Effects of Vaccine Treatment and Temperament Classification on Intake and Feeding Behavior Responses to Bovine Viral Diarrhea Virus Challenge in Beef Steers

Objectives of this study were to examine the effects of multi-viral BRD vaccine treatment (VT) and temperament classification on DMI and feeding behavior responses following a BVDV challenge. Nellore-Angus F2 and F3 steers (N =364; BW 330 ± 48 kg) were assigned to 1 of 3 vaccine treatments within sire groups: non-vaccinated (NON), modified live (MLV), and killed (KV). Performance, DMI, and feeding behavior traits (bunk visit (BV) duration, BV eating rate, and meal duration) were monitored for 56 d during four 14-d periods, using a GrowSafe^® system. All steers were inoculated intranasally with BVDV type 1b field strain at the end of the first 14-d period. Exit velocity (EV) was measured and used to assign steers to 1 of 3 temperament classifications (TC; calm, moderate, or excitable) based on mean EV ± 0.5 SD. As expected DMI, ADG, gain:feed (G:F), BV and meal durations all decreased (P < 0.01) during period 2 post BVDV challenge, and subsequently increased during periods 3 and 4. ADG and G:F were not affected by VT or VT x period interaction. However, the BVDV-induced reduction in DMI was less for MLV than KV and NON steers (VT x Period; P < 0.05). Although there was not a VT x period interaction (P > 0.2), MLV steers had increased BV and meal durations (P < 0.01) and slower (P < 0.01) BV eating rate compared to KV and NON steers. Calm steers consumed more (P < 0.01) DMI (9.23 vs. 8.63 ± 0.23 kg/d) and had a numerically higher ADG (1.12 vs. 1.01 ± 0.11 kg/d) then excitable steers. Calm steers had 10% higher (P < 0.01) BV duration, 17% higher (P < 0.01) meal duration, and a 5% slower (P < 0.01) BV eating rate compared to excitable steers. The VT x TC interaction was not significant for DMI and ADG, but was for feeding behavior traits. Compared to KV and NON steers, MLV steers had higher (P < 0.01) BV and meal durations in both calm steers (11% and 13%) and excitable steers (6% and 13%, respectfully), but not in moderate temperament steers. These results suggest that the MLV vaccine mitigated the negative effects of BVDV challenge on DMI, which supports previous immune response findings. Moreover, VT appeared to alter feeding behavior patterns, with MLV steers having longer BV and meal durations and slower eating rates compared to KV and NON steers.