Effects of different levels of ruminal undegraded protein in beef cattle diets/establishment of in vitro systems (dual-flow continuous culture and gas production) for ruminants' nutrition studies

Abstract

High producing beef animals are highly dependent of rumen undegraded protein (RUP) to reach their metabolizable protein requirements. The extension of ruminal protein degradation of protein sources may vary according to their intrinsic characteristics or by applying different processing methods. This project will be developed performing several trials in two phases, with the following objectives: Phase A) To evaluate different processing methods that aim to increase the RUP content of most common protein sources (soybean meal, cottonseed meal, and peanut meal) used in Brazil; Phase B) To evaluate the influence of increasing dietary RUP of beef cattle on ruminal fermentation, intestinal digestibility, and gas production (CO2 and CH4) using different in vitro systems. In Phase A, the three protein sources will be processed using different methods to increase it RUP content, totaling 114 ingredients. The rumen degraded protein (RDP) and RUP of the feedstuffs will be determined according to in situ technique recommended by NRC (2001). Thereafter, crude protein intestinal digestibility will be determined using the three-step in vitro procedure. In Phase B, two gas production systems (24 bottles each, IVGP automated system, Reno, NV, USA) will be used in six 48-hour consecutive runs to evaluated total gas production and profile (CH4 and CO2), pH, NH3-N, VFA, and metabolizable energy from the feedstuffs with better results from Phase A. Then, 10 fermenters will be used in a replicated 5x5 Latin square arrangement with five periods of 10 d each, with 7-d for diet adaptation and 3-d for sample collections. Variables evaluated will be: DM, OM, CP, and NDF ruminal and intestinal digestibility, ruminal parameters, nitrogen metabolism, microbial efficiency, and amino acid profile escaping ruminal fermentation. The accomplishment of this project has the potential to increase the knowledge of protein utilization by beef cattle, thus developing a more efficient and sustainable beef cattle production system. Furthermore, the establishment of the in vitro systems will complement and improve the ruminant nutrition research of the "Instituto de Zooctenia", thus providing tools to development of new technologies that will positively impact the beef cattle industry locally and globally. (AU)