**5. Conclusions**

This study showed that discarded durian peel fermented with a combination molasses and *L. casei* TH14 (FDPML) had significantly greater nutrient digestibility and propionate concentration, while estimated methane production, the acetate-to-propionate ratio and urinary nitrogen decreased when compared with untreated discarded durian peel (FDP). Therefore, a combination treated discarded durian peel with molasses and *L. casei* TH14 could add 25% of dry matter to the diet for growing goats without a negative impact. Further studies should evaluate the effect of fermented discarded durian peel with an additive content of higher than 25% in the diet on feed utilization, digestibility, rumen characteristics, blood metabolites, and nitrogen balance in ruminants.

**Author Contributions:** N.P. and P.C. conceptualized and designed the experiment. N.P. conducted laboratory and statistical analyses. N.P. and S.S. wrote the first draft of the manuscript. A.C. and P.C. reviewed and edited the manuscript. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was supported by the Center of Excellence in Agriculture and Natural Resources Biotechnology (CoE-ANRB: phase 3).

**Institutional Review Board Statement:** The study was conducted under approval procedure no. MHESI 68014/674 of the Institutional Animal Care and Use Committee, Prince of Songkla University.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** Authors are grateful for the support from Seahorse Intertrade Company Limited, Songkhla province. Additionally, authors would like to thank the Animal Production Innovation and Management Division, Faculty of Natural Resources, Prince of Songkla University, Hat Yai campus, Songkhla, Thailand, and Research Program on the Research and Development of Winged Bean Root Utilization as Ruminant Feed (RP64-6/002), Increase Production Efficiency and Meat Quality of Native Beef and Buffalo Research Group, and Research and Graduate Studies, Khon Kaen University (KKU).

**Conflicts of Interest:** Authors declared that research was conducted without any conflicts of interest.
