By vet Victor Oudhuis
A substantial proportion of heifers calve with intramammary infections. When caused by major pathogens such as Staphylococcus aureus or Streptococcus uberis, this will on average result in flawed udder health and suboptimal milk production in the first lactation, which can have severe financial consequences. A certain level of heifer mastitis in unavoidable, but we consider a herd to have a heifer mastitis problem if more than 15% of heifers have clinical mastitis around calving and/or if more than 15% of all heifers have a first test-day SCC (measured between 10 and 35 DIM) more than 150,000 cells/ml or 10% if cut off is 200,000 cells/ml.
Causes of Heifer Mastitis
One major cause is poor environmental hygiene. Heifers raised in dirty, wet, or muddy conditions are exposed to large numbers of mastitis-causing microorganisms.
Contaminated bedding, manure accumulation (heifers resting underneath trees during hot weather), and exposure to adult cows increases the risk of bacterial invasion into the teat canal.
Another important factor is fly control. Flies (mainly Horn flies) can carry pathogens from infected animals to healthy heifers, particularly during warm seasons. They often congregate around the udder and teats, facilitating the transmission of bacteria such as Staphylococcus aureus.
Teat and udder injuries also increase susceptibility to infection. Cuts, abrasions, and irritation caused by rough housing conditions, thorny vegetation, cross suckling, or aggressive behaviour among animals can damage the natural protective barriers of the teat, allowing bacteria to colonise the skin and increase the likelihood of mastitis at calving.
Nutritional deficiencies may weaken the immune system and reduce the animal’s ability to resist infections. Excessive body condition loss and elevated concentrations of β-hydroxybutyrate around calving are all associated with an increased risk of clinical mastitis in heifers. Inadequate levels of vitamins A and E, selenium, and other essential nutrients can compromise udder health and increase mastitis risk. Several host factors influence susceptibility to heifer mastitis. Older age at first calving, reproductive disorders, udder and teat edema, milk leakage, and premature opening of the teat canal before calving all increase the risk of early-lactation mastitis. These findings emphasize the importance of minimizing stress around calving, optimizing calving management, and reducing the incidence of dystocia and metabolic disease. Emerging evidence also suggests that genetic and immunological differences between heifers contribute to variation in susceptibility, indicating potential for long-term prevention through breeding strategies.
Prevention of Heifer Mastitis
Heifers are particularly susceptible to udder infections during late gestation and the periparturient period underscoring the importance of targeted preventive management during this critical window.
Farm-specific interventions that should be in place on any farm are:
1. Keep young and in calf heifers in a clean and hygienic environment and separate from adult animals – provide as much attention to this group of animals as spent on lactating animals.
2. Implement an effective and efficient fly control system.
3. Minimize the risk of negative energy balance before and after calving through appropriate transition feeding systems.
4. Reduce the incidence of udder edema through optimized peripartum management.
5. Minimize stress around calving (e.g. don’t move heifers to the calving pen when already in labour) and minimize incidence of dystocia and peripartum disease.
6. Improve general udder health management at the farm level to decrease the pressure of infection from older cows to heifers.
7. Control cross-suckling in calves and young stock.
8. Consider internal teat sealants prepartum where there is a high risk of environmental mastitis in the peripartum period. Confirm the presence of environmental mastitis first by bacteriology as some intramammary infections generally do not have a negative effect on milk production and might even protect against the major pathogens.