Comportamento ingestivo e parâmetros ruminais de novilhos recebendo suplementação proteica em pastagem

Abstract

The main goal of this study was to evaluate the ingestive behavior and ruminal parameters of cattle being fed by supplements with increasing levels of crude protein (0, 20, 40 and 60%). We used four crossbred steers, who were approximately 24 monthsold, 400kg average body weight, steers, fitted with ruminal cannula, allotted to a 4x4 latin square, managed in four paddocks of Brachiaria brizantha cv Marandu Stapf, with an area of 0.3 hectares. The total availability of pasture was determined on the first day of each experimental period. The extrusa collection occurred on the twelfth day of the experiment. The eating behavior of animals, receiving concentrated supplements, was determined by the weight of the supplement remains in the troughs 20, 40, 60, 90, 120, 180, 300, 420, 540 and 1440 minutes after the delivery of the concentrate. The dry matter intake (DMI) was estimated by use of an external marker (chromium oxide), for ten days and the internal marker (iNDF), obtained after 144h of incubation in situ. The faecal dry matter was estimated by use of an external after supply a single dose and faecal samples obtained at 0, 4, 8, 12, 16, 22, 28, 34, 40, 52, 64, 76 and 100 hours after the dosing. The pH and ammonia (NH3-N) were collected rumen and ruminal fluid measured before (0) and 2, 4, 6 and 8 hours after the diet. Samples for quantification of the concentration of short chain fatty acids (SCFA) in rumen fluid were collected at 0 and 6 hours after delivery of the supplement. The ruminal pH values were affected by treatments 6 hours after feeding the animals, which decreased the pH in the rumen in animals receiving concentrate supplement (20, 40 and 60% CP), and the averages were found for the pH of 6 , 73, 6.80, 6.78 and 6.74 and the concentration of ammonia-N were 11.22, 20.88, 28.96 and 21.66 for the treatments of 0, 20, 40 and 60% . The Nvalues of ruminal ammonia were higher in animals that received supplementation concentrated until the time of six hours after feeding. There was no effect on the levels of crude protein, the concentration of short chain fatty acids studied (acetic, propionic, isobutyric, butyric, isovaleric, valeric, total concentration and ratio C2: C3), at 0 and 6 hours, their average 92.27 and 85.87, 18.67 and 17.49, 4.40 and 4.08, 11.20 and 10.38, 1.58 and 1.37, 2.14 and 2.07 , 130.28 and 121.23, 4.94 and 4.91 mmol / mL respectively. The rate of intake of supplements was influenced by the amount of urea in supplements. Consumption of Total Dry Matter (CMST) was 5.436, 4.525, 5.389 and 5.205 kg / DM / day for treatments 00, 20, 40 and 60 respectively. The lowest daily intake of dry matter was obtained by treating the animals with 20% CP. There was no difference between treatments for ruminal parameters (urine volume (VU), allantoin (ALA), uric acid (UA), purine derivatives (PD), microbial nitrogen (N mic), microbial efficiency (Emic), creatinine in urine , plasma urea, plasma creatinine, and fractional excretion of urea).