followed by hand milking was used to estimate milk production within 4 days of parturition and then at weekly intervals during a 12-week lactation period. At each milking the milk from each ewe was retained for analysis. Herbage samples for analysis were cut by hand shears at weekly intervals at a height simulating the harvesting by the sheep. In vitro analysis showed a decline in the digestible organic matter in the herbage from approximately 75% in the early stages, to around 67% at the end of lactation. The percentage crude protein in the dry matter of the herbage was variable but tended to increase towards the end of the lactation period. The estimated mean total milk production values were 125, 176 and 193 kg for single-, twin- and triplet-suckled groups of ewes, respectively. Almost all of the difference in total yield between the groups of multiplesuckled ewes occurred in the first 4 weeks of lactation. Analysis of variance showed no significant differences between suckling groups in the concentration of any of the milk constituents. Regression analysis showed significant evidence for differences between the linear and quadratic components of the regressions on stage of lactation for the suckling groups only in respect of daily milk yield, energy and protein production. The concentration of constituents other than lactose was higher in colostral milk but the differences were statistically significant only in respect of energy, total solids and fat. The lactose content of ordinary milk was significantly higher than that of colostral milk. The mean daily live-weight gains of the single- and twin-suckled lambs were significantly greater than that of the triplet-suckled group.