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Title: Forage nutritive value of Texas bluegrass harvested in the morning and afternoon in northwest Oklahoma.

Author
item Goldman, Jason
item Gunter, Stacey

Submitted to: Grassland Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2012
Publication Date: 9/4/2012
Citation: Goldman, J.J., Gunter, S.A. 2012. Forage nutritive value of Texas bluegrass harvested in the morning and afternoon in northwest Oklahoma. Japanese Society of Grassland Science. 58:147-152.

Interpretive Summary: Texas bluegrass (Poa arachnifera Torr.) is a perennial, cool-season grass native to southern Kansas, Oklahoma, western Arkansas and most of Texas. This native species is of particular interest for development into an improved cool-season forage plant because of its heat tolerance and persistence under the extreme environmental conditions of the southern Great Plains. Knowing forage nutritive value parameters for Texas bluegrass should enable managers to optimize its use; therefore, the objective of this experiment was to determine the nutritive value of Texas bluegrass during the growing season in Northwest Oklahoma. Texas bluegrass was harvested in November, December, February, and March and used to estimate forage dry matter yield, crude protein concentration, total non-structural carbohydrate concentration and ruminal digestion from morning and afternoon harvested samples. Dry matter yield ranged from 1,902 to 4,982 pounds/acre depending on the harvest date. Crude protein concentration and ruminal organic matter digestion were similar to other cool-season grasses (i.e. tall fescue, brome, orchard, Timothy) and ranged from 9 to 12% and approximately 70%, respectively. Total non-structural carbohydrate ranged from 11 to 26% and was generally greater from the afternoon harvest. The forage nutritive parameters estimated in this study indicate that Texas bluegrass has a good potential to be used as an improved cool-season pasture grass and can complement the nutrient inadequacies normally observed with dormant warm-season grasses present in pastures during the winter months.

Technical Abstract: Texas bluegrass (Poa arachnifera Torr.) is a highly rhizomatous, dioecious, sexual, perennial, cool-season grass native to southern Kansas, Oklahoma, western Arkansas and most of Texas. This native species is of particular interest for development into an improved cool-season forage plant because of its heat tolerance and persistence under the extreme environmental conditions of the southern Great Plains. The objectives of this experiment were to determine total non-structural carbohydrate and crude protein concentrations, forage dry matter yield, and in situ organic matter and crude protein disappearance from Texas bluegrass as affected by germplasm, maturity, and time of harvest (morning and afternoon) at Woodward, Oklahoma. Crude protein concentrations ranged from 9 to 12% and did not differ between a morning and afternoon harvest. Dry matter yield (kg ha-1) ranged from 2130 to 5580 over all harvest dates. Total non-structural carbohydrate concentration was generally greater in the afternoon compared to morning harvests and ranged from 11 to 26%. After a 48 hour rumen incubation, organic matter and crude protein disappearances were 70 to 71% and did not differ among harvest dates or time of day. Based on estimates from in situ digestion, the ratio of ruminally degradable crude protein to ruminally degraded organic matter in Texas bluegrass may compensate for the ruminally degraded nitrogen deficiency associated with dormant warm-season grass during the winter. The forage nutritive value parameters estimated in this study indicate that Texas bluegrass has potential as an improved cool-season pasture grass.