Kudzu [Pueraria phaseoloides] supplementation offsets maturity effects on tropical forage degradability and lowers enteric methane emissions

Legume supplementation as a fraction of the basal feed can fall short of the animal’s requirements due to variations in the nutritive value of the grass forage. Therefore, the objective of this study was to determine the effects of supplementing Brachiaria hybrid cv Mulato II and elephant grass (Cenchrus purpureus) with tropical kudzu (Pueraria phaseoloides) to a target crude protein (CP) content of 130 g/kg DM on in vitro dry matter degradability (DMD), estimated metabolizable energy (ME) content and methane production. Brachiaria hybrid was harvested at 4 (Brac.4) and 8 (Brac.8) weeks of regrowth, while elephant grass was harvested after 8 (EG.8) and 12 (EG.12) weeks of regrowth. Forage samples were incubated in buffered rumen inoculum for 0, 3, 6, 12, 18, 24, 36, 48 and 72-h to determine in vitro ruminal DMD and degradation kinetics. Ruminal degradation of the immediately soluble fraction “a” was lowest in kudzu (208 g/kg DM). Kudzu supplementation reduced the lag phase of EG.8 from 2.5 to 1.9 and EG.12 from 5.7 to 1.8, respectively, compared to the un-supplemented grasses. Ruminal DMD and ME content of the supplemented grasses were similar (p > 0.05) but they were 21 and 25%, respectively, higher than the un-supplemented grasses. Estimated CH4 yield decreased by approximately 17% with kudzu supplementation. It was concluded that supplementation of Brachiaria hybrid cv Mulato and elephant grass with tropical kudzu to a target CP content offsets the negative effects of maturity on DMD and ME content and reduces CH4 yield in ruminants.