Effects of Twinning on Reproductive Efficiency in a Holstein-Friesian Herd

Abstract

Out of 7,387 calvings in a Holstein-Friesian herd covering a 30-yr. period, 338, or 4.58%, were multiple births. Two of these were triplets. The twin combinations were 1083 3 : 1543 9 : 742 Q. An estimated 13.68 0.90% of the like-sexed twins were monozygous (maximum likelihood method). Twin calves were 55% males, as compared with 51.65% for the herd. Twinning rate was 1.3% for heifers and 4.4% at second calving (P < 0.001): Rates increased to 7.1% at the tenth calving (not significant). Mortality among twin calves was high by parturition time, averaging 41% of the males and 35% of the females. Twin cows reproduced as well as their singly born herd mates. Cows having twins before the fourth calving reproduced fewer times subsequently. Incidence of relative infertility was significantly greater after twinning, though average services per conception and calving intervals were not consistently different. Twinning is undesirable in dairy cattle because of increased infertility and a reduced number of female progeny from cows which have twins.