Two hundred and forty animals from of the Instituto de Zootecnia will be used, evaluated in performance test for two consecutive years, in collective pickets equipped with electronic troughs (GrowSafe® and Intergado®). The animal diet during the performance tests will be composed of corn silage, brachiaria hay, soybean meal, ground corn and mineral salt + urea (67% NDT, 13% CP). The characteristics of dry matter intake (DMI), average daily gain (ADG), as well as the characteristics of feed efficiency, residual feed intake (RFI), gross feed efficiency (FE), residual gain and intake residual will be evaluated, besides carcass traits obtained by ultrasonography.Enteric methane emission estimated (CH4 in g/day) will be obtained in the same animals described previously (240 animals), using SF6 tracer gas methodology in 5 consecutive periods of 24-hour, starting daily before feeding, using collection tanks (metal cylinders of about 500 to 800 cc) evacuated to 0.03 atm.Methane production rate (g / day), methane production (CH4 / DMI, g / kg), residual methane emission 1 (CH4 observed - CH4 expected by the regression equation of CH4 on DMI) residual methane emission 2 (CH4 observed - CH4 expected by the equation of Johnson et al., 1995) and residual methane emission 3 (observed CH4 - CH4 expected by the IPCC equation, 2006). Enteric methane emission will also be expressed in relation to the gross energy intake (CH4 Mcal / 100 Mcal EB), digestible energy (CH4 Mcal / 100 Mcal ED) and metabolizable energy (CH4 Mcal / 100 Mcal EM) obtained in the digestibility assay. Digestibility will be determined through of daytime fecal collection of the animals, during four consecutive days at 7:30 am; 10:30 a.m.; 1:30 p.m. and 4:30 p.m. Fecal excretion will be estimated using as internal indicator the indigestible neutral detergent fiber (INDF), obtained by ruminal incubation, for 240 hours.The data will be checked for frequency distribution and homogeneity of variances using histograms and formal statistical tests. To explore the relationship between feed efficiency, enteric methane emission and digestibility variables described above, simple and partial correlations (Pearson) will be estimated. When the relationship between the variables is strong, this will be quantified through regression analysis.The development of the project will allow a) to set up a database containing information on animals evaluated for characteristics related to the enteric methane emission; b) evaluate different ways of expressing characteristics related to the enteric methane emission; c) to explore the relationship between enteric methane emission and residual feed intake traits; d) to explore the relationship between characteristics related to the enteric methane emission and nutrient digestibility; e) to explore the relationship between nutrient digestibility and residual feed intake; f) quantify the proportion of dietary energy lost as methane; g) compare enteric methane emissions observed with predicted by published and widely used equations in greenhouse gas emission inventories.
News published in Agência FAPESP Newsletter about the scholarship: