Immunostimulating effects of a commercial feed supplement in dairy heifers vaccinated with a Staphylococcus aureus bacterin
Eubanks, Valerie Joanne
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The purpose of this study was to evaluate the effect of a general immunostimulant feed supplement on amplifying dairy heifers’ immune response to Staphylococcus aureus vaccination. Blood and mammary immune parameters were measured. Serum anti-S.aureus titers were similar between supplement-treated heifers and unsupplemented controls indicating no beneficial effect of the feed supplement. Prevalence of overall intramammary infections (86% of heifers, 58% of quarters) and S. aureus intramammary infections (62.1% of heifers, 25.3% of quarters) was similar between treated heifers and unsupplemented controls. Musculoskeletal growth was also similar between treated and control heifers. However, L-selectin mRNA expression, phagocytic activity, and reactive oxygen species production was greater in treated heifers compared to controls, suggesting enhanced immunity in supplemented heifers prior to calving. Furthermore, treated heifers exhibited decreased prevalence of postpartum mastitis, decreased somatic cell counts, and increased milk yield compared to control heifers, although these differences were not statistically significant.