A review of the welfare consequences of surgical castration in piglets and the evaluation of non-surgical methods

Abstract

Male piglets are castrated primarily to prevent the unpleasant odours and flavours of entire male pig meat (boar-taint). Although castration can be legally performed without analgesia in the first seven days of life, available evidence shows that castration at any age is painful and may have a detrimental influence on health. Few anaesthetics or analgesics are licensed for use in piglets. The known methods for general and epidural anaesthesia cannot be run at the farm level for practical and/or legal reasons. Use of the local anaesthetic lidocaine is easy and allows the pain resulting from castration to be alleviated. Local destruction of testicular tissue by intra-testicular injection of chemical compounds (salts and acids) is an alternative to surgical castration but needs further investigation regarding welfare improvement and boar taint reduction. Immunocastration, by which castration is achieved using active immunisation (anti–GnRH immunisation) is an efficient alternative to surgical castration; however, there are no licensed vaccines in the EU and the consequences, in terms of pig welfare as well as its acceptability among EU consumers, need further evaluation.

Welfare of pigs on farm

“…There is an increasing number of studies demonstrating that the neural pain pathways in pigs and humans are very similar and that a strong homology between porcine and human nociceptive neuron exist (Prunier et al, 2021), suggesting that castration can result in severe pain to piglets. These results align with previous studies reporting pain in piglets during (Taylor and Weary, 2000;Taylor et al, 2001;Kluivers-Poodt et al, 2012;Viscardi and Turner, 2018) and after the castration procedure (Prunier et al, 2006;Kluivers-Poodt et al, 2007).…”

“…A later study found that piglets castrated at 3 days stood more in the first hours after castration than those who were castrated as older piglets, while no effects were observed regarding time spent nursing, lying, standing or sitting (Carroll et al, 2006). While previous studies noted increased vocalisations in older piglets compared to younger animals during castration (Geetha et al, 2008), a further review study hypothesised that the influence of age on calls at castration could be mainly attributable to an increase in vocal capacity in older piglets (Prunier et al, 2006). To conclude, no evidence exists that castration at a younger age is less painful than if implemented at a later stage.…”

Validation of the Unesp-Botucatu pig composite acute pain scale (UPAPS) in piglets undergoing castration

“…In the United States (US), approximately 94 million pigs are castrated annually to prevent unwanted breeding [1], reduce aggression [2] and improve meat quality [3]. Despite the acknowledgment that castration is painful [4][5][6][7], and the economic benefits associated with pain relief and long-term weight gain in pigs [8], this procedure is not commonly performed in conjunction with pharmaceutical pain control in the US [9][10][11]. From a European perspective, many countries have passed legislation requiring mandatory pain relief for castrated piglets.…”

Astragalus polysaccharide (APS) supplement in beagle dogs after castration: Effects on the haematology and serum chemistry profiles, immune response, and oxidative stress status

“…In fact, castration has been shown to prevent diseases of the reproductive system, such as diseased testicles and enlarged prostates, and modify undesirable behaviors, including urine marking, wandering, undue sexual excitement, and intermale aggression (Aengwanich et al., 2019 ). However, based on increasing evidence, male animals experience significant pain after castration, which is disadvantageous in terms of physiological, behavioral, and health consequences, especially inflammatory and oxidative stress (Prunier et al., 2006 ). The percentage of neutrophils and the neutrophil/lymphocyte ratio were found to be higher after castration in dogs (Aengwanich et al., 2019 ).…”

“…According to Bretschneider ( 2005 ), castration is an acute stressor, and plasma cortisol values are significantly elevated after the surgical procedure. Thus, animal welfare concerns are increasing pressure on farmers that perform castration (Prunier et al., 2006 ).…”