Build 42 Animals — Livestock Systems Re-Checked on 42.20

Live, interactable animals are the headline feature of Build 42 — but PZwiki's main Animals page still carries a "based on 42.6.0, needs rework" banner, so most of what you'll find floating around is stale. This guide only uses what the updated per-species pages confirm: cow, chicken, sheep, and animal care pages stamped 42.14–42.18 at check time, re-checked against stable 42.20.0 on 2026-08-04. Where a detail is unconfirmed, it says so instead of guessing.

What animals exist in Build 42

Build 42 shipped animals with basic AI (they do not yet use the full NPC AI system) focused on husbandry chains — milk, hide, wool, leather, eggs, and meat.

Wild species also roam: deer (fawn/doe/buck), rabbits, raccoons, rats, and mice — mostly relevant to trapping and hunting rather than pens.

Livestock zones: the core mechanic

Every domestic animal lives in a livestock zone, created from the zoning icon on the left HUD. Fence it or don't — animals stay in the zone unless stressed — but it must contain:

• Food: a feeding trough (built via carpentry or found on farms) holding hay, grass, vegetables, fruits, or animal feed for cows; chickens can graze grass tiles and supplement with wheat seeds and insects. A trough holds either food or water, never both — empty it before switching.
• Water: trough, or buckets for chickens. An unroofed empty trough collects rainwater.
• Shelter: required for zone health; chickens specifically need a hutch, or the nighttime predator meta-event can kill them.

Animals eat and drink autonomously; you can also hand-feed. Chickens need no feeding on sufficient grass, but the hutch must be cleaned with water and a stain-cleaning item or the birds sicken and die. Stress comes from zombies, loud noises, and players sprinting nearby; stressed animals can bolt out of the zone and must be led back. Keep one male per zone — bulls and cockerels fight, causing stress and health loss.

Products: milk, eggs, wool, and meat

• Milk: cows begin producing a few days after pregnancy. Milk with buckets, pots, or trays. A cow that isn't milked (and whose calf doesn't nurse) dries up within days. Calves must share their mother's zone to drink.
• Eggs: hens lay in the hutch's egg-laying boxes; if the hutch is missing or full, eggs scatter across the zone. Fertilized eggs (from a hen mated with her zone's cockerel) are heavier, hatch into chicks, and survive removal from the hutch.
• Wool: sheep are confirmed as a renewable wool and milk source; per-breed wool yields are not documented on the updated wiki pages yet, so treat exact numbers as unverified.
• Meat and byproducts: a butchered chicken yields 1 whole chicken, 1 head, 2 feet, and 70–80 feathers (plus a possible egg from hens). Cows and bulls butcher into beef products; use a butcher hook or you lose the hide. Feathers feed tailoring; droppings from all livestock go to the composter for fertilizer.

Community-reported from returning-player testing: animal milk powder works as emergency feed for hungry or thirsty animals, especially orphaned babies, and leather drying on racks takes roughly a week.

Moving animals home

Right-click an animal → "Attach animal to rope" and lead it on foot, or lead it into a livestock trailer and transport it by vehicle. Find starter herds in farm pens — chickens at places like Ovo Farms — and move them before you zone them.

Breeding and genetics

Cows breed year-round; you need one adult cow and one bull, and calves nurse in the mother's zone. Chickens breed as one cockerel with multiple hens.

Under the hood is a genetics system: each animal carries two alleles per gene — milk quantity, life expectancy, strength, appearance, max weight, fertility, meat ratio, and more — one inherited from each parent, with dominant and recessive expression. Inbreeding risks recessive genetic disorders; the "skinny" disorder, for example, divides base weight by three. Characters with enough Animal Care skill can inspect an animal to read its health-related genes.

Weight and enclosure sizes

Actual weight = base range × the maxWeight gene (typically 0.5–0.8; Angus 0.45–0.65, Simmental 0.5–0.7, Holstein 0.6–0.8, Suffolk sheep 0.55–0.75). Undersized enclosures cut daily weight gain eightfold, so pen size directly decides how much meat and how many resources you get:

Age gates everything: calves are babies until day 180 (chickens 126), and animals die of old age (cows max around 4,320 days, sheep 3,600).

The Animal Care skill

Animal Care (skill ID Husbandry) unlocks more inspection info, increases harvested yields, and keeps stressed animals from breaking out of milking or shearing. XP comes from milking, shearing, giving water, petting, and collecting eggs. The Rancher occupation starts at level 4 and the Farmer at +1; five skill books (Animal Care I–V) carry you to level 10.

One warning that surprises B41 veterans: animal noise attracts zombies, even though zombies won't attack animals (confirmed by The Indie Stone). Pens belong behind your perimeter, not in front of it.

Verified on 42.20 · Last checked 2026-08-04

Species, breeds, ages, enclosure sizes, and care mechanics come from PZwiki's Animal, Cow, Chicken, Sheep, and Animal Care pages (42.6–42.18 stamps) and were re-checked against 42.20.0 on 2026-08-04. Omitted because unverifiable: exact wool yield per sheep breed, precise milk volumes per cow breed, and genetics odds — none are on the updated pages yet.