Table 4.

Plasma metabolites and hormones in feedlot steers receiving diets containing (2 × 2 factorial arrangement): 1) monensin + tylosin (360 mg/steer daily from Rumensin 90 and 90 mg/steer daily from Tylan 40; Elanco Animal Health, Greenfield, IN) and 2) Y. schidigera extract (4 g/steer daily, as-fed basis; Micro-Aid Feed Grade Concentrate; DPI Global, Porterville, CA)^1,2

Item	Monensin + tylosin (A)			Y. schidigera extract (B)			P-values
	Yes	No	SEM	Yes	No	SEM	A	B	A × B
Glucose, mg/dL	99.8	101	1	100	101	1	0.35	0.77	0.70
Insulin, ng/mL	18.6	17.7	0.9	17.6	18.8	0.9	0.47	0.35	0.23
Insulin-like growth factor I, ng/mL	168	172	5	170	171	5	0.55	0.83	0.55
Urea-N, mg/dL	14.5	14.0	0.3	14.0	14.3	0.3	0.16	0.40	0.74

¹Steers were housed in four drylot pens equipped with electronic feed bunks (GrowSafe Systems Ltd, Airdrie, AB, Canada) that measured individual feed intake from day −14 to slaughter. Steers were slaughtered (STX Beef; Corpus Christi, TX) in three groups that contained an equivalent number of steers/treatment combination (36 steers on day 114, 36 steers on day 142, and 48 steers on day 170). Treatments were offered to cattle from day 0 to slaughter. Pens housed cattle from the same treatment combination, and cattle rotated across drylot pens every 14 d to account for any potential pen effect.

²Blood samples were collected from all steers prior to feeding on days 0, 28, 56, and 84. A final blood sample was also collected when steer body weight was recorded the day before shipping to slaughter (days 112, 140, and 169). Results from day 0 were included as independent covariate in each respective analysis. No interactions of factor with day were detected (P ≥ 0.23).