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Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions

Ruminal Infusions of Cobalt-EDTA Reduce Mammary 9-Desaturase Index and Alter Milk Fatty Acid Composition in Lactating Cows^1–3,

⁴ Animal Production Research, MTT Agrifood Research Finland, Jokioinen, FIN 31600, Finland; and ⁵ Department of Animal Science, University of Helsinki, FIN 00014, Finland

^* To whom correspondence should be addressed. E-mail: kevin.shingfield{at}mtt.fi.

Ruminal administration of a triple indigestible marker system comprised of cobalt EDTA (CoEDTA), ytterbium acetate (YbAc), and chromium-mordanted straw (CrS) decreases product:substrate ratios for 9-desaturase in bovine milk fat. This experiment was designed to identify the marker(s) responsible and develop an alternative system for simultaneous determination of nutrient flow in the gastro-intestinal tract and milk fatty acid composition. Five lactating dairy cows were used in a 5 x 5 Latin square with 21-d periods to evaluate the effects of YbAc, CoEDTA, and CrS independently or as part of a triple marker system (TMS), and CrEDTA as an alternative to CoEDTA on milk fat composition. Markers were administered in the rumen over a 7-d interval and samples of milk were collected on d –1, 3, 7, and 11. Both TMS and CoEDTA alone reduced the concentrations of milk fatty acids containing a cis-9 double bond, whereas YbAc, CrS, and CrEDTA had no effect. Reductions in product:substrate ratios for 9-desaturase were time dependent and evident within 3 d of administration. Ruminal infusion of CoEDTA for 7 d induced mean decreases in milk cis-9 14:1/14:0, cis-9 16:1/16:0, cis-9 18:1/18:0, and cis-9, trans-11 conjugated linoleic acid/trans-11 18:1 concentration ratios of 47.7, 26.7, 40.3, and 42.6%, respectively. In conclusion, ruminal infusion of CoEDTA alters milk fatty acid composition and appears to inhibit 9-desaturase activity in the bovine mammary gland. Results indicate that a TMS based on CrEDTA, YbAc, and indigestible neutral detergent fiber can be used for estimating nutrient flow without altering milk fat composition in lactating cows.

This article has been cited by other articles:

				O. Taugbol, I. J. Karlengen, T. Bolstad, A. H. Aastveit, and O. M. Harstad Cobalt supplied per os reduces the mammary {Delta}9-desaturase index of bovine milk J Anim Sci, November 1, 2008; 86(11): 3062 - 3068. [Abstract] [Full Text] [PDF]