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Musculoskeletal Development of the Puppy: Birth to Twelve Months


Abstract and Figures

Dogs are one of the most morphologically diverse species as they can range from a 1kg Chihuahua to a 100kg English Mastiff. With gestation ranging from 58 to 68 days all puppies begin life at a similar size, with no teeth and their eyes closed. There is little difference between gestation timescales, however growth and size post-partum varies greatly, depending on the breed (Table 1). Although there is such a variation in size, nutritional and exercise advice for the first twelve months of life scarcely differs. This can have an impact on the growth of a puppy and result in a number of pathological and skeletal conditions.
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41 Animal Therapy Magazine | ISSUE 15
DOGS are one of the most
morphologically diverse
species as they can range
from a 1kg Chihuahua to a
100kg English Masti. With gestation
ranging from 58 to 68 days all puppies
begin life at a similar size, with no
teeth and their eyes closed. ere is
little dierence between gestation
timescales, however growth and size
post-partum varies greatly, depending
on the breed (Table 1). Although there
is such a variation in size, nutritional
and exercise advice for the rst twelve
months of life scarcely diers. is
can have an impact on the growth
of a puppy and result in a number of
pathological and skeletal conditions.
Long bones, are responsible for
providing strength and structure to the
body to enable locomotion (Figure 1).
e cartilaginous precursors of long
bones are laid down during the foetal
period. At birth the scapula, os ischi,
os ilium and the cartilaginous scaold
of the diaphysis are almost totally
replaced by bone. Ossication begins
in the diaphysis where cartilage is
enclosed by forming an outer layer
of bone. As a result, the still rapidly
dividing chondrocytes (cartilage cells),
are forced to arrange themselves on
top of each other forming columnar
cartilage. e growing cartilage is
forced to grow in peripheral directions
as the cortex now prevents outward
expansion and makes bone form
lengthways. As the cortex thickens,
diused chondrocyte nourishment
decreases. Capillary vessels begin to
sprout through gaps in the bone
cortex and supply nutrients, osteoblasts
and osteoclasts to the diaphysis,
enabling the initiation of endochondral
ossication (Figure 1).
Endochondral ossication continues
until the animal has reached maturity.
e process involves the replacement of
hyaline cartilage to bone by osteoblastic
cells. Primary ossication centres are
located in the diaphysis of long bones
where osteoblasts lay down new bone
towards bone ends. Secondary centres
of ossication then develop at the
epiphysis, where mineralisation occurs
and results in the development of true
articular cartilage. Osteoclastic cells
then begin to remove bone from the
centre of the diaphysis which forms
the marrow cavity and trabeculae of
the cancellous bone. e epiphyseal
(growth) plate remains cartilage-bound
to enable bone to continue lengthening.
Once the dog has reached its full size,
growth will cease and the cartilage in
the growth plate is replaced by bone,
creating a total and bony skeleton
(Figure 2). Depending on bone type
and region within the body, growth
plates will close at dierent times
(Table 2).
Development of the Puppy
Birth – Twelve Months
continued overleaf
by Georgia Lewis PhD Candidate, BSc (Hons) VN RVN
Dog Dog Breeds Weight Rapid Growth Timescale to Fully
Size Range (kg) Period Grown (Entire)
Toy Chihuahua, Pomeranian, < 5 Birth–11 weeks 6 – 12 months
Maltese, Toy Poodle
Small Jack Russell Terrier, 5 - 10 Birth–14 weeks 8 – 12 months
Dachshund, Pug,
Miniature Schnauzer
Medium Border Collie, Cocker 10 - 25 Birth–16 weeks 8 – 18 months
Spaniel, Beagle
Large German Shepherd, 25 - 40 Birth–18 weeks 11 – 18 months
Labrador Retriever,
Golden Retriever,
Bulldog, Boxer,
Siberian Husky
Giant Great Dane, Masti, > 40 Birth–20 weeks 12 – 24 months
St. Bernard
Figure 1: Development of a Long Bone; Le:
Open Growth Plate During Endochondral
Ossication, Right: Ceased Cell Proliferation
and Maturation in Closed Growth Plate.
