Estimation of heritabilities, genetic correlations, and breeding values of four traits that collectively define hip dysplasia in dogs.
ABSTRACT OBJECTIVE-To estimate heritabilities and genetic correlations among 4 traits of hip joints (distraction index [DI], dorsolateral subluxation [DLS] score, Norberg angle [NA], and extended-hip joint radiograph [EHR] score) and to derive the breeding values for these traits in dogs. ANIMALS-2,716 dogs of 17 breeds (1,551 dogs in which at least 1 hip joint trait was measured). PROCEDURES-The NA was measured, and an EHR score was assigned. Hip joint radiographs were obtained from some dogs to allow calculation of the DI and DLS score. Heritabilities, genetic correlations, and breeding values among the DI, DLS score, NA, and EHR score were calculated by use of a set of multiple-trait, derivative-free, restricted maximum likelihood computer programs. RESULTS-Among 2,716 dogs, 1,411 (52%) had an estimated inbreeding coefficient of 0%; the remaining dogs had a mean inbreeding coefficient of 6.21%. Estimated heritabilities were 0.61, 0.54, 0.73, and 0.76 for the DI, DLS score, NA, and EHR score, respectively. The EHR score was highly genetically correlated with the NA (r = -0.89) and was moderately genetically correlated with the DI (r = 0.69) and DLS score (r = -0.70). The NA was moderately genetically correlated with the DI (r = -0.69) and DLS score (r = 0.58). Genetic correlation between the DI and DLS score was high (r = -0.91). CONCLUSIONS AND CLINICAL RELEVANCE-Establishment of a selection index that makes use of breeding values jointly estimated from the DI, DLS score, NA, and EHR score should enhance breeding programs to reduce the incidence of hip dysplasia in dogs.
- SourceAvailable from: Dennis F Lawler[show abstract] [hide abstract]
ABSTRACT: To determine prevalence of radiographic evidence of osteoarthritis in 4 diarthrodial joints of dogs with restricted feed intake, compared with dogs without restricted feed intake. Paired feeding study. 48 Labrador Retrievers. Dogs in litters from 7 dams and 2 sires were paired by sex and weight within litters and randomly assigned to a control-fed group or a limit-fed group that received 25% less food than the control-fed group. Radiographic evaluation of prevalence and severity of osteoarthritis in the hip, shoulder, elbow, and stifle joints was performed when dogs were 8 years of age. Radiographic evidence of osteoarthritis that affected multiple joints was significantly more common in the control-fed group than in the limit-fed group. Prevalence of lesions in the hip joint was 15/22 in the control-fed group and 3/21 in the limit-fed group. Prevalence of lesions in the shoulder joint was 19/22 in the control-fed group and 12/21 in the limit-fed group; lesions in this joint were generally mild. Severity, but not prevalence, of osteoarthritis in the elbow joint was greater in the control-fed group than in the limit-fed group. Prevalence and severity of osteoarthritis in several joints was less in dogs with long-term reduced food intake, compared with control dogs. Food intake is an environmental factor that may have a profound effect on development of osteoarthritis in dogs.Journal of the American Veterinary Medical Association 01/2001; 217(11):1678-80. · 1.72 Impact Factor
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ABSTRACT: To determine whether dorsolateral subluxation (DLS) scores in young dogs could be used to reliably predict which dogs would develop evidence of hip osteoarthritis and whether DLS scores measured at various ages correlated with each other. 129 Labrador Retrievers, Greyhounds, and Labrador Retriever-Greyhound crossbreds. DLS scores were measured on radiographs taken at 4, 8, and 12 months of age and at necropsy (8 to 36 months of age). At necropsy, the hip joints were examined macroscopically and a score assigned for degree of cartilage degeneration. DLS scores at 4 (n = 35, r(s) = -0.62), 8 (n = 106, r(s) = -0.54), and 12 (n = 15, r(s) = -0.87) months of age were significantly correlated with cartilage degeneration scores, and DLS scores at 8 months of age were significantly correlated with scores obtained at the time of necropsy (n = 39, r(s) = 0.87). The DLS scores at 4 months of age were significantly different from scores at 8 months of age, but scores did not differ significantly thereafter. Likelihood ratios for cartilage lesions for low (< 45%), intermediate (> or = 45 but < or = 55%), and high (> 55%) DLS scores at 8 months of age were 8.0, 2.6, and 0.2, respectively. Results suggest that DLS score at 8 months of age was a reasonable, albeit imperfect, predictor of the condition of the hip joint cartilage at necropsy. Thus, the DLS method might be useful for early identification of dogs with hip dysplasia.American Journal of Veterinary Research 12/2001; 62(11):1711-5. · 1.35 Impact Factor
