Indicadores de digestão total, parcial e síntese de proteína microbiana em bovinos

Abstract

The development of new markers and improvement in the use of existing ones, is a topic of great interest in studies of animal nutrition. Thus, several trials were performed for evaluation of markers of total digestion, partial, kinetics and microbial protein synthesis in cattle. In the first study, the objective was to evaluate the estimates of fecal output and digestibility in cattle using different markers (LIPE®, NANOLIPE® and Cr2O3). To this end, two experiments were conducted. The experiment 1 had a focus on the evaluation of different fecal collection periods on estimates of the marker LIPE®. In experiment 2, the central objective was to evaluate the adaptation time required to NANOLIPE® reach the steady state. The Cr2O3 overestimated the fecal output, and therefore underestimated digestibility in both experiments. The external markers LIPE® and NANOLIPE® allowed to estimate fecal output and digestibility accurately. The protocol for use of the marker LIPE® can be changed to only three days of fecal collection. The protocol to be employed in use of the marker NANOLIPE® may be of two days administration with single day sampling fecal in four equidistant points throughout the day. In the second study sought to measure the intake and total and partial digestibility of nutrients in heifers fed with diets based on different forages (corn silage, sugar cane and tifton hay), and concomitantly, to evaluate the use of the LIPE® as marker of partial digestion compared with the iDM and iNDF. Diets affect nutrient intake fractions NFC and iNDF from the forages, the total digestibilities of CP, NDF, and NFC and ruminal and intestinal digestibility of NFC fraction. The rumen was the main site of digestion of NDF, NFC and CT. The iNDF overestimated flows omasal, leading to underestimation of ruminal digestibility and overestimation of intestinal digestibility. The markers LIPE® and iDM can be used in studies of partial digestion, especially the first, due to greater precision and practicality of application. The third study had the objective of quantifying microbial protein synthesis from 2,6-diaminopimelic acid (DAPA) in heifers fed with diets based on different forages (corn silage, sugar cane and tifton hay). The flow of nitrogen compounds as well as the efficiency of microbial protein synthesis was similar between diets evaluated. The objective fourth study was to evaluate the kinetics of passage, from the comparison of technical markers and ruminal emptying technique in heifers fed the same sources forages of the second and third studies. The kinetics of passage of fluid and particles was not affected by diets. The marker Co-EDTA overestimated ruminal volume. Thus, in studies that address the rumen emptying measuring this parameter should be made from this technique. The technique of the marker can’t be removed of trials passage of fluid kinetics, considering that its use is essential for obtaining the other parameters in this type of study. The kinetics of passage as measured by ruminal emptying technique allows a specific study for each fraction of the food as well as the content, volume and weight of rumen digesta, allowing an integrated understanding of the factors related to the effects of filling.