Citation: Suntara, C.; Sombuddee, N.; Lukbun, S.; Kanakai, N.; Srichompoo, P.; Chankaew, S.; Khonkhaeng, B.; Gunun, P.; Gunun, N.; Polyorach, S.; et al. In Vitro Evaluation of Winged Bean (Psophocarpus tetragonolobus) Tubers as an Alternative Feed for Ruminants. Animals 2023, 13, 677. https://doi.org/10.3390/ ani13040677 Academic Editor: Adriana Bonanno Received: 4 January 2023 Revised: 10 February 2023 Accepted: 12 February 2023 Published: 15 February 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). animals Article In Vitro Evaluation of Winged Bean (Psophocarpus tetragonolobus) Tubers as an Alternative Feed for Ruminants Chanon Suntara 1 , Napudsawun Sombuddee 1 , Saowalak Lukbun 1 , Natdanai Kanakai 1 , Pachara Srichompoo 1 , Sompong Chankaew 2 , Benjamad Khonkhaeng 3 , Pongsatorn Gunun 4 , Nirawan Gunun 5 , Sineenart Polyorach 6 , Suban Foiklang 7 and Anusorn Cherdthong 1, * 1 Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand 2 Department of Agronomy, Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand 3 Department of Agricultural Innovation and Technology, Institute of Interdisciplinary Studies, Rajamangala University of Technology Isan, Nakhon Ratchasima Campus, Nakhon Ratchasima 30000, Thailand 4 Department of Animal Science, Faculty of Natural Resources, Rajamangala University of Technology-Isan, Sakon Nakhon Campus, Phangkhon, Sakon Nakhon 47160, Thailand 5 Program in Animal Production Technology, Faculty of Technology, Udon Thani Rajabhat University, Udon Thani 41000, Thailand 6 Department of Animal Production Technology and Fisheries, Faculty of Agricultural Technology, King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand 7 Faculty of Animal Science and Technology, Maejo University, Chiangmai 50290, Thailand * Correspondence: anusornc@kku.ac.th Simple Summary: Cassava is becoming increasingly popular in the worldwide market, thus leading to price surges. This phenomenon has a direct influence on ruminant farming, as cassava is used as an energy source in more than half of their meals. Accordingly, we have been searching for an alternative feed to compensate for this uncertainty and, more specifically, for tuberous crops such as winged bean tubers (WBTs) that have the potential to deliver nutrition equivalent to or even greater than conventional cassava chips. It was hypothesized that WBTs would be ideal for usage as animal feed and a unique alternative feedstock for ruminants. We identified that, when associated with grass, WBTs may be effectively utilized to substitute cassava chips without impairing rumen function. To summarize, even though it is too early to determine if WBTs can be utilized as a substitute for cassava, there are aspects of our study that indicate this possibility, and further research is required to evaluate the practicability of this alternative feedstuff. 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 a3 × 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 (NH 3 -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. Animals 2023, 13, 677. https://doi.org/10.3390/ani13040677 https://www.mdpi.com/journal/animals