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ABSTRACT: In dogs hip joint laxity that can lead to degenerative joint disease (DJD) is frequent and heritable, providing a genetic model for some aspects of the human disease. We have used Portuguese water dogs (PWDs) to identify Quantitative trait loci (QTLs) that regulate laxity in the hip joint. A population of 286 PWDs, each characterized by ca. 500 molecular genetic markers, was analyzed for subluxation of the hip joint as measured by the Norberg angle, a quantitative radiographic measure of laxity. A significant directed asymmetry was observed, such that greater laxity was observed in the left than the right hip. This asymmetry was not heritable. However, the average Norberg angle was highly heritable as were the Norberg angles of either the right or left hips. After correction for pedigree effects, two QTLs were identified using the metrics of the left and right hips as separate data sets. Both are on canine chromosome 1 (CFA1), separated by about 95 Mb. One QTL, associated with the SSR marker FH2524 was significant for the left, but not the right hip. The other, associated with FH2598, was significant for the right but not the left hip. For both QTLs, some extreme phenotypes were best explained by specific interactions between haplotypes.American Journal of Medical Genetics Part A 02/2004; 124A(3):239-47. · 2.30 Impact Factor
AJVR, Vol 70, No. 4, April 2009 483
osteoarthritis, lameness, and physical disability.1 Medi-
cal and surgical management of the condition have
economic and emotional impacts on dog owners and
breeders. As a complex trait, HD is caused by genetic
and environmental factors that influence expression of
the primary trait and the severity of secondary osteo-
arthritis.2 Factors that affect expression of HD and de-
velopment of secondary osteoarthritis in dogs include
sex, age, and body weight.2–6 Many genes likely under-
lie expression of HD, most of which have a small addi-
tive effect (polygenes), but some of which likely have
ip dysplasia in dogs is a polygenic disease charac-
terized by hip instability that results in secondary
Estimation of heritabilities, genetic correlations,
and breeding values of four traits
that collectively define hip dysplasia in dogs
Zhiwu Zhang, PhD; Lan Zhu, PhD; Jody Sandler, DVM; Steven S. Friedenberg, BS, MBA;
Jill Egelhoff, BS; Alma J. Williams, BS; Nathan L. Dykes, VMD; William Hornbuckle, DVM;
Ursula Krotscheck, DVM; N. Sydney Moise, DVM, MS; George Lust, PhD; Rory J. Todhunter, BVSc, PhD
Objective—To estimate heritabilities and genetic correlations among 4 traits of hip joints
(distraction index [DI], dorsolateral subluxation [DLS] score, Norberg angle [NA], and ex-
tended–hip joint radiograph [EHR] score) and to derive the breeding values for these traits
Animals—2,716 dogs of 17 breeds (1,551 dogs in which at least 1 hip joint trait was mea-
Procedures—The NA was measured, and an EHR score was assigned. Hip joint radio-
graphs were obtained from some dogs to allow calculation of the DI and DLS score. Heri-
tabilities, genetic correlations, and breeding values among the DI, DLS score, NA, and EHR
score were calculated by use of a set of multiple-trait, derivative-free, restricted maximum
likelihood computer programs.
Results—Among 2,716 dogs, 1,411 (52%) had an estimated inbreeding coefficient of 0%;
the remaining dogs had a mean inbreeding coefficient of 6.21%. Estimated heritabilities
were 0.61, 0.54, 0.73, and 0.76 for the DI, DLS score, NA, and EHR score, respectively. The
EHR score was highly genetically correlated with the NA (r = –0.89) and was moderately ge-
netically correlated with the DI (r = 0.69) and DLS score (r = –0.70). The NA was moderately
genetically correlated with the DI (r = –0.69) and DLS score (r = 0.58). Genetic correlation
between the DI and DLS score was high (r = –0.91).
