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Article

A National Census of Birth Weight in Purebred Dogs in Italy

by
Debora Groppetti
1,*,
Alessandro Pecile
1,
Clara Palestrini
1,
Stefano P. Marelli
1 and
Patrizia Boracchi
2
1
Department of Veterinary Medicine, Faculty of Veterinary Medicine, Università degli Studi di Milano, via Celoria 10, 20133 Milan, Italy
2
Department of Clinical Sciences and Community Health, Università degli Studi di Milano, via Vanzetti 5, 20133 Milan, Italy
*
Author to whom correspondence should be addressed.
Animals 2017, 7(6), 43; https://doi.org/10.3390/ani7060043
Submission received: 23 March 2017 / Revised: 26 May 2017 / Accepted: 27 May 2017 / Published: 30 May 2017
Versions Notes

Abstract

:

Simple Summary

Birth weight is a key factor for neonatal mortality and morbidity in most mammalian species. The great morphological variability in size, body weight and breed, as well as in skeletal and cranial conformation makes it challenging to define birth weight standards in dogs. A total of 3293 purebred pups were surveyed to study which maternal aspects can determine birth weight considering head and body shape, size, body weight and breed in bitches, as well as litter size and sex in pups. In our sample, multivariate analysis outcomes suggested that birth weight and litter size were directly proportional to maternal size. The maternal body shape influenced both birth weight and litter size, whereas the maternal head shape had impact only on birth weight. Sex differences in birth weight were found. Birth weight and litter size also varied among breeds. The results of the present study could have practical implications allowing one to identify pups in need of admission to intensive nursing care, as occurs in humans. A deeper knowledge of the factors that significantly influence birth weight could positively affect the canine breeding management helping to prevent and reduce neonatal mortality.

Abstract

Despite increasing professionalism in dog breeding, the physiological range of birth weight in this species remains unclear. Low birth weight can predispose to neonatal mortality and growth deficiencies in humans. To date, the influence of the morphotype on birth weight has never been studied in dogs. For this purpose, an Italian census of birth weight was collected from 3293 purebred pups based on maternal morphotype, size, body weight and breed, as well as on litter size and sex of pups. Multivariate analysis outcomes showed that birth weight (p < 0.001) and litter size (p < 0.05) increased with maternal size and body weight. Birth weight was also influenced by the maternal head and body shape, with brachycephalic and brachymorph dogs showing the heaviest and the lightest pups, respectively (p < 0.001). Birth weight decreased with litter size (p < 0.001), and male pups were heavier than females (p < 0.001). These results suggest that canine morphotype, not only maternal size and body weight, can affect birth weight and litter size with possible practical implications in neonatal assistance.

1. Introduction

Birth weight has an important effect on fetal and neonatal health in humans. Due to their immature development and adaptive postnatal failure, underweight babies are prone to potential complications, especially impaired thermoregulation and hypoglycemia [1]. Therefore, they are susceptible to mortality and morbidity, developing cerebral palsy, hyaline membrane disease, apnea, intracranial hemorrhage, sepsis, retrolental fibroplasia, growth and neurocognitive deficiencies [2]. Low birth weight can result from either a short gestation period or retarded intrauterine growth (or a combination of both) [2] as reported for humans and animals of many polytocous species, including dogs [3]. Based on evidence of embryo transfer studies in the human, horse and sheep, the intrauterine environment in which the fetus develops seems to exert a profound effect on birth weight, suggesting a central maternal role in determining the birth weight [4]. Anthropometric parameters, mainly head circumference, provide an indirect measure of low birth weight in babies and may thus be of prognostic significance [5,6]. Moreover, maternal factors such as height and weight of the woman are positively related with term fetal weight [2,7,8]. The same implication could be assumed in the canine species.
Due to the wide phenotypic variability among breeds, dogs offer a unique opportunity to study correlations between morphology and birth weight. In fact, there are 337 breeds of domestic dogs (Canis familiaris) recognized by the Fédération Cynologique Internationale (FCI). Bench standard defines the ideal characteristics for each breed including size (height at withers), body weight and morphometry of the adult dogs, while no specific information on the birth weight is provided. To date, despite a large number of studies on the puppy growth chart [9], the influence of the morphotype on birth weight has never been studied in dogs. The cephalic index or cranial index is the ratio between maximum width and length of the skull of an organism (human or animal). This index is used to classify animals into three groups: brachycephalic, mesocephalic and dolichocephalic [10]. Similarly, the relationship between height at withers and thoracic conformation determines the division of dog breeds into brachymorph, mesomorph, dolichomorph and anacholicomorph type [11,12].
The pursuit of an optimal model to classify the purebred dog still represents an important goal for scientific purposes. This study for the first time correlates birth weight with phenotypic aspects in purebred dogs, namely considering the impact of different morphometric characteristics. The objective of the study was to detect which parameters can influence the birth weight of pups and the litter size among maternal morphotype (head and body shape), size (height at withers) and body weight (BW). An exploratory investigation of the influence of breed on birth weight was conducted in selected groups of dogs with the same morphotype.

2. Materials and Methods

This study is based on data collected through an on-line questionnaire administered to Italian dog breeders from February 2014–September 2015 in the context of a national census promoted by the Università degli Studi di Milano in collaboration with the Ente Nazionale della Cinofilia Italiana (ENCI) to register the birth weight in the Italian purebred dog population. Participation in the questionnaire was freely decided by the breeders. In this case, the approval of the Ethics Committee does not apply.
A large-scale prospective study to survey the birth weight (body weight of pups at birth (bBW)) of 3293 pups from a sample population of 588 purebred bitches of 99 breeds from a population of 154,195 dogs in Italy (see Appendix A) was performed (Table 1). Litter size, breed, as well as birth weight and sex of pups were recorded by the census. Maternal data, such as head shape (cranial index), body shape, size (height at withers) and body weight, were taken from FCI, ENCI and kennel clubs.