Table 1: Table Depicting Dog Size, Typical Breeds, Average Weights and Growth Timescales.
(Hawthorne et al., 2004)
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42 Animal Therapy Magazine | ISSUE 15
Aside from the size of the dog,
there are a number of factors that
can contribute to their growth and
development. Depending on the
size of specic breeds, puppies have
exponential growth until they reach
certain ages (See Table 1). Males take
longer to reach adulthood than
females, so their sustained growth
needs to be considered with the
following factors.
Puppies begin weaning and start
eating solid food from three weeks
of age. ey are fully weaned from
their dams by the time of rehoming at
typically around eight weeks. During
the rst twelve months, it is crucial
that growing puppies have a sucient
diet which meets their high energy
requirements. Dietary imbalances are
commonly seen in growing dogs, so
it is important to ensure a dog’s diet is
suitable for its age and breed.
Resultant malnutrition from under-
feeding can cause stunted growth
and overfeeding can result in obesity.
Obesity has a direct impact on joint
and limb formation due to increased
loading forces on joints. is can
result in the malformation of a
joint, leading to conditions such as
secondary osteoarthritis. Although
obesity is a risk factor in all young
breeds, it can have a greater impact
on larger breeds due to excess
weight being carried on growing
bones for longer growing periods.
In order to ensure prevention of
malnutrition, puppies should be fed
a diet that consists of a calculated
calorie intake, utilising an individual
resting energy requirement (RER)
(Table 3). e RER, is the minimum
amount of energy a dog requires to
maintain homeostasis at rest, and can
be calculated by the formula; 70 x
(Bodyweight [kg]) 0.75
To avoid malnutrition and
consequential pathological conditions
or skeletal deformities, a sucient diet
must also include specic nutrients
and minerals. Larger breeds are
susceptible to over supplementation
of nutrients, which can result in a
number of skeletal conditions. It is
important to be aware of the size of
the puppy and its potential growth
to ensure it is given a diet with the
correct amounts of the following;
Calcium is vital for the development
and maintenance of bone and is
absorbed through the intestines.
e average adult healthy dog
requires 0.1 to 0.2 mmol/L per day,
however growing dogs will require
a higher level of calcium in their
diet to account for bone growth. It
is especially important to ensure
puppies have ample time to feed
from their dams and avoid premature
weaning. Increased levels can result
in hypercalcaemia. is is detrimental
in giant breeds as more than 3.3g
of calcium per 100g can cause
osteochondrosis, whereas this only
results in microscopic irregularities
in miniature breeds. Low levels of
calcium; less than 0.55g per 100g
Growth Plate/ Physis Approximate Age Closure
Scapula: Supraglenoid tubercle 4 – 7 months
Proximal humerus: greater tubercle to humeral head 4 months
Proximal humeral physis 10 – 13 months
Distal humerus: lateral and medial condyle parts 6 weeks
Distal humerus: medial epicondyle 6 months
Distal humerus: condyle to diaphysis 5 – 8 months
Proximal radius 5 – 11 months
Proximal ulna: olecranon 5 – 10 months
Proximal ulna: anconeus 3 – 5 months
Distal radius 6 – 12 months
Distal ulna 6 – 12 months
Accessory carpal bone 2 – 5 months
Proximal metacarpal i 6 months
Distal metacarpals ii – v 5 – 7 months
Phalanges 4 – 6 months
Pelvis: acetabulum 4 – 6 months
Pelvis: iliac crest 12 – 24 months
Pelvis: tuber ischii 8 – 10 months
Proximal femur: neck 6 – 11 months
Proximal femur: greater trochanter 6 – 10 months
Proximal femur: lesser trochanter 8 – 13 months
Distal femur 6 – 11 months
Proximal tibia: medial and lateral condyle 6 weeks
Proximal tibia: tuberosity to condyle 6 – 8 months
Proximal tibia: condyle to diaphysis 6 – 12 months
Proximal bula 6 – 12 months
Distal tibia: physis 5 – 11 months
Distal tibia: medial malleolus 5 months
Distal bula 5 – 12 months
Tuber calcis 3 – 8 months
Lifestage RER Requirements
< 4 months 3.0 x RER
50% - 80% of adult weight 2.5 x RER
> 80% of adult weight 1.8 – 2.0 x RER
Table 2: Approximate Ages for Epiphyseal Plate Closure. (Hammond and McConnel, 2013)
Table 3: RER Requirements for First Twelve Months of Age. (Hemmings, 2018; Gajanayake et al., 2011)
43 Animal Therapy Magazine | ISSUE 15
for giant breeds and 0.05g per 100g
for miniature breeds, can cause
pathological fractures as a result of
osteopenia and osteoporosis.
