Monitoring Hip and Elbow Dysplasia achieved modest genetic improvement of 74 dog breeds over 40 years in USA - PubMed (original) (raw)

Monitoring Hip and Elbow Dysplasia achieved modest genetic improvement of 74 dog breeds over 40 years in USA

Yali Hou et al. PLoS One. 2013.

Erratum in

Abstract

Hip (HD) and Elbow Dysplasia (ED) are two common complex developmental disorders of dogs. In order to decrease their prevalence and severity, the Orthopedic Foundation for Animals (OFA) has a voluntary registry of canine hip and elbow conformation certified by boarded radiologists. However, the voluntarily reports have been severely biased against exposing dogs with problems, especially at beginning period. Fluctuated by additional influential factors such as age, the published raw scores barely showed trends of improvement. In this study, we used multiple-trait mixed model to simultaneously adjust these factors and incorporate pedigree to derive Estimated Breeding Values (EBV). A total of 1,264,422 dogs from 74 breeds were evaluated for EBVs from 760,455 hip scores and 135,409 elbow scores. These EBVs have substantially recovered the reporting bias and the other influences. Clear and steady trends of genetic improvement were observed over the 40 years since 1970. The total genetic improvements were 16.4% and 1.1% of the phenotypic standard deviation for HD and ED, respectively. The incidences of dysplasia were 0.83% and 2.08%, and the heritabilities were estimated as 0.22 and 0.17 for hip and elbow scores, respectively. The genetic correlation between them was 0.12. We conclude that EBV is more effective than reporting raw phenotype. The weak genetic correlation suggested that selection based on hip scores would also slightly improve elbow scores but it is necessary to allocate effort toward improvement of elbow scores alone.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1

Figure 1. Number of dogs with hip and elbow scores during 1974 to 2009.

Red bar indicates the number for hip scores, and blue bar for elbow scores. There were 760,455 and 135,409 hip and elbow scores, respectively, in 74 dog breeds collected by the Orthopedic Foundation for Animals (OFA) during this period.

Figure 2

Figure 2. Distribution of hip and elbow scores released between 1974 and 2009.

Figure 2A: Only three categories of hip scores (Excellent, Good and Fair) were jointly released as Normal between 1974 and 1985 and separately reported after 1985. There was no release on other categories before 2000. Then, all categories were released and reported separately; Figure 2B: Elbow I meant “Normal”, Elbow II, III, IV meant osteoarthritis (degenerative joint disease) level I, II and III respectively. Few elbow scores were released except for category “Normal” before 2000. The reports were heavily biased against reporting poor hip and elbow scores in the first 30 years.

Figure 3

Figure 3. Breed effects on hip and elbow scores and their standard errors.

A breed was required to have a minimum of 10 dogs recorded as “degenerative joint disease I or II, or III” to be included in the analysis, which led to only 21 breeds remaining for elbow scores evaluation. All the 74 breeds satisfied the requirement on hip scores.

Figure 4

Figure 4. The phenotypic and genetic trends of hip and elbow scores.

Figure 4A shows the trends for hip scores while figure 4B shows the elbow scores. The trend lines represent the mean within each year for phenotype (the vertical axis on the right) and estimated breeding value (EBV; the vertical axis on the left) for the 1,264,422 dogs born between 1970 and 2009. The phenotype was presented as the deviation from the score (1) of the best hip or elbow.

Figure 5

Figure 5. The annual genetic improvement in each breed over 40 years.

The annual genetic improvement is represented by the average increments of estimated breeding value (EBV) per year and its standard errors. The blue bar indicates the genetic change for hip dysplasia on the vertical axis on the left, the red bar indicates the genetic change for elbow dysplasia on the vertical axis on the right. A breed was required to have a minimum of 10 dogs recorded as “degenerative joint disease I or II, or III” to be included in the analysis, which led to only 21 breeds remaining for elbow scores evaluation. All the 74 breeds satisfied the requirement on hip scores.

Figure 6

Figure 6. The joint and marginal distribution of breeding values of hip and elbow scores.

Estimated breeding value (EBV) of hip scores is displayed on the vertical axis and EBV of elbow scores is plotted on the horizontal axis for 1,264,422 dogs born between 1970 and 2009. The marginal distributions of hip and elbow EBVs are indicated by both the total number of dogs and percentile in each category.

Figure 7

Figure 7. Trends of inbreeding coefficients over 40 years for small- and large-population breeds.

The small and large population breeds were separated by a threshold value of 50,000 dogs. Breeds with 50,000 or less dogs were defined as small population breeds, while breeds with more than 50,000 dogs were the large population breeds, which included the Labrador Retriever, Golden Retriever, German Shepherd Dog, and Rottweiler.

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