عنوان مقاله [English]
نویسندگان [English]چکیده [English]
This trial was conducted to evaluate the effects of different dietary factors that affect egg cholesterol concentration in laying hens of 56 to 70 weeks of age. Three hundred and ninety six Hy-Line W36 laying hens were subjected to 11 experimental treatments, each treatment consisting of 4 replicates, each replicate of 9 hens. Dietary treatments included the control, made up of corn plus soy meal with an AME content of 2750 kcal/kg; vs. experimental treatments comprised of control diet supplemented with 2 and 4% canola oil, 2 and 4% tallow, 1 and 2% garlic powder, 0.1 and 0.2 % probiotic and finally 125, vs. 250 mg/kg of copper in the form of cupric sulphate. All experimental groups received AME plus other nutrients on an equal basis. Egg production and weight were assessed on a daily basis. During the laying period from 58 to 70 weeks of age, egg production rate, egg, feed intake, FCR, albumin quality and weight, shell thickness and fractional shell weight were found out as not differing among treatments. Yolk weights were significantly higher when 1%, and 2% garlic powder as well as 125, 250 mg/kg of Cu were added to the diets (P<0.05). Adding 125 and 250 mg/kg of copper to the laying hens' diets reduced egg cholesterol concentration by 23.4 and 26.5 percent respectively (P<0.01). Egg yolk cholesterol concentration decreased significantly in birds fed 1 and 2 percent of garlic powder (14.47 and 16.2% as compared to control group) (P<0.01). Probiotic treatment increased the serum cholesterol level significantly. In conclusion, it was found out that an inclusion of 125 mg/kg of cu plus 1% of garlic powder in the laying hens' diets can decrease yolk cholesterol concentration without bringing about any adverse impacts on the hens' production performance.