My livestock breeding philosophy is simple in theory and difficult in practice. It can be summed up in two words: Problem-Free. Problem-free livestock are under-appreciated and difficult to observe. It often requires a problem to present itself before you can fully appreciate the absence of the problem.
The good thing about my 40 plus years experience in the livestock industry is the amount of problems I have observed and worked through. And I always choose to work through problems as that is the way I was taught by my parents and makes the most sense. I’ve never succumbed to the siren call of all-new breeding stock as common sense tells me I’ll just be trading known problems in my own stock for the unknown and possibly worse problems in the new stock. Because all stock has problems, its just that very few problems are visible with one viewing.
I have had very good luck with herd health by practicing a modified closed system with breeding stock. Meaning I never bring in animals from an outside herd, but I get new genetics through purchased boar semen. There are some diseases that can be transmitted through semen, but the reputable boar studs regularly test the studs for those diseases.
I would practice a completely closed system if I could figure out a way I wouldn’t be losing too much efficiency from inbreeding depression. Inbreeding depression is the tendency for animals that are inbred to perform worse than the average of their parents. Conversely, crossbreeding results in hybrid vigor, which is the tendency for crossbred animals to perform better than the average of their parents.
However, I’m not afraid of linebreeding. A fun definition for linebreeding is that it is successful inbreeding. Practical examples of inbreeding and linebreeding in my mind are: a brother/sister mating is inbreeding, a first cousin mating is linebreeding. This is just my own way of looking at it. A geneticist will tell you that all linebreeding is technically inbreeding.
A geneticist can analyze the full pedigree of an animal and calculate the inbreeding coefficient, which is the probability that any one pair of genes is identical. So it is expressed from 0 to 1. For example, a full brother/sister mating if the parents of the siblings were completely unrelated, would have an inbreeding coefficient of .5, meaning there is a 50% likelihood that any pair of genes is identical.
So along with a modified closed herd, I practice my own unusual combination of crossbreeding and linebreeding. I guess my curiosity makes me want to sample different genetics to see what I may be missing, but my practical side makes me want to not change my herd too rapidly, especially if I have no perceived problems.
What does this look like in practice? The boar in the top photo is Drew, his paternal grandsire was Dru, terminal line semen from SGI. Everyone knows what maternal is, but in livestock breeding we use the phrase terminal when we want to ignore the maternal side and concentrate on the meat traits. Obviously no line is completely terminal or their would be no reproduction.
So I kept no gilts from the offspring of the Dru semen. I did however keep a few boars. The litters were born in the blizzard of March, 2013 when I was having a difficult time keeping the piglets from freezing. Drew’s sire was one of three piglets which survived out of a litter of 12. He looked good and I figured I had inadvertently selected for piglet survivability. So I kept him as a boar and he turned out to be a great sire of robust, meaty piglets.
Drew’s maternal grandsire was the Landrace, True Blue semen I wrote about in my last post. True Blue sired two litters, 30 and 31. I kept about four gilts out of each litter and they’ve been excellent mothers, with the 31 litter gilts a little more to my liking phenotypically.
So I planned and kept four boars out of one of the 31 litter sows. I sold a couple of boars to a local producer and I kept a couple and they were breeding fine. A competitor at my farmers’ market called and said he really needed a working boar. Some people are very competitive at farmers markets, but I prefer to be collaborative as I feel our real competition is Walmart and the whole idea that cheap food is good. So I sold him one of the boars. I guess those genetics will be well represented in the pork at the Madison farmers markets.
How I linebreed: I really like the 31 litter sows. I have a planned mating with my favorite with Duroc semen, a Waldo boar called Red Zone. I asked SGI for their most maternal Duroc and he’s what they gave me. I plan on keeping all the boars from that litter and possibly adding a couple as sires.
I have another mating with various sows, some of which are the 31 litter sows, AId to a Chester White boar, Mr. Longevity. I wanted to sample the Chester White as it is an American heritage breed. I plan to keep gilts out of these litters if they meet my standards.
If all goes as planned I will be mating the Red Zone sons with the Mr. Longevity daughters, some of which will be a first cousin mating if each of their respective moms is a 31 litter sow as the 31 litter sows are full sisters of course. This is as tight of linebreeding as I like to practice.
And while I will be evaluating the new genetics, which could still become a terminal line in my herd if I don’t like their performance, I’m also evaluating and looking for any genetic problems which are more likely to show up in the offspring of this first cousin mating. Because even at this point I can choose to make the 31 litter a terminal line.
Larry, the boar in the photo below, represents my established genetics. I am really happy with how these hogs perform, mostly because they are problem-free. I have to keep reminding myself of this, though. Because as geneticists we are taught to always be selecting and moving the genotype in some direction.
Well, I gave myself permission to stop thinking like a geneticist, and start thinking like a busy farmer who direct-markets meat on Saturdays and plays disc golf on Sundays. I select animals for breeding within this herd based on what I like to look at, mostly interesting color patterns. This has been one of the most difficult admissions I’ve made on this blog as my old geneticist buddies would be laughing or crying if they read this, but they know me, so they probably wouldn’t be surprised!
For a good example, Larry was selected because I missed a boar piglet when I was castrating litters. I usually castrate at a couple days of age. By the time I saw him, he was weaning age, and he looked pretty good, and he has this interesting brindle color pattern, and I realized I could use a boar about the time he would come of age… Well Larry has been terrific, a good breeder, sires great pigs, and I’ll be keeping his first daughters back as breeders soon.
This concludes my two parter on Swine Genetics. I hope its comprehensible for any of you who made it all they way through. Any questions or comments as always welcome.
Posted by Curiousfarmer 
