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Inbreeding - fooling nature

"Breeders walk a tightrope between needing to reduce genetic variation to maintain uniform breed type and needing to maintain genetic diversity " I think this statement hit the nail on the head!
Replies (10)
  • [size=12]It has been a while since we had an intelletcual discussion about genetics or breeding practices in general, so I am posting this snippet from an article that is also available in the content section of this site. So, please read this carefully and make a comment with your opinion. [quote="Vargas, Cargill, Coile"] INBREEDING AND INBREEDING DEPRESSION: You can't fool Mother Nature Evolution is thought to be a gradual change in the kind and frequencies of alleles. Those mutants that are harmful are either eliminated or kept at low frequencies by natural selection. However; with artificial selection , especially when a breed is being developed, it is the individuals that exhibit the greatest expression of the desired traits that are chosen to breed the subsequent generations. When only a few dogs are used to produce the next generation, a high proportion of their genes will be in the next population of potential breeding animals. When these related dogs are then interbred, the chances of them passing on the same allele that they both received from their sire and dam is 25%. Thus, inbreeding increases the chance that subsequent offspring will carry identical copies of the same allele (be homozygous at that locus). Increasing inbreeding increases the chance of homozygosity and can lead to the loss of one of the alleles from the population. Breeders walk a tightrope between needing to reduce genetic variation to maintain uniform breed type and needing to maintain genetic diversity to avoid inbreeding depression, which results from homozygosity of deleterious alleles. The majority of alleles detrimental to life and reproduction tend to be recessive, for the simple reason that if they were dominant, they would have been expressed in the individual's phenotype, and that individual would have been less likely to reproduce. If recessive, only those individuals with homozygous recessive alleles would be reproductively compromised; heterozygotes would be unaffected. Every dog (and every human) carries deleterious recessive alleles, so the chances of the foundation stock carrying them is virtually 100%. If very few dogs were used as foundation stock, their progeny would have to be interbred, and in only a few generations all of the dogs would be closely related. Breeding closely related dogs is inbreeding. An inbred dog has a greater likelihood of receiving the same allele from both its sire and dam, and thus a greater likelihood of being homozygous for a deleterious trait. In an inbred population, as long as the animals can still reproduce, this homozygosity can become fixed in the population due to the chance loss of the other allele. What this means for the breeder is that too great a reliance on inbreeding will lead to loss of 'fitness', i.e., failure to reproduce. Fewer litters are produced, the number of whelps will decrease and those that are born will fail to thrive. Taken to extreme, the effective breeding population could be so diminished that the breed would face extinction. [/quote][/size]
    • "Breeders walk a tightrope between needing to reduce genetic variation to maintain uniform breed type and needing to maintain genetic diversity " I think this statement hit the nail on the head!
      • There is no fooling mother nature. There are things you can do to twist and turn it, but she always comes out on top. If you try to hard to control her, she lashes out. Look at what has happened to breeds with unnatural characteristics and what nature is doing to them. Short life spans, extreme ailments, inability to procreate naturally etc... She always wins.
        • Good points there. Yet it does not stop breeders from following the practice in order to establish "their line." I think this kind of practice eventually contributes to problems in the breeds and does nothing but boosts a breeders ego.
          • All things in moderation.....
