Effects of whole wheat supplementation on gastrointestinal tract development and growth performance of two broiler strains fed diets differing in energy and nutrient density from 0 to 40 days of age

Two experiments, using the same protocol and experimental procedures, were conducted to study the effects of whole wheat (WW) supplementation to diets varying in energy and nutrient density, on gastrointestinal tract development and growth performance from hatch to 40 days of age of either Ross 308 or Cobb 500 broilers. The experimental design was completely randomized with 6 treatments organized as a 2 × 3 factorial with energy and nutrient density of the diet (low; LD vs. high; HD) and WW supplementation (control vs. low vs. high) as main effects. Each treatment was replicated 6 times and the experimental unit was a pen with 16 chicks. The feeding program consisted of three phases in which the HD diets contained 0.419 MJ AME n /kg and 5% digestible lysine more than the LD diets. In addition, the LD and HD diets were supplemented with 30 g WW/kg from 0 to 14 days and either 75 or 150 g WW/kg from 15 to 40 days of age. At 40 days of age, broilers fed the HD diets were heavier and had better feed and energy conversion ratio (P < 0.100), in both experiments, than broilers fed the LD diets. Whole wheat supplementation increased the weight and decreased the pH of the gizzard (P < 0.05), but impaired BW gain and feed efficiency (P < 0.01). In summary, an increase in diet density improved broiler performance of both strains from 0 to 40 days of age with opposite effects observed with WW supplementation. • An increase in energy and diet density improved broiler performance without affecting feed intake. • Whole wheat, supplemented on top of the diet, impaired broiler performance at all ages. • Whole wheat supplementation increased gizzard weight and reduced gizzard pH. • -Both strains responded similarly to an increase in diet density and whole wheat supplementation.