2.1. Definitions

The Total Cephalic Index (TCI) is the ratio between the cranium width and the head length (tip of the nose-tip of the occiput). Based on their head shape, dogs were classified as brachycephalic (TCI > 50), mesocephalic (TCI = 50) and dolichocephalic (TCI < 50) [11]. The Corporal Index (CI) is the ratio between the length of the body (point of shoulder-ischiatic tuberosity) and the thoracic girth. According to their body shape, dogs were divided into: brachymorph (CI = 60–70), mesomorph (CI = 71–84), dolichomorph (CI = 85–100) and anacholicomorph [11,12]. Anacholicomorph, a term derived from Greek, means short legged: basset-like proportion [11]. Dogs were also categorized into groups according to maternal size, i.e., height at withers (<20 cm: toy; 20 cm ≤ small ≤ 40 cm; 40 cm < medium ≤ 65 cm; >65 cm: large) [13] and maternal body weight (<5 kg; 5 kg ≤ BW ≤ 10 kg; 10 kg < BW ≤ 25 kg; 25 kg < BW ≤ 45 kg; >45 kg) [14]. The sex of pups was recorded at birth and stated as undefined when it was ambiguous or pups were malformed. We included both live and stillborn pups in the database.

2.2. Statistical Analysis

The distribution of birth weight and number of pups according to the maternal characteristics mentioned above was synthesized by the following indices: minimum, first quartile (1st Q), median, mean, third quartile (3rd Q) and maximum.
The relationship between birth weight of the pups (response variable) and litter size, maternal characteristics and sex of pups (explicative variables) was evaluated by linear mixed regression model. Litter size, maternal characteristics and sex of pups were considered as fixed effects. The correlation among pups from the same litter was accounted for including in the model the mother’s identification code as a random effect. The categorical maternal characteristics and sex of pups were included in the regression model as dummy variables. For a categorical variable with k categories, one of the categories is considered as the “reference”, and k-1 dummy variables are generated to compare the mean of the response variable in each category with the mean of the response variable in the reference category. The number of pups per litter was included in the regression model in its original measurement scale. Residual analysis suggested the use of the logarithmic transformation of the birth weight. After logarithmic transformation, the regression coefficients can be related to the geometric mean of the response variable (i.e., the mean of the logarithm of birth weight is the geometric mean of birth weight rather than the usual arithmetic mean of the birth weight). For categorical variables, the exponent of the regression coefficient of each dummy variable was the estimate of the ratio between the geometric mean of birth weight of the category represented by the dummy variable and the geometric mean of the birth weight of the reference category. For litter size, the exponent of the regression coefficient was the estimate of the ratio between the geometric mean of the birth weight for each of two consecutive litter size values.
The null hypothesis of the regression coefficient equal to 0 for fixed effects was tested by the t statistic. To perform adequate inference procedures, Satterthwaite’s approximation of the degree of freedom of the t statistic was applied. The relationship between the litter size (response variable) and the maternal characteristics (explicative variables) was evaluated by a generalized linear model with Poisson error. As the considered maternal characteristics are categorical, each characteristic dummy variable was generated as previously described. In this generalized linear model, the exponent of the regression coefficient of each dummy variable was the estimate of the ratio between the mean litter size of the category represented by the dummy variable and the mean litter size of the reference category. The null hypothesis of each regression coefficient equal to 0 was tested by the Wald statistic. For both Poisson and linear mixed regression models, the following results related to the explicative categorical variables are reported: model estimated mean of the response variable for each category; ratio between the estimated mean of the response variable in each category and the estimated mean of the response variable in the reference category; and the 95% confidence interval of the ratio. For the numerical explicative variable, the following results are reported: model estimated mean of the response variable for the lowest value of the explicative variable and the increase of the mean of the response variable for a one-unit increase of the explicative variable. For both the Poisson and linear mixed model, the effect of each explicative variable was evaluated firstly by univariate analysis, then a multivariable regression model was used to evaluate the joint role of all of the explicative variables. The authors consider the maternal body weight and size as correlated, so two alternative multivariable regression models were performed including weight and size, respectively. A parsimonious final model was obtained by the stepwise selection procedure.
An exploratory analysis was performed to evaluate the association between breeds and birth weight and between breeds and litter size in dogs sharing the same morphotype. To obtain reliable results, only breeds represented by at least 15 litters were considered.
Statistical significance was accepted at p < 0.05.
The analysis was performed by the R Core Team (2016) software; R: A language and environment for statistical computing; R: Foundation for Statistical Computing, Vienna, Austria. ISBN 3-900051-07-0 [15]; package lme4 for bBW [16]; and the glm function for the number of pups.

3. Results

The distribution of pup number and birth weight according to combinations of maternal morphotype, size and body weight of dogs in the study is summarized in Table 2.

3.1. Birth Weight

The birth weight ranged from 40–1250 g. The lightest pup was a German Spitz (Pomeranian-Zwergspitz) that died within 24 h after birth; its surviving littermate weighed 124 g. The heaviest pup was from a Mastino Napoletano dog that delivered eight healthy pups.
For statistical purposes, 45 pups whose data were incomplete were excluded from our investigation, thus including a total of 3248 pups.
In univariate analysis, maternal head shape significantly influenced the mean birth weight of brachycephalic dogs when compared to mesocephalic dogs (Table 3). Similarly, in brachymorph dogs, birth weight was related to maternal body shape when compared to mesomorph dogs. In the remaining morphological categories, no statistical differences in bBW were observed with respect to brachymorph.
The mother’s size was directly related to the bBW. Similar results were obtained considering the mother’s body weight. Concerning the relationship between the logarithm of the bBW and the litter size, no evidence for a non-linear effect was found. The estimated bBW increased with the increase of the number of pups per litter. To clarify this result, the effect of litter size on birth weight was adjusted for mother’s size. In this case, the impact of litter size was not statistically significant and inversely proportional to birth weight (mean ratio 0.99, p > 0.3).
When maternal head shape, body shape, body weight, number of pups per litter and the sex of pups were jointly considered, the mother’s head shape did not contribute significantly to the bBW (p = 0.0558) and was excluded from the final regression model by the stepwise procedure. Concerning the body shape, the mean bBW of brachymorph dogs was significantly lower than that of all other categories. As already mentioned, the average bBW increased with the decreasing of the litter size. Results of the final regression model are reported in Table 4.
When the mother’s size was considered instead of the mother’s weight, all variables showed a significant contribution (Table 5). The mean bBW of brachycephalic dogs was significantly greater than that of mesocephalic and dolichocephalic dogs. Concerning maternal body shape, the mean bBW of anacholicomorph dogs was significantly greater than that of brachymorph dogs, and no significant differences were found among the other maternal body shape categories. The results for litter size were similar to those reported above.
The contribution of maternal body weight and size to the model was F = 341.32, p < 0.0001 and F = 273.47, p < 0.0001, respectively.

