Date of Award


Document Type


Degree Name

Master of Science (MS)

Legacy Department

Animal and Veterinary Sciences


Andrae, John G

Committee Member

Stringer, William C

Committee Member

Jenkins, Thomas C


Extensive research has been done on the effect of diet on rumen methane (CH4) production, and on developing equations to accurately predict CH4 in cattle. However, the majority of this research has been gathered from feedlot cattle or cattle fed a total mixed ration (TMR). To date, no studies have examined nutrient correlations with CH4 when feeding an all pasture diet of warm season or cool season grasses. This study included two in vitro experiments, one with a warm season forage and one with a cool season forage to see which nutrient characteristics of each forage best correlated with CH4 production. Rumen microorganisms from a lactating Holstein cow were incubated in dual-flow ruminal continuous cultures for 7 days and thirty g of either Tifton 85 bermudagrass in experiment 1 or Marshall Annual Ryegrass in experiment 2 at 5 different days regrowth (14 d, 21 d, 28 d, 35 d, and 42 d) were fed twice daily in equal amounts. Methane concentrations were measured hourly to determine differences in CH4 production with time, forage species and regrowth. In experiment 1, feeding bermudagrass at 28 d regrowth resulted in CH4 production (32.13 mmol/d) which was higher than all others except for 35 d. The three nutrients included in the forward regression, were starch, sugar, and acid detergent lignin (ADL). In experiment 2, feeding annual ryegrass at 21 d regrowth produced the highest amount of CH4 (17.21 mmol/d) compared to all other days regrowth. The three nutrients included in the forward regression were starch, ADL, and hemicellulose (HC). For both experiments, measured values were lower than predicted ones from equations. These experiments conclude that starch is the strongest predictor of CH4 in grazed forages but other predictors may vary based on grass type.



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