In vitro ruminal fermentation kinetics of alternative supplemental feeds formulated with by-products from food crops

Commercial feed is an important component of ruminant production systems in Trinidad and Tobago. However, recent price hikes have made commercial feeds unaffordable for many farmers, leading them to seek alternative feedstuffs. This study evaluated the in vitro ruminal fermentation kinetics and fermentative profile of three feed treatments: a commercial feed and two supplemental feeds formulated from agriculture by-products available in Trinidad and Tobago. The objective was to assess their potential as substitutes for commercial feeds in ruminant nutrition. Two iso-nitrogenous and iso-caloric alternative supplemental feeds were formulated with available agriculture by-products (cocoa hulls and shells, coconut meal, powdered bean, rice bran, hulls and corn stover). One was formulated without coconut meal (Supp.-CM) and the other without corn stover (Supp.-CS). All three feed treatments were incubated with buffered rumen inoculum and their in vitro ruminal gas production was measured at 2, 4, 6, 8, 10, 12,18, 24, 36, 48, and 72 h post incubation. Gas production rate peaked 6-h post incubation in the commercial feed and around 12 – 18-h post incubation in the alternative supplemental feeds. Gas produced from the immediately soluble fraction (a) and potential degradability was highest in the commercial feed. However, gas production from the insoluble fraction (b) was similar for the commercial feed and Supp.-CS (246 – 262 g/kg−1). Gas production rate constant for insoluble fraction (c), the lag phase, ruminal pH and partitioning factor did not differ between feed types. The estimated amount of methane produced from the commercial concentrate feed (49.1 ml/g DM−1) were significantly higher when compared to the Supp.-CM which had 40.5 ml/g DM−1 and Supp.-CS which had 41.5 ml/g DM−1. Organic Matter Digestibility was highest in the commercial feed at 586 g/kg. Supplemental feeds from available agriculture by-products has potential to be used as alternatives to commercial concentrate feeds for ruminants in Trinidad and Tobago due to comparable fermentation efficiency, fermentation of insoluble fraction and reduced estimated methane production. However, potential deleterious effects of Supp.-CM and Supp.-CS at the on-set of ruminal fermentation is concerning and may require further investigation.