Effects of bacterial direct-fed microbial mixtures offered to beef cattle consuming finishing diets on intake, nutrient digestibility, feeding behavior, and ruminal kinetics/fermentation profile.

Effects of bacterial direct-fed microbial (DFM) mixtures on intake, nutrient digestibility, feeding behavior, ruminal fermentation profile, and ruminal degradation kinetics of beef steers were evaluated. Crossbred Angus ruminally cannulated steers (n = 6; body weight [BW] = 520 ±â€…30 kg) were used in a duplicated 3 × 3 Latin square design and offered a steam-flaked corn-based finisher diet to ad libitum intake for 3, 28-d periods. Treatments were 1) Control (no DFM, lactose carrier only); 2) Treat-A (Lactobacillus animalis, Propionibacterium freudenreichii, Bacillus subtilis, and Bacillus licheniformis), at 1:1:1:3 ratio, respectively; totaling 6 × 109 CFU (50 mg)/animal-daily minimum; and 3) Treat-B, the same DFM combination, but doses at 1:1:3:1 ratio. Bacterial counts were ~30% greater than the minimum expected. Data were analyzed using the GLIMMIX procedure of SAS with the model including the fixed effect of treatment and the random effects of square, period, and animal (square). For repeated measure variables, the fixed effects of treatment, time, and their interaction, and the random effects of square, period, animal (square), and animal (treatment) were used. Preplanned contrasts comparing Control × Treat-A or Treat-B were performed. Intake and major feeding behavior variables were not affected (P ≥ 0.17) by treatments. Steers offered Treat-A had an increased (P = 0.04) ADF digestibility compared with Control. Steers offered Treat-A experienced daily 300 min less (P = 0.04) time under ruminal pH 5.6, a greater (P = 0.04) ruminal pH average and NH3-N concentration (P = 0.05) and tended (P = 0.06) to have a lower ruminal temperature compared to Control. Ruminal VFA was not affected (P ≥ 0.38) by treatments. Steers offered Treat-A increased (P = 0.02) and tended (P = 0.08) to increase the ruminal effective degradable NDF and ADF fractions of the diet-substrate, respectively. When the forage-substrate (low quality) was incubated, steers offered Treat-A tended (P = 0.09) to increase the effective degradable hemicellulose fraction compared to Control. In this experiment, the bacterial combinations did not affect intake and feeding behavior, while the combination with a greater proportion of B. licheniformis (Treat-A) elicited an improved core-fiber digestibility and a healthier ruminal pH pattern, in which the ruminal environment showed to be more prone to induce the effective degradability of fiber fractions, while also releasing more NH3-N.

During the finishing phase, a high-energy diet offers benefits related to beef cattle growth and development. However, it is essential to acknowledge that finisher diets are energy-dense and can pose digestive challenges, such as subacute ruminal acidosis. Digestive disturbances negatively affect animal well-being, growth performance, and economic returns. To address digestive challenges endured by animals on high-energy diets, the current experiment focused on the addition of bacterial direct-fed microbial (DFM) mixtures. A unique combination of bacterial DFM containing Lactobacillus animalis, Propionibacterium freudenreichii, Bacillus subtilis, and Bacillus licheniformis was evaluated. These bacteria have been individually reported to improve cattle nutrient utilization, digestibility, ruminal function, and maintain ruminal pH. The study aimed to investigate the effects of this specific microbial combination and doses when added to beef cattle finisher diets. The DFM mixtures offered seemed to not affect intake and major feeding behavior variables. The DFM combination containing a greater proportion of B. licheniformis (Treat-A) seemed to elicit an improved total tract core-fiber digestibility, and a safer ruminal pH pattern. The ruminal environment was shown to be more prone to improve the ruminal effective degradability of fiber fractions, while also releasing more NH3­N.

The effects of a Nutritional Packet (live yeast, vitamins C and B1, and electrolytes) offered during the final phase of feedlot steers on growth performance, nutrient digestion, and feeding behavior.

The effects of a Nutritional Packet offered to beef steers during the final 64 d of the feedlot-finishing phase on growth performance, carcass characteristics, nutrient digestibility, and feeding behavior were evaluated. Angus-crossbred steers (N = 120; initial body weight = 544 ± 52 kg) were assigned to 30 pens (4 steers per pen; 15 pens per treatment) in a randomized complete block design where pen was the experimental unit. A steam-flaked corn-based finishing diet was offered to ad libitum, and the treatments were as follows: 1) control and 2) 30 g per steer-daily (dry matter basis) of the Nutritional Packet. The Nutritional Packet was formulated to provide 1.7 × 1010 CFU per steer-daily of Saccharomyces cerevisiae, 162 mg per steer-daily of vitamin C; 400 mg per steer-daily of vitamin B1; 2.4 g per steer-daily of NaCl, and 2.4 g per steer-daily of KCl. Data were analyzed using the GLIMMIX procedure of SAS with the fixed effect of treatment and the random effect of block. The average daily gain (P = 0.89), dry matter intake (P = 0.57), and gain efficiency (P = 0.82) were not affected by the inclusion of the Nutritional Packet. Digestibility of dry and organic matter, and neutral and acid detergent fiber increased (P ≤ 0.02) for steers offered the Nutritional Packet, while a trend for the same response was observed for hemicellulose (P = 0.08). The 12th rib backfat thickness increased (P = 0.02) for carcasses of steers offered the Nutritional Packet, followed by a greater (P = 0.03) calculated yield grade, whereas other carcass traits were not affected (P ≥ 0.32). While the steers under the control diet decreased behavior activities on day 63, a consistent pattern of feeding behavior measurements (activity min/d and min/kg of dry and organic matter, fiber fractions, and digestible nutrients) were observed for steers consuming the Nutritional Packet during both feeding behavior assessment periods (treatment × period interactions, P ≤ 0.03). Overall time (min/d) spent on rumination, drinking, active, chewing, and resting were not affected (P ≥ 0.28) by treatments. The Nutritional Packet offered to steers during the final 64 d on feed induced an improvement in apparent digestibility of nutrients and carcass fat deposition, without affecting growth performance or other carcass quality indices. Such effects associated with the more consistent feeding behavior of steers receiving the Nutritional Packet may warrant a shorter time on feed during the final portion of the finishing phase.

Excessive intake of rapidly fermentable nutrients by feedlot cattle can result in clinical or subclinical disorders that impair nutrient digestion, while negatively affecting animal development and health. Incidences of subclinical digestive disturbances may increase during the last days on feed in cattle fed in confinement. Manipulation of diets with probiotics (live yeast), vitamins (C and B1), and electrolytes (NaCl and KCl) to aid subclinical digestive disorders faced by cattle offered high-energy diets was addressed in the current experiment. The use of such nutritional technologies is based on previous reports that these technologies can stabilize ruminal pH, improve nutrient digestibility, enhance rumen microbial growth and energy metabolism, reduce oxidative stress, augment immune function, and prevent vitamin deficiencies induced by energy-dense diets. Therefore, it was important to investigate the effects of a packet containing these technologies during the feedlot final days on feed. When offered to steers during the final 64 d prior to harvest, a Nutritional Packet containing live yeast, vitamins C and B1, and electrolytes improved digestibility of nutrients and carcass fat deposition, while reducing variation in feeding behavior. Such effects may warrant an earlier harvest date when animals receive the packet.