Desarrollo de sub-sistemas de alimentación de bovinos con rastrojos de frijol (Phaseolus vulgaris L.).II.Balance metabólico a varios niveles de energía y proteína suplementaria

In order 10 effectively develop cattle feeding systems based on the me of common black bean crop residue, a nitrogen balance and digestibility study was conducted wing 15 Romo Sinuano bull calves averaging 150 kg in liveweight (LW) and 12 months of age Ding 35 days, the animals were gradually adapted to management in individual cages and feeding regimes consisting of bean straw ad libitum, blackstrap melasses and a protein supplement containing 92 per cent crude protein (CP). The later o feed ingredients were varied sub that al the end of the adaptation period 13 treatments resulted from the modified factorial combination of the following levels: 0, 100, 200, 500, and 400 y CP/100 ky LW/day (variable X,) and 0,05, 10, 15, and 20 kg of molasses, as fed,/100 kg 1 /day (variable X.) Daily records of feed intake were kept. In addition, fees and mine were collected during 7 days. The chemical analyzer were conventional Bran straw consumption, in the absence of both protein and molasses supplementation, was 182 kg/100 kg LW/day. The intake tended 10 increase with additions of X, and slightly diminish as X2 increased. The maximum valve for total di matter consumption was 37 kg/100 kg LW/day The variable X, was transformed to Z (total CP intake, g/100 kg LW/day) considering 1be N contributed by all feed ingredients. Absolve N retention increased nearly linearly due to direct effects of both variables 7 and X, according 10 the function Y, = 1365 + 0132 + 438X, — 0 000027: — 0 006ZX, (R2= 099, P <£ 001), where Y, = g N retained/100 kg LW /day The efficiency of this retention is described by the function Y, = — 1436 4 0217 + 937 X— 000027" —003ZX, (R* 093 P < 001), where Y, N ret:11 01 as “4 of the N consumed. At an intake of 365 g CP/100 kg LW?/day, the efficiency of retention was 33 per cent regardless of the molasses level At higher CP intakes, Ibe efficiency increased when molasses was absent or fed al low level but decreased when molasses vas fed al high levels. This result could be attributed to the laxative effect impacted by the molasses, decreasing the CP digestibility. This was supported by the CP digestibility data showing improvement as CP consumption was increased although the extent of it was attenuated by increments in molasses intake Since 60 per cent of the supplementary CP vas of non-protein nature (mea) the increases noted in apparent CP digestibility ae explainable by an increase of 1he N-solubility in the rumen 11 is conduced 1hat in cases like this be evaluation of N sources should be based on N retention parameters The relatively high intakes obtained and the data on N retention allow the conclusion that the common bean crop residue is a roughage that could utilized adventurously in ruminant feeding