BULLS OR HEIFERS

Hawke's Bay Tribune, Volume XXIV, Issue 96, 6 April 1934, Page 10

BULLS OR HEIFERS

Sex Ratio in Calves Investigations carried out at the Wisconsin University Agricultural Experiment Station by Ivar Johansson, of Sweden, in co-operation with L. J. Cole, Professors of Genetics, show that the belief that certain bulls or cows have a specific tendency to produce a preponderance of male or female calves is incorrect. The research work of these men shows clearly that such variations in the sex of calves from particular parents are due to chance alone. The study was based on a large number of carefully-compiled private herd records of three Swedish breeds of cattle —Swedish Red and White, Swedish Friesian, and Swedish Landraces (the native Swedish cattle)—and also East on data obtained from the herd books of the Finnish Ayrshire breed and the East >nd West Finnish Landrace breeds. The births that were tabulated and classified totalled over 124,000. It was found thalj the normal ratio of male calves born was 106.2 to every 10Q females, with no significant variation in this respect between the various breeds studied. This ratio checks closely with data secured by other investigators based on studies . with breeds of cattle kept tn the United States. Another discovery was that there is no significant tendency for a cow or bull to have more heifer calves when a particular parent is young or relatively old. The ratio between male and female calves remains practically constant regardless of the age of the cow or of the sire. The season of the year when the calf is born likewise has no effect in determining the sex. Twin calves, on the other hand, are more likely to be females than males. On the average there are only 96.34 twin calves of male sex for every 100 that are females. This lower ratio of male calves in instances of multiple birth is probably explained by the largs r umber wale voting that are born so i»r>. n the gestation period that th-- '-t ■ • - ve. ft has been de-Tuon-truted that .n th.- case of abortion* ..n i t.. with ninny species of mammals, n.< well as cattle, appreciably more n.n' - than females arc expt . '■ ] from the '.i' ru» prematurely or dead Data secure-! in this investigation -effie* c that wttb aborted edves

the ratio is 143.07 males for every 100 females. The conditions in the maternal uterus thus seem loss favourable for a male faetns than for a female. This study has confirmed tho common observation that twins are less rugged and strong than calves horn singly, so it is natural to suppose that a larger than normal number of male calves will be expelled prematurely from the uterus when tho Cow is carrying twins. This result would" correspondingly increase the ratio of twin calves carried the full term which arc of the female sex, due to the selective early mortal iQ of th* male salve*.