Elsevier

Journal of Veterinary Behavior

Volume 4, Issue 5, September–October 2009, Pages 203-210
Journal of Veterinary Behavior

In Brief: Practice and Process
Periods of Early Development and the Effects of Stimulation and Social Experiences in the Canine

https://doi.org/10.1016/j.jveb.2009.03.003Get rights and content

Abstract

It is not capacity that explains the differences that exist between individuals, because most seem to have far more capacity than they will ever use. The differences that exist between individuals seem to be related to something else. Researchers have studied these phenomena and have looked for new ways to stimulate individuals to improve their natural abilities. Some of the methods discovered have produced lifelong effects. Today, many of the differences between individuals can now be explained by the use of early stimulation methods, socialization, and enrichment experiences. For example, early life has been found to be a time when the physical immaturity of an organism is susceptible and responsive to a restricted but important class of stimuli. Because of its importance, many studies have focused on the first year of life. Newborn pups are different from adult dogs in several respects. When born, pups' eyes are closed, their temperature is subnormal, and their digestive system has a limited capacity, requiring periodic stimulation by their dam, who routinely licks them to promote digestion. Other mammals such as mice and rats are also born with limitations, and they also have been found to show a similar sensitivity to the effects of early stimulation. Studies show that removing them from their nest for 3 min each day during the first 5–10 days of life causes body temperatures to fall below normal. This mild form of stress is sufficient to stimulate hormonal, adrenal, and pituitary systems. When tested later as adults, these same animals were better able to withstand stress than littermates who were not exposed to the same early stress exercises. As adults, they responded to stress in “a graded” fashion, whereas their nonstressed littermates responded in an “all or nothing way.” The results show that early stimulation can have positive results but must be used with caution. Too much stress can cause pathologic adversities rather than physical or psychologic superiority. Socialization and enrichment experiences have also been found to make important differences in the development of the adult dog.

Introduction

Surprising as it may seem, it does not seem to be capacity that explains the behavioral differences that exist between individuals, because most seem to have far more capacity than they will ever use. The performance differences that exist between individuals seem to be related to something else. The ones who achieve and outperform others tend to have within themselves the ability to use hidden resources. In other words, it is what they are able to do with what they have that makes the difference.

For centuries man has tried various methods to improve performance. Some of the methods used have stood the test of time, others have not. Those who first conducted research on this topic believed that early age was important because of its rapid growth and development. Today, we know that early life is a time when the physical immaturity of an organism is susceptible and responsive to a restricted, but important class of stimuli. Because of its importance, many studies have focused on individuals from the newborn stage through the first 12 months of life. This time frame is important because, in many animal breeding programs, the entire process of selection and management is founded on the belief that performance is inherited. Attempts to analyze the genetics of performance in a systematic way have involved some distinguished names such as Charles Darwin and Francis Galton. It has only been in recent decades that good estimates of the heritability of performance have been established. Some researchers have, based on scientific data, looked for new ways to stimulate individuals to improve their natural abilities. Several of these methods produce lifelong and lasting effects. Today, many of the differences between individuals can be explained by the use of early stimulation methods, socialization, and enrichment experiences. Thus it seems that the first year of life is a time that can be divided into 3 periods of development.

Three important periods of development have been identified during the first year of life in many species. Once birth occurs, canines grow and learn rapidly while their nervous systems are developing and storing information. During the first year of life, 3 important periods of development have been identified in canines that have been used to explain differences between individuals and their ability to respond and perform. Each period is different in length, with some overlapping. As each animal grows and develops, experiences during the 3 time periods affects and influences how dogs will develop and be shaped as individuals. The first period of development can be called the “primary” or “neonatal” period because it begins on about the third day of life and ends on about day 16 of life. The second period is called the “socialization” period that begins at about 3 weeks of age and lasts until a pup is about 12–14 weeks of age. The third period of development is called the “juvenile” period during which enrichment that follows socialization occurs. This last period continues through 12 months of age.

Fox (1972) reported that each period can be related to the degree of maturity of the animal at the time of stimulation. Whitney (1975) described these 3 periods of development in canines and reported that they begin with the neonatal period from birth to 11 days followed by a second period of rapid development and involvement with the dam and owner. His third period was called a juvenile period that begins after the weaning process and continues until adulthood. Many writers have described these periods slightly differently, but all have pointed out their importance to the final development of the individual.

When Lorenz (1935) first wrote about the importance of the stimulation process, he focused on “imprinting” during early life and its influence on the later development of the individual. He pointed out that there were differences between imprinting, conditioning and other forms of experiences that occur early in life and take place very rapidly producing results that seem to be permanent. The importance of these and other types of stimulation during early life was also identified by Fox, 1972, Dunbar, 1979, Scott et al., 1959, Scott and Fuller, 1965, Hoffman et al., 2004, and the U.S. Department of Defense (1967) in their Bio Sensor breeding program.

Fox (1972) was one of the first to study the primary period using electrical encephalogram (EEG) experiments with rats, mice, and later dogs. His studies noted that there was a period of sensitivity that begins at birth and extends for ∼3 weeks of age. Scott and Fuller (1965) also found that during the first 8 weeks of life the very immature canine is able to benefit from stimulation in a way that helps them begin to develop some of their adult behaviors.

