Enhancing bypass starch in cassava chip to sustain growth in goat

Context Reducing fermentation rate to enhance bypass starch through simple treatment can be a viable way to better utilise tropical high-energy starch-rich feed such as cassava chip for ruminant production. Combining tannic acid and temperature treatment could possibly achieve the above. However, the optimal combination level of the above two factors and the efficacy of such treatment need to be tested. Aims The aims of the present study were to determine an effective tannic acid × temperature treatment to reduce degradation of starch in cassava chip and to evaluate its efficacy to enhance growth, using goats as study model. Method The study consisted of two experiments. In the first, cassava chip treated with four tannic acid levels × two temperatures combinations were evaluated using in sacco procedure to determine the effectiveness of the treatments in reducing the degradation of cassava chip. This was followed by an in vivo feeding trial to evaluate the efficacy of the treated cassava chip, on the basis of the most effective treatment from Experiment 1 on growth and digestion parameter in goats. Key results Results of the first experiment showed that the most effective treatment to reduce degradation of cassava chip was by treating it with 7.5% tannic acid at 120°C. Results of the in vivo trial showed that feeding the goats 30% treated cassava chip in the diet did not affect their daily feed intake, average daily gain and feed conversion ratio compared with their counterparts that were fed the control diet made up of similar proportion of untreated cassava chip. Treated cassava also did not affect rumen pH, volatile fatty acid (except acetate) production, rumen microbial population (except methanogen) and apparent DM, crude protein and starch digestibility. However, there was a drastic reduction in the estimated total and digestible starch intakes, apparently due to the low starch content in the treatment diet. Conclusions Treating cassava chip with 7.5% tannic acid and 120°C reduced in sacco effective degradation by 23% compared with the control. However, this beneficial effect was not reflected in the in vivo trial, which needs further evaluations. Implications The present study addressed a practical approach and its challenges to reduce degradation rate of high-energy feed to enhance bypass starch in ruminant nutrition.