Effects of β-Carotene and α-Tocopherol on Rumen Bacteria in the Utilization of Long-Chain Fatty Acids and Cellulose

Abstract

Addition of safflower oil to a growth medium depressed the growth of mixed rumen bacteria above 200 mg/L and did not significantly increase bacteria, even at lower concentrations. However, when 10 mg/L of β-carotene were added to 50 to 100 mg/L of safflower oil, bacterial growth was significantly increased. When more than 200 mg/L of safflower oil were present, β-carotene markedly restored the growth capacity. α-Tocopherol was more effective than β-carotene, although it inhibited growth at high concentrations. The combination of β-carotene and α-tocopherol (each 5 mg/L) exerted partially additive effects. β-Carotene plus α-tocopherol enhanced bacterial cell yield in the presence of safflower oil, caprate, stearate, or linoleate, suggesting that β-carotene and α-tocopherol increase the utilization of fatty acids. β-Carotene plus α-tocopherol also stimulated cellulose digestion in the presence of 100 mg/L of safflower oil, evidently through the increased growth of cellulolytic bacteria. © 1993, American Dairy Science Association. All rights reserved.