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from the how-much^W-big-is-that-doggie-in-the-window? dept.
Big Dogs Face More Joint Problems if Neutered Early:
It's standard practice in the U.S. and much of Europe to neuter dogs by 6 months of age. This study, which analyzed 15 years of data from thousands of dogs at UC Davis Veterinary Medical Teaching Hospital, suggests dog owners should consider their options carefully.
"Most dogs are mixed breeds," said lead author Benjamin Hart, distinguished professor emeritus at the UC Davis School of Veterinary Medicine.
[...] Researchers examined common joint disorders including hip dysplasia, elbow dysplasia and cranial cruciate ligament tears, a knee injury, in five weight categories.
[...] The risk of joint disorders for heavier dogs can be up to a few times higher compared to dogs left intact. This was true for large mixed-breed dogs. For example, for female dogs over 43 pounds, the risk jumped from 4 percent for intact dogs to 10-12 percent if spayed before a year of age.
"The study raises unique challenges," noted co-author Lynette Hart, professor at the UC Davis School of Veterinary Medicine. "People like to adopt puppies from shelters, but with mixed breeds it may be difficult to determine just how big the dog will become if you don't know anything about the dog's parents."
Neutering prior to adoption is a common requirement or policy of humane societies, animal shelters and breeders. [...] Shelters, breeders and humane societies should consider adopting a standard of neutering at over a year of age for dogs that will grow into large sizes.
Journal Reference:
Hart, Benjamin L., Hart, Lynette A., Thigpen, Abigail P., et al. Assisting Decision-Making on Age of Neutering for Mixed Breed Dogs of Five Weight Categories: Associated Joint Disorders and Cancers, Frontiers in Veterinary Science (DOI: 10.3389/fvets.2020.00472)
(Score: 2) by Reziac on Saturday August 15 2020, @02:33PM (2 children)
See my long rant, er, response above, You do not know what you're talking about. In fact the more extreme breeds (and there are a few) are generally LESS inbred; the problem is lack of selection for functionality, and dogs are so genetically variable that you can produce an extreme example in just a couple generations. No inbreeding required. (One of the most extreme cases is a new breed that was produced by crossbreeding two unrelated gene pools, and selecting the most unusual specimens for the next generation. In only 3 generations they had a whole new type of dog, as weirdly abnormal as can be.)
Also, despite the extreme examples, once you get away from show ring judging (and lay the blame where it belongs: judges who tend to reward extremes), the average tends toward normal, because ordinary people like normal.
And there is no Alkibiades to come back and save us from ourselves.
(Score: 0) by Anonymous Coward on Saturday August 15 2020, @08:31PM (1 child)
There are dog breeds whose skulls are literally too small for their brains, yes or no? Purebred dogs that mate outside their breed are no longer purebred, yes or no? Closed stud books are common in dog breeding, yes or no? Your own example is an "arrow pedigree" with an inbreeding coefficent of over 37%, yes or no?
(Score: 2) by Reziac on Monday August 17 2020, @12:41AM
Cherrypick much?
Purebred is a relative state. Generally the stud book requirement is 3 generations recorded as the same breed; crossbreedings beyond that are not considered significant. And while stud books may be generally closed, most breeds number in the thousands or tens of thousands, so the gene pools are overall neither small nor narrow, even despite widespread spay/neuter destroying large chunks of it.
If you breed a total outcross, then breed two of those offspring, while that next generation is technically 'inbred' -- if you chart a mere two genes each with two alleles into a Punnett square, you will make the peculiar discovery that it is functionally the opposite. The first generation have all the same genotype; the second generation has 9 genotypes, including a double-recessive, which is likely to be a new phenotype (or new defect) that you'd never seen before in either parent breed.
Here's a basic example:
https://en.wikipedia.org/wiki/Labrador_Retriever_coat_colour_genetics#Eumelanin_gene_interactions [wikipedia.org]
One achieves this particular assortment thus:
Cross a pure yellow dog with a pure liver (chocolate) dog; it does not matter what breed they are.
ALL the first generation puppies will be black.
Breed together two of those first-generation black puppies (which all carry both liver and yellow).
The 2nd generation will be black, yellow, liver (in two distinct shades, since liver carrying yellow iooks different from pure liver), and a peculiar unpigmented tan color (double recessive) that was never seen before the original 'outcross'. Four phenotypes, nine genotypes, and good luck guessing which dogs carry what.
So what it really does is repeat the outcross and fragment the gene pool, and the result is very difficult to do any sort of sane selection from (let alone track and select against defects). And that's with just two apris of alleles; imagine the mess with 25,000 genes and their multitude of alleles. However, if the double recessive type happens to be what you're after, you can have that type breeding true this fast. Well, at least for these traits...
Any experienced dog breeder figures this out, and realizes that the old timers were wise when they'd pick a bloodline and stick to it, and not introduce random outcrosses that when later doubled (even if accidentally due to being back before living memory) produce rude surprises.
As to structural defects that have become 'part' of a breed -- I'll be the first to beat dog show judges with a stick and make them reward typical, correct specimens rather than extremes and outliers. If show judges did not reward extremes, show breeders would not strive to produce them. (Tho show breeders are a tiny minority, less than 1% for common breeds.) And I speak as one qualified to be a show judge, who has bred and handled my own Best In Show winner....the only 100% working-line Lab to go BIS anywhere in the world since 1974.
And there is no Alkibiades to come back and save us from ourselves.