In Vitro Evaluation of Winged Bean (Psophocarpus tetragonolobus) Tubers as an Alternative Feed for Ruminants

Abstract

The purpose of the current study is to determine the effects of the replacement of cassava chips with winged bean (Psophocarpus tetragonolobus) tubers (WBTs) on gas production parameters, in vitro degradability, and ruminal fermentation in ruminant diets. The study was performed using a 3 × 4 factorial arrangements and was designed using a completely random method. Factor A employed three various roughage sources that were frequently used by locals to feed ruminants: Oryza sativa L. (a1), Brachiaria ruziziensis (a2), and Pennisetum purpureum (a3). The levels of WBTs substitutions for cassava chips at 0%, 33%, 66%, and 100% in the diet were selected as factor B. The experiment's findings revealed that replacing the cassava chips in the diet with WBTs at levels of 66 and 100% enhanced the fermentation process by producing a high gas volume at 96 h when Ruzi grass (RZ) was used as the main source of roughage (p < 0.01). The interaction between the roughage source and WBTs showed that organic matter (OM) degradability improved markedly in the case of RZ grass in combination with WBTs at all levels. Both the total volatile fatty acids (TVFAs) at 8 h of incubation and the average value decreased when a complete substitution of casava chips with WBT (WBT 100%) was employed or when employing rice straw as the main source of roughage (p < 0.01). There was no interaction between WBTs and roughage source on the ammonia-nitrogen (NH₃-N) concentration (ml/dL) and rumen microbial count (p > 0.05). In summary, WBTs can be used effectively when combined with grass (Ruzi and Napier). The implementation of WBTs as a novel alternative feed may effectively replace cassava chips without affecting rumen function.

Keywords: alternative energy; degradability; in vitro gas production; roughage; winged bean tubers.

Figure 1

Cumulative gas production curves using observed data fitted by the gas production model for the combination of roughage sources and level of replacement of cassava chips with winged bean tubers in the concentrate diet throughout the incubation period (0 to 96 h). RS: rice straw; RZ: Ruzi grass; NP: Napier grass; 0WBT: 0% replacement of cassava with winged bean tubers; 33WBT: 33% replacement of cassava chips with winged bean tubers; 66WBT: 66% replacement of cassava chips with winged bean tubers; 100WBT: 100% replacement of cassava chips with winged bean tubers (roughage source × level of WBT p < 0.01, SEM = 7.79). Significant differences are indicated by different letters a and b.

Figure 2

The in vitro dry matter degradability of diets in response to different roughage sources. All values are mean ± SEM. ^a,b, Means that are sharing different superscripts are different (p < 0.05) within the same incubation stage.