BRIEF COMMUNICATION: Birth weight of calves born to dairy cows in New Zealand

Introduction The expansion of the dairy industry in New Zealand has resulted in increased opportunities for beef production from the dairy herd. Of 4.1 million dairy calves born in 2014, only 26% were required as replacements, leaving more than 3 million calves that could potentially be reared for beef. The majority (56%) of these potential beef calves were processed as veal at less than two weeks of age, and only 836,000 were reared and finished (Cook 2014). This opportunity for increased production of finishing animals from the dairy industry is recognised by many beef cattle breeders, and some breeders are seeking to produce sires that are suitable for use over dairy cows to produce highquality finishing cattle. The historical advantage of beef bulls has been to produce a calf of greater value than a calf sired by a dairy bull, and to produce calves that look different to dairy-sired calves so that farmers know with certainty which calves can be considered as replacements for their herd. In a climate of high milk value and relatively low calf value, dairy farmers prioritise days in milk and cow health above potential sale value of calves (Cook 2014). This has resulted in a shift in the dairy industry to using Jersey bulls when historically a beef bull would have been used. If beef bulls are to return to favour in the dairy herd, they need to be able to compete with dairy bulls in terms of their impact on the cow by producing calves of comparable birth weight. The aim of this paper was to examine the birth weight of calves born to dairy cows that were sired by dairy breed bulls and to determine how they differed for heifer dams compared with mature dams, and for Jersey, Holstein Friesian and Crossbred cows.