Effect of different levels of zinc-methionine compared to zinc oxide on growth performance, microbial population and intestinal morphology of broiler chickens

Abstract

Introduction: The aim of this study was to compare the effects of using different levels of zinc oxide and organic source (zinc-methionine) in feed on growth performance, morphology, and intestinal microbial population of broiler chickens.
Materials & methods: This experiment was conducted on 320 one day old broilers in order to compare different sources and levels of zinc in a completely randomized design through a factorial arrangement (2×4) with five replications and 8 chickens in each replication. Zinc sources included zinc oxide and zinc-methionine combination at various levels (0, 60, 120 and 180 mg/kg).
Results: Diets contained no Zn supplement increased feed intake during starter and grower period (p<0.05). There was a linear relationship between the level of zinc intake and the reduction of feed intake during starter and grower period (p<0.05). In the final period as well as the total period of the experiment, the highest level of zinc supplement in ration (180 mg/kg) increased the body weight gain (p<0.05). In all experimental periods, diets contained no Zn supplement increased the food conversion ratio (p<0.05). In the entire experimental period, the highest level of zinc consumption in the feed initiated a significant improvement in the feed conversion ratio (FCR) compared to other experimental treatments (p<0.05). The interaction effect between source and level of zinc on FCR in starter was significant (p<0.05); in order to both zinc-methionine and zinc oxide treatment at the level of 120 mg/kg had the lowest FCR. The use of organic zinc supplement in feed significantly increased the enumeration of lactic acid bacteria (p<0.05). The interaction between zinc source and level on lactic acid bacteria was significant (p<0.05); so that the main population of these bacteria was observed in the treatments containing zinc methionine at 60, 120 and 180 mg/kg levels. The effect of zinc source added to the ration on the length and width of the villi and also on the depth of the crypt was significant (p<0.05); length and width of the
intestinal villi in birds fed zinc-methionine were increased (p<0.05). The supplemental zinc level increased the length of the intestinal villi (p<0.05) and the level of 180 mg/kg had the greatest effect on the length of the villi. The highest level of zinc consumption in feed significantly increased the length of villous compared to other levels.
Conclusion: According to the desired results in this study on growth performance, increased length and width of intestinal villi and improvement in population of intestinal lactic acid bacteria, it is recommended that the amount of 180 mg/kg of zinc-methionine to be used in the diet of broiler chickens.