Gut morphology and nutrient retention responses of broiler chicks and White Pekin ducklings to dietary threonine deciency

Abstract

Growth performance, villi length and width, nutrient digestibility, basal short-circuit current, and glutamine transport were investigated in male broilers and White Pekin ducklings offered diets containing 3.3, 5.8, or 8.2 g of threonine (Thr) kg-1 in four studies. Seventy-two birds of each species were fed a standard broiler starter diet from 1 to 14 d of age followed by assignment to three dietary treatments in a randomized complete block design for a 7-d feeding trial in exp. 1 (broilers) and exp. 2 (ducklings). The dietary treatments consisted of an isonitrogenous, corn-soybean-meal-based diet with the addition of crystalline amino acids and graded levels of Thr. Dietary formulation and experimental design for exp. 3 (broilers) and exp. 4 (ducklings) were similar to exps. 1 and 2 except that birds were fed 3.3 or 8.2 g Thr kg-1 for a duration of 14 d. Chromic oxide was added to the dietary treatments as an indigestible marker. Excreta were collected on day 19 to 21 of age for exps. 1 and 2, and from day 26 to 28 of age for exps. 3 and 4. For chicks, there was no effect of dietary treatment on gain for birds fed treatments for 7 d, whereas gain increased (P < 0.001) as dietary Thr increased in birds fed dietary treatments for 14 d. Dry-matter retention increased (P < 0.05) as dietary Thr increased in chicks fed for 7 and 14 d. Threonine increased P retention (P = 0.02), but not Ca or N retention in chicks fed dietary treatments for 14 d. Increasing dietary Thr increased gain (P < 0.05) for ducklings fed dietary treatments for 7 and 14 d. Furthermore, DM retention increased (P < 0.05) as dietary Thr increased for ducklings fed dietary treatments for 7 and 14 d. Nitrogen retention increased (P = 0.04) as dietary Thr increased in ducklings fed dietary treatments for 14 d, but there was no effect of dietary treatment on P or Ca retention. There was no effect of dietary treatment on villi characteristics, basal short-circuit current, or glutamine transport in chicks or ducklings. The data established a link between dietary Thr and nutrient retention in broiler chicks and ducklings, although villi characteristics and permeability measurements were not altered.