Conclusions and Clinical Relevance—Establishment of a selection index that makes use
of breeding values jointly estimated from the DI, DLS score, NA, and EHR score should
enhance breeding programs to reduce the incidence of hip dysplasia in dogs. (Am J Vet Res
In North America, selection methods to improve the
genetic composition of dog breeds and, in so doing, im-
prove hip joint conformation have been based on radio-
graphic hip joint screening, semiopen (OFA) and closed
(PennHIP) hip joint registries, and organized breeding
programs.9–11 Through these breeding strategies, HD
was determined to be heritable, and selective breeding
efforts reduced the prevalence of HD.12 For example,
the prevalence of HD in German Shepherd Dogs at 12
to 16 months of age decreased from 55% to 24% after
5 generations of selection,12 and the prevalence of HD
in Labrador Retrievers decreased from 30% to 10%.13,14
Selective breeding is less effective when a single phe-
Received March 27, 2008.
Accepted July 22, 2008.
From the Institute for Genomic Diversity (Zhang), the Department
of Clinical Sciences (Friedenberg, Egelhoff, Williams, Dykes, Horn-
buckle, Krotscheck, Moise, Todhunter), and the Baker Institute for
Animal Health (Lust), College of Veterinary Medicine, Cornell Uni-
versity, Ithaca, NY 14850; the Department of Statistics, College of
Arts and Sciences, Oklahoma State University, Stillwater, OK 74078
(Zhu); and Guiding Eyes for the Blind, 611 Granite Springs Rd,
Yorktown Heights, NY 10598 (Sandler).
Address correspondence to Dr. Todhunter.
484 AJVR, Vol 70, No. 4, April 2009
notype is used as the selection criterion15–22 than when
estimated breeding values are used.23,24
Because HD has been so difficult to accurately de-
fine and eliminate in dogs, much effort has been di-
rected at developing and comparing the accuracy of
radiographic screening tests.3,25 The most widely used
method for diagnosis in North America is the ventro-
dorsal EHR, commonly referred to as the OFA meth-
od.26 From this radiographic image, a subjective EHR
score is obtained. Objective measurements include the
DI,27 DLS score,3,28,29 and NA.30 Heritabilities of these
traits reportedly range from 0.10 to 0.68.31
Because the objective hip joint traits and the EHR
score are modestly correlated with each other at the
phenotypic level,25,29,32,33 the estimates of heritabili-
ties and breeding values derived from a multiple-trait
model, which incorporates genetic and environmental
correlations among the traits, would be more accurate
than if they were derived from a single trait.34,35 More
importantly, the genetic correlations estimated from a
multiple-trait model would provide the essential values
by which a selection index could be derived to integrate
the breeding values of all the traits.36 Selective breed-
ing based on these combined breeding values should
be more effective in reducing the prevalence of such a
complicated trait than breeding decisions made on the
basis of a breeding value for a single trait.37
Although heritabilities of radiographic hip joint
measurements have been investigated in various dog
breeds in various environments,33,38–41 estimates of ge-
netic correlations among values used to judge hip joint
quality are limited. The purpose of the study reported
here was to estimate genetic correlations among the DI,
DLS score, NA, and EHR score and their heritabilities in
a multiple-trait model for subsequent use in deriving a
breeding value for each of these 4 traits of hip joints.
Materials and Methods
Animals—Dogs used in the study originated from
closed breeding colonies at the Baker Institute for Ani-
mal Health at Cornell University, the Guiding Eyes for
the Blind in Yorktown Heights, NY, or those admitted to
the Cornell University Hospital for Animals for radio-
graphic evaluation from January 1999 through October
2007. Multiple radiographic evaluations were available
for some dogs. The hip joints of the Baker Institute dogs
were commonly radiographed at 8 to 12 months of age.
The hip joints of the dogs at the Guiding Eyes for the
Blind were routinely radiographed at 14 to 18 months of
age. Dogs admitted to the Cornell University Hospital for
Animals were radiographed at any age > 8 months.
