Effects of supplementing direct-fed microbials on health and growth of pre-weaning Gyr × Holstein dairy calves.

This study aimed to evaluate the effects of direct-fed microbials (DFM) on health and growth responses of pre-weaning Bos indicus × B. taurus (Gyr × Holstein) crossbred calves. Ninety newborn heifer calves [initial body weight (BW) 35 ± 4.0 kg] were used. At birth, calves were ranked by initial BW and parity of the dam and assigned to: 1) whole milk without DFM supplementation (CON; n = 30), 2) whole milk with the addition of 1.0 g/calf per day of a Bacillus-based DFM (BAC; n = 30), or 3) whole milk with the addition of 1.0 g/calf per day of BAC and 1.2 g/calf per day of Enterococcus faecium 669 (MIX; n = 30). Milk was fed individually during the study (77 d) and the BAC and MIX treatments were offered daily throughout the 77-d pre-weaning period. All calves were offered a starter supplement and corn silage starting on d 1 and 60 of age, respectively. Milk and starter supplement intake were evaluated daily, and BW was recorded on d 0 and at weaning (d 77). Diarrhea and pneumonia were assessed daily, and fecal samples were collected on d 0, 7, 14, 21, and at weaning (d 77) for assessment of the presence of bacterial and protozoal pathogens via qPCR. All data were analyzed using SAS (v. 9.4) with calf as the experimental unit and using single-df orthogonal contrasts (BAC + MIX vs. CON; BAC vs. MIX). Daily feeding of DFM, regardless of type, improved weaning BW. Odds ratio for occurrence of pneumonia was lower for DFM-supplemented calves, but occurrence of both did not differ between BAC and MIX calves. No Salmonella spp. or E. coli F41 were detected in any of the calves. The proportion of calves positive for E. coli F17 was greater for DFM calves on d 7 (92 and 96% vs. 81% for BAC, MIX, and CON, respectively), 21 (13 and 26% vs. 7% for BAC, MIX, and CON, respectively), and at weaning (48 and 35% vs. 22% for BAC, MIX, and CON, respectively). For C. difficile, more DFM calves were positive on d 7 (65 and 30% vs. 35% for BAC, MIX, and CON, respectively) and 14 (20 and 28% vs. 7% for BAC, MIX, and CON, respectively), but also greater for BAC vs. MIX on d 7. More CON calves were positive for C. perfringens on d 14 (14% vs. 3 and 8% for CON, BAC, and MIX, respectively) compared with DFM-fed calves. Incidence of calves positive for C. perfringens was greater in BAC vs. MIX on d 7 (50 vs. 18%), and greater for MIX vs. BAC at weaning (9 vs. 0%). For protozoa occurrence, a lower proportion of DFM calves were positive for Cryptosporidium spp. on d 7 (58 and 48% vs. 76% for BAC, MIX, and CON, respectively), but opposite results were observed on d 21 for Cryptosporidium spp. (3 and 11% vs. 0% for BAC, MIX, and CON, respectively) and Eimeria spp. on d 14 (7 and 8% vs. 0% for BAC, MIX, and CON, respectively) and 21 (50 and 59% vs. 38% for BAC, MIX, and CON, respectively). In summary, DFM feeding alleviated the occurrence of pneumonia, improved growth rates, while also modulating the prevalence of bacteria and protozoa in pre-weaning Gyr × Holstein calves.

Effects of supplementing a Bacillus-based direct-fed microbial on performance, nutrient digestibility, rumen fermentation characteristics, and metabolic responses of lactating dairy cows.

