74. Twinning in Cattle

Abstract

1. The incidence of twins has been one twin birth in every forty-eight Red Poll births, and one twin birth in every thirty-three Friesian births.2. So far as is known no identical twins have been dropped.3. Thirteen of the fourteen freemartins reared have been barren.4. The birth weight of twin calves has been only slightly lower than that of single calves. Bull calves have been approximately 6 lb. heavier than heifer calves.5. The mortality amongst twins is approximately equal to that amongst single calves.6. Twinning appears to be inheritable and to run in strains.7. The gestation period of a cow bearing twins has been from 8 to 10 days shorter than that of a cow bearing a single calf.8. The percentage of twins dropped increased as the age of the dam at calving increases.9. Twinning is not influenced by the season of the year.10. The twins and dams of twins have been consistently heavier producers of milk and butterfat than the other herd members.11. There is some evidence to suggest a close genetic relationship between the following three characters: (i) multiple births, (ii) high milk and butterfat production, (iii) long life and fertility.