Effects of administration of a modified-live virus respiratory vaccine and timing of vaccination on health and performance of high-risk beef stocker calves

Abstract

A randomized, controlled field study was conducted to evaluate the efficiency of various management regimens using a pentavalent modified-live virus (MLV) respiratory vaccine containing bovine herpesvirus-1, bovine viral diarrhea virus types 1 and 2, parainfluenza-3 virus, and bovine respiratory syncytial virus. Crossbred beef calves (n=370) weighing 466 +/- 5.5 lb (212 +/- 2.5 kg) were acquired from auction markets. Calves were stratified by castrate status on arrival and assigned randomly to 1 of 3 experimental treatments: (1) initial MLV vaccine on day 0 (AMLV), (2) initial MLV vaccine on day 14 (DMLV), or (3) no vaccination with MLV vaccine until the end of the 42-day receiving period (NMLV). Least-squares means were evaluated using the contrasts: (1) vaccinated (VAC) vs NMLV, and (2) AMLV vs DMLV. Body weight was recorded on days 0, 14, 28, 42, and at the end of the grazing period, and health was monitored daily. Average daily gain was greater for DMLV vs AMLV from days 14 to 28 (P less than 0.01), and VAC vs NMLV from days 28 to 42 (P=0.04). However, performance was not different (P greater than or equal to 0.16) between VAC and NMLV from days 0 to 42. The overall incidence of clinical bovine respiratory disease did not differ (P greater than or equal to 0.82); however, there was a tendency (P=0.08) for increased relapse rate in NMLV calves compared to VAC. Results suggest that MLV vaccine administered to high-risk stacker calves on day 0 or 14 may reduce relapse rate; whereas, gain was reduced transiently when MLV vaccine was administered at day 0.