EFFECTS OF SUCKLING REGIME ON LAMB GROWTH-RATES AND MILK YIELDS OF DORSET EWES

Poll Dorset ewes on a commercial sheep-milking enterprise were used in two experiments to determine the effects of restricted access of lambs to ewes on milk yield and composition, and on lamb growth rates. In Experiment 1, 75 ewes were allocated to four treatments: control (C) ewes whose lambs were artificially reared and the ewes milked twice a day; once-a-day (OAD) ewes whose lambs were artificially reared but the ewes were milked once a day; night-suckling (NS) ewes which had access to one lamb for 16 h following afternoon milking; and day-suckling (DS) ewes which had access to one lamb for 8 h following morning milkings. The NS and DS ewes were milked once a day before the lambs had access to the ewes and after weaning the ewes were milked twice a day. Total milk yields over the 91 days of milking were 141.1 +/- 6.4 l milk for C ewes and 15% (20.5 l) and 17% (24.5 l) lower for NS and DS ewes respectively. OAD ewes produced 48% less milk than C ewes over the lactation which was 15-16 days shorter for OAD ewes. Mean growth rates of NS lambs (299g/day) were higher than those of DS lambs (197g/day) and artificially reared (AFR) lambs (140/day). Lambs were weaned progressively as they reached either 10 kg liveweight or 7 weeks of age. The mean ages at weaning were 48, 43, and 32 days for AFR, DS, and NS lambs respectively. In Experiment 2, 60 ewes were randomised into two groups. Lambs in both groups had access to the ewes for 16 h between afternoon and morning milkings but one group was milked once a day (NSOD) and the other group was milked twice a day (NSTD). Milk yields were 5.4 l higher for NSTD than NSOD ewes over the 29 days of the lactation. The growth rates to weaning at 29 days of age were 253g/day and 218g/day for NSTD and NSOD lambs respectively. These results indicate that Poll Dorset lambs can be effectively reared by giving them restricted access to their mothers, with only small reductions in the ewe's total dairy milk yield.