a1 Royal (Dick) School of Veterinary Studies, Department of Veterinary Medicine, Field Station, Easter Bush, Roslin, Midlothian EH25 9RG
a2 Edinburgh School of Agriculture, West Mains Road, Edinburgh EH9 3JG
Some factors affecting perinatal lamb mortality were studied with 63 Finn × Dorset Horn ewes and 85 Scottish Half bred and Greyface ewes, having an average litter size of 2·26. Total perinatal lamb mortality averaged 29 % of which 44% were stillborn, 1 % attributed to dystocia, 35 % died between birth and 48 h of age, 14 % from 48 h to 10 days, and 5 % after 10 days.
For the Finn × Dorset ewes, the 41 viable twin lambs weighed at birth 3·47 kg and 12 twin lambs which did not survive weighed 2·51 kg. Triplet weights were: viable 2·98 kg (34 lambs) and nonsurviving 2·00 kg (14). Quadruplet weights were: viable 2·79 kg (12) and non-surviving 1·90 kg (16). Quintuplet and sextuplet weights were: viable 2·45 kg (2) and non-surviving 1·35 kg (14).
In the aggregated Halfbred and Greyface breeds, viable twin lambs weighed 4·5 kg at birth (91) and non-surviving 3·64 kg (11). Viable triplets weighed 3·77 kg (23) and non-surviving 2·68 kg (16).
Serum gamma-globulin and total serum protein values were lower in the lambs which failed to survive, and this was particularly marked with triplets. Fractionating the gamma-globulins (IgG) indicated that IgGi was particularly low in non-viable lambs.
Litter size, lamb birth weight, and colostrum intake by the lamb had important effects on perinatal lamb mortality.
(Received October 12 1978)