Linköping University, 581 83 Linköping, Sweden, 1IFM Biology, AVIAN Behaviour Genomics and Physiology groupFind articles by
Due to the large amount of neural immaturity in dog puppies at birth, the nervous system is susceptible to environmental influences very early in life. Early experiences, like maternal care, have been shown to have profound and long-lasting effects on the behavior and physiology of offspring in primates and rodents. With significant implications for the breeding of working dogs, we hypothesized that this would also be the case for dogs. By videotaping 22 mothers with their litters during the first three weeks after delivery, the present study examined variations in the mother-offspring interactions of German Shepherd dogs within the Swedish breeding program for military working dogs. The purpose of a standard temperament test administered to puppies at around 18 months of age was to categorize mothers according to their level of maternal care and investigate how this care affected the behavior of the puppies. The findings demonstrate that females differed consistently in their maternal care, which had a significant impact on the offspring’s adult behavior, particularly with regard to behaviors categorized as physical and social engagement and aggression. Thus, considering maternal quality in breeding programs may enhance the selection of working dogs.
Numerous studies in various species have demonstrated that early experiences have an impact on the phenotypic, genomic, and behavioral traits of the adult animals. For example, Levine et al. 1, compared to controls, adult rats that had previously experienced maternal separation were less reactive, more explorative, and emotionally stable. They also showed decreasing plasma corticosterone levels over time. Altricial species give birth to offspring with high levels of neural immaturity, and the nervous system quickly develops through intense synaptogenesis2, during which environmental factors can have a significant and long-lasting impact on an animal’s behavior3. The neonatal period is crucial for the development of social behavior and the stress response in mammals because it is a period of intense social interaction.
Early postnatal handling by humans in rodents has significant long-term effects that have motivated numerous experiments. It is evident that human handling of newborns causes increased maternal care, which is the primary cause of the most significant effects5,6. For example, Caldji et al. 7 demonstrated that rat offspring’s reactions to novelty and restraint varied depending on the amount of maternal care they received, as indicated by low and high levels of licking/grooming and arched-back nursing (LG-ABN). This study found that the adult offspring of low LG-ABN mothers had a greater startle response, less open-field exploration, and a longer latency for eating food in an unfamiliar environment. Studies on cross-fostering have also demonstrated that individual variations in maternal care and fearfulness can be a result of the behavior of the mother who is raising the child rather than the biological mother8,9. It has been hypothesized that the mother gives her young primary environmental cues in the early postnatal period, adapting their behavior to their anticipated future environment. Therefore, postpartum experiences can affect neurological development11 and have a significant impact on how rodents respond to stress in terms of their physiological and behavioral responses9.
Early mother-offspring interactions have an impact on offspring behavior in other mammalian species, including prairie voles12, monkeys13, and sheep15. Similar effects in dogs could have a significant impact on dog breeding if they exist. Dogs are bred for a variety of work purposes, and the selection processes are primarily based on the assessment of behavior after puberty, which is predicated on the idea that genetic factors account for the majority of the variation in adult behavior16. However, heritability studies have shown that genetics only contributes a small amount to phenotypic variation17,18,19, and that elements of the upbringing environment have a noticeable impact on adult behavior20. Consequently, it is conceivable that early experiences and the variety of maternal care may be at least as significant as genetics.
In order to assess variations in maternal care and their effects on behavior and temperament in puppies at about one and a half years of age, records and observations of 22 litters of German Shepherd dogs bred to serve in the Swedish Armed Forces (SAF) were examined. We carefully observed the behavior of the puppies during the nursing stages and collected the adult behavioral characteristics from a standard temperament evaluation test (SAF T-test) that the SAF uses as a tool to choose suitable military working dogs (MWD). Since 2005, the SAF has operated a German Shepherd breeding program. About 30% have received approval to work as MWDs or for the police so far. Most dogs are turned down because they don’t have the temperament profiles required by the military, but some are turned down for medical reasons. We looked into the effects of early maternal care on the behavior of adult dogs because of the relatively high number of dogs that were rejected due to temperamental mismatch and a potential relationship between early experiences and later temperament.
This study’s objective was to evaluate individual variations in maternal care and look at how they affect the behavior and temperament of the young. We reasoned that during the nursing period, maternal care would vary between dogs in a consistent manner, and that greater maternal care would result in puppies who were more self-assured, less reactive, and explorative.
