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Differences in methane production, yield, and intensity and its effects on metabolism of dairy heifers.

L. G. R. Pereira



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Differences in methane production, yield, and intensity and its effects on metabolism of dairy heifers.
L. T. C. Ornelas1, D. C. Silva1, T. R. Tomich2, M. M. Campos2, F. S. Machado2, R. M. Maur�cio3, A. L. Ferreira2,3, L. G. R. Pereira*2. 1Universidade Estadual do Sudoeste da Bahia Itapetinga, BA, Brazil, 2Brazilian Agricultural Research Corporation � Embrapa Juiz de Fora, MG, Brazil, 3Universidade Federal de S�o Jo�o del-Rei S�o Jo�o del-Rei, MG, Brazil.

The effects of divergent phenotypic classification in crossbreed Holstein � Gyr dairy heifers for methane emissions in relation to performance, digestibility, energy and nitrogen partition, blood metabolites and temperature of body surface were evaluated. Thirty-five heifers were classified as high and low emission for CH4 production (g/d), yield (g/kg dry matter intake) and intensity (g/kg average daily gain). Digestibility was evaluated by total collection of feces and urine. Gas exchanges were obtained in open-circuit respiratory chambers. A completely randomized design was used and divergent groups was compared by Fisher's test. No differences were found in intake traits between groups of CH4 production and intensity. The low yield group had higher intake (6.20 vs. 7.02 kg/d, P = 0.003). For digestibility and temperature at different body sites were no differences between variables. High production group had higher energy losses as methane (1.95 vs. 1.68 Mcal/d, P = 0,01) and heat production (13.0 vs. 11.5 Mcal/d, P < 0.001). Low intensity group had higher digestible energy intake (19.8 vs. 22.5 Mcal/d, P = 0.04), energy balance (4.78 vs. 8.02 Mcal/d, P = 0.02) and ratio between metabolizable and digestible energy (0.87 vs. 0.89, P = 0.01). Urinary nitrogen was 14.3% lower for low production group. There was a difference between methane yield divergent groups for nitrogen intake (170 vs. 188 g/d, P = 0.001), digestible (133 vs. 150 g/d, P = 0.003) and retained (27.7 vs. 54.3 g/d, P = 0.001). Energy and nitrogen partitioning traits are correlated with the animals divergent for methane production and yield. The low production group presented lower blood insulin concentration (39.8 vs. 30.6 μIU/mL). It was not possible to identify divergent animals for CH4 emission using the infrared thermography technique.

Keywords: calorimetry, greenhouse gas, nitrogen utilization.