59 Neutrophils and respiratory health of feedlot cattle supplemented with autolized yeast

Abstract

Abstract The objective of this study was to evaluate whether autolyzed yeast (AY) in the diet interferes with the innate immunity and healthy of feedlot finished steer. At 0, 14, 42, 70, and 105 days of feedlot, the following were measured: neutrophil-lymphocyte ratio (N/L), neutrophilic oxidative metabolism, and respiratory disease indicators (frequency of animal with mucopurulent nasal secretion and orbital temperature) and frequency of pneumonia (histopathological analyses at slaughter day). For this, 36 ½ Angus steers (average BW 330kg and 11 months of age), were distributed in three treatments, with 12 animals each: Control; YA 4g (4g/animal/day, RumenYeast®); and AY 7g (7g/animal/day, RumenYeast®) for 105d. For all results, significant data were considered that show significance level P ≤ 0.05 and statistical trend, 0.05 > P < 0.1. On days 42 and 70, the AY 4g increased neutrophil oxidative metabolism (P = 0.06 and 0.01) and reduced N:L ratio (P = 0.08 and 0.01) comparing to the control group. This neutrophil oxidative metabolism increase was punctual for AY 7g, at 70d (P = 0.01), but the reduction of the N:L ratio occurs at 42 and 70d (P = 0.08 and 0.01). These immune increments promoted fewer respiratory diseases indicators, especially in the AY 4g, observed by a higher frequency of animals without nasal secretion at 42, 70 e 105d comparing to the control group (P = 0.03, 0.001 and 0.001), a lower orbital temperature at 105d (P = 0.02), and a lower frequency of pneumonia (P = 0.06). The AY 7 showed a higher frequency of animals with nasal secretion 14d (P = 0.04) and a lower frequency of animals without mucopurulent nasal secretion at 42 and 70d (P = 0.03 and 0.001), without significant difference for orbital temperature or pneumonia comparing to the other groups. We conclude the autolyzed yeast included in the diet improved the neutrophils functions of the animal and the health of the respiratory tract of feedlot cattle, especially when used at 4g/animal/day.