Influence of autolyzed yeast on the health of immunologically immature calves

Autolyzed yeast is a supplement option for calves due to its ability to stimulate the immune system and performance; however, there are few studies about the effect of different yeast derivatives. Autolyzed yeast is rich in immunomodulatory substances, such as mannan oligosaccharides and β-glucans. These substances enhance the innate and humoral immunity of calves, resulting in greater intestinal and respiratory health. Thus, the objective of the study was to evaluate whether supplementation with autolyzed yeast improves the health of calves, in the challenge of naturally acquired Eimeriosis and bovine respiratory disease (BRD). Twenty Holstein calves aged 15 days, which had already suckled colostrum, were studied for 36 days. At 15 days of life all animals had naturally acquired Eimeriosis. They were challenged with an intranasal BRD vaccine at 30 days of age. The Supplemented group (n=10) received autolyzed yeast (10 g animal -1 day -1), once a day in milk for 36 days, and the Control group (n=10) was not supplemented throughout the experiment. Blood neutrophil: lymphocyte ratio, oxidative metabolism of neutrophils (OM), serum immunoglobulins and haptoglobin, occurrence of diarrhea, BRD, and weight gain were measured. After vaccination, all animals increased the blood neutrophil: lymphocyte ratio, but only the control group showed a 20% reduction in OM three days after the vaccine. The supplement affected the immune response, preserving OM, increasing serum IgA levels by 10% (P=0.006), and reducing haptoglobin serum levels (P=0.05). In addition, the supplement attenuated diarrhea and BRD, which allowed for greater weekly weight gain (difference of 2 kg between treatments, P