ABSTRACT

Background and Aim: Papaya peel (PP) is an agro-industrial by-product containing nutrients and bioactive compounds with potential for use as an alternative ruminant feed ingredient. However, information on the effects of graded dietary PP inclusion on rumen fermentation, methane production, and nutrient degradability remains limited. This study evaluated the effects of dietary PP inclusion on in vitro rumen fermentation characteristics, methane production, and degradability using sheep rumen fluid.

Materials and Methods: A completely randomized design comprising four dietary treatments with eight incubation units per treatment was used. PP was included at 0% (PP-0), 10% (PP-10), 20% (PP-20), or 40% (PP-40). Rumen fluid was collected from five Garut-cross male lambs (37.03 ± 1.05 kg), pooled, and mixed with McDougall buffer. Experimental diets were incubated for 48 h. Total gas and methane production, rumen pH, ammonia nitrogen (NH₃-N), volatile fatty acids, in vitro dry matter (DM) degradability, and in vitro organic matter degradability were determined. Data were analyzed using one-way analysis of variance followed by Tukey’s test when treatment effects were significant.

Results: PP inclusion significantly increased gas production at 12, 18, and 24 h (p ≤ 0.006), with the highest 24-h value observed in PP-20 (32.5 mL) compared with PP-0 (25.0 mL). NH₃-N increased from 3.88 mM in PP-0 to 8.65 mM in PP-40 (p < 0.001). Total volatile fatty acid concentration was highest in PP-20 (29.4 mM) compared with PP-0 (18.0 mM; p = 0.010), while acetate increased significantly (p = 0.031). PP inclusion did not significantly affect 48-h gas production, methane production, rumen pH, DM or organic matter degradability, propionate, butyrate, or valerate concentrations (p > 0.05).

Conclusion: Dietary PP, particularly at 20% inclusion, enhanced selected in vitro rumen fermentation responses without adversely affecting rumen pH or degradability; however, it did not significantly reduce methane production. Because the experiment used a single pooled rumen fluid inoculum batch, these findings should be interpreted as preliminary. Further in vivo studies are required to determine effects on nutrient utilization, animal performance, and methane emissions.

Keywords: agricultural by-product, feed degradability, methane production, PP, rumen fermentation, sheep nutrition, sustainable feed, volatile fatty acids.