3.2. Litter Size

Litter size ranged from 1–14 pups with the largest litter delivered by a Rhodesian ridgeback dog. In univariate analysis, the mother’s head shape was related to litter size with mesocephalic dogs delivering litters at a mean 1.2-times more numerous than brachycephalic ones (Table 6). Similarly, mesomorph dogs had litters at a mean more numerous than brachymorph dogs. Litter size was directly proportional to maternal size. Likewise, the litter size increased proportionally to the maternal body weight.
When maternal head shape, body shape and body weight were jointly considered, the contribution of head shape was not statistically significant, and the final model excluded this variable (Table 7). The maternal body shape influenced litter size with brachymorph dogs delivering the lowest number of pups. The mean number of pups increased with the increase of the maternal BW. Similarly, when maternal size was considered in the model instead of BW, the head shape did not contribute significantly to litter size and was not included in the final model (Table 8). However, the impact of maternal body shape on the number of pups showed a minor contribution with a difference in litter size only emerging between brachymorph and anacholicomorph dogs. The mean number of pups increased with the increasing of the maternal size.

3.3. Breed

According to our inclusion criteria, five breeds were considered for exploratory analysis: German shepherd, golden retriever, Jack Russel terrier, Labrador retriever and West Highland white terrier (WHWT) (Table 9). German shepherd, golden retriever and Labrador retriever belong to mesocephalic, mesomorph, medium sized, 25–45-kg weighing dogs. Jack Russel terrier and WHWT belong to mesocephalic, mesomorph, small-sized, 5–10-kg weighing dogs.
The bBW was lower in WHWT than in Jack Russel terrier (p < 0.05), while no significant differences were recorded among the other breeds. Few differences were found between mean bBW of German shepherd, golden retriever and Labrador retriever (reference): the estimated mean ratio was 0.9 and 1.03, respectively.
The ratio between mean litter size of Labrador retriever and golden retriever was 0.77 (p = 0.01). The ratio between mean litter size of German shepherd and golden retriever was 0.85 (p = 0.12). Only the comparison between Labrador and golden retriever was statistically significant. No significant differences in mean litter size between Jack Russel terrier and WHWT were recorded (mean ratio = 0.951).

3.4. Sex of Pups

In our samples, 1559 pups were females and 1665 males. In the remaining 24 pups, the sex was not defined, as it was ambiguous or they were malformed. In univariate analysis, mean bBW of males was greater than mean bBW of females (mean ratio = 1.04, p < 0.001; Table 3). The mean bBW of pups with undefined sex was lower than mean bBW of females (mean ratio = 0.86, p < 0.001). These results were confirmed by multivariate analysis (p < 0.001; Table 4 and Table 5).

