Effect of different levels of dietary metabolizable energy on performance and immune response in Iranian native hens

Determination of energy requirement and its effect on the immune system is one of the most important research topics in poultry and avian research area. To determine the effect of different levels of metabolizable energy (ME) on the production performance and immune responses of Iranian native hens. The experiment was conducted based on a completely randomized design with 6 treatments (2400, 2500, 2600, 2700, 2800 and 2900 kcal/kg ME) and 5 replicates of 10 samples each. Egg production and feed intake were measured both daily and weekly. Humoral immune function was measured by hemagglutination inhibition (HI) test on the 6th and 12th days after intramuscular injection of sheep red blood cells (SRBC). Cellular immunity was determined using responses of cutaneous basophil hyper-sensitivity (CBH) to phytohemagglutinin injection. Data were analyzed using GLM procedure. The results showed that dietary energy had a significant effect on the feed intake in such a way that increasing dietary energy linearly decreased the feed intake (p<0.05). There was no significant difference among the treatment groups in egg production, egg mass and egg weight (p>0.05). There were not significant difference among groups in terms of total antibodies against SRBC, IgG and IgM. However, IgM showed increase in response to different levels of energy on day 12 of injection (p<0.05) with the highest response for the diet contained 2800 kcal/kg ME. The CBH response showed a gradual increase based on increasing the dietary ME levels over 24 and 28 h after injection. Meanwhile diet contained 2900 kcal/kg ME showed the maximum CBH response at 24 and 28 h (0.28± 0.017 and 0.34±0.026mm, respectively). The results of this experiment showed that the dietary ME in the range of 2800 to 2900 kcal/kg made the highest effect on immune responses of Iranian native hens.