In vitro rumen fermentation and methane production from diets containing cottonseed cake

Abstract

This study evaluated the effect of replacement of soybean meal protein by protein from cottonseed cake in diets for beef cattle on their carbohydrate and protein fractions, in vitro rumen fermentation kinetics and methane production. The cottonseed cake protein replaced 0,0; 0,25; 0,5; 0,75 and 1 kg kg-1 CP of soybean meal protein in diets with forage:concentrate ratio of 60:40. In vitro gas production technique was used. Variations in the composition of carbohydrates and protein fractions from formulated diets supported the discussion of results of the rumen fermentation and methane production. Although fibrous carbohydrates degradation rate has presented a quadratic effect to treatment, the final gas volume produced by its degradation was not affected. Non-fiber carbohydrates degradation kinetics was not influenced by replacement of soybean meal protein by cottonseed cake protein, since their degradation rates and final gas volume had no significant effect on treatments, as well as, the lag time. Between zero and 12 hours of incubation the treatments affected both, production and proportion of methane, with a negative quadratic effect. The highest incubation times, between 12 and 24 hours, produced on average 73% of the amount of total methane, without effect of treatments. As a result of methanogenesis observed for all diets after 12 hours of incubation, there was no difference in total methane production in the DM incubated and amount of digestible energy (DE) between treatments, in other words, there was no mitigation or increase in methanogenesis by any inclusion level of cottonseed cake compared to the control treatment. Meat or milk come from animal production systems using co-products of biodiesel produced from oleaginous seeds, such as, soybean and cotton have similar environmental performance as enteric methane emissions.