Effects of High Dietary Zinc and Biotin Levels on Development and Severity of Foot Pad Dermatitis in Broilers Housed on Litter with Critical Moisture Content

摘要

This experiment was designed to test the hypothesis that higher levels of zinc (methiomne or oxide)and biotin than are normally present in commercial diets can reduce/prevent foot pad dermatitis (FPD)in broilers reared on litter with critical moisture content (35％ water).Two trials were done.in each four groups of 1-wk-old ♂ broilers were reared during 33 days.All groups (25 birds in each)were littered with wood shavings (5 kg/m2)of critical moisture content (35％ water)experimentally maintained by adding water.Two groups were fed upper levels of Zn as zinc-oxide (150 mg Zn/kg diet)with control level of biotin (300 μg/kg diet)or high biotin (2000 μg/kg diet).The other two groups were fed Zn as zinc-methionine (150 mg Zn/kg diet)with control level of biotin (300 μg/kg diet)or high biotin (2000 μkg diet).External assessment of foot pads and weighing of birds were done weekly.Moisture contents of litter and excreta were measured weekly and at trials' end.too.The results showed that high biotin supplementation was accompanied with a reduction by-40％ and 20％ (trials l/2)of foot pad lesions.Using dietary Zn-Met in comparison to ZnO showed a decrease in the severity of FPD lesions by (-10％ )in both trials.The combination of Zn-Met and high biotin levels led to reduced scores at poor litter conditions by-50％ (trial l )and 30％ (trial 2).No significant differences were found among the experimental groups for the performance parameters; however,high dietary biotin levels were accorupanied with the highest final body weight.It is recommended to combine the upper level of zinc (especially of Zn-Met)and high levels of biotin (～ 2000 vs.normal levels of ～ 300 μg/ kg)when clinicallv relevant alterations in foot pad occur.