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257
Ruminal Volatile Fatty Acid Concentration and Microbial Populations As a Proxy for of Feed Efficiency in Beef Steers

Sunday, July 9, 2017
Exhibit Hall (Baltimore Convention Center)
P.B. Anusha I.K. Bulumulla, Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, Canada
Meng M Li, Department of Dairy Science, Virginia Tech, Blacksburg, VA
Yanhong Chen, Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, Canada
Fuyong Li, Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, Canada
Robin R. White, Virginia Tech, Blacksburg, VA
Mark D. Hanigan, Department of Dairy Science, Virginia Tech, Blacksburg, VA
Graham Plastow, Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, Canada
Le Luo Guan, Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, Canada

Breeding and management of animals to achieve improved feed efficiency is a significant priority for the beef industry. Feed conversion ratio (FCR) and residual feed intake (RFI) have become popular measurements for feed efficiency, although both have limitations and practical challenges. The identification of additional, cost-effective indicators of feed efficiency is needed to improve breeding programs. We hypothesized that volatile fatty acids (VFAs), the end products of rumen microbial fermentation and the primary energy source for ruminants, could potentially dictate feed utilization for growth and production. In this study, we tested whether residual VFA (rVFAs) could serve as a predictor of feed efficiency. Rumen content was collected from a total of 204 beef (Angus, Charolais and Kinsella composite) steers raised under a Growsafe® system, and VFA concentrations (mol/L) were analyzed by gas chromatography. Microbial populations were estimated using total copy numbers of 16S rRNA genes for bacteria and archaea using quantitative PCR (qPCR). Animal phenotypic measures including body weight (BW), dry matter intake (DMI), average daily gain (ADG), feeding frequency, RFI and carcass performances were collected. The feed was collected at the time of rumen sample collection, and its nutrient content was analyzed. VFA concentrations and production rates were predicted using the Molly mathematical model for each animal based on observed BW, DMI, and ration composition. Residual VFA concentrations were calculated as observed minus predicted VFA concentration. The relationships among digestion parameters and rVFA were tested using stepwise, backward linear regression, which was also used to test rVFA as a predictor of feed efficiency. Residual acetate (ResAc), propionate (ResPro) and total VFA concentrations were significantly correlated with BW, DMI, and breed. Residual butyrate (ResBu) was correlated only with DMI. Total bacterial copy number was negatively correlated with eating frequency (p<0.05) and ResAc (p<0.01), and positively associated with ResPro (p<0.01) concentrations. Total archeal copy number was inversely related to ResPro. RFI was significantly affected by DMI (p<0.01), ResAc, and showed a significant negative relationship with ResPr and ResBu (p< 0.05). Similarly, FCR was significantly affected by DMI, ADG, and breed. Both ResPr and ResBu had non-significant (p<0.1), inverse relationships with FCR. Although the work needs to be independently evaluated, our preliminary results identified the potential of using rVFA concentrations to predict feed efficiency traits in beef steers.

See more of: CSAS Graduate Student Poster Competition
See more of: CSAS Graduate Student Poster Competition
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