Researchers create scales to evaluate pain in bovines, equines and swine
November 06, 2013
By Noêmia Lopes
Agência FAPESP – Despite growing national and international concern over animal well-being, the issue of pain is still neglected for several species of livestock. “The lack of scientifically validated scales that help producers, veterinarians and researchers to recognize and measure pain in the animals contributes to inappropriate or insufficient pain treatment,” affirmed Stélio Pacca Loureiro Luna, professor at Universidade Estadual Paulista’s Botucatu School of Veterinary Medicine and Zootechny (FMVZ/Unesp-Botucatu).
Since 2010, Luna has coordinated a Thematic Project that seeks to propose and validate scales that indicate whether the use of analgesics should be recommended. The principal focus is acute post-operative pain in bovines, equines and swine.
The scales are based on the analysis of behavioral changes related to factors such as posture, head position, locomotion, interaction with the environment, food ingestion and attention to the surgical wound.
To identify and analyze the behavioral changes, researchers recorded videos at different stages: before the procedure, when the animals are without pain; soon after surgery, when pain peaks; and after the application of analgesics, when pain is expected to cease.
“The procedure we have adopted for the three species studied was castration because it is relatively invasive, reaches high-sensitivity tissues, generates major inflammation and is among the most frequently conducted procedures in these animals,” explained Luna.
The researchers have recorded around 700 hours of video. The videos of swine captured from camera installed in the pens are being analyzed by FMVZ/Unesp. The images of equines (also taken from stalls) and bovines (filmed in pastures with shields separating the observer and the animal, so that the human presence did not affect the behavior of the animals) have already progressed to external validation and statistical calculations.
Validation of the content that serve as the basis of the scales is performed by specialists and researchers linked to partner institutions in Brazil, England, the United States, Spain and other countries in South America, such as Uruguay and Argentina.
Each evaluator receives a section of the videos without information on chronological order; i.e., without knowing whether the animal in question was filmed before or after the surgery or while it was medicated. They then select whether they would recommend the application of analgesics, classifying the pain according to a simple descriptive scale (without pain = 0; light pain = 1; moderate pain = 2; intense pain = 3) and indicate which behavioral changes they manage to see based on the images.
To complete their analysis, the FMVZ/Unesp team received the materials from specialists, made comparisons with their initial conclusions and conducted statistical analysis to construct validated scales in three languages (Portuguese, English and Spanish). These scales are tables that describe the most relevant behavioral changes, coupled with videos and classified with notes that result in a total score. “Based on the mathematical calculations, at around a third of the maximum score, the specialists believe that the animal should receive analgesics,” affirmed Luna.
“When finished, the final products of the study will be pioneers for sharp pain in bovines and swine, which still do not have nationally or internationally validated scales,” said the researcher. “For equines, there is only an orthopedic scale, but nothing about soft tissue affected, for example, by castration.”
The new tools will be made available for free on the website Animal Pain, where FMVZ/Unesp has published an acute pain scale for cats, resulting from a post-doctoral project under Luna’s supervision that FAPESP funded. Two articles related to the study can be found through links to the Journal of Feline Medicine and Surgery and BMC Veterinary Research.
“Broadening knowledge about pain and, in doing so, applying analgesics with more propriety is important for animal well-being from a practical standpoint. This is because there will be gains [for the producer] like shorter post-operative recovery time and a reduction in inflammation,” said Luna.
Anesthesia in swine
Under the auspices of the same Thematic Project, Luna supervised a Scientific Initiation on the effects of castration in piglets with and without the use of local anesthetics.
The investigation concluded that the weight gain in animals castrated with anesthesia is greater than that of animals that do not receive an anesthetic.
“In financial terms, there is a significant gain for properties with thousands of animals. The surgical procedure takes much longer, but the cost-benefit is promising, not to mention that the measure aids in animal well-being and adds value to the product through the consumer market,” said Luna.
Based on that finding, researchers hope to inspire the use of anesthetics in swine during other procedures that are generally performed without anesthesia, such as the cutting of tails and tooth extraction.
Chronic pain in dogs
Through a post-doctoral project, the Luna team is also seeking to establish correlations with the Helsinki Chronic Pain Index (HCPI) – created by the University of Helsinki (Finland) to evaluate pain in dogs – and experiments conducted at FMVZ/Unesp.
“This type of scale, referring to chronic problems, is based on reports from dog owners, who, because they live with the animals, can form impressions on the animal’s humor and willingness to play, among other factors. We sought to incorporate more objective elements to this type of tool, using analysis of the animal’s movement (kinetics) and foot pressure (baropodometry),” affirmed Luna.
With this goal, they observed animals with coxofemoral dysplasia (a joint problem in the articulation between the femur and coxa) during a period of walking on a pressure platform. The researchers collected data on movement, the angulation of paws, pressure on the device and the weight distribution on each member.
“We intend to correlate the objective measures of locomotion with IDCH to improve pain measurement and indicate possible treatments,” said Luna.
Nociceptive stimulus in equines
Two other projects, both doctoral studies, are linked to the Thematic Project and interconnected: a dissertation to standardize and validate different nociception methods and thermal, mechanical and electrical stimulation – capable of causing a certain discomfort – in equines; and a project to evaluate the different effects of different forms of administration of analgesics, also in horses.
To this end, healthy and conscious animals receive analgesia. Afterwards, they are stimulated thermally (with sensors that heat the area via remote control), mechanically (with a device similar to that used to measure arterial pressure in humans) or electrically (through small shocks).
“If there is discomfort, the animal raises its paw and we interrupt the stimulus. That way, we can evaluate whether the analgesic works, if it influences the pain threshold – instead of a horse pulling its hoof when the sensor hits 45 degrees Celsius, it does so at 48 degrees, for example – and for how long the medication is effective,” adds the FMVZ/Unesp professor.
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