| Abstrakt: |
The effects of supplementation with nitrogenous compounds on intake, digestibility, and microbial protein synthesis in cattle fed low-quality tropical forage were assessed. Five rumen fistulated crossbred Holstein × Gir heifers were used, with initial average live weight of 180 ± 21 kg. Signal grass ( Brachiaria decumbens) hay (48.6 g kg of crude protein (CP), on a dry matter (DM) basis) was used as roughage. Five treatments were defined according to nitrogen supplementation level (0, 20, 40, 60, and 80 g of CP kg above the CP level of the hay). A mixture of urea, ammonium sulfate, and albumin at the ratios of 4.5:0.5:1.0, respectively, was used as nitrogen source. The experiment consisted of five experimental periods, according to a 5 × 5 Latin square design. The average CP contents in the diets were 51.9, 71.1, 86.0, 116.7, and 130.2 g kg, on a DM basis. A quadratic effect was detected ( P < 0.10) of the CP levels in the diets on DM and neutral detergent fiber intake (kg/day), with maximum response at the levels of 102.4 and 100.5 g CP kg DM, respectively. The average daily concentration of rumen ammonia nitrogen showed increasing linear pattern ( P < 0.01) as function of CP levels in the diet, with estimated value of 9.64 mg dL equivalent to the maximum DM intake. Microbial nitrogen flow in the intestine was linearly and positively related ( P < 0.01) with the CP levels in the diet. [ABSTRACT FROM AUTHOR] |
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