The Benefits of Early Neurological Stimulation (ENS)
When discussing how to provide optimal support for the development and well-being of puppies, various factors such as the puppy's growth and the duration of time spent with its mother and littermates are typically taken into account. Recently, there has been a growing emphasis on the significance of environmental enrichment, such as providing puppies with toys, outdoor playtime and human and animal interaction. Simple interactions early in a puppy's life can increase its capacity to learn and successfully manage stress later in life, resulting in better welfare outcomes. Early Neurological Stimulation (ENS) is a technique involving the application of mild stressors to young animals for brief periods, which is believed to improve their stress responses later in life. These stressors, which can include short-term separation from their litter, brief exposure to cooler temperatures, holding them in different positions and gentle body touches, are applied for a few seconds once a day, for at least 10 days.
The correlation between stress and the activation of the endocrine system is widely acknowledged. Stressful events trigger the adrenal cortex to release glucocorticoids, a group of stress hormones that affect numerous processes in the body. These changes underpin the body's "fight or flight" response. Short-term, mild stress can be advantageous, building resilience in the body and equipping it to manage future stressors more effectively (Levine, 1960; as reviewed in Meaney, 2001; Pryce and Feldon, 2003). Nonetheless, not all stress is equal. Prolonged or high-intensity stress is often harmful because it can overwhelm the body's ability to respond or cause adverse effects from a sustained "fight-or-flight" response, draining energy and weakening the body's capacity to resist disease (Selye, 1956).
Studies of Early Neurological Stimulation (ENS) began with rat pups and presently, most research on the topic is focused on rodents. Early handling of rat pups resulted in a reduced fear response when exposed to auditory stimuli (Schaefer, 1963), lower levels of corticosterone when restrained by humans (Plotsky and Meaney, 1993), and enhanced compliance when captured after stress (Núñez et al., 1996). These discoveries have stimulated interest in examining the effects of ENS in other species, including dogs.
Similar to rodents, it is thought that early neurological stimulation (ENS) can benefit the development of a puppy's endocrine system, enabling them to handle stress better later in life. This can result in improved learning and the ability to cope with adversity. Although the belief in the benefits of ENS for puppies comes in part from other species, it is also based on unpublished work carried out as part of the "Bio Sensor" program for the US Military Working Dog (MWD) training, as described by Battaglia in 2009. According to Battaglia, the program has been found to improve heart rate, increase stress tolerance and disease resistance, and create stronger heartbeats and adrenal glands, but the specific measures used were not stated. The "Bio Sensor" exercises consist of various tactile and thermal stimulation techniques and changes in posture.
Only a few studies have been conducted on ENS in dogs using different handling exercises, and the results have been mixed. One study by Fox and Stelzner (1966) involved exposing puppies to light and sound, movement, cold, swimming, grooming, and reflex tests for an hour daily from day one to 5 weeks of age. After three weeks, 10 minutes of play with the researcher was added in. Puppies were weighed and their heart rates were measured weekly. They were then behaviorally tested at 5 weeks of age, and compared to puppies that did not receive ENS treatment. Handled puppies were more confident, more social towards humans, better problem solvers, and explored more, but had higher heart rates than non-treated puppies. Another study by Gazzano et al. (2008) looked at the effects of ENS on dogs raised in homes and those kept in professional breeding kennels. The ENS involved a 5-minute gentle whole-body massage with the puppy lying on both its back and stomach daily for days 3-21 of life. All handled puppies, regardless of housing, explored the environment more in an isolation test, but there were no differences between any groups in heart rates or reactions to unfamiliar objects or environments.
Some studies have shown that using ENS in dogs can have positive effects, but others have found no significant differences. For example, Schoon and Berntsen (2011) discovered that when puppies bred for mine detection underwent "Bio Sensor" along with their usual socialization program, there were no discernible differences in their performance on a test measuring search behavior, reactions to novel stimuli, and developmental milestones. However, since these puppies were already receiving extensive socialization, it is possible that the benefits of ENS were masked. It may be more apparent if ENS is used with puppies raised in less stimulating environments.
Because of the limited number of studies and the variety of test methods used, it is currently difficult to determine which types of ENS are most effective. Further research is necessary to identify the most effective types of ENS for dogs.
When using ENS to enhance puppy welfare, it is crucial to exercise caution to avoid unintentionally causing harm. Overstimulating puppies during ENS can be easy, and the amount of stimulation required for any benefits is unclear. This is problematic because there is no clear threshold for over- or under-stimulation. Separating young animals from their mothers is a common component of ENS, but prolonged separation can result in long-term negative effects on puppies' brain chemistry and stress responses. It is uncertain how long the separation should be to achieve benefits. Additionally, a slight, brief temperature change may be beneficial, but a severe or prolonged change may harm the puppy's health. Therefore, individuals implementing cold stress in ENS protocols should be cautious not to expose puppies to very cold temperatures or cooler surfaces or air temperatures for extended periods. Regardless of the ENS method used, puppies must be monitored continuously for signs of distress, and the ENS treatment should be discontinued immediately if any distress is detected.
Research suggests that ENS may have potential benefits for dogs' long-term stress coping abilities. Several of the proposed ENS techniques are low-cost and easy to implement, and could lead to significant behavioral benefits for dogs in the long run. It is important for breeders to be educated about ENS, so that they can implement it effectively without causing undue stress to puppies. Furthermore, more research is needed to determine the most effective methods of ENS, in order to maximize the benefits to both dogs and breeders. By incorporating ENS into their practices, breeders may be able to improve the overall health and welfare of puppies, potentially leading to greater owner satisfaction.
