Mastitis in dairy heifers: initial studies on prevalence and control

Area of Science:

• Veterinary Medicine
• Animal Science
• Dairy Science

Background:

• Intramammary infections (IMI) are prevalent in dairy heifers, with high rates observed in heifers of breeding age and pregnant heifers.
• Subclinical and clinical mastitis present challenges, impacting mammary tissue development and leading to inflammation.

Purpose of the Study:

• To determine the prevalence of mastitis in heifers.
• To evaluate the efficacy of prepartum antibiotic infusion for controlling mastitis.
• To assess the impact of treatment on somatic cell count (SCC) and milk yield.

Main Methods:

• Prevalence assessment of IMI in heifers using bacterial isolation and SCC measurements.
• Histological examination of mammary tissues to evaluate inflammation and tissue damage.
• Evaluation of a one-time antibiotic infusion for nonlactating cows in infected quarters prepartum.
• Assessment of prophylactic treatment for uninfected quarters prepartum.
• Comparison of milk yield and SCC between treated and untreated heifers.

Main Results:

• IMI prevalence was 97% in heifers and 75% in quarters, with Staphylococcus aureus being a common isolate.
• Prepartum antibiotic infusion reduced IMI incidence by 59% at calving and achieved >90% cure rate for Staph. aureus.
• Prophylactic treatment reduced new Streptococcus sp. IMI by 93%.
• Treated heifers had 50% lower mean SCC and 10% greater milk yield over the first two months of lactation.
• Fly control in herds was associated with lower IMI prevalence.

Conclusions:

• Mastitis prevalence and SCC in dairy heifers are higher than previously recognized.
• Therapeutic products for nonlactating cows administered during pregnancy effectively control mastitis at calving.
• Prepartum treatment strategies improve udder health and milk production in dairy heifers.