I keep coming back to one number from swine production: nearly 60 percent. That’s the share of sows in U.S. herds that get culled or die each year, and a lot of them are gone before parity three or four, before they’ve earned back the cost of raising them. Replacement gilts are the whole foundation of a breeding operation, so how you feed them in those early months decides a lot about whether they stay. Here’s the problem producers wrestle with. You want gilts bred at the second or third estrus, somewhere around 135 to 160 kg. Breed them too early and litters come up small. Let them get underweight…