In puppies, this period of early life is often studied because it is a time of immaturity and underdevelopment when the pup is sensitive to a restricted, but important, class of stimuli that includes thermal and tactile stimulation, motion, and locomotion (Fox, 1972, Dunbar, 1979, Hoffman et al., 2004). Scott and Fuller (1965) showed that newborn pups experience great change in body and behavioral development especially during the period of 1–6 weeks of age. They described this early life as a “critical” period that they defined as “a special time in life when a small amount of experience will produce a great effect on later behavior.” They concluded that the effect of contact is inversely proportional to age, i.e., the younger the animal the greater the effect. Dunbar (1985) reported that newborn puppies are able to respond/reflex to certain stimuli with limited motor capacities and live in a “sensory void” but are responsive to touch and movement. Hoffman et al. (2004) showed that newborn puppies respond to different levels of dietary docosahexaenoic acid (DHA) which affects brain and eye development. Hoffman et al. study involved feeding the dam dietary DHA from proestrus until the puppies were weaned, and noted important diet-associated behavioral effects. Post-weaned puppies were fed the same diet as the dams. Using an experimental and control group, testing began at 9 weeks of age. Puppies fed the enhanced diet with DHA were found to be more “trainable” than the control group. Similar findings were also reported by Hamazaki et al. (1999) using mice. By varying DHA dietary supplementation, stress-related behavior responses (as calculated by an anxiety index) were found to be lower.

Other studies of early stimulation have involved both cats and dogs. Fox (1971) and Werboff et al. (1968) used electroenchephalograms to measure the electrical activity in the brain of puppies because of the brain is sensitive to changes in excitement, emotional stress, muscle tension, changes in oxygen, and breathing. Fox (1971) showed that pups and kittens, when exposed to early stimulation exercises, matured at faster rates, measured by electroencephalograpic changes, and performed better in certain problem-solving tests than nonstimulated littermates. Holst et al. (2002) found that postnatal oxytocin treatment or stroking lowered blood pressure in young dogs. Strandberg et al. (2005) studied German Shepherd dogs and tested broad behavioral traits to determine if there was a maternal and litter influence on 4 traits (playfulness, chase-proneness, cupidity/fearfulness, aggression). They concluded that there was a substantial additive genetic variation and that the dam had little influence on her pups, either genetically or environmentally. Strandberg et al. (2005) found that the littermates, themselves, seemed to have a major influence on the development of these 4 traits.

Other mammals such as mice and rats are immature at birth and show many of the same limitations as puppies. Mice and rats have also been found to show a similar sensitivity to the effects of early stimulation. Studies show that removing mouse and rat pups from their nest for 3 min each day during the first 5–10 days of life causes body temperatures to fall below normal. This mild form of stress is sufficient to stimulate hormonal, adrenal and pituitary systems (Fox, 1972). Although experiments have not yet produced specific information about the optimal amounts of stress needed to make young animals psychologically or physiologically “superior”, researchers generally agree that some forms of stress have value.

On the other hand, tolerance to stress can vary between individuals. What may be too intense for one may not be for another. Newell (1967) studied the effects of early handling and stimulation in both, perinatal and postnatal (maternal deprivation) environments, and showed that there are differential effects on development for animals of different strains or genetic backgrounds. Freeman (1958) reported that there are distinct breed differences and that there are certain sensitive periods when a particular stimulus has a maximal effect. Studies by Denenberg (1964) and Denenberg and Kline (1964) using newborn rodents reported similar findings. Shaw (1962) showed that sensory deprivation with fish during early life makes a difference in their later behavior. Schaefer (1963), using rats, and Fox (1972), using pups, reported similar results.

One of the best examples of the importance of the “primary” period was shown by the U.S. military in a canine breeding program, the “Bio Sensor” program, (1968–1976) developed to provide dogs to support troops for the Viet Nam War. This program focused on both breeding and training and became popularly known as the “Super Dog” program. As part of this program early neurological stimulation exercises (ENS) for very young pups were developed in the belief that these early experiences could make a positive and long lasting difference in performance. The Bio Sensor program focused part of their effort on the window of time that began on about Day 3 of life and continued until Day 16. This interval of time was recognized as a period of rapid neurologic growth and development and a time of great importance to the individual. This time frame of immaturity was identified as the period when ENS exercises would benefit a newborn even though pups at this age lack regular brain waves (EEG), motor coordination, and normal vision, and are unable to sustain body functions without outside stimulation from their dam. There are no public records of this program. In writing this review, interviews were held with the former director of the program (Col. M.W. Castleberry) and a lead research geneticist. Contacts were also made with breeders from >35 American Kennel Club recognized breeds that used the ENS exercises on pups used in guide dog work, the show world, performance events and hunting. The feedback from breeders confirms that there is a specific time period early in the life of a pup when ENS stimulation has beneficial results.

At birth, newborn pups are uniquely different from adults in several respects. They can not see because their eyes are closed and their digestive system has limited capacity requiring periodic stimulation by their dam who routinely licks them to promote digestion. Newborns are able only to smell, suck, and crawl and they are unable to shiver, carry out adult body functions, or maintain normal body temperatures or adult heart beats. Other indicators of immaturity (Table 1) include their unusually high heart rate and their rapid increase in body weight.

Section snippets

Methods and Materials

The objective of the Bio Sensor program was to produce a dog that would have a superior advantage for military work. One of the techniques involved the use of 6 exercises that were designed to stimulate the neurological system. Only 5 of the exercises are reported in this article. Each workout involved handling puppies once each day. The workouts required that each pup be handled one at a time while carrying out a series of 5 exercises. They are listed in no order of preference. The handler

Conclusions

Breeders can take advantage of the information available about the 3 periods of development to improve and enhance performance. Literature suggests that the cumulative effects of the 3 periods of development can be useful to those who seek high levels of performance. Each period provides experiences that have a cumulative effect on the development and potential of the individual. Ignoring pups during their first 2 months of life while they are still with their mothers may have detrimental

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