EFFECT OF IODINE SUPPLEMENTATION TO LOW ENERGY DIETS ON PRODUCTIVE AND REPRODUCTIVE PERFORMANCE IN LAYING HENS OF LOCAL SINAI STRAIN

Abstract

A total number of 297 Sinai hens (270 females and 27 males) 42-wks-old were used, weighed and divided into nine treatment groups, three replicates each, to investigate the effect of Iodine supplementation to low metabolizable energy (ME) layer diets in a factorial design (3x3) on laying performance, egg quality parameters, reproductive performance and nutrients digestibility as well as some blood constituents during the late stage of laying period (42-58 wks of age). The dietary ME of treatments were 2766 (as control); 2655 and 2565 kcal ME/kg, with three iodine levels of 0.3 (as control); 1.2, or 2.4, mg iodine/ kg diet. Results obtained could be summarized as the following: 1- Decreasing ME content in the Sinai layer diet resulted in a significant decrease in body weight and body weight gain (BWG) while diet supplemented with 2.4 mg/ iodinekg diet had the highest BWG compared to other groups. Also, BWG was significantly affected due to the interaction between iodine and ME. 2- Laying rate percentage and egg mass (g/hen) was significantly decreased by dietary contained 2565 Kcal/Kg diet. Conversely, the hens fed diet 1.2 and 2.4 mg I/Kg diet significantly improved the laying performance. Also, the superiority of the diet contained 2655 Kcal/Kg with 2.4 mg iodine /Kg diet where it was significantly greater laying performance than all other treatments. 3- No significant effect was observed on reproductive performance by feeding different levels of ME, while hatchability percentage was significantly improved as dietary supplemented with 1.2 and 2.4 iodine/ kg diet. Also, the best significant value of hatchability was recorded by the interaction between 2655 Kcal ME/ kg and 2.4 mg iodine/ kg diet. 4- Decreasing ME content from 2766 to 2655 and 2565 Kcal/kg diet showed linear significant higher feed consumption. While, only the low level of ME (2565 Kcal/Kg diet) significantly decreased feed conversion ratio compared to the control. 5- Iodine supplementation (1.2 and 2.4 mg/kg diet) resulted in a significant linear feed consumption decreased compared to the control diet. Also, hens fed diet contained 1.2 and 2.4 mg iodine/Kg diet produced significantly better feed conversion than control diet. 6- Feed conversion ratio was significantly improved by the diet containing ME 2655 Kcal/Kg diet + 2.4 mg I /Kg diet as compared to the control diet by about 15.5 %. 7- Digestion coefficient of Ether extract (EE) and ash retention were significantly increased by decreasing the ME to 2565 Kcal/Kg diet compared to the control diet (2766Kcal/Kg diet). All values of nutrients digestibility tend to be significantly linear increase for birds fed diets supplemented with 1.2 and 2.4 mg iodine/Kg layer diet as compared to control diet (0.3 mg I/Kg diet). 8- Dietary energy level has significant effect on blood metabolites, except triglycerides, and improved HDL concentration and thyroxin level, especially the low followed by the median ME level. 9- Dietary iodine supplementation, up to 2.4 mg/ kg diet improved blood parameters, hematological traits, T3 level, and T3/T4 ratio without any negative effects on liver function and immune responses, in terms of ALT, AST activity and WBC′s count. 10- The combined effect between low and median ME and high iodine is the best for different productive and physiological parameters. 11- Decreasing dietary ME content from 2766 to 2655 Kcal/Kg diet resulted in no significant effect in economic efficiency. On the other hand, the high level of iodine (2.4mg/Kg diet) with decreasing ME from 2766 to 2655 Kcal/Kg diet resulted in significantly higher economic efficiency than all other treatments. The results illustrated that the adequate level of ME for Sinai laying hens was 2655 Kcal/Kg diet to maximize the productive performance under the condition of this study, however the combination of same level of ME (2655 Kcal/ Kg diet) and 2.4 mg iodine/ Kg diet is the most successful requirement for improving laying performance and reproductive performance for Sinai laying hens during the late stage of laying period (42- 58 wks of age).