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Short Communication: Absorption of 2-Hydroxy-4-Methylthiobutanoate in Dairy Cows

H. Lapierre^*,1, M. Vázquez-Añón, D. Parker, P. Dubreuil and G. E. Lobley

^* Dairy and Swine Research & Development Centre, Agriculture and Agri-Food Canada, Sherbrooke, Quebec, Canada, J1M 1Z3
Novus International, St. Louis, MO
Faculté de médecine vétérinaire, Université de Montréal, St-Hyacinthe, Quebec, Canada, J2S 7C6
Rowett Research Institute, Aberdeen, UK, AB21 9SB

¹ Corresponding author: lapierreh{at}agr.gc.ca

The objective of this study was to measure net portal absorption of 2-hydroxy-4-methylthiobutanoate (HMTBA) in dairy cows. Four multicatheterized lactating cows were used in a cross-over design with 7-d experimental periods. They were fed every other hour a total mixed ration and received, in addition, twice a day, 12.5 or 25 g/meal of HMTBA. On the last day of treatment, net portal absorption of HMTBA was numerically greater after the 25-g compared with the 12.5-g bolus meal of HMTBA, and the amount absorbed relative to the dose ingested was unchanged between treatments averaging 11.2 ± 4.7% of the dose. This represents a minimum value of HMTBA availability because it does not take into account any HMTBA metabolized to Met by gut tissues (in sheep this amounted to another 5% of the dose). A rapid method to estimate net portal absorption based on temporal variations of the peripheral plasma HMTBA concentrations following the HMTBA meal is also presented. Based on the good relationship (concordance correlation coefficient = 0.97) observed between direct measurements and estimations, this simplified approach offers a reasonable approach to assess HMTBA absorption under different feeding situations.

Key Words: dairy cow • methionine analog • absorption • 2-hydroxy-4-methylthiobutanoate