بررسی تأثیر سطوح مختلف انرژی و نسبت انرژی به پروتئین جیره بر عملکرد مرغ‌های تخم‌گذار بومی استان فارس در مرحله دوم تخم‌گذاری

The effects of different levels of metabolizable energy and energy to protein ratios on the performance of Fars native laying hens were examined during the second laying phase. In a feeding trial, 216 Fars native hens 42 weeks old were randomly allotted to 9 experimental diets using 6 replicated groups of 4 birds per cage. The diets were formulated with 3 levels of ME (2700, 2900 and 3100 kcal/kg diet). At each level of energy, 3 energy to protein ratios (195, 215 and 239) were considered. The diets were fed ad libitum for a period of 20 weeks (42-62 weeks). The results indicated that there were no significant differences in egg production, egg weight, body weight gain and livability at the end of the experiment (65 week of age) (P>0.05). Daily feed intake was significantly lowered in hens fed the first (ME=3100 Kcal/kg, CP=15.87), second (ME=3100 Kcal/kg, CP=14.43), third ration (ME=3100 Kcal/kg, CP=12.99) and fifth (ME=2900k Kcal/kg, CP=13.5%) as compared with the seventh ration (ME=2700 Kcal/kg, CP=13.82). Feed intake and feed conversion ratios (FCR) significantly decreased as the dietary energy level increased (P<0.05). Feed consumption at the highest energy level was significantly lower than that at the lowest energy concentration. FCR was influenced by dietary energy level. Hens on the diet with 3100 Kcal ME /kg had lower FCR compared to 2700 Kcal ME/kg. The feed cost per 1 Kg egg production increased significantly with the elevation of dietary energy and protein levels (P<0.05).The results showed that a diet containing 11.31% CP and 2700 Kcal ME/kg adequately satisfied the maintenance and production requirements of Fars native hens during the second phase of production. Also, this ration was more economical.