Assessing the effect of varying levels of poultry manure and fermentation periods on chemical composition, digestibility and rumen fermentation of kinetics of coffee husks

Abstract

This study evaluated the effect of poultry manure inclusion and fermentation periods on the chemical composition, in vitro digestibility, and rumen fermentation kinetics of coffee husks for the development of ruminant feed. Coffee husks, though abundant in Uganda, are underutilized due to their high fiber content and anti-nutritional compounds such as tannins, caffeine, and polyphenols, which limit digestibility and nutrient absorption. While microbial fermentation has been shown to improve feed quality, access to commercial inoculants remains limited in rural areas where livestock are produced. Poultry manure offers a low-cost, locally available source of fermentative microbes, yet its optimal inclusion levels in coffee husk silage remain undefined. A 4×2 factorial experiment was conducted in a completely randomized design at Makerere University’s Animal Science Laboratory. Coffee husks and poultry manure were mixed at 0%, 5%, 10%, and 25% PM (Poultry Manure) inclusion levels and fermented for 28 and 38 days. Post-fermentation, samples were dried, ground, and analyzed for dry matter, ash, crude protein, fiber fractions (NDF, ADF, ADL), calcium, and phosphorus using standard AOAC and Van Soest procedures. In vitro gas production was assessed using rumen liquor from freshly slaughtered cattle, and fermentation kinetics were modelled using Groot’s equation. Organic matter digestibility and short-chain fatty acid production were estimated from gas volumes and chemical composition. Results showed that crude protein and phosphorus content increased significantly with poultry manure inclusion, while ash content declined. Fiber fractions varied, with ADL increasing at higher PM levels. Gas production kinetics revealed enhanced microbial fermentation at moderate PM inclusion, with significant increases in asymptotic gas volume and gas at the point of inflection. However, in vitro digestibility and SCFA production declined at higher PM levels, indicating a trade-off between nutrient enrichment and fermentability. The findings suggest that moderate inclusion of poultry manure (5–10%) in coffee husk improves nutritional value and fermentation efficiency, offering a sustainable feed alternative for ruminant production in Uganda.