Effect of Dietary Inclusion of Fermented Anchomanes difformis Rhizome Meal on Nutrient Digestibility and Nitrogen Utilization in West African Dwarf Goats

Abstract

The increasing cost and seasonal scarcity of conventional feed resources have intensified the search for alternative feed ingredients capable of sustaining ruminant production in tropical regions. This study evaluated the effects of dietary inclusion of fermented Anchomanes difformis rhizome meal (FADRM) on nutrient digestibility and nitrogen utilization in West African Dwarf (WAD) goats. Fresh rhizomes of A. difformis were harvested, fermented for 14 days, air-dried, and milled into meal. Four concentrate diets containing 0, 7, 14, and 21% FADRM were formulated and designated as T1, T2, T3, and T4, respectively. Four WAD bucks (8–10 months old) with an average body weight of 8.35 ± 0.42 kg were assigned to a 4 × 4 Latin square design comprising four dietary treatments and four experimental periods. Each period lasted 28 days, including 21 days of dietary adaptation and 7 days of total faecal and urine collection for digestibility and nitrogen balance determination. Samples of the experimental diets, faeces, and urine were analysed using standard AOAC procedures, and data were subjected to analysis of variance at a 5% level of significance. Fermentation improved the nutritional quality of A. difformis rhizome meal by increasing dry matter, crude protein, ash, nitrogen-free extract, and gross energy contents while slightly reducing crude fibre. Dietary treatments significantly (P < 0.05) influenced nutrient digestibility. Goats fed the diet containing 14% FADRM (T3) exhibited the highest dry matter digestibility (79.12%), whereas those receiving the 21% inclusion level (T4) recorded significantly lower dry matter, crude protein, and crude fibre digestibility coefficients. Nitrogen intake, nitrogen absorbed, nitrogen balance, and nitrogen retention were significantly (P < 0.05) higher in goats fed T1, T2, and T3 than in those fed T4, indicating more efficient utilization of dietary nitrogen at lower inclusion levels. The findings demonstrate that fermented A. difformis rhizome meal is a promising unconventional feed resource for WAD goats. Dietary inclusion of up to 14% supported efficient nutrient digestibility and nitrogen utilization without adverse effects on protein metabolism, whereas higher inclusion (21%) reduced nutrient utilization efficiency. Therefore, fermented A. difformis rhizome meal can be recommended as a sustainable alternative feed ingredient in goat diets at inclusion levels not exceeding 14%.