BUGGED BY HEIFER MASTITIS? THE WHYS AND WHAT CAN BE DONE

Is heifer mastitis a problem? Several overseas studies have shown heifers have higher incidence of mastitis than older cows, and anecdotal evidence would say that is also the case in N.Z, although there is little local published data to support this. An unpublished Dexcel survey found an average 13 % of heifers were diagnosed with mastitis in the early postpartum period, with a within herd range of 0-61 % (Williamson 2002). This compares to the findings of McDougall (1999) that approximately 10 % of cows had one or more cases of mastitis in the first 2 months of lactation, and that the herd prevalence was higher where the proportion of heifers was also higher. The published study by Pankey (1996) in eleven Waikato dairy herds found an average 8.1 % of heifers calved with clinical mastitis, and that the environmental pathogen Streptococcus uberis was isolated from 67.6 % of these clinical cases. Williamson (2002) reported results from another Dexcel study on 195 heifers on No. 2 dairy showing 15.3 % had intramammary infections (IMI) due to Streptococcus uberis post-calving. No studies from New Zealand have been published on the risk factors for mastitis in heifers around the time of calving. Overseas studies show that pre-calving intramammary infection, udder oedema and short distance of teat ends to the ground (Slettbakk, Jorstad, et al. 1995), blood in th