Submitted to: Beef International Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/17/2016
Publication Date: N/A
Interpretive Summary: Bovine respiratory disease is the leading cause of morbidity and mortality in feedlots in the United States and represents a major economic burden on the producer with an average cost of $23.60 spent per head for treatment. Currently, there are limited tools available to combat this disease. The primary treatment strategy currently implemented in feedlots today involves the use of antibiotics; however, increased scrutiny is being placed on the use of antibiotics in animal agriculture. Therefore, alternatives to antibiotics must be explored to combat respiratory disease. We have previously reported that yeast supplements can modulate the innate immune response in association with an acute immune challenge. Therefore, the objective of this study was to determine the effects of a yeast supplement on the immune response and to quantify differences in the breakdown of metabolic substrates in beef heifers fed a yeast supplement during a combined viral-bacterial challenge. Results from this study demonstrate that supplementation with a live yeast and a yeast cell wall product prior to exposure to a respiratory disease challenge reduced the severity of the illness. Specifically, the yeast supplemented cattle had reduced nasal lessions, lower neutrophil counts, and lower serum urea nitrogen consentrations. While there was no difference in the febrile response when cattle were fed the yeast supplement, the yeast supplemented cattle had decreased circulating neutrophils and a decreased inflammatory response in comparison the control cattle. Also, yeast supplementation tended to decrease the severity of nasal lesions in yeast supplemented heifers. Collectively, this data suggests that providing a combination of live yeast and yeast cell wall products may be beneficial in reducing the severity of bovine respiratory disease in feedlot cattle. This information will be of interest to feedlot producers, feedlot veterinarians, and scientists working in the field of beef cattle health and management.
Technical Abstract: Two treatments were evaluated in commercial feedlot heifers to determine the effects of a yeast supplement on immune and metabolic responses to a combined viral-bacterial respiratory disease challenge. Beef heifers (n = 32; 324 ± 19.2 kg BW) were selected and randomly assigned to one of two treatments and fed for 31 d: Control (CON), receiving no yeast supplement in the ration, or yeast (YEAST), control ration plus a combination live yeast (2.5 g'hd-1'd-1) and yeast cell wall (2.5 g'hd-1'd-1) supplement (Phileo-Lesaffre, Milwaukee, WI). On d -3 all cattle were challenged intra-nasally with 1x108 pfu BHV-1 and allowed to rest in outdoor pens for 3 d. On d 0, all cattle were challenged intra-tracheally with an average dose of 3 x107 cfu Mannheimia haemolytica, fitted with an indwelling jugular catheter and indwelling vaginal temperature recording device, and were moved into individual stanchions in an enclosed barn. Whole blood samples were collected at the time of BHV-1 challenge at 1-h (serum) or 2-h (complete blood cell counts) intervals from 0 to 8 h, and at 12, 24, 36, 48, 60, and 72 h relative to M. haemolytica challenge. Data were analyzed using the mixed procedure of SAS specific for repeated measures with fixed effects of treatment, time, and their interaction. There was no difference in cortisol concentration or vaginal temperature between treatments (P = 0.37). Although there was no treatment difference in total white blood cell count following BHV-1 challenge (P = 0.21), there was a tendency (P = 0.07) for cattle in the CON group to have greater neutrophils than YEAST. Serum haptoglobin concentration tended (P = 0.13) to be decreased in the YEAST group compared to CON. Cattle in the YEAST group had a greater serum glucose concentration relative to administration of the M. haemolytica challenge (P = 0.01) and decreased concentrations of serum urea nitrogen compared to CON (P = 0.03). There was no difference in serum NEFA concentration between YEAST and CON (P = 0.37). Nasal lesion score tended to be decreased in YEAST cattle compared to CON (2.5 vs. 3.19, P = 0.07). In summary, feeding a combination live yeast and cell wall yeast supplement tended to reduce the inflammatory response in beef heifers. Feeding the supplement also decreased the breakdown of metabolic substrates required to provide energy for the immune response to a respiratory disease challenge.