The Effect of Stocking Density and Different Dietary Energy Levels on Immune System Response and Body Weight of Broiler Breeders in Rearing and Laying Period

The objective of the current research was to investigate the influence of different levels of dietary energy and stocking density on body weight and immune system response in Ross 308 broiler breeder hens. For this purpose, a completely randomized design with 9 treatments included three diet energy levels 2600, 2750 and 2900 ME/Kg and three levels of stocking density (4, 6.5 and 9 birds/m2 in rearing and 3.5, 5.5 and 7.5 birds/m2 in laying period), were used with factorial arrange (3×3) and 4 replicates The results showed that, with increasing dietary energy level, live weight of hens increased significantly from 21 weeks to the end of the experiment (P <0.05), on the other hand, high density from the beginning of the experiment until 31 weeks had no significant effect on live weight of hens, but in the last 10 weeks, higher density caused more weight gain (P<0.04). The percentage of lymphocytes, monocytes, heterophiles and the ratio of heterophiles to lymphocytes did not show a significant difference between the three energy levels. However, the percentage of heterophils, lymphocytes and the ratio of heterophils to lymphocytes were higher in the high-density treatment (P <0.05). There was also no significant difference between the treatments in the observed titers including infectious bursal disease (IBD), bronchitis (IBV), reovirus (REO), Newcastle (ND) and influenza (AI). The results showed that increasing stocking density can cause stress in the herd and if the herd stocking density increases, it is necessary to re-evaluate the energy requirement.