Effects of prepartum supplementation of β-carotene in Holstein cows

Whether supplemental dietary beta-carotene affects periparturient cows and vitamins A and E in cows when dietary vitamin A is adequate remains uncertain. Our objective was to assess the effect of beta-carotene supplementation during the close-up dry period in a herd with adequate status of vitamins A and E but low in beta-carotene. The study was conducted on a large commercial dairy farm in Indiana during early summer of 2015. Ninety-four multiparous Holstein cows were assigned to either control (CON; n = 47) or beta-carotene (BC; n = 47) treatments. When locked in headgates each morning, each cow received a topdress of beta-carotene (Rovimix, 8 g/d; provided 800 mg of beta-carotene) or carrier from 21 d before expected calving until calving. Blood samples were collected at 21 +/- 1 d (mean +/- standard deviation) before expected calving (before treatments began), 7 +/- 1 d before calving, immediately following parturition, and 7 +/- 1 d postpartum. Blood serum was analyzed for vitamins A and E, beta-carotene, cholesterol, and other metabolites and enzymes. Data were analyzed using the MIXED procedure in SAS (SAS Institute Inc.). Cows had low beta-carotene concentrations (0.85 mu g/mL) in blood serum before treatments began. Compared with CON cows, BC cows had higher overall mean concentrations of beta-carotene (2.87 mu g/mL vs. 0.73 mu g/mL) and retinol (165 vs. 143 ng/mL). Cows fed BC had lower alpha-tocopherol in serum than cows fed CON (2.26 vs. 2.46 mu g/mL). Cows fed BC had lower peak milk than cows fed CON (50.9 vs. 55.3), but total lactation milk yield did not differ significantly. No effects of BC were observed on days to conception (100 d) or times bred (2.4). Treatments did not affect incidences of ketosis, retained placenta, displaced abomasum, off feed, lameness, footrot, mastitis, or metritis. In conclusion, in pregnant cows already receiving adequate vitamin A but with low serum beta-carotene concentration, supplementation of beta-carotene increased concentrations of beta-carotene and vitamin A in blood serum, but did not affect production, reproduction, or health.

Automated summary

This study assessed the effect of beta-carotene supplementation in cows with adequate vitamin A and E, but low beta-carotene levels. The results showed that beta-carotene supplementation increased the concentrations of beta-carotene and vitamin A in blood serum, but did not affect production, reproduction, or health.