Objective

To evaluate the in vitro gas production technique as method to estimate in vivo a global warming indicator, in diets with different levels of metabolizable energy and crude protein.

Materials and Methods

The in vitro gas production technique was used to obtain a global warming indicator from CO2 and CH4 production, the potential emission of fermentation gases and digestibility of five diets: three balanced diets at low (2,7:12,8); medium (2,7:15,3) and high levels (3,0:17,6) and two unbalanced diets in metabolizable energy and crude protein, with which 30 lambs (26,5 ± 3,7 kg LW) were fed in individual pens. Fattening lasted 60 days (three periods of 20 days). In each period samples of the offered and rejected feedstuff, and feces were taken per animal, which were fermented with the GPT during 24 h. The design was complete randomized with 5 x 3 factorial arrangement (diet x period).

Results

The in vitro dry matter digestibility and in vitro ruminal fermentation were 6 and 13 % higher for the balanced diets compared with the unbalanced ones, respectively. Regarding CH4 production and the global warming potential indicator, higher production was observed in the third period of fattening with regards to the first 40 days. In addition, the diets high in metabolizable energy were the ones with higher environmental impact on global warming (p < 0,05).

Conclusions

The global warming potential indicator obtained with the gas production technique is useful to estimate the environmental impact of the diets for ruminants; and the balanced diets, independently from the energy and protein level, they had higher digestibility and fermentation.

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