This experiment was conducted to evaluate the effects of feeding a Bacillus-based direct-fed microbial (DFM) on performance, nutrient digestibility, rumen fermentation, and metabolic response of lactating dairy cows. Sixty-eight lactating (50 ± 6 d in milk) Holstein-Friesian (n = 20) and Swedish Red (n = 48) cows were enrolled to a 15-wk experiment. Cows were blocked by breed, lactation number, and days in milk and, within blocks, assigned to 1 of the 2 treatments: (1) basal partial mixed ration (PMR) without DFM (n = 34; CON) or (2) basal PMR with the addition of 3 g/head per day of a DFM containing Bacillus licheniformis and Bacillus subtilis (n = 34; DFM). The DFM was mixed in a protein pellet, whereas the CON group was fed the same pellet without DFM (1 kg/cow per day). The PMR contained 53% clover grass silage and 47% compound feed plus 3 kg of a concentrate (dry matter basis) offered during milking. Milk yield and production efficiency were recorded daily, whereas milk samples were collected for 24 h every second week of the study for milk composition. During the experimental period, fecal, rumen fluid, and blood samples were collected from each cow for apparent nutrient digestibility, rumen fermentation, and metabolic responses, respectively. All data were analyzed using the MIXED procedure of SAS. No treatment effects were observed on cows final body weight and daily dry matter intake. However, cows fed DFM had a greater milk yield, milk production efficiency, lactose and total solids yield, and also tended to have a greater energy-corrected milk production efficiency and milk protein yield. No significant differences were observed on nutrient digestibility and total volatile fatty acids, but molar proportion of acetate was greater for cows fed DFM. In contrast, molar proportion of propionate was greater and butyrate tended to be greater for CON. Cows fed DFM had greater mean plasma insulin-like growth factor-I (IGF-I), but no differences were observed for plasma glucose and insulin. In summary, supplementing a Bacillus-based DFM benefited productive responses of lactating dairy cows, while also modulating rumen fermentation and serum IGF-I.

Evaluation of a Bacillus-based direct-fed microbial probiotic on in vitro rumen gas production and nutrient digestibility of different feedstuffs and total mixed rations.

We evaluated the effects of a Bacillus-based direct-fed microbial (DFM) on total in vitro gas production, dry matter (DM), neutral detergent fiber (NDF), and starch disappearance of different feedstuffs and total mixed rations (TMR) in three different experiments. In experiment 1, six single fiber-based feedstuffs were evaluated: alfalfa hay, buffalo grass, beet pulp, eragrostis hay, oat hay, and smutsvinger grass. Experimental treatments were control (with no probiotic inoculation; CON) or incubation of a probiotic mixture containing Bacillus licheniformis and B. subtilis (3.2 × 109 CFU/g; DFM). The calculation of DFM dose under in vitro conditions was based on the assumption of a rumen capacity of 70 liter and the dose of 3 g of the DFM mixture/head/d (9.6 × 109 CFU). Total in vitro gas production, DM, and NDF disappearance were evaluated at 24- and 48 h posttreatment incubation. Mean treatment effects were observed at 24- and 48 h gas production (P < 0.0001), as DFM incubation increased in vitro gas production by 5.0% and 6.5%, respectively. For nutrient digestibility, mean DM digestibility was increased at 48 h (P = 0.05), whereas mean NDF digestibility increased at both timepoints by incubating DFM in vitro (P ≤ 0.02). In experiment 2, nine commercial dairy TMR were collected and evaluated for the same variables and treatments described in experiment 1, with the additional analysis of starch digestibility at 7 h post in vitro incubation. The only difference was the concentration of the DFM included, being representative for a dosage of 8.8 × 109 CFU/head/d. In vitro gas production was increased only at 48 h due to DFM incubation (P = 0.05), whereas DM and NDF digestibility were improved at 24 and 48 h (P ≤ 0.02). No treatment effects were observed on in vitro starch digestibility (P = 0.31). In experiment 3, a combined analysis of DM and NDF digestibility was performed by using quality values (NDF and crude protein or CP) of 16 substrates. Regardless of CP and NDF levels of the substrates, DFM improved in vitro 24 and 48 h DM and NDF digestibility (P ≤ 0.03). In summary, incubating a Bacillus-based DFM (B. licheniformis and B. subtilis; BOVACILLUS) improved mean in vitro gas production, DM, and NDF digestibility of single feedstuffs and commercial dairy TMR, highlighting the potential of this combination of Bacillus spp. to improve nutrient utilization, mainly fiber.