Vitamin D
Vitamin D is crucial for the growth
of bones and calcium absorption. It
has a signicant role in maintaining
the skeletal calcium balance which
promotes bone reabsorption
and subsequent function of the
parathyroid hormone. A diet
decient in vitamin D can result in
osteomalacia and rickets in all breeds.
It is imperative puppies are fed a
good quality diet, recommended
by a veterinary surgeon, as they
require supplementary amounts of
vitamin D, due to their inability to
photosynthesise sucient amounts
through their skin from natural
Protein is also an important factor
for a dog’s growth. A puppy’s protein
requirement peaks at weaning and
generally requires 22% to 23% of
protein daily. A diet low in protein
will result in weight loss and
retardation or cessation of growth. As
larger dog breeds will continue their
growth for longer, it is important
their diet does not reduce protein
at the same stage as small and
miniature breeds. Increased protein
in a puppy’s diet can result in skeletal
abnormalities and become a potential
contributing factor for conditions
such as hip dysplasia due to increased
development of the acetabulum and
femoral condyles. As a result of the
ill-tting joints, this can progress
into degenerative joint disease and
secondary osteoarthritis.
Phosphorus is believed to combine
with calcium to strengthen and aid
the structure of bone. It is important
to maintain the calcium-phosphorus
ratio to ensure there is adequate
calcium within the bones. Young,
growing dogs are recommended to
have a daily phosphorus intake of 2 to
3 mmol/L.
Home Environment
Puppies can be rehomed from eight
weeks of age. is results in a variation
of environmental factors impacting
how the puppy will develop. In a new
home, owners should avoid allowing
puppies the use of stairs and also from
playing on slippery surfaces to avoid
harsh impact on growing bones and
joints. e handling of puppies is
important and should be carried out
with great care. Owners with young
children should be especially mindful
when the children interact with the
puppy to ensure no injury is caused.
Similarly, it is also advised that puppies
within multi-dog households should
be monitored when interacting with
other dogs in the home. Young dogs’
bones are not fully developed and are
unable to sustain stress or force due
to their epiphyseal plates still being
cartilaginous (Figure 3). Exercise
therefore must be limited until dogs
have reached maturity to prevent
injury. It is advised that a dog is
exercised for ve minutes per month
of age. Stairs and large slopes should be
avoided to prevent any damage to the
puppy’s growth plates.
Typically dogs reach adolescence and
sexual maturity between six to 18
months. For behavioural and potential
health reasons, dogs are usually
neutered between six and 24 months
of age. Neutering is the removal of
reproductive organs and results in a
consequential decrease in gonadal
steroid production. Gonadal hormones
regulate skeletal growth and it was
Figure 3: Depiction of Radiographic Puppy Bone Development; Le: at 1 week,
Centre: at 6 weeks, Right: at 12 weeks of age.
