Hereditary occurrence of intra-uterine growth retardation and weak calves in Japanese Black cattle.
Neonatal death occurred in 182 of 7737 newborn Japanese Black calves. Of these, 107 (59%) showed neonatal weakness. 68 calves (37%) that suffered intra-uterine growth retardation (IUGR) had abnormally low body weight (<20 kg) although delivered after normal pregnancy period (275 days or longer). They were related to 3 of 9 bulls used for breeding with significantly higher incidence of IUGR compared with the remaining bulls. A family of cows related to these bulls had significantly higher incidences of IUGR than other families. It is suggested that genetic factors may be involved in the incidence of IUGR and weak calves in Japanese Black cattle.