Table 5.

Concentrations of insulin and insulin-like growth factor 1 (IGF-1) in serum from beef heifers as influenced by vitamin and mineral supplementation [VMSUP; not supplemented (NoVTM) or supplemented (VTM)] and two different rates of gain [GAIN; low rate, 0.28 kg/d (LG) or moderate rate, 0.79 kg/d (MG)].

Item	NoVTM 1		VTM 2		SEM 4	p-Values
	LG	MG 3	LG	MG 3		Day	VMSUP	GAIN	VMSUP × GAIN	VMSUP × Day	GAIN × Day	VMSUP × GAIN × Day
Insulin, pmol/L
Prior to VMSUP 5	31.07	27.58	29.22	16.56	5.97	<0.01	0.01	0.16	0.36	0.30	0.09	0.74
Pre-breeding 6	46.47	36.09	34.00	20.61	5.97
d 83 of gestation 7	54.92	62.86	45.55	40.94	5.97
IGF-1, nmol/L
Prior to VMSUP 5	17.51	20.91	19.24	19.24	1.38	<0.01	0.49	0.25	0.47	0.42	<0.01	0.30
Pre-breeding 6	19.17	18.95	21.36	19.06	1.38
d 83 of gestation 7	12.42 b	15.99 a	13.83 b	17.54 a	1.38

¹ NoVTM: No vitamin and mineral supplement was a pelleted product fed at a 0.45 kg•heifer⁻¹•day⁻¹ with no added vitamin and mineral supplement. ² VTM: Vitamin mineral supplement was a pelleted product fed at a 0.45 kg•heifer⁻¹•day⁻¹ (consisting of 113 g of a mineral and vitamin supplement, formulated to deliver similar levels of vitamins and minerals that were fed pre-breeding and 337 g of a carrier). ³ Heifers fed a pelleted blend of ground corn, dried distillers grains plus solubles, wheat midds, fish oil, urea, and ethoxyquin fed at rate to achieve targeted gain of 0.79 kg/d. ⁴ NoVTM-LG (n = 9); NoVTM-MG (n = 9); VTM-LG (n = 9); VTM-MG (n = 8). ⁵ Blood was collected before VMSUP factor initiation (71 to 148 d before artificial insemination). ⁶ Blood was collected pre-breeding (at the time of CIDR insertion—9 d prior to artificial insemination). ⁷ Blood was collected at the time of ovariohysterectomy (d 83 ± 0.27 after artificial insemination).