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Project Zomboid Build 42: Animal Husbandry Server Guide

Project Zomboid Guide • Updated Mar 26, 2026

Project Zomboid Build 42: Animal Husbandry Server Guide

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 (March 2026): Build 42 multiplayer has been updated to B42.15 on the Unstable branch. Animal husbandry is fully functional in multiplayer. The stable branch still runs B41 — only Unstable branch supports B42 animals.

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 set in your server's sandbox.ini file or via the in-game sandbox editor (if starting a new world).

Key Animal-Related Sandbox Settings

[Animals] # Overall animal population multiplier (1.0 = default, 0.5 = half, 2.0 = double) AnimalPopulationMultiplier=0.75 # Whether wild animals spawn in the world WildAnimalsEnabled=true # Whether farm animals spawn in abandoned farms at world start FarmAnimalsEnabled=true # Maximum number of animals that can exist in a loaded chunk at once MaxAnimalsPerChunk=8 # Rate at which animal needs (hunger, water) deplete (higher = faster depletion) AnimalNeedsDepletionRate=1.0 # Genetics simulation detail level (Low/Medium/High) # Lower = less CPU but simpler breeding outcomes GeneticsSimulationDetail=Medium

Performance recommendation: Set AnimalPopulationMultiplier=0.5 on servers with 30+ players or limited hardware. This halves the default wild animal count while keeping the breeding system fully functional for player-owned livestock.

Disabling Animals Entirely

If your server focuses on pure survival/PvP gameplay and doesn't want the animal overhead:

[Animals] WildAnimalsEnabled=false FarmAnimalsEnabled=false AnimalPopulationMultiplier=0.0

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

B42 adds new admin console commands for managing animal entities:

# Show count of all animal entities currently loaded /countanimals # Remove all wild animals from the current loaded area /removewildanimals # Set the animal population cap server-wide (persists until restart) /setanimalpop [multiplier] # Teleport an animal entity (by ID) to your location /tpaanimal [animalID]

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:

[AnimalSim] Chunk (45,23) exceeded max animal density: 14 entities (max: 8) [AnimalSim] Bear entity ID 2847 pathfinding timeout in chunk (31,15)

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. Use /removewildanimals in those areas to clear stuck entities.

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:

# Check current TPS from the server console /servermsg [your message here] # Use to alert players before restart # Check memory usage (Linux) free -h # Check Java heap usage (if you have a monitoring tool, look for MemoryUsed) # Ideal: server should use <80% of allocated heap at peak # Check how many animals are loaded across the entire server /countanimals

If TPS drops below 20 consistently, reduce AnimalPopulationMultiplier 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.

Running Project Zomboid B42 with full animal simulation? Supercraft Project Zomboid hosting provides the RAM and CPU resources B42's expanded simulation requires.

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