4. Discussion

Despite its relevant impact on neonatal and adult health, deep knowledge of factors affecting birth weight in dogs is still lacking. As already noted, low birth weight in pups, as well as in babies, kittens and piglets, leads to higher risk of neonatal morbidity and mortality compared with normal weight littermates [17,18,19]. Mortality of pups attributed to low birth weight is reported from 1.4% [20] to 2.1% [21]. In large-sized breeds, birth weight in dogs dying during the first week after birth was 100 g lower than in surviving pups [22,23]. Moreover, pup weight at birth has a significant influence on the outcome of parturition [24], and being oversized in pups may be responsible for uterine inertia and consequent fetal distress [25,26]. Pups being oversized in the case of singleton pregnancy, as well as disproportion between maternal pelvic and pup head dimensions are known to be predisposing factors to dystocia since more uterine force is needed to expel these pups [25]. Namely, dystocia is reported to occur more likely in some canine breeds and morphotypes, with increasing cranial circumference of the pups, that is in brachycephalic dogs [24,26,27,28,29,30].
Theoretically, in all mammalian species, there is an ideal range of birth weight associated with eutocic parturition and neonatal well-being [4]. To date, due to a wide morphological and morphometric variability within canine breeds, no criteria are available to recognize which range of birth weight is to be considered physiological. Even the present study has no claim to provide a birth weight cut-off for each breed, rather to investigate associations among birth weight, litter size and morphology by an original canine classification. Although the effect of maternal phenotype on birth weight was investigated by a multivariate regression model, our result cannot be used for predictive aims. Indeed, a suitable predictive model would require a very large population with independent case series for model validation. To the authors’ knowledge, this is the first study evaluating the influence of maternal morphotype, namely head and body shape and not only size and weight, on pup birth weight and number. Given that studies on the average weight of purebred pups at birth are few and based on a small scale, a thorough comparison with the available literature is not possible. However, the birth weights of the German shepherd, Labrador retriever and Rottweiler pups in our sample were similar to those previously described [31].
The body weight was reported to vary up to 40-times among adult dogs from different sizes and breeds, while it was only 10-times different at most among pups at birth [32]. Our results showed a greater range of birth weight than those reported by Fiszdon et al. (2009) with the thinnest pup about 31-times lighter than the heaviest one [32]. This aspect can be justified by both a different sample size of our study (n = 501 versus n = 3293 pups) and our inclusion of either live or stillborn pups. Severely underweight pups are not likely to survive. However, the relation between birth weight and neonatal mortality has not been investigated, beyond the aim of the present study.
Data shown in this study are from a census, so they do not represent the registered database of ENCI during the same period (see Appendix A). Being that participation in the census was based on the voluntary participation of breeders, a potential bias of our sample in relation to the distribution of the whole canine Italian population is possible. Moreover, a possible ‘kennel effect’ on birth weight and litter size of dogs from the same breeder (Table 1) should not be neglected, as well as the involvement of the bloodlines.
In our canine population, the maternal head shape had a significant impact on birth weight of pups when morphotype, litter size and sex of pups were considered together with maternal size. Brachycephalic dogs had the heaviest pups. These data are consistent with studies reporting an association between low birth weight and small head circumference at birth in babies [6,33]. However, the head shape contribution was not significant when the same variables (morphotype, litter size and sex of pups) were considered together with maternal body weight. We speculate that maternal body weight may have a more powerful impact on birth weight than size. Conversely, litter size was not affected by the head shape.
The maternal body shape influenced significantly both birth weight and litter size with brachymorph dogs delivering the lightest pups and a lower number of pups than anacholicomorph ones. Studies in humans highlighted the importance of maternal phenotype influence on birth weight, indicating that weight at birth is attributable to maternal anthropometry differences and not to maternal size variability alone [34].
Maternal size and body weight were directly proportional to both birth weight and litter size in our sample. The same observation was reported in cats with birth weight increasing as maternal weight and height increased [35]. Similarly, observational epidemiological studies have revealed that both maternal height and weight are associated with birth weight in babies [7]. These associations have been interpreted based on a mechanistic assumption that maternal dimension sets a physical constraint on the intrauterine environment that affects fetal growth [7].
A limit of the present study is the lack of data on the real maternal body weight, body condition score, gestational weight gain and caloric intake of the dogs included in the census. Therefore, we cannot exclude that the nutritional status of bitches may also affect the birth weight of pups as described in humans [36,37]. Moreover, maternal size and weight were taken from FCI, ENCI and kennel clubs and not directly recorded by the questionnaire. Although the used classifications are reliable [13,17], a partial loss of information on the relationship between these two variables and bBW or litter size could be possible. Finally, a possible bias on birth weight recording is intrinsic in a study based on data directly collected by the owner.
As expected on the basis of the literature, litter size was inversely proportional to birth weight, with weight reduction for each additional pup per litter [26,35].
A significant sex difference in birth weight was recorded, with male pups being the heaviest. Data reported in literature on this topic are conflicting. Some authors have found no difference on birth weight between male and female pups [23,26]. On the contrary, other studies have shown an increased birth weight in male compared with female pups [38,39], as described in humans and sheep [2,4]. These heterogeneous results could be due to different sample sizes and different distributions of dog’s morphologic characteristics in case series. A comparison of results should be performed after taking into account litter size, maternal weight and morphotype in a multivariate analysis.
As previously observed, ambiguous or malformed pups resulted in lighter birth weight than healthy ones [40]. In humans, congenital malformations seem to be the most important factor that determines low birth weight [41].
Heritability for body weight at birth has been demonstrated in boxers [42]. A significant breed-dependent difference in birth weight and litter size among breeds of the same size and weight was recorded in our sample, even though only five breeds have been compared. These data suggest a non-negligible role of the breed, not only size, weight and morphotype, in determining birth weight. However, the breed influence should be further investigated to be verified in very large datasets.

5. Conclusions

There is strong evidence that birth weight results from a complex interaction between genetic and environmental factors of parental, placental and fetal origin in humans [43]. Due to some above-mentioned limitations, besides the lack of paternal information, the outcomes of this survey should be generalized with caution, as it represents a definite sample of pedigree dog population in Italy. Studies in human reported that paternal birth weight and height are significant and independent predictors of birth weight in offspring [44,45], although maternal factors make bigger contributions to babies’ birth weight [46]. This large-scale study provides evidence that canine morphotype, not only maternal size and body weight, together with breed are involved in determining birth weight and litter size. Results of the present study have concrete implications in canine neonatal practice allowing one to deepen the knowledge of factors that significantly influence variation in birth weight and to identify pups in need of admission to intensive nursing care.

Supplementary Materials

Supplementary File 1

Acknowledgments

The authors are grateful to ENCI for contributing to the census questionnaire distribution among Italian canine breeders.

Author Contributions

Conceived of and designed the study: Debora Groppetti, Alessandro Pecile; Collected data: Clara Palestrini, Stefano P. Marelli. Performed the statistical analysis: Patrizia Boracchi. Wrote the paper: Debora Groppetti, Alessandro Pecile, Patrizia Boracchi. All of the authors participated in the drafting and critical reading of the manuscript.

Conflicts of Interest

There is no conflict of interest that could be declared.

