اثرات سطوح مختلف کنجاله کانولا و آنزیم بتاماناناز بر عملکرد مرغ های تخمگذار از سن 37 تا 47 هفتگی

Background: canola meal contains high levels of non-starch polysaccharides, which can reduce its energy bioavailability. objectives: this experiment was conducted to investigate the effects of different substitution levels of soybean meal with canola meal with or without enzyme b-mannanase on performance, egg quality characteristics, internal organs weight, bone ash and thyroxin hormone level. methods: in this study, 216 leghorn hy-line laying hens, at 37 wk of age, were assigned into 6 experimental groups. a 2×3 factorial experiment based on completely randomized design was performed with 6 replications for 10 wk. the treatments consisted of three levels of canola meal (0, 10 and 20% of the diet) and two levels of the enzyme (0 and 0.05% of diet). results: among productive traits, only egg weight was decreased by dietary inclusion of canola meal at the level of 20% of diet (p < 0.05). except for the yolk color index, other egg quality parameters were not affected by different levels of canola meal and enzyme. in contrast, shell weight, shell thickness, eggshell calcium and egg-specific gravity were affected by the interactions between the canola meal and enzyme (p < 0.05); so that the addition of enzyme to the diet containing 20% canola meal improved the mentioned parameters. after 10 wk of experiment, the inclusion of 20% canola meal in the diet of laying hens had no negative effects on toe bone parameters (toe ash, calcium and phosphorous), internal organs weight and serum t4 hormone level. conclusions: in general, regarding no negative effects of canola meal on productive parameters and observing the positive effects of b-mannanase on eggshell quality at the high level of canola meal, it is suggested that canola meal can be included up to 20% with b-mannanase enzyme in the diet of laying hens