Hip dysplasia scoring—As is typical in North
America, an EHR was used to assess conformation of
each hip joint by assigning a subjective rating of ex-
cellent, good, or fair to the joint and borderline and
mild, moderate, or severe to the degree of hip dysplasia
evident (EHR score). The NA30 was measured from the
EHR and ranged from 50° (a subluxated hip joint) to
123° (a hip joint phenotypically unaffected by HD). The
maximum amount of lateral femoral head distraction
from the acetabulum (ie, the DI) was measured through
the PennHIP by means of a radiograph obtained with
the hip joint in the distraction position. Labrador Re-
trievers with a DI < 0.3 to 0.4 at 8 months of age were
presumed to have a > 80% probability of not develop-
ing secondary osteoarthritis in hip joints and were clas-
sified as unaffected by HD. Those with a DI > 0.7 were
presumed to have a high probability of developing os-
teoarthritis in hip joints and were classified as affected
with HD.42–46 The PennHIP also involves assessment of
EHRs to determine hip joint conformation and whether
secondary osteoarthritis exists. When no indication of
trauma was evident on the EHR, detection of secondary
osteoarthritis in hip joints was believed to be indica-
tive of antecedent HD. The DLS score was measured as
the percentage of femoral head covered by the dorsal
acetabulum with the hip joint in a natural, weight-bear-
Higher breeding values for the NA and DLS score
indicated a better hip joint (ie, less dysplastic), whereas
lower breeding values for the DI and EHR score in-
dicated the same thing. Body weight, breed, and sex
were recorded when the hip joints were radiographed.
Breeds represented by < 10 dogs were removed from
subsequent statistical analyses.
Pedigree—Ancestors of each dog were traced back
until no parent could be identified. Dogs for which hip
joint traits had not been measured were used to geneti-
cally connect the dogs from which measurements had
been obtained. The additive relationship (kinship) ma-
trix (2,716 X 2,716) was calculated from the pedigree
by means of the tabulate method.48,49 The calculation
began with dogs at the highest (earliest) generation
and carried all the way to the dogs without progeny.
The diagonals of the matrix were equal to 1 plus the
inbreeding coefficient.50 The inbreeding coefficient was
set at 0% for dogs with unknown parents or no com-
mon ancestor within the depth of pedigree tracked for
their parents. The kinship coefficient (ie, coancestry)
between each pair of dogs was also calculated and was
equivalent to the inbreeding coefficient of the hypo-
thetical progeny of each pair (ie, the probability that 2
alleles, sampled at random from each dog, were identi-
cal by descent).
Statistical analysis—Summary data regarding sig-
nalment of dogs are presented as mean ± SD. A mul-
tiple-trait model was used to fully explore relationships
among dogs and among hip joint traits. The most dys-
plastic hip joint of each dog (highest EHR score and
DI and lowest DLS score and NA of the 2 hip joints for
each dog) was used as the measurement. To improve
the accuracy for the prediction of breeding values for
each dog and its relatives, multiple measurements from
different ages were used whenever available. In addition
to providing estimates of genetic correlation among hip
joint traits, the multiple-trait model provided accurate
predictions of breeding values. In matrix notation, the
multiple-trait model was as follows:
y = Xβ + Zu + e,
in which y is the vector of phenotypic values for the
4 traits (DI, DLS score, NA, and EHR score), β is the
vector of fixed effects for sex and breed (categoric vari-
AJVR, Vol 70, No. 4, April 2009 485
ables) and age and body weight (continuous variables),
u is the vector of unknown random additive genetic ef-
fects (the estimate of u is referred to as the BLUP or the
breeding value), and e is the vector of residual terms.
The X and Z are known incidence matrices.
For the random effects, it was assumed that u was
normally distributed with a mean of 0 and a variance of
G, where G = G0 ⊗ A. It was also assumed that e was
normally distributed with a mean of 0 and a variance
of R, where R = R0 ⊗ I. The variables G0 and R0 are un-
known 4 X 4 genetic and residual covariance matrices,
respectively, for the 4 hip joint traits; A is the additive
relationship matrix; and I is the identity matrix. Opera-
tor ⊗ is the direct product of 2 matrices, which is also
referred to as the Kroneker or Zehfuss product. Con-
sequently, the covariance of y (V) is calculated as V =
ZGZT + R, where operator T is transposed. The estimate
of β and prediction of u are β = (XTV–1X) X (–XTV–1y) and
u = (GZTV–1) X (y –
and the symbol – represents general inverse.
