Absorption of 14 C-2-Hydroxy-4-(Methylthio)Butanoic Acid (Alimet®) from the Hindgut of the Broiler Chick

Abstract

The purpose of these studies was to examine the role of the hindgut of the broiler chick in the absorption of 2-hydroxy-4-(methylthio)butanoic acid (HMB). When 14C-HMB was delivered directly into the hindgut, the rate of absorption from this gastrointestinal site was about 40% of the administered dose per hour. Plasma radiolabel appearance indicated that the 14C-HMB lost from the hindgut was being absorbed into the bloodstream of the bird. Decarboxylation experiments using cecal microorganisms showed that the loss of 14C-HMB could not be accounted for by bacterial metabolism. When birds were dosed with radiolabelled HMB and tissue samples were tested, results showed that the 14C-HMB that was absorbed from the hindgut was incorporated into protein in a dose-related manner. In addition, an equimolar, equal specific activity intraperitoneal dose of HMB did not alter the rate of HMB adsorption from the hindgut. This indicates that HMB absorption from the gut is not limited by HMB already in the body tissues. This result confirmed that the rate of HMB diffusion into the blood and its conversion to methionine in body tissues were sufficient to maintain the concentration gradient required for the continued absorption of HMB. Finally, whole body autoradiography comparing 35S-HMB and 35S-DL-methionine showed no substantial differences in terms of label density or distribution. These studies demonstrate that 14C-HMB disappears from the lumen of the large intestine and ceca when it is administered directly into the hindgut. This research confirms that HMB is absorbed throughout the entire gastrointestinal system.

Biology of the Gastrointestinal Tract in Poultry

“…The methionine analog, 2-hydroxy-4-(methylthio) butanoic acid (Alimet) is absorbed in the chicken colon, as well as in the small intestine (chicken: Knight and Dibner, 1984;Dibner et al, 1988).…”

Effect of Heat Stress on 2-Hydroxy-4-(Methylthio)Butanoic Acid and DL-Methionine Absorption Measured In Vitro

“…Primarily, HMB is absorbed by passive diffusion (Knight and Dibner, 1984;Dibner et al, 1988;Puigserver, 1987, 1989), and the kinds of changes that would increase its rate of absorption would include factors that increase the concentration gradient of the absorbed form of HMB or that decrease the distance over which it must diffuse to reach the blood stream. The HS could reduce intestine wall thickness although reduced feed intake alone has been reported to be associated with thinning of the gut wall and increased in vitro nutrient transfer (Newey et al, 1970).…”

Poly(A)+ RNA Encoding Proteins Capable of Transporting l-Methionine and/or dl-2-Hydroxy-4-(Methylthio) Butanoic Acid Are Present in the Intestinal Mucosa of Broilers

“…In vivo chicken experiments have shown that the small intestine had similar capacities to absorb DL-HMB and L-Met (4,18,19). However, when the mechanisms of transport were examined, L-Met transport appeared to be Na ϩ -and energy-dependent carrier mediated and HMB transport appeared to be comprised of Na ϩ -independent and proton-dependent carrier mediated and diffusion (3,4,20). The discrepancy between the results from the in vivo chicken studies and the present study might be due to the presence of other transport proteins involved in HMB absorption, but more likely, the diffusion component of HMB absorption was not examined in the present study.…”