Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 2, 2008
Publication Date: April 13, 2009
Citation: Powell, J.M., Broderick, G.A., Grabber, J.H., Hymes Fecht, U.C. 2009. Effects of Forage Protein-Binding Polyphenols on Chemistry of Dairy Excreta. Journal of Dairy Science. 92:1765-1769. Interpretive Summary: Environmental concerns related to livestock impacts on greenhouse gas emissions and global warming requires new information on impact of livestock diets and management on atmospheric and terrestrial carbon and nitrogen (N) cycles. Results of this study demonstrate that the type of forage consumed by lactating dairy cows impacts concentrations of N in feces and urine, N excretion rates, concentrations of fiber fractions in feces, and the relative partitioning of N in fecal fiber fractions. These factors need to be considered when collecting dairy manure for environmental studies. Diet selection criteria may need to be expanded to include not only impacts on dairy cattle health and milk production, but also on forage impacts on manure chemistry and the environment.
Technical Abstract: The collection of dairy excreta for use in environmental studies can be costly and labor intensive. Whereas short-term collection may suffice for small-scale laboratory studies, longer term collection may be required for large-scale field studies. The objectives of this study were to determine diurnal and forage tannin impacts on fecal N and urinary N concentrations and excretion rates; and to assess forage tannin impacts on fecal fiber fractions and their N concentrations. Significantly (P<0.05) higher concentrations of N were excreted in urine by cows fed low-tannin birdsfoot trefoil (LTBT) and red clover (RCL) than by cows fed alfalfa (ALF), or high-tannin birdsfoot trefoil (HTBT) silages. Cows fed RCL also had higher rates of urinary N excretion and lower rates of fecal N excretion than cows fed any of the other silage types. Fecal N excretion rates were greatest for cows fed LTBT and HTBT, followed by ALF and RCL. The mass ratio of fecal N to urinary N was higher in excreta collected in morning than evening. Concentrations of neutral detergent fiber (NDF) in feces, of N in NDF (NDIN) and acid detergent fiber (ADIN), and relative amounts of excreted NDIN and ADIN were significantly higher from cows fed HTBT than the other silage types. Study results imply that excreta collection for environmental studies needs to consider diurnal and forage tannin impacts on chemistry of dairy excreta.