Appendix A

Table
Table A1. Number of Dogs Registered in the Genealogical Book ENCI from 1 January 2015–31 December 2015.
Table A1. Number of Dogs Registered in the Genealogical Book ENCI from 1 January 2015–31 December 2015.
BreedNumber
Affenpinscher13
Afghan Hound81
Airedale Terrier63
Akita Inu1283
Alaskan Malamute562
Alpenlaendische Dachsbracke536
American Akita461
American Cocker87
American Staffordshire T.4484
Anatolian Shepherd26
Anglo Francais De Petite Venerie66
Appenzeller Mountain dog48
Argentine Dogo1124
Ariegeois663
Australian Cattle Dog396
Australian Kelpie39
Australian Shepherd1567
Australian Silky Terrier7
Azawakh8
Basenji60
Basset Fauve De Bretagne16
Basset hound338
Beagle1402
Beagle Harrier79
Bearded Collie49
Beauceron132
Bedlington Terrier15
Belgian Shepherd Dog886
Bergamasco Shepherd Dog63
Bernese Mountain Dog1554
Bichon A Poil Frise232
Bichon Havanais75
Black Russian Terrier41
Bloodhound 86
Bobtail28
Bolognese358
Border Collie3135
Border Terrier13
Borzoi89
Boston Terrier338
Bouledogue 1822
Bouvier des Flandres22
Boxer3682
Bracco Italiano694
Braque d'Auvergne1
Braque français172
Brazilian Mastiff35
Briard58
Briquet Griffon Vendeen654
Broholmer4
Brussel Griffon31
Bull Terrier516
Bulldog2153
Bullmastiff346
Byerischer gebirgsschweisshund179
Cairn Terrier39
Canaan Dog14
Cane Corso3957
Cao De Agua32
Cao De Castro Laboreiro3
Catalan Shepherd Dog10
Caucasian Shepherd Dog418
Cavalier King Charles Spaniel1313
Central Asian Shepherd Dog394
Chesapeake Bay Retriever10
Chihuahua5794
Chin58
Chinese Crested Dog74
Chow Chow179
Cirneco dell’Etna105
Clumber Spaniel59
Coton De Tulear99
Czechoslovakian Wolfdog1362
Dachshund2904
Dalmatian146
Deerhound9
Dobermann1693
Dogo Canario73
Dogue De Bordeaux801
Dutch Shepherd Dog33
English Cocker Spaniel2084
English Pointer2339
English Setter13,702
English Springer Spaniel1773
Entlebucher Mountain Dog13
Epagneul Breton3275
Epagneul Nain Continental Papillon108
Erdélyi Kopó14
Eurasier25
Flat Coated Retriever 205
Fox Terrier Wire181
Galgo Espanol1
Gascon Saintongeois194
German Jagdterrier176
German Shepherd14,369
German Shorthaired Pointer2435
German Spaniel59
German Spitz 905
German Wirehaired Pointer763
Giant Schnauzer339
Golden Retriever5692
Gordon Setter357
Grand Griffon Vendeen2
Great Dane1075
Greyhound50
Griffon Belge13
Griffon Bleu De Gascogne319
Griffon Nivernais42
Hannoverischer Schweisshund83
Hokkaido5
Hound of the Maremma2923
Hovawart232
Hungarian Vizsla SH259
Irish Soft- Coated Wheaten Terrier43
Irish Terrier31
Irish Water Spaniel1
Irish Wolfhound24
Istrian Hound Rough Hair 19
Istrian Hound Short Hair212
Italian Greyhound295
Italian Hound Rough Haired 1070
Italian Hound Smooth Haired3570
Italian Spinone506
Jack Russel Terrier5257
Japanese Spitz26
Karelian Bear Dog39
Kerry Blue Terrier25
King Charles Spaniel8
Komondor3
Kooikerhondje5
Labrador Retriever9414
Lagotto Romagnolo2341
Lakeland Terrier98
Landseer14
Lappinkoira16
Leonberger161
Lhasa Apso129
Little Lion Dog2
Maltese1631
Manchester Terrier16
Maremma and the Abruzzes Sheepdog993
Mastiff32
Miniature English Bull Terrier222
Mudi7
Neapolitan Mastiff514
Newfoundland406
Norfolk Terrier30
Norwich Terrier20
Nova Scotia Duck Tolling Retriever61
Parson Russell Terrier174
Pekingese17
Perdigueiro Português1
Petit Basset Griffon Vendeen56
Petit Bleu De Gascogne148
Petit Brabançon9
Pharaon Hound1
Picardy Shepherd2
Pinscher23
Podenco Ibicenco6
Podengo Portugues1
Polish Greyhound1
Polish Lowland Sheepdog5
Poodle2072
Porcelaine153
Posavatz Hound48
Pug632
Puli1
Pumi2
Pyrenean Mastiff91
Pyrenean Mountain Dog115
Pyrenean Shepherd14
Rhodesian Ridgeback318
Romanian Shepherd Bucovina10
Romanian Shepherd Dog Mioritic27
Rottweiler4080
Rough Collie391
Russian Toy16
Saarloos Wolfdog48
Saint Bernard Dog629
Saluki34
Samoiedo304
Schapendoes16
Schipperke13
Scottish Terrier113
Sealyham Terrier5
Segugio dell’Appennino197
Segugio Maremmano2923
Serbian Hound1
Serbian Tricolour hound7
Shar Pei551
Shetland Sheepdog168
Shiba Inu701
Shih Tzu604
Shikoku9
Siberian Husky857
Skye Terrier12
Sloughi1
Slovakian hound103
Smooth Collie1
Smooth Fox Terrier80
Spanish Mastiff11
Staffordshire Bull Terrier1266
Standard Schnauzer208
Swiss hound248
Swiss Mountain Dog86
Tibetan Mastiff124
Tibetan Spaniel5
Tibetan Terrier48
Tosa2
Volpino Italiano130
Weimaraner1158
Welsh Corgi Cardigan2
Welsh Corgi Pembroke195
Welsh Springer Spaniel3
Welsh Terrier36
West Highland White T.592
Whippet489
White Swiss Shepherd Dog438
Xoloitzcuintle1
Yorkshire Terrier551
Yugoslavian Shepherd Dog25
Zwergpinscher454
Zwergschnauzer785
Total154,195