            • First Post I chose this forum because it always comes up in search engines with the particular keywords I look for and it is bilingual, which appears to have international input. At the outset, I have watched the Presa for decades grow into a respectable breed despite all the controversy. It is still one of the best dry mouth breeds for personal protection. My thread is intended to reach out to the older breeders and trainers with personal experience to share with a fellow enthusiast who will appreciate the input greatly. My intention is to retire with a legacy that will last longer than me with all of the knowledge I have gained about working dogs throughout my life. That legacy will be a new breed named the Vorax. This breed will receive the same investment as would my own family if I had one. I'm sure those of you who have always had a dog in your life know that they are like your children. I have always personally preferred the Rottweiler for it's intelligence, energy and bite force. As has been seen with some "rare breeds" over the decades the Rottweiler has been incorporated in the breeding program. Bite force as some of us know is not breed specific, but the size of a particular dog's head. This is why monks in the Swiss Alps bred a dog to drag a man through mountain snow and the result is the St Bernard. Considering the consistency of the Swiss from Banking to watches and the Swiss guard and foreign legions, this breed has gone untapped except by Alaskan weight pulls. Rather than the Neapolitan, English,Japanese, Brazilian or French Mastiffs so widely crossed, the St Bernard is the obvious choice for bite force. (The Boerboel at 23-27" and 110-175 lbs. appears to be an even better choice than what has been used.) Following this line we find the Newfoundland, a dog bred to drag a man through rough seas and still in use for water rescue. Coincidentally the Newfoundland and St Bernard made the Guiness Book of World Records, obviously being more athletic than it's Brachycephalic cousins. The Newfoundland also appears to be more obedient than the St Bernard, probably from Retriever crossing, still it is not incorporated in these "recreated breeds" of legend. Some of you may already be thinking instead of using a Retriever for intelligence use an intelligent guard dog. Ironically Jack London, author of Call of the Wild thought of this already when he wrote about Buck, the St Bernard/German Shepherd cross. Interesting the Tibetan Mastiff originated in California as well. I was fortunate enough to speak with the creator before the filming of one of his dogs in the horror movie Man's Best Friend. Intelligent and powerful, yes, just not so attractive. I have decided on a 75 lb. American Pit Bull Terrier stud, most weight per pound champion, to bring down the height and weight closer to that of a hog catcher(22" 90 lbs.) for my Rottweiler/Newfoundland cross. I have seen that crossing in the Pit Bull will make it hard to breed true as the Pit Bull eventually comes out down the line, as seen with Bandogges. The Cane Corso, Argentine Dogo, and originally American(Pit)Bulldog appear to have solved this problem, although they do produce some dogs that look more Pit Bull than others. The Presa on the other hand does have a unique look. I remember when they first appeared in the states looking very much like Bully Pits and am happy to see they did not stay on that path. What would be of great help to me and prevent unwanted pups is a breeding program that would result in the Rottweiler's double coat and character with the Newfoundland's head and webbed feet with the Pit Bull's proportions and endurance.
              • Inbreeding, linebreeding, and outcrossing occurs in nature...with performance for survival being the selection method. Nature doesn't prejudge. It is not prejudice. There is no affirmative action or nurses saving the weak. Instead, it simply says...get er done or die. As a result, each method of breeding is used in nature and when things get "out of balance" going "too far" with any detrimental trait, variation of a superior alternate phenotype (and genotype) is RIGHT THERE waiting for the oppertunity to bring things back into balance.
                • Lee, Thanks for the post. Surprising to see a familiar name replying. Brings back memories of when I first learned of Bantu and the problems Dr. Swinford had trying to breed the Bandogge true. If I remember correctly he said that eventually a Pit Bull was produced and not a very good one. Hindsight I don't think the Game dogs were the best choice, nor the Neapolitan Mastiff, the former not being as strong as the bigger non-game dogs and the latter not being actively used. I think if Dr. Swinford could do it over he would have used the Boerboel for the bite force and the red nosed Pit Bulls(Leri Hanson's Capone)for performance in French Ring, Schutzhund, Hog Catch, and Most Weight Per Pound. I did notice your reference to epigentics at the outset and it is an honor and great pleasure to have your input after all you have invested in your breed.
                  • Vorax, are you actively working on creating a breed? I would to know more about your work. Please do share some more info and if you have a breed profile I would love to adde it to our list.
                    • MD, Yes and i was going to upload more than one photo and start my own thread but I am not allowed to do so yet by the site settings. I was also disappointed that Chimera Kennels "Swinford K9" was not in the list of breed profiles. At this point I am only at the Rottweiler/Newfoundland cross and have yet to see if my standard will breed true. If I were to make a breed profile it would not be from experience but copy and paste from parts of the standards for the Schutzhund 3 Rottweiler, Water Rescue Newfoundland, and Southern White American Bulldog Pro Catcher. Basically a Newfoundland head and Rottweiler coat on an American Bulldog with the Rottweiler temperament for Schutzhund 3 and French Ring Sport Level 3 as well as Hog hunting, weight pulling, agility and water rescue if need be.
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