Using different levels of direct-fed microbials during an acidosis challenge and the effects of distillers grains on feeding behavior in the feedlot

Ruminal acidosis is a prevalent, costly metabolic disorder in beef feedlot cattle characterized by low rumen pH and can lead to a multitude of health problems and poor animal performance. Direct-fed microbials (DFM) are naturally occurring microorganisms that can be used to improve rumen fermentation and alleviate nutritional disorders. The objective was to determine the effect of different levels of a DFM to mediate a subacute acidosis challenge in beef cattle. Eighteen ruminally-cannulated steers (BW = 662 ± 90 kg) were used in a completely randomized design with 6 steers in each period. Two steers in each period were randomly assigned to one of three treatments: blank media (NCON), a low dose of Megasphaera elsdenii at 108 CFU/day and proprietary strain (LME), and a high dose of Megasphaera elsdenii at 109 CFU/day and proprietary strain (HME). A basal diet (45% forage) was fed ad libitum on d 1-7. On d 6-12, all treatments were dosed before feeding. To induce acidosis, steers were fasted for 24 h on d 8 and were fed the challenge diet (10% forage) ad libitum on d 9-15. On d 16-18, all steers were fed the basal diet for the recovery phase. Data were analyzed as repeated measures using the MIXED procedure of SAS 9.4. Dry matter intake was not affected (P = 0.76) by treatment. Rumen pH, redox, ammonia, and volatile fatty acids were not affected by treatment (P ≥ 0.11). A treatment by time effect (P < 0.01) was observed for lactate levels; LME and HME had decreased lactate levels from 9-15 h after feeding on d 9 compared with NCON. A tendency for a treatment by time effect (P = 0.08) was observed for butyrate; HME had greater butyrate 21 and 24 h after feeding on d 9 compared with NCON and LME. Time affected (P < 0.01) ruminal pH with a marked decrease on d 9 and increase on d 18. Rumen redox was also affected by time (P < 0.01) and peaked on d 10, but did not return to baseline until d 18. Overall, results indicate M. elsdenii in HME and LME can decrease initial lactate accumulation during subacute acidosis in feedlot cattle.\nThe objective of experiment 2 was to determine the effect of low inclusion levels of DDG on feeding behavior in heifers consuming a high moisture corn-based diet in the finishing phase. Simmental × Angus heifers (N = 90; 323 ± 50 kg) were fed for 180 d. Heifers were blocked by initial BW into 2 groups, stratified by sire, and assigned to 15 pens with 6 heifers each. Pens were randomly assigned to 1 of 3 dietary treatments: 1) 0% dried distillers grains inclusion (0DG), 2) 7% dried distillers grains inclusion (7DG), or 3) 14% dried distillers grains inclusion (14DG). Heifers were fed in GrowSafe (GrowSafe Systems Ltd., Airdrie, AB, Canada) bunks for determination of individual feed intake and feeding behavior. Distillers grains was replaced with high moisture corn, soybean meal, and urea. Heifers were weighed on consecutive days upon start of trial and before slaughter. On d 181, heifers were slaughtered, and carcass data were collected. Data were analyzed using the MIXED procedure of SAS 9.4. Dietary treatments did not affect (P > 0.59) body weight, average daily gain, and G:F. Longissimus muscle (LM) area was affected (P = 0.02) by distillers inclusion with 7DG having the smallest LM area, 14DG being intermediate and 0DG the largest. There was a treatment by time effect (P = 0.05) for DMI with 0DG having increased DMI compared to 7DG and 14DG for the last 70 d of the trial; however, differences in overall DMI were not detected. Treatment affected (P > 0.01) bunk visit duration and head down count with 7DG and 14DG having less minutes per day. Bunk visit frequency was also less variable (P = 0.02) for both distillers treatments despite no effect (P ≥ 0.58) on variation in bunk visit duration and head down. Both diets including DDG also had a tendency (P = 0.08) to have decreased variation in DMI. Heifers fed 14DG also had a tendency (P = 0.06) to have less variation in meal frequency. However, heifers fed 0DG had a tendency (P = 0.07) less variation in meal duration. While dietary inclusion of distillers grains had minimal effects on overall heifer performance, bunk visit duration and head down count was decreased with dietary inclusion of distillers grains. Therefore, low levels of distillers inclusion can affect feeding behavior of heifers fed high moisture corn-based diets during the finishing phase.

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