Effects of feeding a Bacillus -based direct-fed microbial during a 60-day receiving program on performance and physiological responses of feeder cattle

Lay Summary The early days after cattle arrive at the feedlot are among the most difficult times in beef production. During this receiving period, calves experience multiple stressors, including weaning, transportation, vaccinations, mixing with unfamiliar animals, and adapting to a new environment, often within a very short timeframe. These stresses can weaken the immune system and negatively affect health and growth. Feed additives known as biotics (also called probiotics or direct-fed microbials) have gained attention because they might improve nutrient digestion, support animal health, help cattle cope with stress, and promote more efficient growth. Among these, Bacillus species are especially promising because they remain stable during feed processing and have been shown to support feed intake, improve nutrient use, enhance feed efficiency, and reduce illness in high-risk cattle. Hence, this study investigated how adding a Bacillus-based direct-fed microbial to the diet affected growth, health, and stress-related responses of feeder calves during the first 60 days after arrival at the feedlot. Results showed a tendency to increase feed intake even though overall performance was not affected. Supplementing cattle diets with a Bacillus-based direct-fed microbial helped reduce stress, as shown by lower levels of stress- and inflammation-related markers in the blood. Overall, these results suggest that supplementing cattle with a Bacillus-based direct-fed microbial can increase feed intake while helping calves better cope with stress during the feedlot receiving period.