Words by: Scott McDougall

A beta-carotene feed additive has been investigated as a way of treating subclinical mastitis.
Control of mastitis in dairy herds is well understood, with adherence to strict protocols generally leading to low levels of infection in most herds. However, even in well-managed herds there remain some animals that carry subclinical infections. Antibiotic treatment of these subclinical infections is generally not advisable as the cost of milk discarded after treatment likely outweighs the benefit. A non-antibiotic approach, however, could be a useful strategy to help the infection.
Veterinarian Scott McDougall from Cognosco, the research group at Waikato’s Anexa Veterinary Services, investigated use of a special form of beta-carotene (the precursor to vitamin A) in treating existing subclinical mastitis cases.
Avivagen, a Canadian animal health company, approached him about running a trial to assess their non-antibiotic OxC-beta product against subclinical mastitis and he was intrigued to investigate further, McDougall said.
“OxC-beta is formed by complete and controlled oxidation of beta-carotene and has been shown to support immune function by increasing the ability of the cows natural defences to detect and destroy bacteria while maintaining moderate levels of inflammation.”
From four spring-calving dairy herds Cognosco selected high somatic cell-count (>200,000 cells/mL) cows with infection confirmed by microbiology and an elevated SCC in one or more quarters. Cows were then randomly assigned within each herd to be fed meal (0.5 kg/cow/day) with OxC-beta or without OxC-beta for six weeks. The two treatment groups were balanced within each herd by breed, age, and days in milk at the commencement of feeding.
Quarter-level somatic cell count data, herd test data, and clinical mastitis treatment records were collected and analysed. A range of different bacterial species was isolated prior to treatment with the most common bacteria being minor pathogens. However, a number of quarters were infected with major pathogens including S. aureus, S. dysglactiae, and S. uberis.
About twice as many quarters from cows fed OxC-beta cured than from the control group (13.9% vs 6.9%). Fewer of the quarters in cows fed OxC-beta had clinical mastitis in the six weeks after the start of feeding compared with quarters from control fed cows (0.8 % vs 4.4%). But there was no effect of OxC-beta feeding on the quarter-level somatic cell count after treatment, the herd test somatic cell count, milk production L/cow/day, or milk fat or protein percentage.
Results suggest the immune supporting actions of OxC-beta may aid in control of mastitis by reducing the number of infected animals and reducing the risk of subsequent clinical mastitis.