Effects of Prepartum Supplementation and Yeast Fermentation Products on the Progesterone‐Modulated Transfer of Passive Immunity in Bos indicus Cows

ABSTRACT Inadequate colostrum intake increases risks of calf morbidity and mortality. This study investigated the effects of prepartum and early postpartum supplementation and yeast fermentation products on late‐pregnant Bos indicus cows, and the role of progesterone in mediating passive immunity transfer. Thirty‐six Brahman cows were allocated to three treatment groups: Control (ad libitum Rhodes grass hay), Supp (Control plus 1 kg/day supplement) and SCFP (Supp plus 14 g/day Saccharomyces cerevisiae fermentation products). Treatments started 30 days before the expected calving date and continued until 14 days postpartum. Cow plasma samples were collected three times a week (Monday, Wednesday and Friday), and modelled to reflect daily changes in progesterone leading up to calving. Calf plasma samples were taken twice within the first 5 days of life, and colostrum samples were collected 6–12 h post‐calving. Live weights of both cows and calves were measured three times a week for 14 days before and after calving. Data were analysed using a linear mixed‐effects model, and plasma progesterone concentration was assessed with a segmented mixed model. Supplementation (Supp vs. Control) improved cow nutritional status during the prepartum period, increasing dry matter, protein and metabolizable energy intake ( p < 0.05), resulting in higher plasma urea ( p < 0.01) and lower plasma non‐esterified fatty acids ( p < 0.01) and beta‐hydroxybutyrate ( p = 0.01) during the last week before calving. Supplementation reduced plasma progesterone concentration during the 3 days before calving ( p < 0.05), which was associated with enhanced transfer of maternal IgG into colostrum ( p = 0.03) and improved calf growth ( p = 0.01). Yeast fermentation products (SCFP) further improved passive immunity transfer to calves ( p = 0.02). These findings highlight the effectiveness of short‐term prepartum supplementation, especially with yeast fermentation products, and the important role of progesterone in mediating passive immunity transfer.