Physiological, Behavioral, and Scientific Impact of Different Fluid Control Protocols in the Rhesus Macaque (Macaca mulatta)

Abstract

Rhesus macaques are an important model in behavioral neuroscience due to their advanced cognitive abilities. To motivate animals to engage in complex tasks, fluid rewards, in conjunction with fluid control protocols, are often used. The impact of these protocols on animal welfare is controversial. We compared two fluid control protocols against a protocol providing free access to water and evaluated the impacts on physiological states of hydration, behavioral measures of welfare, and scientific output. Blood physiology did not significantly differ between any of the protocols, and urine measures were indicative of well functioning, healthy kidneys. Changes in behaviors were limited, the main one being an increase in motivation to drink on the stricter fluid control protocol, and improved task performance early in the week. Overall, fluid control protocols had little measurable impact on the welfare of rhesus macaques while ensuring that scientific data of high quality could be obtained.

Assessment of stress responses in rhesus macaques (Macaca mulatta) to daily routine procedures in system neuroscience based on salivary cortisol concentrations

“…Repeated short-term stress responses do not necessarily lead to long-term consequences. Neither blood values nor kidney controls indicate any lasting consequences, such as kidney dysfunction, even after years of routinely applied fluid protocols [ 15 ]. This suggests that while causing mild short-term stress responses, the variable availability of fluid does not overtax regular physiological compensation mechanisms.…”

“…Here we investigated the effects of routinely used experimental procedures in systems neuroscience, namely, controlled fluid access, cleaning of chronic implants, and training behavioral tasks while being separated from the group and seated in a primate chair, on salivary cortisol levels in behaviorally trained male rhesus macaques in captivity. Based on a previous study that observed no adverse effects of fluid control on blood or renal physiology [ 15 ], we predict fluid control to induce no or only short-term HPA responses, which do not lead to lasting health effects. No published data exist on the effect of the regular cleaning of chronic implants in rhesus macaque.…”

Improving quality of science through better animal welfare: the NC3Rs strategy

“…NC3Rs-funded PhD student Helen Gray and colleagues at Newcastle University recently reported the effects on physiology, behavior and task performance of different fluid restriction protocols in rhesus macaques, which are commonly used to motivate monkeys to perform behavioral and cognitive tasks in neuroscience studies 14 . The research suggests that fluid restriction (14-26 ml/kg/d) has less of an effect on animal welfare than previously proposed (although the sample size was small, only four adult males).…”

Stimulus dependence of directed information exchange between cortical layers in macaque V1

“…After initial training, monkeys were implanted with a head holder and recording chambers above V1 under general anesthesia and sterile conditions (for details of surgical procedures, postsurgical analgesics, and general postsurgical treatment, see Thiele et al, 2006). wellbeing (Gray et al, 2016).…”