References

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Table
Table 1. Distribution of the bitches based on their breed, morphotype, size, body weight and the corresponding number of litters and pup birth weight.
Table 1. Distribution of the bitches based on their breed, morphotype, size, body weight and the corresponding number of litters and pup birth weight.
BreedHead Shape aBody Shape bSize cBW dNL eNP fNK gNpbBW h
MedianQ1 iQ3 lMedianQ1 iQ3 l
Afghan HoundDD43212265.56.5500480562.5
Akita InuMM349574658401367420
Alaskan MalamuteMM3421527.57.257.75468429480
American AkitaMM442142777576494.5695
American CockerMM23317265.56200160220
American Staffordshire T.MM34111111500500500
Appenzeller Mountain dogMM3342225.54.56.5357321.2424.5
Australian ShepherdMM33750676.58350320390
Basset HoundMA23751375.59448350510
BeagleMM2342847.56.58303.5278.8352.8
Bearded CollieMM33161666395371.8403.2
BeauceronDM44161666535523,8542.5
Belgian Shepherd dogMM345312758425387.5460
Bernese Mountain dogMM343319610638541490600
Bichon HavanaisMM2183734.53.756195165215.5
Black Russian TerrierMM45181888475457.5491.2
BologneseMM21310332.54137.5130145.5
Border CollieMM33138310757350300378
Border TerrierMM22151555193190200
BorzoiDD441111111111446390.5480.5
Boston TerrierBM22820331.753200178226
BouledogueBB239464546184150.2235.8
Bouvier des FlandresMM342161888463.5438.5500
BoxerBM3412821084.759449.5400410
Bracco ItalianoMM341101101010405400410
Brussel GriffonBM212112777120106.5135
BulldogBB239326324316280368.8
BullmastiffBM453223768.5597.5579.2630
Bull TerrierMM23425474.259330273.0350
Cane CorsoBM3443046.568494437682.5
Caucasian Shepherd DogMM45151555720680730
Cavalier King Charles SpanielBM22104684.53.255.75230210252
ChihuahuaBM11195712324140111.5160
Chinese Crested DogMM211031332.253.75155118.8176.2
Chow ChowMM3417713436400360420
Cirneco dell’EtnaMM32212265.56.5290273.8308.8
Epagneul Nain Continental PapillonMM215185757142134.2158
Czechoslovakian WolfdogMM343203767.5390362.2410
DalmatianMM3343639810368297.5413
DeerhoundMM44161666480476.2487.5
DobermannDM44756696.59457330510
Dogue de BordeauxBM35181888565496.2585
DrahthaarMM34191999308294329
DachshundMA1/22145911435173146.5217.5
English Cocker SpanielMM2317965547287.5250320
English PointerMM332723.53.253.75465427445
English SetterMM33532264.757.5389.5340427.2
Entlebucher Mountain DogMM33171777344336357.5
Epagneul BretonMM337435757255234311.5
Fox Terrier WireMM2226232.53.5225215237.2
German Shepherd dogMM34352321874.58.5503435600
German Spitz KleinMM2112232.53.5125.5125.2125.8
German Spitz Zwerg-PomeranianMM213111434.5124114150
Giant SchnauzerMM341101101010357315370
Golden RetrieverMM34191481085.510235228.8245
Gordon SetterMM342162879406.5388.8428
Great DaneMM45544510911647512.5698.2
HovawartMM34868397.759.25560500590
Italian GreyhoundDD2118595324185167.5208
Italian SpinoneDM34216287.58.5450415600
Jack Russel TerrierMM221567853.55200180220
Labrador RetrieverMM344426426657.25405.5369.5450
LagottoMM3321728.58.258.75264237282
Lakeland TerrierMM22151555209205214
LeonbergerMM452122657615505685
Little Lion DogMM22141444190190190
MalteseMM213123334.5110.098.75131.8
Maremma SheepdogMM443232769595491.2688.5
Mastino NapoletanoBM45321285.59790609912
NewfoundlandMM45421263.258600550670
Poodle (miniature and toy)MM21612521.252116.599155.5
PugBB2283243.52.755.5164.5135.5192.8
PumiMM33171777232222238
Rhodesian RidgebackMM447763128.512.5390358.5420
RottweilerBM3543046.55.58.5360322.5399.5
Saint Bernard dogBM451121121212370355375
SamoiedoMM33171777229218.8248
SchapendoesMM33181888229218.8248
Rough CollieDM33111111155155155
Scottish TerrierMD22131333210205210
Segugio dell’AppenninoMM33161666337326365.2
Shar PeiMM333113325450425475
Shetland SheepdogMM22151555150143150
Shiba InuMM22261333241223.5282.5
Shih TzuBM2228143.54.5155144.5178
Siberian HuskyMM33315354.55.5556497.5593.5
Staffordshire Bull TerrierBM2310506546319.5297.2463.5
Standard SchnauzerMM333302119.511280262.5297.5
Tibetan MastiffMM35151072768450385490
Tibetan TerrierMM22121222217215.5218.5
VizslaMM331616664004000437.5
Volpino ItalianoMM21622443.254132.585173.8
WeimaranerMM3442536.53.759450410495
West Highland White T.MM2216687435.25180150200
WhippetDD3321326.56.256.75352332380
White Swiss Shepherd dogMM343222878352323.5460
Yorkshire TerrierMM115143324120106.2128.8
ZwergpinscherMM216244435.75145123176.8
ZwergschnauzerMM221040643.254184.5165.5193.5
a Head shape: B = brachycephalic; M = mesocephalic; D = dolichocephalic; b body shape: B = brachymorph; M = mesomorph; D = dolichomorph; A = anacholicomorph; c size: 1 = toy; 2 = small; 3 = medium; 4 = large; d BW means maternal body weight: 1 = <5 kg; 2 = 5 ≤ BW ≤ 10 kg; 3 = 10 < BW ≤ 25 kg; 4 = 25 < BW ≤ 45 kg; 5 = >45 kg; e NL means number of litters; f NP means number of pups; g NK means number of kennels; h bBW means body weight of pups at birth (grams); I Q1 means first quartile; l Q3 means third quartile.
Table
Table 2. Combinations of maternal morphotype, size and body weight and the corresponding pup number and birth weight in our canine sample.
Table 2. Combinations of maternal morphotype, size and body weight and the corresponding pup number and birth weight in our canine sample.
