effect of quantitative feed restriction on performance, stress index and reproduction properties in native hens of khorasan station

introduction under commercial conditions broiler are feed restricted during rearing to limit growth rate. this quantitative restriction of feed intake aims at avoiding rapid growth and high body weights, which are associated with pathological conditions, such as ascites, lameness, and mortality. feed restriction (fr) in breeder layer hens was rarely and fr used for poor reproductive results and low fertility. native poultry population is developing and the role of these birds in the production of animal protein is increasing. native hens of khorasan breeding station and most stations in country feed adlibitum. add feed intake on the one hand leads to economic loss and also leads to increase weight in laying hens that may interfere with the process of egg production and hatchability. this experiment was conducted to evaluate of different levels of quantitative feed restriction (fr) on performance, stress index and reproduction properties of native hens of khorasan station. materials and methods to investigate the effects of feed restriction, an experiment with 350 hens in the form of completely randomized design with seven treatments, five replicates and 10 hens in each replicate of age 36 to 52 weekly implemented. treatments based on corn, soybean and wheat with different levels of fr, including 125,120,115,110,105 and 100 g/ days for layer hens and control groups feed intake was adlibitum. during the trial period, all eggs produced by hens in each pen were measured on a daily basis. amounts of feed added to the feed troughs were recorded daily. after each week, the weights of feed in the troughs of adlibitum fed birds were recorded. from these data, daily mean intakes per bird were calculated for this pen. during the experimental period the birds were free of water and 16 hours of light and 8 hours of darkness were used. at the end of the experiment (52 weeks) two birds of each experimental pens were slaughtered and immediately different organs weight of each birds were measured. on the same day, three hens per pen were randomly collected blood from the vein under the wing. blood containing edta anticoagulant were then transferred to the laboratory and a development staining by method of may grunwald- giesma were prepared. results and discussion the results showed that fr as soon as 110 g/days had no significant effect on egg production (ep), but in another groups of fr (105 and 100 g/days) decreased ep. the results showed that native hens feed intake less than 110 g/ day, decreased ep. the results of this study indicated when we are to the end of the weeks of experimental periods, the ep more decline caused by fr. levels of 100 and 110g/days fr and control group (adlibitum feed intake) has no significant effect on egg weight (p>0.05). the best feed conversion ratio (fcr) was observed in 110 g/days of fr (p<0.05). the results of the fcr showed that the highest fcr were observed in groups without limitation and with 125 g/days feed consumption. in the early weeks of the experiment (39-36 weeks), different between the fcr in the group without restriction and with a fr of 100/ day, was 0.46 and this data the week-end test this data was 0.31unit. perhaps reducing egg production this would be effective. fr in 100 and 105 g/days levels decreased the fat pad and gizzard weight, but was no effects on oviduct and ovary weight. increasing fat liver is one of the basic reasons for fatty liver syndrome. the results showed that fr decreased liver weight, although in this experiment the amount of fat in the liver not detected, but the problems associated with fatty liver syndrome and reduce the economic life of commercial layer hens is one of the problems in this industry. methods of feed restriction causes decreased liver weight and fat less likely that this is a good strategy forto dealing fatty liver syndrome. fr at 100 g/days increased the heterophil/lymphocyte ratio (p<0.05), but another levels of fr no effect on it. the heterophil to lymphocyte ratio has become widely accepted as a reliable and accurate physiological indicator of the stress response in chickens and layer hens. because exposure to stressors causes it to increase progressively. this ratio may be a more reliable indicator of mild to moderate stress than plasma corticosterone concentration. in more study, suggested that reference values for the heterophil to lymphocyte ratio of about 0.2, 0.5, and 0.8 are character is tic of low, optimal, and high degrees of stress, respectively. heterophil to lymphocyte ratio was increased 0.1 unite for fr at 100 g/days comparable with another groups. conclusion overall, the results of this study showed that fr in 110 g/days no decreased ep and h/l ratio, this level of fr reduced feed conversion ratio in native hens.