Cobalt supplied per os reduces the mammary ⁹-desaturase index of bovine milk

¹ Department of Animal and Aquaculture Sciences, Norwegian University of Life Sciences, 1432 Ås, Norway
² Department of Chemistry, Biotechnology and Food Science, Section for Bioinformatics and Analytical Methods, Norwegian University of Life Sciences, 1432 Ås, Norway

^* To whom correspondence should be addressed. E-mail: ole.taugbol{at}umb.no.

	Abstract

Results indicated that the dual marker system of Yb-acetate and Co-EDTA supplied per os reduced the proportion of fatty acids in bovine milk that were products of ⁹-desaturase. To verify this effect and identify the responsible marker component, 18 cows (3 cows per treatment) were administered per os 0.25 L solution of either Co-acetate, Co-EDTA, Co-EDTA + Yb-acetate, EDTA, Yb-acetate, or water twice daily for 5 d. The daily amounts of Co, Yb and EDTA were 3.50, 3.44, and 21.00 g per cow, respectively. Milk and blood were sampled and analyzed for content of fatty acids, and blood for Co and cobalamin. Only solutions containing Co had a reducing effect (P 0.01) on fatty acids that were products of ⁹-desaturase in milk; cis-9 10:1, cis-9 14:1, cis-9 16:1, cis-9, trans-11 18:2, and cis-9 18:1 with exception of the solution containing Co-EDTA + Yb-Acetate for cis-9 18:1. Of the substrate fatty acids of ⁹-desaturase, only 18:0 increased (P < 0.001) in all groups supplied with Co-containing solutions. Thus, Co had a reducing effect (P 0.004) on the ⁹-desaturase indices ([product of ⁹-desaturase]/[product of ⁹-desaturase + substrate of ⁹-desaturase]) of milk for cis-9 14:1, cis-9 16: 1, cis-9 18:1, and cis-9, trans-11 18:2. There were no differences on ⁹-desaturase indices between Co-EDTA or Co-acetate. None of the marker solutions influenced the fatty acid composition of blood plasma, and Co was detected only in the blood samples from cows treated with solutions containing Co. Based on these results we concluded that Co given per os decreased the ⁹-desaturase indices of bovine milk.

Key Words: bovine milk, cobalt, ⁹-desaturase, stearoyl-CoA desaturase, oleic acid, rumenic acid