Project Zomboid Build 42: Animal Husbandry Server Guide
Build 42.20 went stable on 29 July 2026. B42 is no longer a beta branch you opt into, it is the supported build, and Project Zomboid passed its all-time peak player count the day it landed. If anything below describes B42 as unstable or upcoming, read it as history: the branch it refers to is now the default. The one live caveat is mods, since a lot of Workshop items have not been republished for stable yet, so a list that worked last week can fail today.
One of the most significant additions in Build 42 is the introduction of a full animal husbandry system. Cows, sheep, pigs, chickens, and wild animals are now persistent entities with a genetics simulation, breeding your healthiest stock leads to higher milk yields, faster growth, and better wool quality. For server admins, this is exciting gameplay but also a serious performance consideration: animals are CPU-heavy entities that run continuously whether players are online or not.
Build status: Build 42.20 is the stable public branch, and animal husbandry is fully functional in multiplayer. Use legacy41 only for an existing Build 41 world or a mod list that has not caught up.
How Animals Work in Build 42 (Server Perspective)
Persistent Entity Simulation
Unlike zombies, which are only simulated within an active chunk radius, Build 42 animals run a continuous simulation regardless of player proximity. Every cow, sheep, deer, and chicken on the map is alive and aging. This design enables realistic breeding mechanics but has direct consequences for server resources:
- 1,000 animal entities can reduce server TPS as significantly as 500 additional zombies
- Animal needs (hunger, water, health, happiness) are ticked on every server frame
- Genetics calculations trigger on breeding events but are otherwise low-cost
- Animal pathfinding (roaming, fleeing from zombies) is the most expensive operation per animal
Animal Types and Their Performance Cost
| Animal | Relative CPU Cost | Notes |
|---|---|---|
| Chicken | Low | Minimal pathfinding range, small entity |
| Rabbit | Low | Fast movement but short range |
| Pig | Medium | More complex needs simulation |
| Sheep | Medium | Wool growth tracking adds overhead |
| Cow | Medium-High | Largest entity, most complex pathfinding |
| Deer (wild) | High | Flee AI is expensive; large roaming range |
| Bear (wild) | Very High | Aggressive predator AI with complex state machine |
Server Memory Requirements for B42 Animals
Build 42's baseline memory footprint is significantly higher than B41, and animal simulation adds further overhead. The old "1 GB per player" guideline is entirely obsolete for B42.
| Server Setup | Minimum RAM | Recommended RAM |
|---|---|---|
| B42, no animals (disabled) | 6 GB | 8 GB |
| B42, default animal settings, 10-20 players | 8 GB | 12 GB |
| B42, default animals, 20-50 players | 12 GB | 16 GB |
| B42, heavy animal use (player farms), 50+ players | 16 GB | 24 GB |
Sandbox Settings: Controlling Animal Populations
Project Zomboid's sandbox settings provide control over animal spawn rates and simulation. These are sandbox vars, set in ~/Zomboid/Server/<servername>_SandboxVars.lua or via the in-game sandbox editor (if starting a new world).
Key Animal-Related Sandbox Settings
Performance recommendation: There is no single population multiplier in Build 42. The levers that exist are AnimalRanchChance, which decides how many farms spawn with livestock at world generation, and AnimalMetaStatsModifier, which governs how animals outside loaded chunks are simulated. Lower the first on a busy server; it only affects new world generation, not animals already placed.
Disabling Animals Entirely
If your server focuses on pure survival/PvP gameplay and doesn't want the animal overhead:
Note: Disabling animals on an existing world does not remove already-spawned animals. You'll need to use the in-game admin command to clear existing animal entities, or start a fresh world.
Managing Animal Populations as a Server Admin
Admin Commands for Animals
Build 42 exposes animals through two admin commands. There is no /countanimals, /removewildanimals, /setanimalpop or /tpaanimal: those appear in several guides but exist in no Project Zomboid build.
/remove needs the AnimalCheats capability and /list needs LoginOnServer, so an admin has both by default. Population itself is not set by a command: it is driven by your sandbox settings, and changes there need the Admin Panel or a config edit plus a restart.
Identifying Overloaded Areas
If your server experiences TPS drops, the first step is identifying where animal populations are densest. Check the server log for lines like:
Server logs do not carry an [AnimalSim] tag or per-chunk animal density lines. That format circulates in guides but the Build 42 server does not emit it. To find where animals are concentrated, use /list animals and watch server TPS.
Animals generating pathfinding timeouts are usually located in terrain where the nav-mesh is poorly generated, near the edges of existing roads, in building interiors, or at map chunk boundaries. These animals burn CPU without moving. /remove animals clears every loaded animal, which includes them; there is no command that targets one area.
Player-Owned Livestock: Best Practices for Server Communities
Enclosures and Performance
Player-built animal enclosures (pens made with fence pieces and gates) reduce pathfinding computation dramatically for contained animals. Encourage your players to keep their livestock properly penned:
- Contained animals have a much smaller pathfinding area to compute, from "entire chunk" down to "enclosure bounds"
- Animals inside a fully enclosed pen stop fleeing from zombies (they have nowhere to flee to), reducing AI state machine complexity
- A well-enclosed cow costs about 60% less CPU than a free-roaming cow in an open field
Breeding Guidelines for Server Admins
The genetics system in B42 rewards players who breed selectively. From a server management perspective:
- Consider setting a per-player or per-tribe animal limit in your server rules to prevent runaway livestock farms
- Large breeding operations (50+ animals in one location) will cause noticeable local TPS drops, enforce a reasonable cap
- Communicate limits in advance in your server Discord or MOTD so players don't invest in a farm only to have it partially removed
Renewable Resources from Animals
The primary reason players want animals on B42 servers is the renewable resource loop:
| Animal | Resource | Frequency |
|---|---|---|
| Chicken | Eggs | Daily (1-3 per hen per day) |
| Cow | Milk | Every 2 in-game days (lactating cows) |
| Sheep | Wool | Every 5-7 in-game days (shearing) |
| Pig | Lard, meat (on slaughter) | One-time (slaughter) + lard from live pig periodically |
| Any animal | Hide, meat, bone (on slaughter) | One-time per animal |
Higher genetics-stat animals produce more of these resources per cycle. A max-stat cow (achievable through several breeding generations) produces roughly 3x the milk of a default wild-caught cow.
Monitoring Server Health with Animals Active
Check these indicators regularly when running B42 with animals enabled:
If TPS drops below 20 consistently, reduce AnimalRanchChance and AnimalMetaStatsModifier in sandbox settings and restart. You will need a fresh world or a manual entity wipe for the setting to take full effect on existing worlds.
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