Tannins of tropical shrub-like legumes: their effect on protein protection of soybean meal

Abstract

For determining the potential of tannins extracted from two tropical shrub-like legumes (Albizia lebbekoides and Acacia cornigera) in the protection of soybean meal proteins and to establish their effects on fermentation indicators, the in vitro gas production technique was applied. A random block design was used. Untreated soybean meal (800 mg) were incubated and treated with aqueous extract of A. lebbekoides and heat, A. cornigera extract and heat, water and heat and only with heat. Treatments were incubated alone and with two levels of soluble starch (150 and 300 mg) for estimating N solubility of the substrate. Gas production was measured until 8 h and short chain fatty acid production and ammonia were determined. There was no effect of the treatments on the production of total SCFA, only the treatment with heat increased gas production (P < 0.05). Neither were there differences in the productions of individual SCFA nor in the acetic/propionic relationship. Albizia and acacia tannins decreased the NH3 levels regarding the untreated substrate (P < 0.05), although the treatment with acacia tannins did not differ from the treated soybean meal with water and heat. Also the decrease of the amounts of solubilized N was established, on treating soybean meal with both tannin sources (P < 0.01). It is concluded that tannins extracted from A. lebbekoides and A. cornigera could be used for protecting of ruminal degradation to proteins of high biological value, as those of soybean meal.

Key words: ruminal degradation, fermentation, in vitro gas production, ammonia, rumen