AUTOMATED TOTAL COLLECTION AND INDICATOR METHODS FOR ESTIMATING DIGESTA FLOW IN STEERS FED ROUGHAGE OR CONCENTRATE DIETS.

Automated total collection (ATC) of digesta from four steers fitted with duodenal re-entrant cannulas was compared with flow estimations based on Cr₂O₃and acid detergent lignin concentrations of ATC samples. In two successive periods, each steer was fed about 4 kg daily of an all-roughage or an 80% sorghum grain diet. Digesta samples were automatically taken and pooled every 2 hr, during 3- to 6-day collections. Sample aliquots, representing 4% of the digesta measured in each 2 hr were pooled to represent 24-hr digesta flow. Data of 2-hr samples were used to study diurnal flow patterns. Duodenal digesta and dry matter flow rates estimated by Cr₂O₃and lignin were greater by (TURN) 15% than flow rates measured by ATC. Mean recoveries of Cr₂O₃and lignin at the duodenum were 93 and 89%, respectively. Animals fed the roughage diet had about 55% greater digesta flow rates than when fed the concentrate diet (42 versus 65 l daily average by ATC). There appeared to be an interaction between diets and markers. Apparent ruminal dry matter digestibility calculated from direct measurements by ATC was 44% for the concentrate diet and 37% for the roughage diet. Rumen digestbility values based on Cr₂O₃and lignin were about 25% lower than the ATC values. Average coefficients of diurnal variation for digesta flow were 29% in the concentrate diet and 34% in the roughage diet. Estimations from Cr₂O₃and lignin based on 2-hr samples could either under- or overestimate digesta flow by 31 to 350% of the 24-hr flow based on ATC. Thus, special emphasis should be given to the problem of sampling procedures when using indicators and spot-sampling technique to estimate digesta flow. There was evidence of a 24-hr cycle for the whole digesta flow in the grain diet, with a period of low flow before the onset of the light hours. No consistent flow pattern could be identified in the roughage diet. Lignin concentration patterns in digesta were somewhat similar for both diets; however, Cr₂O₃patterns were different between diets. Digesta dry matter concentration followed a similar pattern to that of Cr₂O₃in the grain diet and to that of lignin in the roughage diet, suggesting that the flow patterns of solid phase components of digesta may also be differentially affected by the dietary concentrate: roughage ratio

Degradabilidade ruminal da matéria seca e da fração protéica da silagem de milho, do farelo de soja e do sorgo grão, em bovinos da raça nelore. Comparação com os dados obtidos pelo CNCPS

The nylon bag in situ degradation thecnique was employed to compare the data of the CNCPS to the ruminal degradability of the dry matter and crude protein in corn silage, soybean meal and sorghum grain, in four rumen fistulated Nellore steers, averaging 36 months of age and 520 kg of liveweight. A randomized complete block experimental design was used, where animals constituted the blocks. Two levels of concentrate, 18 and 39 %, were used in the diets. The forage used in the diets was corn silage and the concentrate ingredients were: soybean meal, cottonseed meal, corn grain and sorghum grain. There was a reduction in the potentially by degradable fraction (B) of the dry matter(DM) of the corn silage and sorghum grain with an increase in the concentrate level of the diet; however, the degradation rate(c) of the silage was similar for the two diets and the sorghum grain showed an increase of 28.4 %. The B fraction of the DM from the soybean meal was not affected by the diet, but its rate (c) was reduced by 18.1 %. The same effect was observed for the rate(c) of crude protein(CP) of the soybean meal, with a reduction of 38.1 %. The values for the effective degradability of the two fractions were not affected by the diet when the lag time was not considered. When lag time was considered, the degradability values of the studied feeds were superior in both fractions

Degradabilidade ruminal do amido de silagem de milho, farelo de soja e sorgo grão, em bovinos da raça Nelore

Four Bos indicus (Nellore) ruminally-fistulated animals, averaging 36 months of age and 520 kg, were used in a randomized block design to study the ruminal degradability of starch in corn silage, soybean meal, and sorghum grain. The experimental diets consisted of two levels of concentrate (18 and 39%) plus corn silage. The concentrate ingredients used were soybean meal, cottonseed meal, corn grain, and sorghum grain. The degradation rate of sorghum grain increased 40.2% in diet 2 . The potential degradability of starch (PDS) was similar in the two diets. There was no difference between the two diets in the effective degradability of starch (EDS) in corn silage. There was a significant increase of 26.5% in the EDS of starch in sorghum grain with the increase of level of concentrate in the diet, and considering the lag time in the calculation. The starch level estimated in this study was lower than the values cited in the literature, probably due to different laboratory methods for determining the starch content in feedstuffs. Previous studies suggested using a minimum of 6 incubation intervals between 2 and 24 hours

Degradabilidade ruminai da fibra em detergente neutro e do nitrogênio insolúvel em detergente neutro da silagem de milho e do farelo de soja, em bovinos da raça nelore

The nylon bag in situ degradation thecnique was employed to study the ruminai degradability of the neutral detergent fiber and neutral detergent insoluble nitrogen of the corn silage and soybean meal in four rumen fistulated Nellore steers, averaging 36 months of age and 520 kg of liveweight. A randomized completelcs block experimental design was used, where the animals constituted the blocks. It was used diets with two levels of concentrate: 20 and 40%.The forage used in the diets was corn silage, and the concentrate ingredients were: soybean meal, cottonseed meal, corn grain and sorghum grain. The NIDN degradation rate of the corn silage and the soybean meal showed a decrease of 32,1% and of 46,0 % as a function of the higher concentrate level of the diet, but the effective and potential degradability of this fraction were not affected. Concerning to the NDF, the soluble fraction, potentially degradable and undegrable , were not affected by the increase on the diet concentrate level, but for the corn silage, there were 21,8% of reduction on the effective degradability of NDF. The use of lag time promoted higher degradability values for the studied fraction. The obtained values for some evaluated parameters, different from that assumed by CNCPS, showed the necessity of more data about brazilian used feeds, for model adjustments