Four experiments were conducted to examine the development of castration-induced behavioral changes, the effects of castration age on pig weight gain, and the efficacy of common analgesics for use in castrated pigs. In Exp. 1, behavioral changes associated with castration of pigs at 1, 5, 10, 15, or 20 d of age were evaluated. Castration caused measurable changes (reduced suckling, reduced standing, and increased lying times, P < .05) in the behavior of young pigs compared with that of intact pigs at all ages tested. Effects of age and interactions between age and castration treatment were not significant (P > .10) for any behaviors evaluated. In Exp. 2, the performance of pigs castrated at 1 d of age was compared with the performance of those castrated on d 14 and female littermates. Birth weights, weaning weights, and mortality were recorded. Pigs that were castrated on d 14 were heavier (P = .05) at weaning and had a higher (P < .05) weight gain during lactation compared to pigs castrated on d 1 of age. Pig mortality was similar among the treatments. In Exp. 3 and 4, the efficacies of pain-reducing drugs (non-narcotic analgesics) were evaluated for effectiveness in reducing castration-induced behavioral changes in 8-wk-old pigs. Although castration reduced (P < .05) feeding time and weight gain, neither aspirin nor butorphanol influenced behavioral changes associated with castration. We conclude that pigs show similar behavioral changes (and probably pain perception) when castrated from 1 to 20 d of age. However, pig performance data favored castration at 14 d rather than at 1 d of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Four experiments were conducted to examine the effects of general and local anesthetics given prior to castration on piglet behavior and weight gain. The first experiment showed that use of general anesthesia by xylazine, ketamine hydrochloride and glyceryl guaiacolate for 2-wk-old piglets resulted in the death of 28% of the piglets and, for those that survived, suppressed nursing behavior. In the second experiment, using 2-wk-old piglets, local anesthesia by lidocaine hydrochloride prevented the slight (30 min) castration-induced nursing behavior suppression. In the third and fourth studies, using 7-wk-old pigs, local or general anesthetic did not overcome castration-induced changes in behavior. Castration affected behavior of 7-wk-old pigs for 6 to 8 h. None of the treatments in any of the studies influenced weight gain. We conclude that castration is painful for 2-wk-old and 7-wk-old pigs. The 2-wk-old pig seems behaviorally less affected by castration than does the 7-wk-old pig. Local anesthetic prevented pain-induced behavior changes for 2-wk-old, but not for 7-wk-old, pigs. At present, the FDA does not permit use of these anesthetics in meat-producing animals.

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