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The objective was to study effects of decreasing CP concentration on CH4 production, C retention efficiency and performance by finisher pigs. Four diets were formulated being: conventional (HP) and CP reduced, amino acid supplemented diets (MP), based on either corn grain/soybean meal (CS) or barley grain (BB). Twelve female pigs were assigned to each of the base ingredients (i.e., CS or BB), and a crossover design with two periods was used to evaluate effects of CP reduced diets. To extend the range of dietary CP studied, the BB-HP diet was also tested against a low CP diet (i.e., BB-LP) based on barley grain plus free amino acids, in a crossover design with 2 periods using 12 additional female pigs. The CP contents were 193g/kg (BB-HP), 160g/kg (BB-MP), 120g/kg (BB-LP), 198g/kg (CS-HP) and 178g/kg (CS-MP).
The CP level of the diet did not affect daily gain (i.e., 780g/day; SE 15.9) or protein deposition. Carbon, lipid and energy retention increased when dietary CP was reduced, while heat production increased. Dietary net energy increased when dietary CP was reduced. Lowering dietary CP concentration reduced enteric CH4 , but did not affect expired CO2 (P=0.19). Corn grain based diets had lower expired CO2 but similar CH4 than BB diets. There was no effect of intake on CO2 and CH4 production. The CH4 production was more closely related to dietary CP than fiber content, and increased by 1.2g/day per 10g/kg increase in dietary CP content. Carbon and N excretion increased by 56.6g/day and 2.85g/day per 10g/kg increase in dietary CP, respectively.
According to these results, dietary CP reduction is a realistic option to reduce environmental impacts of pig production without reducing animal performance.
Jacob K.A. Atakora, Soenke Moehn, Ronald O. Balle. Enteric methane produced by finisher pigs is affected by dietary crude protein content of barley grain based, but not by corn based, diets. Animal Feed Science and Technology. 2011. Vol. 166: 412-421.