For three weeks postpartum, continuous video recordings of 22 different litters (a total of 94 pups: 42 males and 52 females) were used to observe mother-pup interactions. The SAF Dog Training database was searched for the results of the later evaluation of the offspring conducted using the standardized temperament test (SAF T-test).
The regional ethical committee for animal experiments in Linköping, Sweden has approved guidelines that were followed by all of the experiments we carried out for this study (permit number: 51-13).
The study’s 22 female dogs and their litters came from a population of outbred German Shepherds that was produced between 2011 and 2013 as part of the Swedish Armed Forces’ selective dog breeding program. The females ranged in age from two to eight (parity/number of previous litters: 1-4), and the litter sizes ranged from one to ten (average: five and two and a half days). e. m). None of the dogs were housed permanently at the kennel in Sollefte, Sweden; instead, the females were brought there about three weeks before the anticipated whelping day from private foster homes spread throughout Sweden.
The females were kept apart in 4 separate kennels for the first week at the kennel. 5-m2 quarantine rooms connected to a 13. 5-m2 outdoor enclosure. After that, they were moved to the 9 m2 whelping room, where they were kept separately until the puppies were born. Each whelping room had a window that let in daylight and direct access to an outdoor enclosure that was 9 m2 in size. The females at the kennel facility received food four times daily (07 30, 11. 00, 14. 00 and 19. 20). Water was freely available, and the lights were turned on at around 07:00. 00 in the morning and switched off at approximately 20. 00 at night. The rooms were cleaned once daily during the morning walks, which involved three leashed walks with a handler. Females nursed their pups until they were eight weeks old, when they were weaned. At that time, separate foster homes were assigned to females and puppies. Puppies were evaluated later when they were between 15-20 months old. Non-approved dogs were sold as companion animals, while approved dogs were kept for additional training.
A video link was used to observe whelping in a nearby room. In the whelping room, there was a 1. 0*1. 0*0. A 3-m puppy box with a bar and a removable front is available. The box’s flooring was a soft bed (Vetbed), and the room’s floor was carpeted with linoleum. The temperature was kept at 21 degrees Celsius. At the conclusion of the third week, the front of the whelping box was removed, and the puppies were given free access to the entire space. In addition, females had access to a wall-mounted elevated shelf and double the space through an elevated connection to the room next door that was exactly like theirs. Puppies were weighed every week, and they received the recommended vaccinations. Puppies were given access to solid food starting in the third week, and starting at six weeks old, they were permitted daily visits to an enriched area, which could be either indoors or outdoors depending on the time of year and weather. As part of their socialization during their stay at the kennel, puppies were also taken on car rides and on walks through the woods.
With a surveillance camera (Sony SNCRZ25N PTZ with IR-led for night vision), behavior was continuously recorded for all litters from birth until three weeks of age. Video files were stored for later scoring and offline analysis. When the puppies were mostly confined to the puppy box (before they were old enough to move around and the front wall of the puppy box was detached), behavioral recordings were carried out continuously for every second hour over a 24-hour period once per week. e. , the first, seventh, 14th and 21st day postpartum. Each female and her litter received 12 hours of uninterrupted recording time per observation day under this schedule. For technical reasons, the last recording (three-week-old pups) was made on day 18, day 19, and day 20 in one case, two cases, and three cases, respectively.
*Mother in Box: the amount of time, measured in seconds, that the mother spent with both of her front legs inside the pup box.
*Lying in contact: the amount of time, measured in seconds, that the mother was in physical contact (tail and limbs excluded) with at least one pup while lying in the pup box with her elbows on the ground.
*Nursing: The number of seconds spent nursing when at least one pup is positioned at the udder.
The durations and frequencies per pup in each litter were the actual measurements examined because all variables, with the exception of Mother in Box, were divided by litter size.
Four different people decoded videos, with one person decoding the majority of them (16/22) (first author) For each observer, three 20-minute video samples were used to calculate inter-observer reliability (i e. , all observers re-coded the same samples). The average level of inter-observer reliability between the primary observer and the others was 89%; the maximum levels were 100% (for Mother in box and Lying in contact) and 65% (for Licking), respectively.
