Australia remains one of the world’s largest producers of wool globally with approximately 70 million head of sheep as of 2018 (FAOUN, 2018) and national wool exports making up approximately 25 per cent of the wool sold on the global market holding an estimated value of $3.615 billion (Department of Agriculture water and environment, 2019).
As time goes on new challenges face the industry from natural disasters and drought natural to societal challenges like producing sustainable product and public perceptions of farm animal welfare. Animal welfare is becoming a national issue as a recent nationwide survey requested by the Department of Agriculture found that out of its 1,521 respondents “95% of people view farm animal welfare to be a concern and 91% want at least some reform” (Futureye, 2018). These consumer beliefs have giving traction to several organisations, most well-known of which include the RSPCA, the Animal Justice Party and Animals Australia, who have begun campaigning and strongly opposing the methods and husbandry practices of the industry particularly on the procedures of castration, mulesing and docking.
With both societal expectations and the expectations of organisations many Australian brands are restricting the product that they purchase depending on the treatment of the animals used to make said products (Terzon, 2020 & Woolworths Group, 2019), with this now comes an economical challenge for the industry to face.
Assessment of Pain in Sheep
The hormone cortisol is a primary physiological indicator of pain in sheep as the glucocorticoid hormone is released in response to stress (Hecter and Pincus 1954). changes in the cortisol plasma concentration have also been studied to have negative effects on sheep particularly in regards to handling procedures (Kilgour and de Langen 1970). Cortisol however can be affected periodic fluctuations (Tapp et al 1984) and other influences that would not be considered negative to the sheep (Colborn et al 1991) and therefore accurate cortisol levels should be taken from samples following the procedure (Kilgour and de Langen 1970) and to include control groups in the experimental design.
Studies by Lester et al (1991) and Kent et al (1993) demonstrated an increase in cortisol levels of castrated lambs compared to their control uncastrated counterparts.
Behavioural pain indicators have been used by studies to assess pain following husbandry practices (Molony & Kent, 1997 & Molony et al., 1993) and define a lamb’s response or husbandry procedures. And the lack or routine behaviour is considered by Anil et al (2002) as a critical indicator of pain
Escaping behaviours can also provide a good indicator of the received pain of the procedure for the lamb as a study by Molony and Kent (1997) suggest that the amount of agitated behaviour shown may echo the severity of the process meaning the greater the attempts to flee or avoid the procedure the greater the pain experienced is. If the lamb has grown tired from escape behaviour it may move onto more passive ways to avoid the pain it is experiencing (Molony & Kent, 1997). In a similar study by Molony et al (1993) the opposite is also observed, as lambs that had just gone through castration and docking procedures minimised movement and stood still or lay down in order to reduce stimulating sensitive areas where the procedures took place, in this case, the more severe the pain, the more still and animal became. Apart from a lack of movement lambs who have just been through husbandry procedures have also been noted to exhibit abnormal walking behaviours and postures including, unsteady walking, hunching their back while they stand and fully extending their legs while lying down (Molony & Kent, 1997). Molony et al (1993) also noted lambs appearing drowsy with a lack of alertness even when nudged by ewe mothers.
Facial expressions are another form of behavioural pain indictor and a Sheep Pain Facial Expression Scale (SPFES) was developed by McLennan, et al (2016) as a way for farm staff to assess pain associated with footrot and mastitis. Multiple studies (Molony & Kent, 1997, Dinniss et al., 1999, Thornton & Waterman-Pearson, 1999) have identified behaviours associated specifically with sheep who have undergone castration and docking procedures, these behaviours include licking or biting the damaged area, lip-curling, as well as increased motor activities like pacing, rolling, , jumping, kicking and stamping. These behaviours are very rarely seen in lambs and such are associated with pain (Dinniss et al., 1999).
Husbandry Procedures for Sheep
Rubber rings (Banding) A rubber ring is placed above the testicles, around the neck of the scrotum eventually resulting in the testicles and scrotum to shrivel up and fall off in a few weeks.
Surgical castration A sharp knife or scalpel is used to remove the bottom one-third of the scrotal sac. The testicles are removed and the wound is allowed to heal.
Emasculator castration The spermatic cord is crushed, which destroys the blood vessels, thus depriving the testicles of blood supply and causing them to shrivel up and die.
Described by the Australian Veterinary Association (2016) as a method to reducing unwanted breeding, castration has in turn exclaimed by Meat and Livestock Australia (MLA) as a procedure that allows greater control over the herd genetic makeup through selective mating. MLA also claims castration also results in less aggressive male rams reducing bruising, injuries whilst making them generally safer to handle for farm staff.
Knife A sharp knife is used to cut the tail down to the desired length.
Hot iron The hot iron method involves severing the tail and cauterizing it simultaneously, using a heated docking iron.
Rubber ring (Banding) A rubber ring is placed along the tail, around eventually resulting a loss of blood supply to the tail leading to the tail shrivelling up and falling off.
The tail of a docked lamb should be docked to the third palpable joint or to the tip of the vulva in ewes, any shorter and lambs have higher chances to suffer from a rectal prolapse (Thomas et al 2003). A bloodless castratior
Studies have demonstrated that the use of a local anaesthetic following rubber ring castration has reduced the behavioural and physiological pain responses in lambs (Graham et al 1997, Moloney et al 1997, Thornton and Waterman-Pearson 1999). Initially it was suggested by Molony et al (1997) that the combination of a rubber ring and a bloodless castrator clamp is the most affective combination to reduce pain following castration procedures and a similar suggestion was proposed by Graham et al (1997) in regards to docking as this method saw a reduction in abnormal behaviours and cortisol peaks from rubber ring only castrated lambs (Thornton and Waterman-Pearson 1999). As the understanding of pain management increased so did the use of local anaesthetics which were found to be more effective in reducing pain than the band and clamp method
In regards to assessing pain in sheep while both physiological and behavioural methods of assessment are helpful and provide a level of understanding with the animal that is beneficial, they both have flaws in the way they are obtained. Physiological methods of measuring pain are generally invasive for example the common act of collecting blood involves moving and/or handling the animal leading to an increase of cortisol in the system (Haresign et al., 1995, Khalid et al., 1998) potentially skewing cortisol levels and thus test results. Behavioural methods of pain assessment may also have their respective consequences, Underwood (2002) demonstrated that prey animals generally hide their pain related behaviours in response to the threat of a predator. Being prey animals’ sheep may mask or show minimal signs of their pain in an effort to appear healthy to any human observers. Another flaw with behavioural observations is they must be done during daylight and generally involve watching only one individual animal at a time, this leads to the process becoming time consuming and slow.
With all this in mind a less intrusive and consistent method of assessing animal pain would be beneficial to the industry and potentially to farming as a whole.
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