In vitro determination of ruminal dry matter and cell wall degradation, and production of fermentation end-products of various by-products

The samples used in the experiment were nine types of by-products: giant pumpkin, red pepper, melon, broccoli, brewer's grains, fresh and boiled artichoke, lemon peel and orange peel. The dry matter degradability of each by-product was determined by in vitro fermentation with ruminal fluid of the goat. The materials were incubated at 39 degreesC for 12, 24, 48 and 72 h. At each time, pH, dry matter disappearance, neutral-detergent fibre disappearance, volatile fatty acids, lactic acid and ammonia productions were measured. Approximately 50% of the total dry matter loss of broccoli, melon and peels occurred at 12 h incubation. In addition, the total dry matter loss of the giant pumpkin, fresh and boiled artichoke, and brewer's grains was low (< 50% of dry matter loss) at 12 h. The molar proportion of acetate and propionate was influenced by the type of the feedstuffs. Thus, the acetate proportion was > 70% for all by-products, except for brewer's grains (63.8%), and the propionate proportion was < 20% for all by-products, except for the brewer's grains (21.3%). In conclusion, the ruminal dry matter and cell wall degradations, and production of fermentation end-products by in vitro determination offers a convenient method to compare the microbial digestion of the different by-products.