Optimum inclusion rate of barley in diets of meat chickens: an incremental and practical program

Context. Barley can be included in poultry diets as a cost-effective energy-contributing ingredient. However, its inclusion in meat chicken diets is limited because it is considered a viscous grain due to high crude fibre and soluble non-starch polysaccharide contents. Aims. The study quantified the optimum inclusion rate of barley in meat chicken diets during different growing phases, using an incremental program. Methods. Eight dietary treatments followed a 4 × 2 factorial arrangement, with three levels of barley inclusion to a wheat-based diet, and a nil-barley control, with or without β-glucanase supplementation. Barley was initially included at 0% (low), 7.5% (medium) and 15% (high) in starter diets (Days 1–9), scaling up by 7.5% for each level in grower (Days 9–21), finisher (Days 23–35) and withdrawal (Days 35–42) diets. Each diet was fed ad libitum to six replicate pens of 18 chicks. On Day 42, four birds per replicate pen were euthanised to determine carcass yield and collect digesta. Key results. During the starter period, a significant (P < 0.05) barley × β-glucanase interaction resulted in lower bodyweight gain (8%) and higher feed conversion ratio (8.5 points) at 15% barley inclusion without β-glucanase, whereas performance was restored with β-glucanase supplementation. No treatment interaction was apparent on growth performance assessed over the entire production period (Days 1–42). Barley inclusion at medium and high levels increased bodyweight gain, and at all levels improved feed efficiency (P < 0.01) compared with the control. β-Glucanase improved (P < 0.05) feed efficiency. Highest (P < 0.01) breast meat yield was measured for diets with medium barley inclusion. There were no interactive or main effects on duodenal digesta viscosity. Barley inclusion increased distal ileal digesta water content by ~8–10% (P < 0.05). Conclusions. Incremental inclusion of barley from 15% in a starter diet, scaling up to 37.5% in a withdrawal diet, does not compromise growth performance or carcass yields in broiler chickens. β-Glucanase supplementation favours both bodyweight gain and feed efficiency. Medium level of barley inclusion favours breast meat yield. Implications. Barley can be considered an economical grain to formulate cost-effective diets for broiler chickens. An incremental program is a practical approach to optimise barley inclusion rate