This study was conducted to evaluate the effects of different nutrient density on performance of Hy-line (W-36) laying hens in late phase of laying. This experiment was conducted with two hundred and fifty six laying hens from 73 to 83 weeks in a completely randomized design with 4 treatments and 4 replicates with 16 birds in each replicate. Experimental diets were isocaloric and included: diet with nutrients recommended by Hy-line company for commercial production of laying hens in late phase of laying (control), diet with 5 percent lower level of nutrients than nutrients recommended, diet with 10 percent lower level of nutrients than nutrients recommended and diet with 15 percent lower level of nutrients than recommended for 10 weeks. The results of this experiment showed that the performance and egg quality in laying hens did not affected by different experimental diets (P>0.05).The comparison of performance and egg quality among treatments showed that 15 percent reduction of nutrient level than recommended by Hy-line company levels for commercial production of laying hens in late laying period not only had not any adverse effect on performance and egg quality of laying hens but also in more circumstance have positive effects on performance and egg quality and can reduce the price of feed production per kg of egg. Based on the results of this experiment reduction of 15 percent nutrient level than nutrients recommended by Hy-line Company for laying hens in late laying period (73 to 83 weeks) had not any adverse effect on performance and egg quality.

This study was conducted to consider the effect of vitamin supplementation on laying hens performance. Commercial egg type Hy-Line hens were used in a randomized complete block design with 8 treatments and 3 blocks for 13 weeks period. The levels of different vitamin supplements (treatments) were: NRC (1994), 1.5 times NRC, 2 times NRC, Supporting of Livestock Affairs Limited (S.L.A.L.), Standards and Industrial Research Institute of Iran, Hy-Line management guide and two vitamin premix provided on the basis of S.L.A.L. recommendation by two factories. Feed consumption, egg mass, egg production, egg specific gravity, Haugh unit, shell weight, percent shell were not significantly influenced by dietary treatments. However egg weight, feed conversion ratio and feed cost per kg of egg were affected (P< 0.05). The best and worst feed conversion ratio was related to treatment of 2 times NRC and NRC, respectively (1.98 vs. 2.20). The lowest egg weight was related to treatment of NRC and 1.5 times NRC. The lowest and highest feed cost per kg of egg were related to treatment of 2 times NRC and NRC, respectively. The results of this experiment suggested that supplemental vitamin levels in twice NRC, not only improved the performance of hens, also reduced feed cost per kg of egg.

An experiment was conducted to evaluate the effects of different levels of mineral and vitamin premix on performance and egg traits of laying hens from 37 to 49 weeks of age. Two hundred and forty laying hens (Hy-Line W-36 strain) were randomly assigned to 5 dietary treatments of four replicates each with 12 hens per replicate). The levels of mineral and vitamin premixes in the experiment were 0, 0.15, 0.25 (as recommended by manufacturer), 0.35 and 0.45% of diets and fed to laying hens for 12 weeks. The results showed that the supplementation of different concentration of mineral and vitamin premix improved (P>0.05) the performance of laying hens. The highest percentage of egg production (83.48), the highest amount of egg mass (47.89 g), the best feed conversion (ratio 2.09 g:g) and the lowest price for production per kilogram of (6760 Rials) were observed in group fed: 0.45% of mineral and vitamin premix. Different levels of dietary mineral and vitamin premix did not affect the eggs weight, the amount of daily feed intake and egg traits of laying hens. The overall results of the present study indicate that during the first phase of egg production in laying hens, increasing the levels of dietary mineral and vitamin premix up to 0.45% can improve the performance and reduce the feed cost of egg production.

