The threat from inside the pen
Yorkshires are one of the largest common pig breeds — long, white, heavy sows and boars with immensely strong necks and snouts evolved to plough ground. Most pig fencing failures are not predator break-ins; they are the pigs' own work. A Yorkshire roots along any fence line where the soil is interesting, gets its snout under a bottom wire or a panel edge, and lifts with enough force to walk the opening wider hour by hour. The pig that gets out is then loose among the dogs, roads, and worse fencing of the neighbourhood, and a sow that farrows outside her pen has put the litter where everything can reach it.
So the specification starts with the ground line: rigid panels fastened to posts the pigs cannot work loose, or woven wire held down by a mesh skirt buried or pinned flat into the soil on the inside, so rooting meets steel instead of a lifting edge.
The low strand that teaches respect
A single electric strand inside the pen, set low at snout height, is the classic pig teacher and it works on Yorkshires within a day or two: the pig meets the strand with the most sensitive part of its body while investigating the fence, and thereafter gives the boundary a respectful margin. Train growers and new sows to that strand in a small, solid pen first, where the lesson is unavoidable and there is nothing flimsy to burst through while learning it, rather than introducing the wire for the first time along the long pasture fence.
On the outside, a strand at dog height adds the predator-facing deterrent, because the predators of pigs are mostly a threat to the young: a healthy adult Yorkshire is a formidable animal, but piglets are prey-sized for dogs, coyotes, and large birds alike.
The farrowing pen is a different fence entirely
Everything said about the main pen understates the farrowing pen. A Yorkshire sow litters large numbers of small piglets, and those piglets can pass through or under fencing that easily contains their mother. The farrowing and nursery pen needs fine, rigid mesh a piglet cannot slip, no gaps at gates or feeders, and ground a dog cannot dig under in one night. Site it close to the buildings and within the farm's most secure perimeter, not at the quiet far end of the pig ground where it feels peaceful to people and exposed to everything else.
Warmth and dryness inside that pen matter to predator safety too: piglets that are warm and settled stay in the creep area near the sow, while chilled piglets wander, squeal, and press against fences — drawing attention and finding gaps.
Checking a pen that strong animals test daily
Inspect at pig height and pig logic: ground freshly rooted along a fence line, a panel bottom edge bright where snouts have been working it, posts with new play in them, the inside strand down or fouled with bedding and soil. Pigs also rub gates and latches constantly, so the gate a Yorkshire leans on daily wants a latch backed up by a chain, and a hinge check before it becomes a lean-to gap at piglet height.
Re-train your eye after heavy rain, when softened soil lets a determined sow excavate in hours what dry ground resisted for months. Any pig with bite injuries, a torn ear, or a litter disturbed overnight should be seen by a veterinarian promptly.
A twice-daily pen check with a name against it in KinsLe Care Teams, closed off with a timestamp, is how small lifts and early digs get fixed before they become an empty pen.