Table 2.

The −log EC₅₀ means and SEM of lateral saphenous veins biopsied from steers that had grazed pastures of bermudagrass (Cynodon dactylon) or toxic endophyte-infected tall fescue (Lolium arundinaceum) not treated or treated with aminopyralid and metsulfuran-methyl (Chaparral) herbicide¹

	−LogEC50, M
Myograph treatment	Bermudagrass	Tall fescue, treated	Tall fescue, untreated	pSEM	P-value
TCB22	4.89	4.93	4.88	0.08	0.91
Ergovaline3	5.44b	6.10a	6.01a	0.16	0.01

¹The effective concentration at which 50% of the contractile response is achieved (EC₅₀). Administration of Chaparral (Dow AgroSciences, Indianapolis, IN) to provide 87.1 g/ha of an aminopyralid (2-pyridine carboxylic acid, 4-amino-3,6-dichloro-) and 13.2 g/ha of metsulfuran-methyl (Methyl 2-[[[[(4-methoxy-6-methyl-1,3,5- triazin-2-yl)- amino]carbonyl] amino]sulfonyl]benzoate) results in suppression of seedhead production by tall fescue.

²A selective agonist for serotonin receptor 2A.

³Ergovaline was applied in the form of a tall fescue seed extract.

^abValues not sharing like superscripts within a row are different (P < 0.05).