Maternal supplementation with <i>Bacillus</i> -based direct-fed microbials altered the maternal and offspring fecal microbiome

This study evaluated the effects of maternal supplementation of a <i>Bacillus</i>-based direct-fed microbial (DFM) on fecal microbiome of heifer-calf pairs. At the start of the study (day 0), 72 pregnant Brangus crossbred beef heifers (20 to 22 mo of age) were stratified by body weight (BW; 431 ± 31 kg) and body condition score (BCS; 6.0 ± 0.36) and randomly allocated into 1 of 12 bahiagrass pastures (1 ha and 6 heifers/pasture). Treatments were assigned to pastures and consisted of heifers supplemented with 1 kg/hd/d of soybean hulls added (BAC) or not (CON) with DFM containing <i>Bacillus subtilis</i> 810 and <i>B. licheniformis</i> 809 (3 g/hd/d; 6.6 × 10⁹ colony forming unit; Bovacillus; Novonesis, Lyngby, Denmark) from day 0 to 242 (139 ± 4 d prepartum to 104 ± 4 d postpartum). Calves were early weaned on day 242 and then allocated to drylot pens and fed the same diet until day 319. On days 271 and 287, calves were vaccinated against pathogens associated with bovine respiratory disease. Fecal samples were collected from 3 heifers per pasture on days 0, 90 and 180 and from 2 to 3 calves per pen on days 242 and 272. Shannon and Simpson diversity indexes tended to be greater (<i>P </i>= 0.09) for BAC vs. CON heifers. <i>Clostridium</i> and <i>Blautia</i> relative abundances on day 90 and average <i>Mogibacterium</i> relative abundance were lower (<i>P </i>≤ 0.03) for BAC vs. CON heifers, whereas <i>Bacteroides</i> and <i>Porphyromonas</i> relative abundances tended (<i>P </i>≤ 0.08) to be greater for BAC vs. CON heifers. Shannon diversity index did not differ (<i>P </i>≥ 0.14) between CON and BAC calves, whereas Simpson diversity index remained constant (<i>P </i>= 0.98) for CON calves from day 242 to 272 but increased (<i>P </i>= 0.02) for BAC calves from day 242 to 272. Effects of maternal treatment × day tended (<i>P </i>= 0.06) to be detected for <i>Paraprevotella</i> genus, which <i>Paraprevotella</i> relative abundance on day 242 was lower (<i>P </i>= 0.05) for BAC vs. CON calves on day 242, and did not differ (<i>P </i>= 0.89) between treatments on day 272. Relative abundance of <i>Bacteroides</i> was greater (<i>P </i>= 0.01), whereas <i>Slackia</i> was lower (<i>P </i>< 0.01) for BAC vs. CON calves. <i>Blautia, Butyrivibrio</i>, and <i>Methanobrevibacter</i> relative abundance tended (<i>P </i>= 0.08) to be lower for BAC vs. CON calves. In conclusion, exclusive maternal supplementation with a <i>Bacillus</i>-based DFM during gestation and early lactation modulated the fecal microbiota of both heifers and their offspring.