Performance of broiler chicks fed high levels of cholecalciferol in diets containing sub-optimal levels of calcium and non-phytate phosphorus.

摘要

An experiment was conducted to study the performance, bone mineralization, mineral excretion and retention in female broiler chicks fed high levels of cholecalciferol (CC) in diets containing sub-optimum levels of calcium (Ca) and non-phytate phosphorus (NPP). Four diets were prepared to contain two sub-optimum levels of Ca (5 and 6 g kg-1) and NPP (2.5 and 3 g kg-1) in 2x2 factorial manner in maize-soyabean meal basal diet. Each combination of Ca and NPP was supplemented with 200, 1200, 2400 or 3600 ICU of CC kg-1 diet. Five hundred and sixty Vencob broiler female chicks were randomly and evenly distributed into 112 stainless steel raised wire-floor battery brooder pens. Each experimental diet was fed ad libitum to seven replicates from 2 to 42 d of age. Majority of parameters responded non-linearly with increase in levels of CC in diet, except the body weight gain and leg abnormality score at 14 d of age, which linearly increased and decreased, respectively, with CC levels. Body weight gain, feed conversion efficiency (FCE) and leg abnormality score at days 14, 28 and 42 were not affected due to variation in dietary Ca level. At 2.5 g NPP kg-1 diet, weight gain, FCE, tibia length and tibia ash content increased non-linearly with increase in CC. Excretion of Ca and P decreased with the levels of these minerals in diet. Retention of Fe, Zn and Mn in liver increased non-linearly with increase in CC levels in diet. Variation in retention of trace minerals in liver due to CC level was influenced by the ratio between Ca and NPP levels in the diet. Based on the results, it can be concluded that 2.5 g NPP and 5 g Ca kg-1 diet was adequate for broiler chicks weighing 1800 g at 42 d of age when the diet contained higher levels of CC compared to those recommended (200 ICU CC kg-1) for commercial broiler chicks..