Milk Yield by Dorset Ewes as Affected by Sibling Status, Sex and Age of Lamb, and Measurement

Abstract

Milk intake (sucking-test weight) by 55 Dorset lambs and milk production (oxytocin-hand milking) by 41 Dorset ewes were measured at 2-wk intervals during the first 8 wk of lactation. Each method indicated that milk yield by ewes was greater at 2 and 4 wk of lactation than at 6 and 8 wk. Daily milk intake by a set of twins (suckling-test weight) was similar to 24-h milk production of their dam (oxytocin-hand milking) when lambs were 2, 4, 6, and 8 wk of age. At 2, 4, and 6 wk postpartum, milk production by ewes nursing single lambs was 200 to 400g greater than milk intake by lambs due to a larger residual milk. Stage of lactation had a significant effect on protein and fat content of milk but not on lactose. Sex of offspring had no effect on milk yield or protein, fat, and lactose content of milk. Lactose was one percentage unit greater in milk of ewes nursing single lambs; however, the amount of lactose secreted daily was similar for ewes nursing single or twin lambs. Twenty-four-hour milk production by the ewe as determined by the oxytocin-hand milking method was correlated with lamb growth (.67 to .86), with milk intake, as determined by the suckling-test weight method, the next most important variable. Milk composition contributed little toward modeling lamb growth.