Head Shape aBody Shape bSize cBW dNL eNP fNpbBW g
MinQ1 hMedianMeanQ3 iMaxMinQ1 hMedianMeanQ3 iMax
BB2283212.753.545.5786135.5164.5161.5192.8230
BB2318761344.336755176241.5243.9288.2510
BM11195612334560111.5140134.8160207
BM2121144.755.55.56.25785117136163227.5260
BM22207412.7533.758120176.5220211.3245306
BM231050345567234297.2319.5394.9463.5766
BM3416108257.57911315409455.5493.3554900
BM355384677.6813248333.8375396.8436.2620
BM457553687.861012500580620677.16921250
MM115141232.84490106.2120129.6128.8202
MM21511821233.515744114142147.8179266
MM22502082344.165790167.8190189.6214.2350
MM23281662565.9379130247.8286287.5330500
MM3221255.5666.57235273.8290289.2308.8335
MM33603921576.55811148280344.5341.1392650
MM3419012031476.3781357400450464.3530900
MM35151054677.13810220390450443490650
MM44131175789.151215220370420459.5530770
MM4513841486.92911200507.5612.5594690900
MA12124712.7543.9257116144.5160170.6187.5250
MA2231533.54568200210230237.1258305
MA2375145.577.2991140350443413.8501580
DM3311111111155155155155155155
DM3421677.5888.59400415450511.2600700
DM448593687.7591360340471434.1530.5780
DD2118592233.2847116167.5185188.8208281
DD3321366.256.56.56.757205332352347.4380417
DD4321155.5666.57420480500516.4562.5600
DD44111111111111111370390.5446438.5480.5500
a Head shape: B = brachycephalic; M = mesocephalic; D = dolichocephalic; b body shape: B = brachymorph; M = mesomorph; D = dolichomorph; A = anacholicomorph; c size: 1 = toy; 2 = small; 3 = medium; 4 = large; d BW means maternal body weight: 1 = <5 kg; 2 = 5 ≤ BW ≤ 10 kg; 3 = 10 < BW ≤ 25 kg; 4 = 25 < BW ≤ 45 kg; 5 = >45 kg; e NL means number of litters; f NP means number of pups; g bBW means body weight of pups at birth (grams); h Q1 means first quartile; i Q3 means third quartile.
Table
Table 3. Birth weight of pups and maternal characteristics: results of linear mixed regression model univariate analysis.
Table 3. Birth weight of pups and maternal characteristics: results of linear mixed regression model univariate analysis.
VariableMean fContrastMean Ratio95% Lower Limit95% Upper Limittp-Value
Head shape a264.36reference
323.37M/B1.221.101.373.57<0.001
269.81D/B1.020.831.250.200.8425
Body shape b221.32reference
322.08M/B1.461.191.78 3.62<0.001
222.16D/B1.000.751.340.030.9794
238.34A/B1.080.801.440.500.6197
Size c146.1reference
203.222/11.391.241.565.52<0.001
423.993/12.902.593.2618.17<0.001
519.264/13.553.074.1117.11<0.001
BW d147.39reference
192.462/11.311.211.416.58<0.001
317.543/12.152.002.3220.38<0.001
455.824/13.092.893.3133.22<0.001
512.145/13.473.143.8523.96<0.001
Litter size *221.91reference one-pup increase1.071.061.099.39<0.001
Sex of pups e303.14reference
314.911/01.041.031.057.30<0.001
260.662/00.860.800.92−4.31<0.001
* When the number of pups is adjusted for maternal size, the estimates for a one-pup increase per litter are: mean ratio = 0.99 (95% confidence limits: 0.98–1.01) t = −1.03 p value = 0.3024; a head shape: B = brachycephalic; M = mesocephalic; D = dolichocephalic; b Body shape: B = brachymorph; M = mesomorph; D = dolichomorph; A = anacholicomorph; c size: 1 = toy; 2 = small; 3 = medium; 4 = large; d BW means maternal body weight: 1 = <5 kg; 2 = 5 kg ≤ BW ≤ 10 kg; 3 = 10 kg < BW ≤ 25 kg; 4 = 25 kg < BW ≤ 45 kg; 5 = >45 kg; the category coded 1 is the reference; e sex of pups: 0 = female; 1 = male; 2 = unidentified; the category coded 0 is the reference; f mean (grams) is the estimated geometric mean of the weight distribution.
Table
Table 4. Birth weight of pups and maternal characteristics: results of final linear mixed regression model multivariable analysis (step-wise selection procedure); body shape and weight, number of newborns, sex of pups.
Table 4. Birth weight of pups and maternal characteristics: results of final linear mixed regression model multivariable analysis (step-wise selection procedure); body shape and weight, number of newborns, sex of pups.
VariableContrastMean Ratio d95% Lower Limit95% Upper Limittp-Value
Body shape aM/B1.291.161.45 4.57<0.001
D/B1.69 1.44 1.986.41<0.001
A/B1.361.16 1.58 3.88<0.001
BW b2/11.41 1.31.548.23<0.001
3/12.45 2.26 2.6522.1<0.001
4/13.48 3.23 3.75 32.82<0.001
5/13.98 3.584.43 25.36<0.001
Litter sizeone-pup increase0.980.970.99−4.36<0.001
Sex of pups c1/01.041.03 1.05 7.13<0.001
2/00.850.80 0.91−4.6<0.001
a Body shape: B = brachymorph; M = mesomorph; D = dolichomorph; A = anacholicomorph; b BW means maternal body weight: 1 = <5 kg; 2 = 5 kg ≤ BW ≤ 10 kg; 3 = 10 kg < BW ≤ 25 kg; 4 = 25 kg < BW ≤ 45 kg; 5 = >45 kg; the category coded 1 is the reference; c sex of pups: 0 = female; 1 = male; 2 = unidentified; the category coded 0 is the reference; d mean ratio means model estimated ratio between geometric means.
Table
Table 5. Birth weight of pups and maternal characteristics: results of final linear mixed regression model multivariable analysis (step-wise selection procedure); head and body shape, size, number of newborns, sex of pups.
Table 5. Birth weight of pups and maternal characteristics: results of final linear mixed regression model multivariable analysis (step-wise selection procedure); head and body shape, size, number of newborns, sex of pups.
VariableContrastMean Ratio e95% Lower Limit95% Upper Limittp-Value