Restricted maximum likelihood estimates were ob-
tained for unknown variables G0 and R0 by use of a set of
multiple-trait, derivative-free, restricted maximum like-
lihood software packages that contained 3 programs.51,a
Through use of the first program, the additive relation-
ship matrix was calculated directly from the pedigree;
then its inverse matrix and the determinant of the origi-
nal matrix were evaluated to estimate the log-likelihood
function. The inbreeding coefficient, defined as the
probability that 2 alleles at any locus are identical by
descent,52 was calculated for each dog. The inbreeding
coefficient was calculated by means of a tabular method
described elsewhere.48,49 The second program was used
to prepare coefficients for the mixed model equation
on the basis of a statistical model with fixed and ran-
dom factors for single- or multiple-trait analysis. The
third program was used to solve the mixed-factor linear
xβ), where the operator –1 is inverse
equation and calculated the estimates of the variance
components that maximized the restricted likelihood
given the phenotypic data.54
A single trait-by-trait analysis was conducted
first. The estimates of additive genetic variance and
residual variance were used as the starting values for
the 2-trait analysis on all pairwise combinations of
the DI, DLS score, NA, and EHR score. Variances from
the single-trait analyses and covariances estimated
from 2-trait analyses were used as the starting values
for the 4-trait analysis. Heritability was defined as
the ratio of the additive genetic variance to the total
variance (the sum of additive genetic variance and
residual variance). In the final multiple-trait analy-
sis, iterations were assumed to have converged when
the variance of –2 times the log-likelihood used in
the simplex search algorithm was < 10–9. To ensure
a global maximization in the log-likelihood, a re-
start of the computer programs was performed, with
the converged values used as the restarting points.
Restarts were performed until the difference of the
–2(log-likelihood) from 2 consecutive runs was
< 0.01. Estimates reported in the results section are
all from the 4-trait analysis. Breeding value accuracy
was estimated as the square root of (1 – PEV/σa
where PEV is the error variance of predicted breeding
values and σa
2 is the additive genetic variance.
Animals—The final data set contained 1,551
dogs with at least 1 of the 4 radiographic hip joint
measurements. Seventeen breeds were represented,
including Labrador Retriever, Greyhound, their cross-
breed offspring, and 14 others. Mean ± SD age of dogs
was 22.98 ± 22.11 months (range, 3 to 136 months).
Mean body weight of dogs was 29.30 ± 6.43 kg
(F1 X L) X (F1 X L)?
F1 X Greyhound?
F1 X L?
German Shepherd Dog? 4?
G = Generation depth. Nt = Total number of dogs. Nb = Number of dogs for which both parents were
known. Np = Number of dogs for which only 1 parent was known. Nu = Number of dogs for which neither par-
ent was known. Ni = Number of inbred dogs. Min = Minimum inbreeding value. Max = Maximum inbreeding
value. F1 = First filial generation resulting from a cross between a Labrador Retriever and a Greyhound. L =
Labrador Retriever. NA = Not available.
Table 1—Pedigree structure and inbreeding coefficient values within breed for dogs with a history of
HD from closed breeding colonies and a veterinary teaching hospital.
486 AJVR, Vol 70, No. 4, April 2009
(range, 5.7 to 57.7 kg). Males (46%) and females
(54%) were approximately equally represented.
Hip dysplasia scores—Most of the dogs were Lab-
rador Retrievers or their offspring from crossbreed-
ing with Greyhounds (F1, F1 backcrosses to Labrador
Retrievers or Greyhounds, and F2 offspring; Table 1).
Some traits were measured at multiple ages. The mean
number of measurements per dog was 1.3, 1.0, 1.2, and
1.1 for the DI, DLS score, NA, and EHR score, respec-
tively. The DLS score ranged from 85% for tight-hipped
Greyhounds to as low as 19% for the most dysplastic
dogs. The NA and EHR score were recorded for most
dogs, but the DI and DLS score were only available
in records from the Baker Institute for Animal Health
at Cornell University. Because the NA and EHR score
were measured on more dogs than were the DI and
DLS score, higher accuracy was expected for the NA
and EHR score. Representation of each variable among
the various breeds was summarized (Table 2). Values
for NA, DLS score, DI, and EHR score were also sum-
marized (Table 3). All 4 hip joint radiographic traits were
measured only for Labrador Retrievers, Greyhounds, and
their crossbreed offspring and German Shepherd Dogs.
For other breeds, only 1 to 3 traits were measured.
Pedigree—A total of 1,165 ancestors was added
to the pedigree, which contained 2,716 dogs, including
1,498 dogs from the Guiding Eyes for the Blind organiza-
tion, 571 from the Baker Institute for Animal Health, 425
from the Cornell University Hospital for Animals, and 222
ancestors traced from the database (Table 1). The role of
the 1,165 dogs without a measurement of hip joint quality
was to genetically connect the 1,551 dogs with measure-
ments. The most complex generation involved a family of
Labrador Retrievers from the Guiding Eyes for the Blind,
which included 1,236 connected dogs over 17 generations
from a particular male dog.