The litter was used as the observation unit because it was impossible to reliably distinguish each individual pup in the videos. The maternal care received by each child in a litter was therefore scored equally in later analyses.
All dogs raised by the mothers who participated in the study were gathered from their foster homes between the ages of 15 and 18 months and put through the SAF T-test, a standardized temperament test used by the Swedish Armed Forces to identify potential MWD candidates. Five different locations were used for the tests: Ronneby, Säve, Märsta, Solleft, and Lule. The dogs were transported to each location by their foster families in personal vehicles a few hours prior to the test’s start.
Wilsson and Sinn21 provide a detailed description of the testing procedures. The SAF T-test, which evaluates dogs’ responses to a variety of situations, including social interactions and cooperation with humans as well as potentially frightening stimuli like loud noises or unexpectedly appearing dummies, is made up of 12 different sub-tests. A Behavioural Rating (BR) protocol with 25 behavioral variables was used to evaluate the dogs. The same skilled test leader graded each variable on a scale from 1 to 5 for all dogs (for more information on scoring, see Wilsson and Sinn (2012)). A handler, typically a member of the foster family, accompanied the dogs during the test and was led by a test leader.
The five variables from the ethogram were used in a principal component analysis (PCA) for the behavioral recordings of the mother-pup interactions (MPI). The aggregated values for each mother were first subjected to a PCA, which is e. Total MPI is the total of all four observation days’ worth of variables. Second, separate PCAs for each of the four sampling days (designated MPI1-MPI4) were conducted, and the appropriateness of the sampling was assessed. In every instance, the correlation matrix for the behavioral recordings was deemed suitable for PCA (Total MPI; Bartlett’s sphericity 2 (10) = 133). 1, P < 0. 001; KMO = 0. 760, MPI1; Bartlett´s sphericity χ2 (10) = 109. 7, P < 0. 001; KMO = 0. 771, MPI2; Bartlett´s sphericity χ2 (10) = 102. 5, P < 0. 001; KMO = 0. 578, MPI3; Bartlett´s sphericity χ2 (10) = 103. 1, P < 0. 001; KMO = 0. 685, and MPI4; Bartlett´s sphericity χ2 (10) = 97. 9, P < 0. 001; KMO = 0. 780). Each mother was given a PC-score, also known as an MPI-score, based on the PCAs.
Pearson correlation coefficients were calculated for MPI1-MPI4 to examine the individual consistency in MPI-scores between the four different measurement days. The mothers were divided into two equal groups based on their Total MPI scores (high and low Total MPI scores), and the means and standard deviations of the five different behavioral variables mentioned above were calculated separately for each group and observation day in order to examine the individual variations in maternal care. To determine the differences in the maternal behavior variables between the groups, independent samples t-tests were used.
Generalized linear models were used to investigate the potential influences on the Total MPI score. Parity, Sex-ratio, Litter Size, and Trimester of Birth (January-March, April-June, July-September, and October-December) were used as predictors, and the Total MPI score served as the response variable. The other variables were removed from the model in subsequent analyses because only the litter size showed significant effects. The link function was “Identity,” and the probability distribution used was “Normal.” A Wald chi-squared test with sufficient degrees of freedom was used to calculate significance levels. When the significance level was below 0, the omnibus (likelihood ratio chi-square) test was used to evaluate how well the model performed in relation to the intercept. 05.
Factors Influencing a Dog Litter Size
Now, even though it is very difficult (if not impossible) to predict and actively choose the size of your upcoming puppy litter, there are a number of factors that can have a significant impact on a dog litter’s size.
The impact of a high coefficient of inbreeding on the size of a puppy litter is one of the most commonly overlooked factors.
The Institute of Canine Biology published a chart illustrating the comparison of data taken from the litter size of six particular breeds of dogs from the records of the Swedish Kennel Club: English Springer Spaniel, Golden Retriever, Labrador Retriever, German Shepherd, Finnish Hound, and the Swedish Elkhound.
Although the results are relative, it is evident that the number of puppies will decrease the more inbred the puppies are. A much smaller litter is the price to pay when a dog breeder uses close inbreeding or linebreeding to correct some desired traits.
The size of the litter is greatly influenced by the dog’s breed. In general, it is understood that smaller breeds produce smaller litters, and similarly, larger breeds produce larger litters.
