For those of you who have eaten pigs older than the standard 6-8 months. Traditionally pigs have been slaughtered in the fall after fattening up on the summer's abundance. It was also beneficial that the cooler weather helped preserve the meat. We have the ability now to feed our pigs throughout the year and we can preserve the pork regardless of the outside temperature. Is a 400 pound sow better than a 180 pounder?
A 400 pound sow will have a lot more fat built up than the 180 pound pig. A lot of old farmers ask me at market stands if I have 'any second year sows that didn't settle'...they always ask it in a way that seems off hand, as if they're just curious. Really what they are trying to do is get the tastiest pig I have for a lowball price. I don't blame them
I agree that a 400-500 pound sow is some of the best eating. There are a lot of people that think that the only thing you can do with them is make lots of sausage, but I totally disagree. I haven't eaten one over three, but I don't think they will get much tougher. They will put on a lot of fat that you can either trim off and compost or sell to people making lard (if you don't want to). This adds lots of flavor to the sows.
The main thing to realize is that all of the muscles get proportionally bigger. This can make selling whole or even half hams difficult. A 30-40 pound ham is expensive. The cut I really like and use most often myself is the chops. I have them cut at an inch to an inch and a half. This gives 1.5 to 2 pound chops that I sell as Pork Porterhouses. They are great on the grill because they have a nice bit of fat to flavor them and I cook them like I would a bone-in ribeye except I go to a medium to medium well on them instead of medium rare.
The reason commercial producers sell market hogs at 200-240 pounds is that at that point the feed conversion peaks and starts to quickly go down. We usually butcher ours at 300-350 pounds because we want more flavorful pork and also that is the point they start getting a good slab of pork belly for bacon.
PS: It isn't just sows that are tasty at older ages. When we decided last summer to switch to just buying weaned pigs instead of raising our own we processed out our three year old boar and he was supper tasty too. Selling him at a sale would have brought maybe $50-$75 since adult boars bring 5 to 20 cents a pound. We ended up eating half ourselves and selling the other half as cuts for more than $500.
I find that the larger sows are the absolute best. 400 to 800 lbs and around two to eight years of age. My absolute favorite cut of pork is the Boston Butt steaks and Country Style Ribs (both the same meat, differently cut) from big sows. By this age they have strong marbling and rich flavoring. Note that this is on pasture with whey as a supplemental feed. On other diets it may be different. The catch is the cuts are huge - more like a steer than a pig. Our sows have about 1" to 1.5" of back fat since they're on pasture which is a low calorie diet.
Our adult boars are also delicious but leaner, less marbled. They taste more like beef than pork. Our boars have about 0" of back fat. They look more like Arnold Schwarzenegger than the fat boars I've seen in some photos. The difference is the pasture and low calorie diet.
The typical market pig is 250 lbs or so because that is where they start putting on marbling and the rate of feed to meat conversion drops. This also represents the typical size many pigs can get to in one warm season thus making them fit with fall or early winter slaughter. Our finisher pigs have about 0.75" (boars) to 1" (gilts) of back fat.
Note all back fat measurements include the skin. On a high calorie diet all of these go to much higher back fat as we've seen with people who buy weaner piglets from us and put them on either whole milk (4" of back fat on gilts at 8 months) or commercial corn/soy based feed (1.5" of back fat at 6 months). What you feed determines the flavor of the pork. Flavor is stored in fat and accumulates in about the last month before slaughter. Inter-muscular fat, marbling, makes the meat more tender and flavorful. Breed makes little difference in flavor in both the taste testing I've done across our four breeds (Yorkshire, Berkshire, Large Black and Tamworth) and this is born out in the scientific literature I've read. Breed sets conformation and to some degree marbling. Age and calories also sets marbling. Feed sets flavor.