Among 2,716 dogs, about half (859 progeny and
552 founders; 53%) had an inbreeding coefficient of
0%. The remainder had a mean inbreeding coefficient
of 6.21%. The highest inbreeding coefficients (31.3%
and 37.7%) were obtained for only a few dogs. Inbreed-
ing coefficients and pairwise kinship coefficients were
summarized (Figures 1 and 2). Because mating did not
occur for any breeds other than Labrador Retriever and
Greyhound, > 80% of the total pairs of dogs had un-
known coancestries of 0.
Hip joint traits—The estimated effects of age,
sex, body weight, and breed on the 4 hip joint traits
were summarized (Table 4). Breed of dog had the
largest influence on the hip joint trait statistics. The
influence of dog age, body weight, and sex on the hip
joint traits was minimal. The mean NA for Labrador
Retrievers was not significantly different from that of
Australian Shepherds, Border Collies, Border Terri-
ers, Bullmastiffs, or Rottweilers. Whereas American
English Coonhounds, German Shepherd Dogs, Gold-
en Retrievers, Great Danes, Newfoundlands, and
Bullmastiffs had smaller NAs (ie, lower-quality hip
joints) than Labrador Retrievers (P < 0.01 for all),
Greyhounds had larger (P < 0.01) NAs (ie, higher-
(F1 X L) X (F1 X L)?
American English Coonhound?
F1 X Greyhound?
F1 X Labrador Retriever?
German Shepherd Dog?
Values in parentheses are the number of dogs evaluated in each category. Some dogs had 1 measure-
ment/type of score.
See Table 1 for remainder of key.
Table 2—Number of measurements used in the calculation of various scores for degree of HD in dogs
from closed breeding colonies and a veterinary teaching hospital that were radiographically evaluated
for hip dysplasia.
DLS score (%)
CV = Coefficient of variation.
See Table 1 for remainder of key.
Table 3—Values of the DI, DLS score, NA, and EHR score in dogs
from closed breeding colonies and a veterinary teaching hospital
that were radiographically evaluated for HD.
AJVR, Vol 70, No. 4, April 2009 487
quality hip joints). A similar pattern was evident for
The 4 hip joint traits had medium to high heritability
(Table 5). The EHR score had a high genetic correlation
with the NA (–0.89), and the genetic correlation between
the DI and DLS score was also high (–0.91). The medium
to high heritability for the 4 traits was also evident in the
pattern of breeding values during the years when dogs
were born (Figure 3). Selective breeding appeared effec-
tive at improving mean scores for the 4 hip joint traits over
time, particularly since the mid-1990s.
The accuracy of a breeding value for a dog was in-
fluenced by whether measurements were made on that
dog, whether the parents were measured, and the num-
ber of measured progeny (Table 6). The more progeny
of a breeding pair that were measured, the higher the
accuracy of the breeding value.
The results of selective breeding were also evident
in the relationship between breeding values and their
accuracy (Figure 4). Over half of the Labrador Retriev-
ers were bred at the Guiding Eyes for the Blind facil-
ity. Dogs with more accurate breeding values produced
more progeny, with a clustering of breeding values with
higher accuracy indicative of better hip joint conforma-
tion. In other words, such dogs had larger NAs and DLS
scores (positive breeding values) and smaller DIs and
EHR scores (negative breeding values), which indicat-
ed that the selective breeding practices of the Guiding
Eyes for the Blind program which are based on the NA
and EHR score, were effective in improving hip joint
conformation in dogs. Because the DI and DLS score
are genetically correlated to the NA and EHR score, an
indirect selection response on the DI and DLS score was
Figure 1—Distribution of inbreeding coefficients among 2,716
dogs from 2 closed breeding colonies and dogs admitted to a
veterinary teaching hospital.
Figure 2—Distribution of pairwise kinship coefficients among
2,716 dogs from 2 closed breeding colonies and dogs admitted
to a veterinary teaching hospital. The nonzero pairwise kinship
coefficient frequencies in the graph sum to 19.6%. The rest
(80.4%) were zeros and removed from the graph.
Table 4—Estimates of the fixed effects of age, body weight, sex, and breed on 4 traits of hip joints in
American English Coonhound?
F1 X Greyhound?
F1 X L?
German Shepherd Dog?
NC = Not calculated. – = Not applicable.
See Table 1 for remainder of key.