Energy evaluation of eight barley cultivars for poultry: effect of dietary enzyme addition

Departamento de Produccion Animal, E.T.S.I. Agronomos, Universidad Politecnica, Madrid, Spain.

Three experiments were conducted to study eight barley cultivars and the effect of enzyme addition on their energy value for poultry. In Experiment 1, the AMEn of a reference barley (Beka cultivar) was calculated by increasing barley concentrations (30, 40, 50, and 60%) that replaced a high protein basal diet. In Experiment 2, eight barley cultivars (four spring and four winter cultivars) replaced the reference barley in the diet with 50% barley inclusion. Two of the winter cultivars were two-rowed and two were six-rowed cultivars. A commercial enzyme was added to these diets to study the effect of enzyme addition. Diets were consumed ad libitum by 27 and 145 21-d-old Arbor Acres broiler chicks, in Experiments 1 and 2, respectively. In Experiment 3, 66 adult roosters were used to determine the TMEn of the eight cultivars used in Experiment 2. Dietary AMEn decreased linearly (P < 0.05) with increasing barley (Beka cultivar) inclusion. Beka barley AMEn was calculated by extrapolation of the linear regression equation be equal to 2,980 kcal/kg DM. Barley energy value was influenced by cultivar (P < 0.001); the spring cultivars showed greater energy value than the winter cultivars (2,963 vs 2,852 kcal AMEn/kg DM; 3,192 vs 2,929 kcal TMEn/kg DM). Two-rowed cultivars showed higher TMEn than six-rowed winter cultivars, although no differences were found for AMEn. The correlation between AMEn and TMEn values of barley was relatively low (r = 0.69); therefore, barley TMEn cannot be extrapolated to AMEn for young chicks. Enzyme addition produced an average increase of 220 kcal/kg DM in barley AMEn (P < 0.001); there was a significant (P < 0.10) interaction between barley cultivar and enzyme supplementation. The increment of barley AMEn caused by enzyme addition was partly explained (47%) by an increase in barley viscosity. This relationship implies that enzyme supplementation significantly improves the feeding value of high as compared to low viscosity barley samples, which involved a decrease in AMEn variation among cultivars for enzyme-supplemented barley. No relationship was found between AMEn of unsupplemented barley cultivars and their chemical composition. Instead, a relationship was detected for enzyme-supplemented barley; therefore two equations were proposed for predicting the AMEn of enzyme-supplemented barley to be used directly in diet formulation.