Table 3.

Plasma concentrations of IGF-1 and insulin of heifers grazing bahiagrass pastures and randomly assigned, in a 2 × 2 factorial arrangement of treatments, to receive concentrate DM supplementation at 1.25% or 1.75% of BW offered either daily (7×) or 3X weekly (3×; Monday, Wednesday, and Friday) from days 0 to 168 (2 yr; 64 heifers/yr; 4 pastures/treatment combination/yr)

	Supplementation amount				P-value3	Supplementation frequency				P-value3
Item1	1.25%	1.75%	P-value2	SEM	Amount × day	3×	7×	P-value2	SEM	Frequency × day
Plasma IGF-1, ng/mL
Days all heifers supplemented	102.3	115.2	0.04	4.54	0.05	115.0	102.6	0.05	4.52	0.06
Days only 7× supplemented	75.9	81.9	0.35	4.54		80.4	92.4	0.64	4.52
P-value4	<0.0001	<0.0001				<0.0001	0.12
Plasma insulin, μIU/mL
Days all heifers supplemented	10.96	9.52	0.20	0.84	0.46	10.13	10.34	0.85	0.84	0.04
Days only 7× supplemented	8.58	7.85	0.49	0.77		7.10	9.33	0.04	0.77
P-value4	0.002	0.007				<0.0001	0.18

¹Blood samples were collected via jugular venipuncture for plasma harvest 4 h after morning supplementation to correspond to the peak of ruminal fermentation and end products release after concentrate intake, and to match with a day that all heifers received concentrate supplementation (Monday; day 69) and a day that only 7× heifers, regardless of supplement amount, received concentrate supplementation (Tuesday; day 70).

² P-value for the comparison of treatments within day of the study.

³ P-value for the effects of supplementation amount × day of the study and supplementation frequency × day of the study.

⁴ P-value for the comparison of days within each respective treatment.