Figure 2: Complete Ossied Skeleton of a Dog Post Growth Plate Closure.
continued overleaf
44 Animal Therapy Magazine | ISSUE 15
Georgia Lewis,
PhD Candidate, BSc (Hons) VN RVN
Animal Department
Hartpury University,
Hartpury, Glos, GL19 3BE
anecdotally believed that early neutering
stunted growth through inhibition of
hormones. Decreased levels as a result
of early neutering in fact delay growth
plate closure and lead to elongated
long bones. ese elongated limbs can
result in altered function of muscular
anatomy which also predisposes the dog
to muscle, tendon and ligament injuries
and calcication. Males take longer to
reach full maturity so early castration
can result in underdeveloped muscles
and denition as well as elongated
limbs. A similar state of poor muscle
development also occurs in premature
spays. Owners and veterinary sta
should be mindful that dogs have
reached their adult size before neutering
to reduce the chance of delayed growth
plate closure, unless it is for a diagnosed
e growth of a dog is very complex.
Due to the diversity within the species,
bone growth can range from six months
to two years. Other factors, including a
puppy’s diet and exercise, can inuence
the development of bones. As a result,
bone malformation leads to secondary
conditions such as degenerative
joint disease and osteoarthritis. It is
important for breeders, owners and
veterinary sta to be aware of these
factors to ensure dogs develop at the
correct rate to reduce the repercussions
of poor development in the dog’s later
life stages.
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... The morphologic examination of 111 Mannara dogs showed that, on average, the indications of the provisional breed standard are satisfied (ENCI 2013): the dogs can be classified as large/giant (mean weight was 41 kg for males and 32 kg for females), with a meso-dolichomorphic body (mean body index was 85 for males and 90 for females) and a mesocephalic head (mean cephalic index was 53 for both the sexes). A certain degree of variability was observed, particularly in the Thoracic index, probably due to the different age of animals (1-5 years old) and therefore their development: due to the diversity of breeds with very different shapes and sizes, growth patterns are also noticeably different, with very small dog breeds reaching maturity between 8 and 12 months of age and larger breeds taking up to 24 months to reach the adult body weight and conformation (Hawthorne et al. 2004;Lewis 2019). The average birth weights measured on 50 puppies, equal to 720 g for males and 580 g for females, are in accordance with published data referred to large/giant dog breeds (Groppetti et al. 2017;Schrank et al. 2019). ...
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Mannara dogs have long been bred in Sicily (Italy) to work alongside shepherds as flock guardians. This study provides a morphologic, genealogic, and genomic characterisation of the Mannara dog, useful in light of its recognition process and to improve the breed standard. Morphologic measurements of body, head, and chest were taken on 111 adult Mannara dogs. The whole population pedigree was used to calculate the inbreeding coefficient (F) and five effective population size (N e) parameters. Twelve Mannara dogs were genotyped using the Canine 230 K SNP BeadChips and compared with Maremma sheepdog, Caucasian shepherd dog, Cane Corso Italiano, and Neapolitan mastiff for population structure, heterozygosity, and runs of homozygosity. The morphometric evaluation showed that Mannara dogs generally accords with the provisional standard and can be classified as a large/giant, meso-dolicomorphic, and meso-cephalic breed. The population consists of 375 individuals, one third of which are founders and the remaining belong to 58 litters; presenting low inbreeding (F = 0.7%) and balanced sires and dams. The N e estimates range widely: two (N eN =159 and N eFi =50) exceed the FCI limit for breed recognition and one (N eCi =25) did not. Genetically, all the included populations are well distinct, with the Maremma sheepdog being the nearest to the Mannara dog. Five Mannara have a single ancestral component, while the others show higher admixed proportions. The genomic inbreeding and heterozygosity confirm the good management of the breed. Our analyses suggest that the Mannara breed should continue the recognition process, pivotal to preserving an invaluable canine resource for the Sicilian agriculture.
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Boston’s “Big Dig” construction project resulted in the excavation of multiple archaeological sites dating from the seventeenth to nineteenth centuries, including the Great House/Three Cranes Tavern in Charlestown, Massachusetts (USA). An otherwise unremarkable pit below the tavern foundation contained bones originally identified as a cat skeleton, which has subsequently been reidentified as a dog. This paper discusses site context, osteological evidence for the dog’s reclassification, and the shifts in cultural meaning this may indicate. Employing an osteobiographical approach, it draws together points of connection between the modern skeletal assessment, a series of 1980s excavations, and the motivations of eighteenth-century tavern inhabitants.
