Effects of herbage distribution, botanical composition, and rumen inoculum source on in vitro gas fermentation kinetics

Abstract

<title>Abstract</title> The random sourcing of rumen liquor from abattoir-slaughtered cattle may influence <italic>in vitro</italic> gas production results due to variations in diet composition. This study evaluated the effects of herbage distribution, botanical composition, and rumen liquor source on rumen fermentation kinetics using the <italic>in vitro</italic> gas production technique. Three districts in Uganda's cattle corridor with different grazing systems and vegetation types were purposively selected: Mbarara (improved mixed pastures), Nakasongola (woody shrublands), and Napak (grasslands). Karamoja had the highest herbage diversity (n = 40), followed by Mbarara (n = 32) and Nakasongola (n = 19), with grasses comprising over 75% of samples from Nakasongola and Mbarara, and 53% from Karamoja. Karamoja herbage had significantly higher crude protein (132.6 g/Kg DM). Gas production varied significantly (P &lt; 0.001) across herbage sources during incubation. Fermentation kinetics were influenced by both the rumen liquor and herbage source (P &lt; 0.001), while gas production rate from the insoluble fraction (b) was only affected by herbage source (P &lt; 0.001). <italic>In vitro</italic> organic matter digestibility (IVOMD) estimated metabolizable energy (ME), and short-chain fatty acids (SCFA) were also significantly influenced by herbage source (P &lt; 0.001). Herbage composition had a greater impact on fermentation kinetics and IVOMD than the source of rumen liquor. These results suggest that rumen liquor from cattle raised under similar grazing systems yields consistent in vitro gas production results.