Maternal pre- and postpartum supplementation of a Bacillus-based DFM enhanced cow and calf performance.

This study evaluated the effects of maternal supplementation of a Bacillus-based direct-fed microbial (DFM) on the physiology and growth performance of Bos indicus-influenced cow-calf pairs. On day 0 (~139 d before expected calving date), 72 fall-calving, Brangus crossbred beef heifers (20 to 22 mo of age) pregnant with first offspring were stratified by their initial body weight (BW; 431†±†31 kg) and body condition score (BCS; 6.0†±†0.36; scale 1 to 9), and randomly allocated into 1 of 12 bahiagrass pastures (1 ha and six heifers per pasture). Treatments were randomly assigned to pastures (six pastures per treatment) and consisted of heifers supplemented with 1 kg/d of soybean hulls (dry matter, DM) that was added (BAC) or not (CON) with DFM containing Bacillus subtilis and B. licheniformis (Bovacillus; Chr. Hansen A/S, Hørsholm, Denmark). Treatments were provided from days 0 to 242 (139†±†4 d prepartum to 104†±†4 d postpartum). Calves were weaned on day 242 (96†±†30 d of age) and then allocated into 1 of 16 drylot pens and fed the same concentrate at 3.25% of BW (DM) until day 319. Maternal treatment effects were not detected (P†≥†0.29) for herbage allowance and forage chemical composition. Heifer BCS on days 39 and 63 tended (P†≤†0.09) to be greater for BAC vs. CON heifers, whereas heifer BCS on day 91 was greater (P†=†0.01) for BAC vs. CON heifers. Heifer BCS did not differ (P†≥†0.20) between treatments on days 179 and 242. Plasma glucose concentration did not differ from days 0 to 63 (P†≥†0.14) but were greater (P†<†0.01) on day 179 and tended (P†=†0.09) to be greater on day 242 for BAC vs. CON heifers. Calf BW at birth, ADG from birth to weaning, and BW at weaning did not differ (P†≥†0.19) between treatments, but calf BW at drylot exit (day 319) was greater (P†=†0.05) for BAC vs. CON calves. Maternal treatment effects were not detected (P†≥†0.42) for calf serum concentration of IgG at birth and postvaccination plasma concentrations of glucose, cortisol, and haptoglobin. Serum titers against bovine respiratory syncytial virus (BRSV) were greater (P†=†0.04) for BAC vs. CON calves on day 287, whereas seroconversion against parainfluenza-3 virus (PI-3) was greater (P†<†0.01) for BAC vs. CON calves on day 271. Thus, maternal supplementation of a Bacillus-based DFM increased prepartum BCS gain and postpartum plasma glucose concentration of heifers and led to positive carryover effects on postweaning BW gain and humoral immune response in their offspring.