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Background Very little is known about neonatal skeletal development in small-sized purebred dogs. In order to improve this knowledge, 27 spontaneously dead puppies belonging to small-sized breeds were enrolled in this study for radiologic, histological and morphometric investigations. Results The appearance of the limb secondary ossification centers and the onset of their formation were clearly observed by x rays and confirmed by histological evidences. Radiographic and anatomic measurements of limb bones length and skull length and width were positively correlated with body weight and age of the subjects and the body weight was positively correlated with radius bone mineral density, as demonstrated by dual-energy x-rays absorptiometry. Conclusions These data provided original information on the growth of newborn small-sized breed dogs, and suggest that cadavers may be useful to study skeletal development. Electronic supplementary material The online version of this article (doi:10.1186/s12917-017-1092-6) contains supplementary material, which is available to authorized users.
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Canine hip dysplasia (CHD) is the most common inherited polygenic orthopedic trait in dogs with the phenotype influenced also by environmental factors. This trait was described in the dog in 1935 and leads to a debilitating secondary hip osteoarthritis. The diagnosis is confirmed radiographically by evaluating signs of degenerative joint disease, incongruence, and/or passive hip joint laxity. There is no ideal medical or surgical treatment so prevention based on controlled breeding is the optimal approach. The definitive CHD diagnosis based on radiographic examina-tion involves the exposure to ionizing radiation under general anesthesia or heavy sedation but the image does not reveal the underlying genetic quality of the dog. Phenotypic expression of CHD is modified by environmental factors and dogs with a normal phenotype can be carriers of some mutations and transmit these genes to their offspring. Programs based on selection of dogs with better individual phenotypes for breeding are effective when strictly applied but remain inferior to the selection of dogs based on estimation of breeding values. Molecular studies for dissecting the genetic basis of CHD are ongoing, but progress has been slow. In the future, the recommended method to improve hip quality in controlled breeding schemes, which will allow higher selection pressure, would be based on the estimation of the genomic breeding value. Since 2012, a commercial DNA test has been available for Labrador Retrievers using a blood sample and provides a probability for development of CHD but we await evidence that this test reduces the incidence or severity of CHD. Keywords: canine hip dysplasia, phenotype, breeding stock, GWAS, screening, diagnosis
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Our recent study on the effects of neutering (including spaying) in Golden Retrievers in markedly increasing the incidence of two joint disorders and three cancers prompted this study and a comparison of Golden and Labrador Retrievers. Veterinary hospital records were examined over a 13-year period for the effects of neutering during specified age ranges: before 6 mo., and during 6-11 mo., year 1 or years 2 through 8. The joint disorders examined were hip dysplasia, cranial cruciate ligament tear and elbow dysplasia. The cancers examined were lymphosarcoma, hemangiosarcoma, mast cell tumor, and mammary cancer. The results for the Golden Retriever were similar to the previous study, but there were notable differences between breeds. In Labrador Retrievers, where about 5 percent of gonadally intact males and females had one or more joint disorders, neutering at <6 mo. doubled the incidence of one or more joint disorders in both sexes. In male and female Golden Retrievers, with the same 5 percent rate of joint disorders in intact dogs, neutering at <6 mo. increased the incidence of a joint disorder to 4-5 times that of intact dogs. The incidence of one or more cancers in female Labrador Retrievers increased slightly above the 3 percent level of intact females with neutering. In contrast, in female Golden Retrievers, with the same 3 percent rate of one or more cancers in intact females, neutering at all periods through 8 years of age increased the rate of at least one of the cancers by 3-4 times. In male Golden and Labrador Retrievers neutering had relatively minor effects in increasing the occurrence of cancers. Comparisons of cancers in the two breeds suggest that the occurrence of cancers in female Golden Retrievers is a reflection of particular vulnerability to gonadal hormone removal.
With a prevalence of over 70% amongst some breeds, hip dysplasia is one of the most common developmental orthopaedic diseases diagnosed in first opinion practice. With a multimodal approach leading to the best form of management of the condition, this two-part article looks at the causes and treatment of the condition, and the role that the veterinary nurse and rehabilitation can play. Part one below focuses on aetiology and treatment.
