A dog with one testicle can kiss a show career goodbye because it fails to meet the minimum threshold of quality for a male dog. Presumably this is because not having a matched pair reveals some deficiency of maleness, despite the fact that the dog can nevertheless be fertile. Most breeders send the cryptorchids on a trip to the vet that removes them from the gene pool before they are sent off to meet the family that will be their wonderful forever home.
If being cryptorchid was really all that bad, we would expect that there would be some detrimental effect to the dog. If not surgically removed, the undescended testicle can develop tumorous tissue. On the other hand, could the cryptorchid dog have some advantage over a normal one?
They looked at the number and sex ratio of the offspring that were produced by three kinds of matings: carrier-to-carrier (CxC), normal-to-normal (NxN), and C females to N males and vice versa (CxN). The data from the CxN crosses were not significantly different from the NxN matings, so we'll just summarize the CxC and NxN data here.
The first surprise was that, in most of the breeds studied, carriers bred to carriers produced significantly larger litters than NxN.
- Gubbels EJ, J Scholten, L Janss, & J Rothuizen. 2009. Relationship of cryptorchidism with sex ratios and litter sizes in 12 dog breeds. Anim. Reprod. Sci. 113: 187-195.
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