Effect of Original XPC in Receiving Diets on Newly Weaned Beef Steer Performance and Response to a Mannheimia Haemolytica Vaccination Challenge

The objective was to determine the effects of Original XPC^TM (Diamond V, Cedar Rapids, IA), a Saccharomyces cerevisiae fermentation product, in the diets of beef steers on total tract nutrient digestibility as well as feeding behavior and acute phase protein (APP) response following a vaccination challenge. Twelve days after arrival, 36 newly weaned crossbred beef steers (323 ± 12 kg) were blocked by BW and randomly assigned to one of three doses of XPC: 0 (CON), 14 (XPC14), or 28 (XPC28) g·steer·d^-1. Steers were fed via bunks capable of measuring individual intake and received ear tags (Cow Manager, Select Sires, Plain City, OH) that recorded real time ear surface temperature, rumination, and eating behavior. Body weights were collected on d -1, 0, 14, 28, 42, and 56. To determine diet digestibility, titanium dioxide was fed from d 12 to 27. All steers received a Mannheimia haemolytica vaccination (One Shot, Zoetis, Kalamazoo, MI) on d 34. Blood was collected prior to vaccination and on d 3, 6, 9, 11, and 14 post-vaccination for analysis of APP. Data were analyzed as a randomized complete block design using Proc Mixed of SAS (experimental unit = steer; 12 per treatment). Post-vaccination eating behavior, APP, and DMI data were analyzed as repeated measures. Digestibility of DM and OM on d 27/28 tended to be greater for XPC14 vs. XPC28 (P ≤ 0.07). Steers fed either dose of XPC exhibited greater CP digestibility compared to CON (P < 0.0001). Steers fed XPC14 exhibited greater ADG from d 28 to 56 vs. XPC28 (P = 0.05) and exhibited greater DMI than CON or XPC28 for the 15 d post-vaccination (P = 0.001). Haptoglobin and serum amyloid A concentrations peaked 3 d post-vaccination (day effect; P ˂ 0.0001) but did not differ due to treatment (P ≥ 0.14). Ceruloplasmin concentrations were lesser on d 14 post-vaccination for XPC14 vs. CON or XPC28 while treatment did not affect ceruloplasmin concentrations on other sampling days (treatment × day; P = 0.02). For the 15 d post-vaccination, CON had more non active min/d than XPC14 or XPC28 (P = 0.02). Steers fed XPC14 or XPC28 had lesser average, minimum, and maximum ear surface temperature vs. CON (P ≤ 0.01) during this period. Overall, these data suggest that steers fed XPC at 14 g/d responded better to a vaccination challenge than steers fed 0 or 28 g/d.