Abstract
BackgroundThere 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.ResultsThere 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).ConclusionsThe 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.
Highlights
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
In studies conducted under tropical conditions, low concentrations of rumen ammonia nitrogen (RAN) have been associated with negative estimates of nitrogen balance in the rumen (NBR), which might increase the mobilization of body proteins to sustain rumen microbial growth [1,2,3,4]
This study evaluated the following treatments: control; ruminal supplementation, with a daily supply of 230 g of supplemental crude protein (CP) in the rumen; abomasal supplementation, with a daily supply of 230 g of supplemental CP in the abomasum; and ruminal and abomasal supplementation, with a total daily supply of 230 g of supplemental CP (115 g of CP in both the abomasum and the rumen)
Summary
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. In this sense, basic research using pure protein sources, such as casein, could be helpful to understand the true effects of protein supplementation on animal metabolism and the utilization efficiency of nitrogen from RDP or RUP in cattle fed tropical forages
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