For instance, Spaniels and retrievers typically have four to eight puppies at a time, whereas smaller dogs like Terriers can only have two or three puppies in a litter.
It is true that a key factor in determining the size of a puppy litter is the female’s age. Dogs younger than seven years old typically have smaller litters than older dogs, but they should never be bred too young or too late. No matter the age, the first litter is typically smaller than subsequent ones.
A female may have permanently smaller litters with fewer puppies if she is not bred until after the age of five. If she was bred earlier than five years ago, her litter size will likely be a little bit larger. Largest litters are typically produced by dogs between the ages of 2 and 5 years.
Typically, a female dog’s first heat cycle occurs between 6 and 18 months of age. For the welfare of the dogs, the AKC advises against breeding females before their second or third heat. At that fertile age, females are at the height of their fertility.
The size of a litter will be influenced by the male’s age, but much less so than by the female’s. A male dog’s sperm production and quality will decline as he ages. Male dogs under the age of five are more likely to have larger litters because the majority of their sperm is of higher quality and can enter the female’s eggs more easily.
This is why the most well-known dog show champions are bred frequently and intensively in order to impregnate the greatest number of high-quality dams. But this can lead to the popular sire syndrome.
Health plays a vital role in litter size. To summarize, both parents must be in great health if they want to increase their chances of having more puppies.
The number of puppies produced by dogs that are genetically sound and healthy will inevitably be lower. A healthier and slimmer female has a better chance of having a larger litter than an overweight female. Reduce the likelihood of having a smaller litter size during pregnancy by increasing the amount of protein in the diet or taking additional protein supplements. The ideal diet for female dogs is premium dog food without supplements.
Providing a quality diet year-round is essential to your female’s health and wellbeing and improves her fertility because a poorly fed female won’t give her body the support needed to produce a larger litter.
In a study by Russ Kelly, a renowned nutritionist, three dams were fed three different diets:
A balanced diet without any supplements produced the largest litters. Diets too high in protein seemed to produce smaller litters. High doses of supplements (e. g. cottage cheese) may have caused fetal abortions.
The study’s conclusions were that adding small amounts of cottage cheese to premium formulated dog food could result in a larger litter at the expense of the dog’s health.
Breeding in gene pools with limited genetic diversity, such as in dogs from smaller breeding groups, is known to result in (much) smaller litter sizes of puppies.
Fertility, while having a high heritability, is unquestionably not one of them. One cannot solely rely on genes to increase litter size because heritability affects litter size by about 10% to 15%.
On the other hand, understanding inherited characteristics in dogs, such as:
You cannot combine two parents who previously had large litters and expect the puppies to have large litters two years later. Factors that influence the size of a puppy litter. An infographic by Breeding Business.
Do Genetics Play a Role in Litter Size?
The answer to that is yes and no.
The genetic component (other than breed) determines the size of the litter by 15% or so. Genetic traits are mainly coat color, eye color, and size.
Are puppies from large litters more aggressive?
Puppies from litters raised by mothers who provided more maternal care scored higher for social engagement, physical engagement, and aggression than those raised by mothers who were less attentive, which had an impact on the behavior and temperament of the offspring later in life.
FAQ
What does it mean when a dog has a small litter?
The size of the litter is significantly influenced by the dog’s age at mating. Particularly in larger breeds, the smaller the litter, the older the dam. Dams bred from 2-5 years usually have the largest litters. The first two litters will typically be smaller than the subsequent ones, regardless of the dam’s age.
Do puppies from small litters grow faster?
Puppies that are born lighter gain weight more quickly and catch up to larger puppies. Puppies from smaller litters are heavier at birth, grow more slowly, and are more likely to develop degenerative changes in the hip joint as they age than puppies from larger litters.
Is the smallest puppy in the litter healthy?
Puppies with low birth weights can grow up to be normal, healthy dogs. The likelihood of medical issues among runts who make it to weaning is the same as that of their littermates. These puppies will catch up eventually and reach their genetic potential if given adequate nutrition and time.
What is considered a small litter of puppies?
Typically, there are 1 to 12 puppies per litter, with an average of 5 to 6 puppies across all dog breeds. But according to AKC registration data, every breed of dog differs when it comes to litter size, just as they do with regard to size, function, and personality.