title: Intake, digestibility and nitrogen utilization in cattle fed tropical forage and supplemented with protein in the rumen, abomasum, or both.
abstract: BACKGROUND
  There is little information in the tropics with regard the comparative understanding of how an increased nitrogen supply in the rumen or in the intestines affects efficiency of nitrogen utilization in cattle. This study evaluated the effects of supplementation with nitrogenous compounds in the rumen, abomasum, or both on intake, digestibility and the characteristics of nitrogen utilization in cattle fed tropical forage. Four rumen- and abomasum-fistulated Nellore bulls (227 ± 11 kg) were used. Four treatments were evaluated: control, ruminal supplementation (230 g/d of supplemental protein in the rumen), abomasal supplementation (230 g/d of supplemental protein in the abomasum), and ruminal and abomasal supplementation (115 g/d protein in both the rumen and the abomasum). The basal forage diet consisted of Tifton 85 hay with a crude protein (CP) level of 78.4 g/kg dry matter. Casein was used as a supplement. The experiment was conducted using a 4 × 4 Latin square.
  
  
  RESULTS
  There were no differences between the treatments (P > 0.10) with regard to forage intake. The intake and total digestibility of CP increased (P < 0.01) with supplementation. The nitrogen balance in the body increased (P < 0.01) and muscle protein mobilization decreased (P < 0.01) with supplementation, regardless of the supplementation site. The efficiency of nitrogen utilization did not differ among the treatments (P > 0.10).
  
  
  CONCLUSIONS
  The supplementation of cattle fed tropical forage with protein in the rumen, abomasum, or both similarly increased the nitrogen accretion in animal, which reflects improvements on nitrogen status in animal body.
authors.affiliation: Department of Animal Science, Universidade Federal de Viçosa, Av. P.H. Rolfs, s/n°, Viçosa, Minas Gerais 36570-900 Brazil.
authors.forename: Luana Marta de Almeida
authors.initials: LM
authors.lastname: Rufino
authors.affiliation: Department of Animal Science, Universidade Federal de Viçosa, Av. P.H. Rolfs, s/n°, Viçosa, Minas Gerais 36570-900 Brazil.
authors.forename: Edenio
authors.initials: E
authors.lastname: Detmann
authors.affiliation: Department of Animal Science, Universidade Federal Rural da Amazônia, Campus de Parauapebas, C.P. 3017, Bairro Cidade Nova, Parauapebas, Pará 68515-970 Brazil.
authors.forename: Daiany Íris
authors.initials: DÍ
authors.lastname: Gomes
authors.affiliation: Department of Animal Science, Universidade Federal de Viçosa, Av. P.H. Rolfs, s/n°, Viçosa, Minas Gerais 36570-900 Brazil.
authors.forename: William Lima Santiago Dos
authors.initials: WL
authors.lastname: Reis
authors.affiliation: Department of Animal Science, Universidade Federal de Viçosa, Av. P.H. Rolfs, s/n°, Viçosa, Minas Gerais 36570-900 Brazil.
authors.forename: Erick Darlisson
authors.initials: ED
authors.lastname: Batista
authors.affiliation: Department of Animal Science, Universidade Federal de Viçosa, Av. P.H. Rolfs, s/n°, Viçosa, Minas Gerais 36570-900 Brazil.
authors.forename: Sebastião de Campos
authors.initials: Sde C
authors.lastname: Valadares Filho
authors.affiliation: Department of Animal Science, Universidade Federal de Viçosa, Av. P.H. Rolfs, s/n°, Viçosa, Minas Gerais 36570-900 Brazil.
authors.forename: Mário Fonseca
authors.initials: MF
authors.lastname: Paulino
keywords: 3-methylhistidine; Casein; Nitrogen balance; Rumen ammonia nitrogen; Supplementation