Aspects of reproduction in New Zealand dairy herds 1. Gestation length

Abstract

Extract In New Zealand dairy cattle, the average gestation length is commonly accepted as 282 days. This is slightly longer than that reported in European and American studies of Jersey and Holstein or Friesian cattle (Anderson and Plum, 1965 Anderson, H. and Plum, M. 1965. Gestation length and birth weight in cattle and buffaloes: A review. J. Dairy Sci., 48: 1224–1235. [Crossref], [PubMed], [Web of Science ®] [Google Scholar] ; O'Conner et al., 1968 O'Conner, L. K. , Wood, P. D. P. and Smith, G. F. 1968. A note on the differences between geographical areas in the gestation length and birth weight of British Friesian calves. Anim. Prod., 10: 125–128. [Google Scholar] ). A feature of these reports and previous New Zealand studies is the differing variation associated with the mean gestation lengths. Part of this may be due to sex, season, breed of sire, age of dam and unspecified herd effects, but is largely the result of excluding or including abnormal gestation periods. The criteria for determining normality have been rather arbitrary in most cases. Abnormally short and long gestation periods may result from disease or from incomplete data recording for conception dates.