Location: Food and Feed Safety ResearchTitle: Developing an in vitro method for determining feed soluble protein degradation rate by mixed ruminal microorganisms Author
Submitted to: Agriculture, Food and Analytical Bacteriology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2012
Publication Date: 12/31/2012
Publication URL: http://handle.nal.usda.gov/10113/57282
Citation: Crossland, W.L., Tedeschi, L.O., Callaway, T.R., Kononoff, P.J., Karges, K. 2012. Developing an in vitro method for determining feed soluble protein degradation rate by mixed ruminal microorganisms. Agriculture, Food and Analytical Bacteriology. 2:246-252. Interpretive Summary: Because cattle ration formulation uses predictive computer models, we need more accurate methods for determining the rate at which soluble feed protein is degraded. In this study, a novel method was described to measure the soluble protein of feeds and their digestibility, especially for use in corn milling by-products. This new method may be a more economical and standardizable method of soluble protein determination.
Technical Abstract: For the purposes of ration balancing using predictive computer models, more accurate content and rumen soluble protein degradability values are needed, especially for highly processed feeds. Consequently, a standardized method of determination is needed. Hence, a novel ruminal in vitro method is described to measure the soluble protein fraction of feeds and their degradability, with adjustments for microbial contributions and contamination. Four corn milling (co)products were used in this study. The feeds (Fd) were dried distillers grain (DDG), one high protein (HP-DDG). One containing added solubles (BPX-DDGS) and the corn (co)products BRAN and GERM concentrated corn kernel components derived during the processing of HP-DDG. The soluble protein content of the feeds was 1.47, 5.05, 4.96, and 6.71 % of DM for HP-DDG, BPX-DDGS, BRAN, and GERM, respectively. These Fd were fermented in vitro in rumen fluid (Rf) with buffered media (Md) along with three respective controls, in duplicate. Each respective feed had one treatment (Fd+Rf+Md) and three controls. Treatment and control 1 (Fd+Md) were compared to the same control 2 (Rf+Md) and control 3 (Md). Subsamples of the treatments and controls were taken for ammonia and bacterial protein determination. Specific activity of ammonia production (SAAP), peak of ammonia production, rate of ammonia production from time zero to peak time, and time to peak were recorded and compared but were not different among feeds (P > 0.05). The SAAP results of the present study (0 and 14.77 nmol•mg protein-1•min-1) were within numerical range of previously reported findings using alternative methodologies (1.8 to 30 nmol•mg protein-1•min-1). Although more research is needed, the current method may be a more economical option to be considered for a standardized method of soluble protein determination.