TY - JOUR T1 - Investigation on the Effects of Different Levels of Energy and Energy to Protein Ratios on the Performance of Fars Native Laying Hens During the Second Phase of Production TT - بررسی تأثیر سطوح مختلف انرژی و نسبت انرژی به پروتئین جیره بر عملکرد مرغ‌های تخم‌گذار بومی استان فارس در مرحله دوم تخم‌گذاری JF - JSTNAR JO - JSTNAR VL - 10 IS - 3 UR - http://jstnar.iut.ac.ir/article-1-601-en.html Y1 - 2006 SP - 457 EP - 470 KW - Energy KW - Protein KW - Native laying hen KW - Productin phase. N2 - 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 M3 ER -