Supplementation of apple pomace with nonprotein nitrogen for gestating beef cows. III. Metabolic parameters.

Blood and ruminal samples were analyzed from gestating cows fed apple pomace or corn silage plus isonitrogenous and isocaloric quantities of cottonseed meal or nonprotein nitrogen containing supplements in four trials. Data were also obtained from steers fed similar diets during a metabolism trial. The supplementary sources of nitrogen supplied 50 to 70% of the total nitrogen in the diet. Feeding apple pomace, compared with feeding corn silage, resulted in greater (P~.01) molar percentages of acetic and valeric acids, lesser (P ( .05 ) molar percentages of propionic, butyric, isobutyric and isovaleric acids and lowered (P( .01) ruminal pH. Ruminal ammonia concentrations were greatest when the urea-corn supplement was fed, next greatest with biuret-corn and lowest with cottonseed meal. Steers in a metabolism trial were fed apple pomace plus either corn-urea or cottonseed meal. Results indicated that the steers excreted less (P( .01) fecal nitrogen and more (P~.05) urinary nitrogen but had similar nitrogen retentions when the urea-corn supplement was fed than when cottonseed meal was fed. Cows and steers fed the urea supplement had lowered plasma concentrations of several of the essential amino acids. Blood mineral profiles in cows were similar regardless of the source of supplementary nitrogen. (