|Runyan, Chase - TEXAS A&M UNIVERSITY|
|Downey-slinker, Erika - ELANCO ANIMAL HEALTH, INC.|
|Hairgrove, Thomas - TEXAS A&M UNIVERSITY|
|Sawyer, Jason - TEXAS A&M UNIVERSITY|
|Herring, Andy - TEXAS A&M UNIVERSITY|
Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2017
Publication Date: 12/12/2017
Citation: Runyan, C.A., Downey-Slinker, E.D., Ridpath, J.F., Hairgrove, T.B., Sawyer, J.E., Herring, A.D. 2017. Feed intake and weight changes in Bos indicus-Bos taurus crossbred steers following Bovine Viral Diarrhea Virus Type 1b challenge under production conditions. Pathogens. 6(4):66. https://doi.org/10.3390/pathogens6040066.
Interpretive Summary: Commercial cattle in the US come from two different groups. Bos taurus breeds are derived from British and European stock, and are best suited to cooler climates. Bos indicus cattle are developed from lines of the Indian Zebu, and are better suited to tropical climates. Many beef cattle raised in the Southwest US are a cross of Bos indicus-Bos taurus. Most of the research done on vaccination to prevent infections with bovine viral diarrhea virus (BVDV) has been done using Bos taurus breeds. The goal of this study was to examine BVDV vaccination in Bos indicus-Bos taurus crossbred steers, of known genetic lines, raised under typical commercial conditions. It was found that the offspring of different sires responded differently to vaccination and viral infection. However, there was not a simple correlation between sires and better response to vaccination and/or resistance to infection. The authors concluded that a number of different traits contribute vaccine response and resistance to disease making identification and selection for traits for improved disease response very complicated. They further noted that fever in vaccinated Bos indicus cattle may not be an indicator of disease, as vaccinated animals that responded to a viral challenge with fever displayed higher performance measures. This finding is important because the development of fever following infection in vaccinated animals has been equated with vaccine failure in the past.
Technical Abstract: Bovine viral diarrhea virus (BVDV) has major impacts on beef cattle production worldwide, but the understanding of host animal genetic influence on illness is limited. This study evaluated rectal temperature, weight change and feed intake in Bos indicus crossbred steers (n = 366) that were challenged with BVDV Type 1b, and where family lines were stratified across three vaccine treatments of modified live (MLV), killed, (KV) or no vaccine (NON). Pyrexia classification based on 40.0 C threshold following challenge and vaccine treatment were investigated for potential interactions with sire for weight change and feed intake following challenge. Pyrexia classification affected daily feed intake (ADFI, P = 0.05), and interacted with day (P < 0.001) for ADFI. Although low incidence of clinical symptoms was observed, there were marked reductions in average daily gain (ADG) and cumulative feed intake during the first 14 day post-challenge; ADG (CV of 104%) and gain efficiency were highly variable in the 14-day period immediately post-challenge as compared to the subsequent 14-day periods. A sire x vaccine strategy interaction affected ADFI (P < 0.001), and a sire by time period interaction affected ADG (P = 0.03) and total feed intake (P = 0.03). This study demonstrates that different coping responses may exist across genetic lines to the same pathogen, and that subclinical BVDV infection has measurable impact on cattle production measures.