ARS | Publication request: Castration is no laughing matter, nitrous oxide can’t even help

Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: February 21, 2011
Publication Date: N/A

Technical Abstract: Castration of pigs is necessary since no other viable alternative is yet available. However, castration is painful and analgesics are being considered to relieve pain. Inhalant gases with analgesic properties allow for a fast induction, short-term and reversible effects, and are a needle-free option. Isofluorane, halothane and carbon dioxide have been tested to alleviate castration-induced pain in pigs with variable success. The use of those gases also raises practical or ethical concerns. Nitrous oxide (N2O), “laughing gas”, has been widely used in human surgery and dental offices as an analgesic, sedative and anxiolytic drug. Yet, N2O has not been thoroughly investigated for use in farm animals. N2O possesses appealing features for the animal industry: It is not regulated as a drug, it is widely available, relatively inexpensive, and harmless. We hypothesized that the analgesic effect of N2O may reduce the pain induced by castration. We used 24 piglets from 12 litters, one piglet receiving N2O (N) and a littermate receiving air as a control (C). After 150 s under the gas, castration was performed while the piglet remained under the gas. Behaviors and squeal lengths were recorded during castration. Behavioral observations were continued for 3 d post-castration using a scan-sampling interval recording method, and weight gain was measured. Data were analyzed using a mixed model in SAS. N2O successfully induced anesthesia in all N pigs, as validated by a skin pinch test and the loss of palpebral reflex. Squeal length was shorter in N pigs during the induction phase (P < 0.001) but not different during castration itself as N pigs awoke and squealed as much as C pigs. Agitation scores during the whole procedure were reduced in N pigs, in both frequency (P = 0.02) and intensity (P = 0.02). For 2 h following castration, N pigs displayed less huddling behavior than C pigs (P < 0.05). Over the 3 d, N pigs performed more tail wagging (P < 0.01) and slept less (P < 0.05) than C pigs. N2O was effective in inducing anesthesia in neonatal pigs. Nonetheless, its anesthetic effect seemed ineffective in preventing castration-induced pain. N2O could be used for other applications to help reduce distress.