title: The physiological and behavioral response of pigs castrated with and without anesthesia or analgesia.
abstract: Surgical castration is a common management practice performed on male pigs to prevent the occurrence of boar taint. Surgical castration is known to cause physiological and behavioral changes in pigs indicative of pain-induced distress; however, it is commonly performed without pain relief. The objective of this study was to evaluate the effectiveness of carbon dioxide gas (CO(2)) anesthesia and a non-steroidal anti-inflammatory drug (NSAID) to alleviate the pain caused by castration. At 3 d of age, male pigs were either control handled (CON), castrated without pain relief (CAS), given an NSAID and then immediately castrated (CAS+NSAID), anesthetized with CO(2) and then castrated (CAS+CO2), or anesthetized with CO(2) and given an NSAID at the time of castration (CAS+BOTH). Blood samples were collected before castration, and at 30, 60, 120, and 180 min, 24 h, and 3 d after castration or handling for analysis of cortisol, C-Reactive protein (CRP), and substance-P (SP) concentrations. This study was then repeated using the same treatment groups, and the behavioral response to castration and handling were measured using a 1-min scan sampling procedure. The percentage of stress vocalizations was recorded during the administration of all treatments. Anesthesia and analgesia did not effectively reduce (P > 0.05) the cortisol response to surgical castration. Overall, CRP concentrations were greater (P < 0.05) in CAS+CO2 pigs as compared with CON pigs. Sixty minutes after castration or handling, SP concentrations were greater (P < 0.08) in pigs given CO(2) anesthesia (CO2, CAS+CO2, and CAS+BOTH) than CON, CAS, and CAS+NSAID pigs. Pigs castrated without pain relief spent more (P < 0.001) time lying without contact than all other treatments during the first 30 min after castration, but thereafter CAS+CO2 pigs spent more (P < 0.001) time lying without contact than other treatments. During the first 30 min after the treatments were applied, CAS+CO2 pigs spent more (P < 0.01) time displaying pain-like behaviors than CON, CAS, CAS+NSAID, and CAS+BOTH pigs. The percentage of stress vocalizations was greater (P < 0.05) in CAS and CAS+NSAID pigs than all other treatments. Neither CO(2) anesthesia nor a NSAID, given separately or combined, markedly reduced the pain-induced distress caused by castration in pigs. More research is needed to evaluate practical methods of on-farm pain relief for pigs.
authors.affiliation: Department of Animal and Food Sciences, Texas Tech University, Lubbock 79409. mhairi.sutherland@agresearch.co.nz
authors.forename: M A
authors.initials: MA
authors.lastname: Sutherland
authors.forename: B L
authors.initials: BL
authors.lastname: Davis
authors.forename: T A
authors.initials: TA
authors.lastname: Brooks
authors.forename: J F
authors.initials: JF
authors.lastname: Coetzee
mesh_terms: D000700:Analgesics / Q000008:administration & dosage / Q000494:pharmacology*; D000758:Anesthesia / Q000662:veterinary*; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000494:pharmacology*; D001522:Behavior, Animal; D001835:Body Weight; D002097:C-Reactive Protein / Q000378:metabolism; D002245:Carbon Dioxide / Q000008:administration & dosage / Q000494:pharmacology*; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D009919:Orchiectomy / Q000009:adverse effects / Q000662:veterinary*; D010146:Pain / Q000188:drug therapy / Q000662:veterinary*; D013552:Swine; D014828:Vocalization, Animal; D014945:Wound Healing
chemical_list: D000700:Analgesics; D000894:Anti-Inflammatory Agents, Non-Steroidal; D002245:Carbon Dioxide; D002097:C-Reactive Protein; D006854:Hydrocortisone