This study was conducted to investigate the effect of licorice (Glycyrrhizaglabra) extract, Active-mos®prebiotic, and flavomycin antibiotic on performance, egg quality, and body mass status in the pre and early laying periods. A total of 180 Leghorn pullets (Hy-line W-36), were assigned into 6 treatments (5 cages/treatment, 6 pullets/cage) in a completely randomized design. The experimental treatments included control (feed additive-free- diet), and control supplemented by licorice extract (5 and 10 g/kg of diet; as LIEX5 and LIEX10, respectively), flavomycin antibiotic (400 and 650 mg/kg of diet; as FL400 and FL650, respectively), and Active-mos®prebiotic (1 kg/ton of diet; as ACPR). Birds were raised in a cage-layer facility. Body weight, feed intake, and feed conversion ratio were determined weekly. Body mass index was recorded before and after using the treatments. Also, the growth, egg quality, egg cholesterol, serum cholesterol, and triglyceride were tested. During weeks 18 to 19 of age, birds received control, FL650, and ACPR treatments showed greater feed intake compared to LIEX10. The body weight of birds that received FL400 diet was greater than LIEX5 and ACPR treatments at weeks 17 to 19 of age. All treatments, except for ACPR, decreased serum cholesterol compared with the control treatment (P < 0.05). No significant effect on feed conversion ratio, egg production, and body mass index was observed by treatments throughout the study (17-25 wk). Furthermore, there was no significant effect of treatments on the eggs' internal and external quality status, egg cholesterol, and serum triglyceride by treatments. However, more research is needed on the use of licorice extract and prebiotics as antibiotic alternatives and their effects on the body mass index in laying hens during pre- and early-laying periods.

An experiment under complete randomized design was' carried out by allotting 300 HY-line layers at 32 weeks old. The birds were divided into five treatments and four replicates (15 birds in each) under 20 experimental groups. The experimental diets were prepared by incorporating different levels of oil extracted propolis (0.0 , 10, 20, 30 and 40 mg / kg of feed). The birds were fed with feed and water ad lib with is nitrogenous and isocaloric diets for 12 weeks. As results indicated that, inclusions of oil extract propels at various levels in diets, had significant effect on performance (p<0.01). Higher feed intake was observed in treatment five (40mg/ kg of feed) vs, to treatment one (no propolis in diets) 121.9 vs 119.7g respectively. The improved feed efficiency was shown in treatment five as a comparison to treatment one 2.2 vs 2.4 respectively and differences were significant (p<0.01). More egg production was recorded in treatment five and less in treatment one, 89.1 vs 59.4 respectively. Egg mass also was affected by inclusions of oil extract propolis at different levels in diets as compared to control groups significantly (p<0.01). High egg mass was observed in treatment five and low in treatment one 55.9 vs 51.8. Increased weight of burs fabricious gland also were observed in treatment five as compared to treatment one 4.4 vs 2.6 g and differences were significant (p<0.01). More antibody titrations against Newcastle disease were observed in treatment five as compared to treatment one 8.9 vs 5.9 and differences were significant (p<0.01).

This experiment was conducted to examine the effect of different levels of protein (13 and 15%) and methionine (0.25, 0.30 and 0.35%) on performance and some egg indices in the late laying period of layer hens. Ninety six leghorn 80 weeks W-36 layers were used as a 2×3 factorial arrangement based on the completely randomized design. The results have shown that as methionine level was increased, the production percentage and egg weight were increased (P<0.05). Different levels of protein had no significant (P>0.05) effect on the production percentage and egg weight. Treatment effect on the production percentage and egg weight was significant (P<0.05), as birds fed diet containing 15% protein and 0.35% methionine had the highest production percentage and egg weight. Experimental treatments had no significant (P>0.05) effect on other parametes (cracked and soft eggs sell, yolk and albumen indices, egg area, egg weight to area ratio, yolk color, haugh unit, egg content and egg shap index). It can be concluded that the best levels of protein and methionine for egg production in the late laying period of laying hens are 15 and 0.35%, respectively.

This study was conducted to evaluate the quality of different mineral- vitamin premixes in performance of laying hens. This experiment was performed with one hundred and ninety two Hay-line W-36 laying hens from 70 to 80 weeks in a completely randomized design. Experimental groups were include ration without using of mineral-vitamin premixes (control), and three brands of mineral-vitamin premixes including Aras Bazar, Tolidaru and Darosazan. For 10 week. There were not significant differences in performance and egg quality among experimental groups (P>0.05). The overall results of the present study indicate that it's possible to remove dietary mineral and vitamin supplements from laying hens diets in late laying period without any adverse effects on performance and egg quality.

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.