Epidemiology and management of mastitis in heifers
Mastitis in heifers differs from the disease in cows in several ways:
- Higher incidence of clinical mastitis in the first few days postpartum: more than 30 % of cases occurring in lactation appear in the first 2 weeks of this period.
- Higher incidence of Streptococcus uberis and CNS.
- Lower incidence of Staphylococcus aureus.
Management practices are a likely cause for these differences, as are physiological differences, since heifers are still growing and have never been milked before. Differences in leukocyte patterns have also been reported.
Mastitis is always a costly disease, but it is even more so in a heifer. After a single mastitis case, a fresh heifer is very likely to produce less milk than her genetic potential would allow and she is also more likely to be culled before she has paid back her rearing costs.
Heifers with an elevated SCC in early lactation maintain a higher SCC throughout the whole period. In general, heifers with low cell counts in early lactation produce more milk than heifers that had an increased cell count after calving. When looking at the underlying cause of the infection, the future of a heifer’s production seems to depend on the pathogen that she has been infected with.
While major mastitis pathogens always have a negative effect, intramammary infections due to CNS in early lactation had no negative effect on the average milk production in the early to mid lactation period. Some researchers even reported that milk yield was increased in heifers infected with CNS in the postpartum period with respect to heifers with no infection. CNS in the udder may protect heifers from infection with other major pathogens, thereby reducing their risk of developing clinical mastitis. It may also be true that heifers with a higher genetic potential are more likely to be infected.
Cure of heifers
Infected heifers are very likely to be cured when treated properly. However, the loss in milk production both during and after the acute phase remains an important point of economic loss.