Head shape aM/B0.8 0.74 0.87−5.42<0.001
D/B0.66 0.53 0.81−3.95<0.001
Body shape bM/B1.070.931.24 0.960.3377
D/B1.24 0.95 1.631.570.1163
A/B1.871.512.325.68<0.001
Size c2/11.78 1.562.028.83 <0.001
3/14.04 3.524.63 20.03<0.001
4/15.15 4.36 6.09 19.22<0.001
Litter sizeone-pup increase0.990.981−2.210.0275
Sex of pups d1/01.041.03 1.05 7.08<0.001
2/00.85 0.80 0.91−4.57<0.001
a Head shape: B = brachycephalic; M = mesocephalic; D = dolichocephalic; b body shape: B = brachymorph; M = mesomorph; D = dolichomorph; A = anacholicomorph; c size: 1 = toy; 2 = small; 3 = medium; 4 = large. The category coded 1 is the reference; d sex of pups: 0 = female; 1 = male; 2 = unidentified; the category coded 0 is the reference; e mean ratio means model estimated ratio between geometric means.
Table
Table 6. Number of pups and maternal characteristics: results of Poisson’s regression model univariate analysis.
Table 6. Number of pups and maternal characteristics: results of Poisson’s regression model univariate analysis.
VariableMean eContrastMean Ratio95% Lower Limit95% Upper LimitWald Statisticsp-Value
Head shape a4.829reference
5.817M/B1.205 1.095 1.325 3.839 <0.0001
5.118 D/B1.060 0.892 1.259 0.662 0.5080
Body shape b4.231reference
5.754 M/B1.360 1.124 1.645 3.168 0.0015
4.130 D/B 0.976 0.742 1.285 −0.171 0.8642
5.136 A/B1.214 0.934 1.579 1.448 0.1476
Size c3.278reference
4.2932/11.310 1.081 1.586 2.76 0.00578
6.4953/1 1.981 1.645 2.3867.208 <0.0001
7.9324/12.420 1.964 2.982 8.299 <0.0001
BW d3.368reference
4.0842/11.212 1.046 1.406 2.552 0.0107
5.969 3/1 1.772 1.555 2.019 8.592 <0.0001
6.657 4/11.976 1.752 2.229 11.082 <0.0001
7.250 5/12.152 1.836 2.523 9.455 <0.0001
a Head shape: B = brachycephalic; M = mesocephalic; D = dolichocephalic; b body shape: B = brachymorph; M = mesomorph; D = dolichomorph; A = anacholicomorph; c size: 1 = toy; 2 = small; 3 = medium; 4 = large; d BW means maternal body weight: 1 = <5 kg; 2 = 5 kg ≤ BW ≤ 10 kg; 3 = 10 kg < BW ≤ 25 kg; 4 = 25 kg < BW ≤ 45 kg; 5 = >45 kg; the category coded 1 is the reference; e mean is expressed in grams.
Table
Table 7. Litter size and maternal characteristics: results of final Poisson regression model multivariable analysis (step-wise selection procedure); body shape and weight.
Table 7. Litter size and maternal characteristics: results of final Poisson regression model multivariable analysis (step-wise selection procedure); body shape and weight.
VariableContrastMean Ratio95% Lower limit95% Upper LimitWald Statisticsp-Value
Body shape aM/B1.303 1.069 1.588 2.619 0.0088
D/B 1.355 1.015 1.808 2.061 0.0393
A/B1.407 1.078 1.837 2.514 0.0119
BW b2/11.23 1.05 1.441 2.567 0.0103
3/1 1.835 1.599 2.105 8.66 <0.001
4/11.991 1.753 2.261 10.593 <0.001
5/12.169 1.84 2.556 9.225 <0.001
a Body shape: B = brachymorph; M = mesomorph; D = dolichomorph; A = anacholicomorph; b BW means maternal body weight: 1 = <5 kg; 2 = 5 kg ≤ BW ≤ 10 kg; 3 = 10 kg < BW ≤ 25 kg; 4 = 25 kg < BW ≤ 45 kg; 5 = >45 kg; the category coded 1 is the reference.
Table
Table 8. Litter size and maternal characteristics: results of final Poisson regression model multivariable analysis (step-wise selection procedure); body shape and size.
Table 8. Litter size and maternal characteristics: results of final Poisson regression model multivariable analysis (step-wise selection procedure); body shape and size.
VariableContrastMean Ratio95% Lower Limit95% Upper LimitWald Statisticp-Value
Body shape aM/B1.0070.8241.2310.070.9442
D/B0.8410.6381.109−1.2280.2194
A/B1.4871.1261.9632.7950.0052
Size b2/11.5061.2251.8523.883<0.001
3/12.2981.872.8257.906<0.001
4/12.8362.263.5598.995<0.001
a Body shape: B = brachymorph; M = mesomorph; D = dolichomorph; A = anacholicomorph; b size: 1 = toy; 2 = small; 3 = medium; 4 = large; the category coded 1 is the reference.
Table
Table 9. Number and birth weight of pups per litter in five breeds.
Table 9. Number and birth weight of pups per litter in five breeds.
BreedNL aNP bNP bbBW c
MinQ1 dMedianMeanQ3 eMaxMinQ1 dMedianMeanQ3 eMax
German Shepherd3523224.576.6298.51257435503510.5 600900
Golden Retriever1914835.587.7891013280426.2461.5 475.1527.5 750
Labrador Retriever4426415667.2510188369.5405.5 412.1450624
Jack Russel Terrier156723.554.46757122180200201.3 220320
WHWT f16682344.255.25 690150180 175200280
a NL = number of litters; b NP = number of pups; c bBW = birth weight of pups (grams); d Q1 = first quartile; e Q3 = third quartile; f WHWT = West Highland White Terrier.

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Groppetti, D.; Pecile, A.; Palestrini, C.; Marelli, S.P.; Boracchi, P. A National Census of Birth Weight in Purebred Dogs in Italy. Animals 2017, 7, 43. https://doi.org/10.3390/ani7060043

AMA Style

Groppetti D, Pecile A, Palestrini C, Marelli SP, Boracchi P. A National Census of Birth Weight in Purebred Dogs in Italy. Animals. 2017; 7(6):43. https://doi.org/10.3390/ani7060043

Chicago/Turabian Style

Groppetti, Debora, Alessandro Pecile, Clara Palestrini, Stefano P. Marelli, and Patrizia Boracchi. 2017. "A National Census of Birth Weight in Purebred Dogs in Italy" Animals 7, no. 6: 43. https://doi.org/10.3390/ani7060043

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