Effect of graded levels of dietary threonine on motility of the small intestine of young pigs

Abstract

Threonine (Thr) plays various roles in maintaining gut functions. The aim of the study was to investigate effects of dietary Thr on smooth muscle mechanical activity in the small intestine of growing pigs. Four cereal diets were used: T0 (unsupplemented, Thr-deficient), T1, T2, and T3 containing 6.5, 7.4, 8.4, and 9.3 g Thr per kg diet, respectively. Pigs of mean initial BW of 12.8 kg were fed diets for 19 days. Each group consisted of six animals. The animals were sacrificed at about 22.0 kg of BW and the longitudinal strips of the duodenum and the mid-jejunum were taken for in vitro measurement. Spontaneous activity, responses to electrical field stimulation (EFS; from 0.5 to 30 Hz), responses to acetylcholine (ACh; from 10 − 10 to 10 − 4 M), and relaxation induced by single administration of isoproterenol (10 − 5 M) were recorded. In the duodenum, the amplitude of spontaneous contractions was similar in all groups, while, in the mid-jejunum, the amplitude was significantly larger in group T3 than in other groups. In the duodenum, only responses to EFS were enhanced in group T1 in comparison to group T2. In the mid-jejunum, no differences in responses to EFS were found, but responses to low doses of ACh were enhanced in animals fed diet T3, in comparison with diets T1 and T2, and relaxation induced by isoproterenol was significantly more profound in group T2, as compared with groups T0 and T1. In conclusion, dietary Thr may affect motility of the small intestine. Most likely, Thr plays role in facilitation of contractile cholinergic pathways in the pig jejunum, while the effect in duodenum is equivocal and may involve other pathways.