Effects of Dietary Amines on the Small Intestine in Calves Fed Soybean Protein

Publisher Website
Google Scholar
Abstract
An experiment was conducted using 16 Holstein male calves from 4 to 21 d of age to compare 1) the effects of an all-milk protein milk replacer (MPR) and a milk replacer with 20% of the protein from soy protein concentrate (SPC) on morphological and enzymic small intestinal variables, and 2) the effects of SPC plus putrescine (SPP) or SPC plus ethylamine (SPE) on intestinal variables. Small intestinal absorption, based on xylose absorption tests, was greater in calves fed MPR than in those fed SPC (P < 0.01) and was intermediate in SPP- and SPE-fed calves. Small intestinal segments were surgically excised from the proximal and distal jejunum of all calves at 7, 14 and 21 d of age. Villus length tended to be greatest in calves fed MPR, and mitotic index was least in SPC-fed calves (P < 0.05). Mucosal protein concentration was 46, 41, 44 and 44 µg/mg mucosa for calves fed MPR, SPC, SPP and SPE, respectively. The ratio of mucosal protein:RNA was greatest in calves fed MPR, least in those fed SPC at d 7 (P < 0.01) and d 14 (P < 0.05), and intermediate in calves fed SPP and SPE. In proximal jejunum, activity of mucosal omithine decarboxylase (ODC, EC 4.1.1.17; the rate-limiting enzyme in polyamine biosynthesis) in calves fed SPP was less than 50% of that in calves fed MPR, SPC or SPE. The activity of lactase (EC 3.2.1.108) and ODC in distal jejunum was 50% less in calves fed soybean protein than in those fed MPR. We conclude that soy protein concentrate reduces small intestinal absorption and enterocyte proliferation in preruminant calves. Furthermore, putrescine and ethylamine, when added to soybean protein diets, enhance enterocyte proliferation and partially prevent reductions in absorption.