T HERE was a need to develop accurate and effective methods for assessing pain in birds in general and in chickens in particular, as chicks are laboratory animals that are easily raised and dealt with, as well as having neurological components to interact and respond to pain the same as in mammals. Birds have physiological and/or behavioral signs of pain. The physiological signs of pain include the change in heart rate, respiratory rate, and blood pressure, and the flapping of the wing. The behavioral signs of pain that extend from the withdrawal response, calling, and the flapping of the wing. This article focused on the methods of pain assessment in birds in the published literature that varying according to the type of stimulus. However, this review offers information on pain assessment approaches and associated behavior, which can enhance specialists' Understanding of the pain causes and, thus, we can evaluate the analgesic drugs for pain in chicks.

The present study was undertaken to explore the analgesic effect of silymarin and ketamine alone or in combination in mice. Analgesia was measured by using a hot plate and the writhing test. The up-and-down method was used to determine the median effective analgesic dosages (ED50s) of silymarin and ketamine administered intraperitoneally (ip) either alone or together. The ED50s of both drugs were analyzed isobolographically to determine the type of pharmacological interaction between them. The analgesic ED50s for silymarin and ketamine in mice were 57.22 and 1.96 mg/kg, ip, respectively. Concomitant administration of the silymarin and ketamine at fixed ration (0.5:0.5) of their individual ED50s was 38.4 mg/kg and 1.28 mg/kg, ip, respectively. Silymarin and ketamine at fixed ration (1:1) of their individual ED50s were 47.54 mg/kg and 1.58 mg/kg, ip, respectively . Depending on the isobolographic analysis and calculating Y value, the type of pharmacological interaction between silymarin and ketamine at a ratio of 0.5:0.5 and 1:1 of their analgesic ED50 values of each drug , was antagonistic .In the writhing test the concomitant administration of silymarin and ketamine at 120mg/kg and 4mg/kg , ip, respectively reduce significantly the numbers of writhing in compare with silymarin120 mg/kg,ip and ketamine 4mg/kg, ip separately. The results suggest that the co-administration of silymarin and ketamine was ineffective to reduce the central pain while the concomitant administration of silymarin and ketamine was effective to reduce the visceral pain.