عنوان مقاله [English]
This study was conducted to evaluate the effects of different nutrient levels on performance of laying hens. This experiment was conducted with 320 laying hens from 32 to 42 weeks in a completely randomized design with five treatments and four replicates with 16 birds in each replicate. Experimental diets were isocaloric and included: diet nutrients recommended by Hy-line company for commercial laying hens (control), diet with 10 percent lower nutrient level than nutrient recommended by Hy-line company, nutrients recommended by NRC (1994), diet 10 percent higher nutrient level of nutrient recommended by NRC (1994) and diet with average energy of nutrients recommended by Hy-line company and NRC (1994). The results of this experiment showed that the performance and egg traits in laying hens were significantly affected by different experimental diets and the egg weight was significantly different between treatments (P<0.05). The highest amount of egg weight (60.35 g) was observed in control group. Also significantly differences were observed in egg mass between treatments (P<0.05). The highest amount of egg mass (53.72 g) was observed in control group, whereas nutrients recommended by NRC (1994) caused the lowest amount of that (49.84 g). Moreover, feed efficiency significantly affected by studied nutrients (P<0.05). The best amount of feed efficiency (2.13) was observed in control group. There was also significant difference between treatments for egg shell weight and the highest egg shell weight (6.07g) was observed in control group. The egg shell thickness was significantly affected by treatments, too (P<0.05) and the lowest egg shell thickness (304mm) was observed in control group. There was not any significantly difference between treatments in other traits such as feed price to produce one kilogram of egg (P>0.05). It can be concluded that performance and egg quality of laying hens can be improved by using nutrients levels recommended by Hy- line company for commercial laying hens.