Intestinal brush border L-threonine transport in pigs and ducks
Abstract
The postnatal development of two intestinal brush-border hydrolases and the effects of a Phaseolus vulgaris bean lectin (erythroagglutinin) on L-threonine transport into jejunal brush-border membrane vesicles (BBMV) were evaluated in pigs. The posthatch developments of digestive functions and the effects of tannins on nutrient utilization were evaluated in ducks. In the developing pig, relative increases in body weight, intestinal weight and mucosa weight normalized to body weight were greater (P < 0.05) for the 3 wk to 5 wk period than for the 1 wk to 3 wk period. Specific jejunum sucrase and alkaline phosphatase activities of mucosa homogenates of pigs were constant (P > 0.05) from 1 wk to 5 wk. The maximal inhibition of transport (Imax) into porcine BBMV by erythroagglutinin, as a fraction of the control, under Na+-gradient and Na+-free conditions were 47.2 and 71.57% (P < 0.05) respectively. Specific jejunum sucrase and alkaline phosphatase activities of mucosa homogenates of ducks were constant (P > 0.05) from 1 wk to 5 wk. The developmental pattern of intestinal L-threonine uptake capacities normalized to body weight of the duck paralleled the course of relative body growth rates. In the duck nutrient balance experiment, the true nitrogen retained (TNR) were 1.33, 1.31, and 0.24 g and the nitrogen corrected true metabolizable energy (TMEn) were 3.57, 3.44 and 3.31 kcal/g for corn, low-tannin sorghum and high-tannin sorghum grains, respectively. As a fraction of the control, the maximal inhibition of threonine transport (Imax) by tannic acid into duck BBMV under Na+-gradient and Na+-free conditions were 77.10% and 45.15% (P < 0.05) respectively. The data from this study suggest that relative increases in body weight of the duck may be confined by the limitations of gut nutrient uptake with a consequential deprivation of nutrients to tissues undergoing hyperplasia. The data also suggest that one mode of action for the detrimental effects of lectins and tannins in feeds involves inhibition of intestinal brush-border amino acid transport. Understanding and manipulating gastrointestinal growth, digestive functions and diets in the pig and the duck should afford improved nutritional management of these species.
Degree
Ph.D.
Advisors
Adeola, Purdue University.
Subject Area
Livestock|Anatomy & physiology|Animals
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