To investigate the impact of a selective reduction in dietary phosphorus (P) supply on healthy growing dogs, a total of 23 Beagles and 30 Foxhound crossbreds (FBI) were used in a feeding trial between 6 and 24 weeks of age. Sixteen Beagles and 19 FBI were fed with selectively reduced P concentrations (low phosphorus, LP). The remaining puppies received a completely balanced control diet (CON). With these diets, the P supply in the Beagles at the age of 12 weeks added up to 2.5 ± 0.6 (LP) and 9.8 ± 1.4 g P/kg DM (CON), and in the FBI 4.3 ± 0.9 (LP) and 13.0 ± 1.6 g P/kg DM (CON). Therefore, the LP Beagles received an average of 33 ± 11% of the recommended daily allowances (RDA) of P, the LP FBI 41 ± 11%. The calcium (Ca) concentration stayed unaltered and led to a Ca/P ratio above the recommended range of 1.3/1 to 2/1. The apparent digestibility (aD) of phosphorus was reduced in the LP Beagle; otherwise, the aD of both minerals was not affected by the P concentration of the diet. The renal excretion of P was reduced to zero in both LP groups while the renal calcium excretion increased significantly. Several of the puppies from both breeds showed impaired appetite, growth, skin and fur quality, and a few also clinically showed relevant signs of a disturbed musculoskeletal system after the LP feeding. A rapid loss of muscle strength and posture within hours led to severe deviation of the limb axis with hyperflexion of the joints but no radiological aberrations or signs of pain. Immediate transition of affected puppies to a balanced diet with sufficient phosphorus resulted in a complete recovery of the puppies in less than one month. The results demonstrate the importance of an adequate P supply on the healthy development of growing dogs.
A 6-month-old intact female giant schnauzer dog fed a nutritionally unbalanced homemade diet was evaluated because of a 1-month history of lameness and difficulty walking. Abnormalities identified on ancillary tests, in conjunction with the dog's clinical improvement following diet change, suggested a diagnosis of vitamin D deficiency and nutritional secondary hyperparathyroidism. This report underlines the importance of appropriate feeding management, especially during the vulnerable growth phase.
This article reviews the development of long bones, the microanatomy and physiology of the growth plate, the closure times and contribution of different growth plates to overall growth, and the effect of, and prognosis for, traumatic injuries to the growth plate. Details on surgical treatment of growth plate fractures are beyond the scope of this article.
The influence of dietary calcium on calcium metabolism was investigated in growing dogs that reach an adult body weight similar to that of humans. Seven groups of dogs (n greater than or equal to 5) were raised on a diet with a composition meeting the National Research Council (NRC) requirements (1974), but differing in calcium content, with or without a constant ratio to phosphorus. Control dogs fed 1.1% calcium and 0.9% phosphorus (all on a dry matter basis) were fed ad libitum (n = 10) or in restricted amounts (n = 6); dogs fed high calcium (3.3%) diets received either 0.9% phosphorus (n = 6) or 3.0% phosphorus (n = 6); dogs fed low calcium (0.55%) diets received either 0.9% phosphorus (n = 5 + 6) or 0.5% phosphorus (n = 8). Food intake, circulating total calcium and inorganic phosphorus concentrations and calcium metabolism, with 45Ca kinetics, were studied at 8, 14, 20 and 26 wk of age. Except for the difference in food intake in two groups at 14 wk (i.e., 0.55% calcium-0.9% phosphorus higher and 3.3% calcium-0.9% phosphorus lower, respectively, than the controls) no differences were noticed during the rest of the study. The mean plasma calcium concentrations did not differ between groups during the studies, whereas that of inorganic phosphorus revealed temporal aberrations in two groups. An absorption coefficient alpha of 45-66% was found for the control group. High and low calcium diets gave rise to values of 23-43% and 70-97%, respectively, for alpha irrespective of the phosphorus content of the diet.(ABSTRACT TRUNCATED AT 250 WORDS)