Abstract
Chickens respond to the signals of other chickens, and as the signals are repeated, the chicken's reactions adapt over time. In studies of chickens responding to repeated playbacks of recorded chicken signals, the word "habituation" has been used to describe both overt behaviours and behavioural responses during specific tests in both field and laboratory settings. Gene silencing, on the other hand, is the regulation of gene expression in a cell that inhibits a particular gene from expressing. The current study aimed to reduce the stress responses of a breed of local chickens by changing their behavioural or genetic factors, and assessed blood traits that reflect their level of welfare. The study used 120 hen chickens obtained at 22 weeks old, divided into six treatments, with four replicates for each treatment (20 chicks per treatment, 5 chicks per replicate) as follows: T1 was a negative control treatment consisting of a local Iraqi chicken breed; T2 was a positive control treatment consisting of a commercial breed of chickens; T3 involved the local breed with siRNA used to silence the corticosterone hormone pathway to the CYP11B2 and CYP11B1 genes by injection in the jugular vein at the age of 24 and 40 weeks; T4 consisted of mixed groups with 25% commercial chicken + 75% local chicks; whilst T5 consisted of 50% commercial chicken + 50% local chicken; and T6 consisted of 75% commercial chicken + 25% local chicken. The results showed a significant improvement (P≤0.05) in Glucose, Cholesterol, Total Protein, LDL, HDL, Globulin and Albumin for T3 and T5 compared with the other treatments; and a significant improvement (P≤0.05) in blood corticosterone in T3 immediately after the injection and two weeks later. The results show that there is an effect of habituation and gene silencing on blood traits, indicating an improved level of welfare for the T3 and T5 chickens.
