# Temporal Changes in Indicators of Testicular Dysgenesis Syndrome in Labrador and Golden Retrievers

## TL;DR

This study found that testicular health in Golden Retrievers has declined over time, while Labrador Retrievers showed no such decline, with crossbred dogs having lower cryptorchidism rates.

## Contribution

The study reveals breed-specific and crossbreed differences in testicular health trends and their interactions with environmental factors in dogs.

## Key findings

- Golden Retrievers showed significant negative trends in semen quality over time, unlike Labrador Retrievers.
- Cryptorchidism incidence increased generally, but F1 crossbreeds had significantly lower rates than purebreds.
- Benign prostatic hyperplasia negatively affected semen traits in both breeds.

## Abstract

Changes in testicular traits over time have been reported in both humans and dogs. Semen quality data for 186 Labrador Retrievers and 113 Golden Retrievers between 2006 and 2023, and incidents of cryptorchidism in over 15,000 dogs of the same breeds and crosses born between 1994 and 2023 were examined to determine changes over time, genetic features, and breed variations. The semen traits (fast, forward progressive motility, and percentage normal live sperm) were both moderately repeatable within individuals, but there were breed differences: For both traits, only the heritability was significantly greater than zero in Golden Retrievers, while only the permanent environment effect was present in Labrador Retrievers. There were significant negative changes over time in Golden Retrievers for both semen traits, but not in Labrador Retrievers; significant negative effects of age (except on motility in Labradors); and significant negative effects of a diagnosis of benign prostatic hyperplasia on both traits in both breeds. A general increase in incidence of cryptorchidism was present with differences between breeds, which remained after accounting for effects of genetics and litter. The incidence in the F1 cross was significantly lower than in either pure breed, suggesting improvements in crossbred offspring. These results reveal complex breed x environment interactions in traits related to testicular form and function.

Temporal changes in testicular traits have been reported in both humans and dogs. Analysis of % living sperm and motility from semen collections from 186 Labrador Retrievers and 113 Golden Retrievers between 2006 and 2023, and of incidents of cryptorchidism in over 15,000 dogs of the same breeds and crosses born between 1994 and 2023 was undertaken to determine influential factors. A general temporal increase in incidence of cryptorchidism masked significant differences in the trend between breeds, which persisted after accounting for genetic and litter effects. The incidence in the F1 cross was significantly lower than in either pure breed, implying hybrid vigour. The semen traits were both moderately repeatable within individuals, but this belied breed differences in its composition; for both traits, only the heritability was significantly greater than zero in the Golden Retriever, while only the permanent environment effect was present in Labrador Retrievers. There were significant negative temporal trends in Golden Retrievers for both semen traits, but not in Labrador Retrievers; significant negative effects of age (except on % motility in Labrador Retrievers); and significant negative effects of a diagnosis of benign prostatic hyperplasia on both traits in both breeds. These results reveal complex breed by environment interactions in traits related to testicular form and function.