The vitamin A precursor β-carotene acts as an antioxidant, able to effectively scavenge free radicals to prevent the formation of secondary reactive oxygen species that can destroy cells and cell components. In vitro incubation of β-carotene resulted in lower NH₃-N concentrations and higher microbial protein concentrations, compared with control, indicating β-carotene may increase utilization of NH₃-N, leading to increased growth of microbes, thereby providing more protein to the cow. The objective of this study was to determine the effects of supplemental β-carotene on immunoglobulin (Ig) concentration of colostrum and subsequent effects on the pre-weaned calf. Eighteen multiparous Holstein dairy cows were blocked by expected calving date and randomly assigned to 1 of 2 treatments: Control or 7 g/d of a 10% β-carotene product. The β-carotene was mixed with 40 g of corn meal and top dressed onto the total mixed ration (TMR), fed once daily. Within 90 min of parturition, the calf was removed, colostrum was harvested and weighed and an aliquot was taken for IgG determination via radial immunodiffusion (RID) assay. Calves were weighed and fed 8 pints of maternal colostrum. Blood samples were collected from calves via jugular vein at 0 (before colostrum feeding) and 24 h of age for analysis of IgG concentration via RID and calculation of apparent efficiency of absorption (AEA). Calves remained on study until weaning at 6 w old. Results are shown in Table 1. The results indicated that supplementing β-carotene to prepartum dairy cows increased colostral IgG concentration, tended to increase protein, fat and solids percentages, but lowered colostrum yield. Supplemental β-carotene also increased 24 h calf serum IgG concentrations in calves fed maternal colostrum. Table 1. Effects of supplementing β-carotene to prepartum cows on colostrum quality and the pre-weaned calf

Item	Treatment		SEM	P-value
	Control	β-carotene
IgG, g/L	72.7	93.3	5.5	0.01
Colostrum Yield, L	11.4	6.9	1.5	0.04
IgG Yield, g	822.1	670.7	127.2	0.41
Protein, %	13.5	15.9	0.9	0.07
Fat, %	4.5	6.9	0.9	0.07
Solids, %	22.5	27.4	1.2	< 0.01
Ash, %	1.03	1.06	0.04	0.66
Lactose, %	3.3	2.9	0.3	0.21
24h calf serum IgG (g/L)	22.3	31.4	2.3	0.01
Apparent efficiency of absorption	37.5	35	3.2	0.57