Bioavailability of three ruminally protected methionine sources in cattle

The bioavailability of three ruminally protected d,l-methionine products (Smartamine M™; Adisseo, Antony, France; Mepron® M85, Degussa AG, Hanau, Germany; and METHIO-BY, Inter-Harz GmbH, Elmshorn, Germany) was assessed in six ruminally cannulated steers by means of a standardized blood test. d,l-methionine was supplemented once daily at 07:00 h in amounts of 50 g of methionine per steer for 5 days. The experimental design was a repeated 3×3 Latin square with 14 days periods. Blood samples were obtained by repeated puncture of the jugular veins at 09:00, 13:00 and 17:00 h 3 days before (control) and 5 days after the start of d,l-methionine supplementation. Blood samples within sampling day and steer were pooled for analyses. All three d,l-methionine sources caused elevations of blood plasma methionine but the magnitude of the response differed among sources. Smartamine M™ caused a 2016% increase (464 μmol/l versus 23 μmol/l for the control), whereas Mepron® M85 and METHIO-BY elevated blood plasma levels by 58 and 82% (39 μmol/l versus 25 μmol/l and 40 μmol/l versus 22 μmol/l, respectively). Smartamine M™ was the most effective source of ruminally protected d,l-methionine.