Enteric methane emission, feed efficiency, and digestibility of Nellore cattle

Abstract

In general, improving the feed efficiency of Brazilian cattle herds is necessary, since the emission of enteric methane is a natural and intrinsic process to the animal and represents an energy loss of up to 12%. Level of intake of the animal, microbial community, in addition to the nutritional value and food chemical composition, are factors that contribute to the individual variation of methane emission. Dietary strategies have been successful in manipulating rumen fermentation, at least in the short term, through direct inhibition of methanogenesis. However, mitigation actions arising from the selection of animals with better feed efficiency can be permanent and cumulative, but so far the results of the relationship between feed efficiency and methane emission are still contradictory. The feces microbial community may also be associated with feed efficiency. Thus, this study aims to evaluate the relationship between residual feed intake (RFI), daily enteric methane emission (CH4), nutrient digestibility and fecal microbiota of Nellore cattle (Bos indicus). Data on growth and feed efficiency traits and CH4 emission from 700 animals (evaluated in performance tests from 2018 to 2024) from the Institute of Animal Science Selection Program will be used. To measure the CH4, the sulfur hexafluoride (SF6) tracer gas methodology will be used. The methane emission rate (g/day), residual methane emission (CH4r) and their emission intensities will be estimated in relation to dry matter intake (DMI) and average daily gain (ADG) in addition to the emission expressed in relation to energy intake, which will be obtained by digestibility test. The digestibility of nutrients will be evaluated in feces samples from 300 animals classified among the others as RFI- and RFI+ -. In a sample of animals from extremes for feed efficiency (RFI-; RFI+), fecal and rumen fluid samples will be collected for analysis of the microbial community. In addition to the important results to define mitigating actions of enteric CH4 without affecting animal performance, a database containing information from Nellore cattle evaluated for traits related to feed efficiency, enteric methane emission and nutrient digestibility will be built for future studies.