1622
Metabolism of nitrogenous compounds in beef cattle fed tropical forage supplemented with protein in the rumen, abomasum or both

Monday, July 21, 2014
Exhibit Hall AB (Kansas City Convention Center)
E. D. Batista , Universidade Federal de Višosa, Višosa, Minas Gerais, Brazil
E. Detmann , Universidade Federal de Višosa, Višosa, Minas Gerais, Brazil
D. I. Gomes , Universidade Federal Rural da Amaz˘nia, Parauapebas, Parß, Brazil
L. M. A. Rufino , Universidade Federal de Višosa, Višosa, Minas Gerais, Brazil
A. R. Lopes , Universidade Federal de Višosa, Višosa, Minas Gerais, Brazil
S. C. Valadares Filho , Universidade Federal de Višosa, Višosa, Minas Gerais, Brazil
M. F. Paulino , Universidade Federal de Višosa, Višosa, Minas Gerais, Brazil
E. C. Titgemeyer , Kansas State University, Manhattan, KS
Abstract Text:

Four Nelore steers, averaging 280 ± 10 kg BW, fitted with ruminal and abomasal cannulas were used in a 4 × 4 balanced Latin square design to evaluate the effect of protein supplementation in the rumen and/or abomasum on N metabolism in cattle fed tropical forage. The treatments were: 1) control (without supplementation); 2) ruminal supplementation (250 g/d casein); 3) ruminal plus abomasal supplementation (125 g/d casein in the rumen and 125 g/d in the abomasum); 4) abomasal supplementation (250 g/d casein). Supplements and hay were provided twice per day at 0600 h and 1800 h. The animals were fed with Tifton-85 hay (9.9% CP; 71.5% NDFap) for ad libitum intake. Each period lasted 20 d, comprising 15 d of adaptation and 6 d for sampling. On d 16 through 19 of each period, eight spot samples of abomasal digesta and feces were collected, oven-dried, composited and subsequently analyzed. On d 20 total urine collection was performed. On d 21 blood samples and ruminal fluid were taken every 6 h (beginning at 0600 h) and composited on a daily basis. Supplementation increased (P < 0.10) N intake, N total digestibility, N balance, ruminal ammonia-N (RAN), serum urea-N (SUN), renal urea clearance (RUC), RUC proportion excreted, and urinary N and urea excretion. However, there were no differences (P > 0.10) between sites of supplementation, except for RAN, SUN, RUC, and urinary N and urea excretion which presented a negative linear effect (< 0.10) by the displacement of supplementation rumen to the abomasum. Ruminal N digestibility, microbial N flow, as well as N retained/N intake were not affected by supplementation (P > 0.10). Intestinal N digestibility was increased (P < 0.10) by supplementation. Moreover, there was a positive linear effect (P < 0.10) on N intestinal digestibility when supplement was changed from the rumen to the abomasum. Fecal N excretion was not affected (P > 0.10) by treatments. These results indicate that protein supplementation either in the rumen or in the abomasum, exerts similar effects on efficiency of N utilization, but with different metabolic events. 

Keywords: beef cattle, metabolism, nitrogen