The effects of stocking density and feed restriction on performance, carcass, meat quality characteristics and some stress prameters in broilers under heat stress

This study was carried out to investigate the effects of stocking density and feed restriction on performance, carcass, meat quality characteristics and some stress pameters in broilers under heat stress. A total of 300 1-day age broiler hybrids (Ross 308) was the material of this study. A 2 X 2 factorial design was used, with two levels of stocking density and two feeding programme. Treatments were subdivided into 3 replicates. Two stocking densities were 12 broiler/m2 and 18 broiler/m2. Broilers in all treatments fed ad libitum to 21 days of age and standard management procedure was used for broilers. From 3 to 6 week, the broilers in all groups were kept at ambient temperature between 32oC and 35oC from 10.00 and 17.00 hours. then broilers in one treatment deprived of feed for 8 h per day (09.00 to17.00 h) from 21 to 42 day and again fed ad libitum remainder time of day (17.00-09.00). Each of stocking density treatment was subdivided into 2 groups according to feeding programme. Broilers in one group fed ad libitum to 42 day of age, however in other group, broilers fed ad libitum from to 21 dayof age, then broilers were deprived of feed for 8 h per day (09.00 to17.00 h).Every week all broilers were weighed. Feed consumption and feed to gain ratio were measured weekly to as group. The number of died birds was recorde daily to determine survivability. Five broilers from every pen, total 60 broilers were randomly selected and bled from the wing vein before heat stress at 21 day and after heat stress at 41 day of age. Blood samples were taken for analysis the heterophil-lymphocyte ratio, serum corticosterone concentration and anti Newcastle disease titer. At 20 day and at 40 day of investigation, 5 broilers from each pen were randomly selected and they were assessed for tonic immobility duration and rectal temperature. At 42 day of age, five birds each pen (total 60 birds) were randomly selected for processing. pH, color and cooking loss of brast muscle were measured and pH and color traits of thigh muscle were measured as meat quality characteristics.In the study it was determined that the effect of stocking density on live weight at 42 day of age, cumulative weight gain and feed consumption was statistically significant and the mean values of these traits were higher in the groups of 12 broiler/m2 than the groups of 18 broiler/m2 (P<0,001). The effect of feed restriction on cumulative feed consumption and feed convertion ratio was significant (P<0,05) and the mean values of these traits were higher in ad libitum feeding group than feed restriction group. In the study, significant differences were observed between stocking densities in terms of hot and cold carcass weights and the weights of carcass cuts (P<0,001), however, the differences between stocking density groups were insignificant in terms of hot and cold dreesing percentages and the percentages of carcass cuts. The effects of stocking densities and feed restriction on meat quality characteristics were insignificant in this study. The effects of stocking density on heterophil-lymphocyte ratio, tonic immobility duration and investigated in periods were significant (P<0,05) and the mean values of these traits were higher in stocking density groups of 18 broiler/m2 than that 12 broiler/m2 group. The differences between the groups of feeding programme in terms of heterophil-lymphocyte ratio were significant (P<0,05) and these traits were higher in the ad libitum feeding group than that feed restriction group. However, the effects of stocking density and feed restriction on serum corticosteron concentration and anti Newcastle disease titer. In this study, it was concluded that the broilers under heat stress should be reared in the lower stocking density than 18 broiler/m2 if appropriate conditions couldn?t be provided and the feed restriction had positive effects both on the production traits having economic importance and on the animal welfare in broilers under heat stress conditions.Key Words:broiler, heat stress, stocking density, feed restriction, performance, carcass, meat quality.