Animals & husbandry — rat care and breeding

Keep animals healthy and organized before chasing better genes. This page currently focuses on rats. Other species have not been verified, so their rules are not assumed to match. For your first colony, start with the rat-care walkthrough.

1. 
   1. Establish care

   Secure food, health and cage space before increasing breeding numbers.

2. 
   2. Inspect both inherited values

   Use the gene scanner; a displayed average does not tell the whole story.

3. 
   3. Separate breeding stock

   Label parents, candidate offspring and meat stock, recording what you want to retain.

1. Pick one breeding goal first

The tutorial covers seven inherited traits: growth speed, expected litter size, immunity, maximum health, lifespan, hunger rate and fertility. Choose what this round should improve instead of trying to perfect everything at once.

For meat production, growth speed is an understandable starting point, but food, health and fertility still matter. Hunger rate is an exception to “higher is better”: faster consumption can be a cost.

2. An ordinary-looking average can hide a valuable trait

The creator explains each trait as a pair of inherited values. A growth pair of 1.36 and 0.69, for example, displays around 1.03, while retaining the possibility of passing on 1.36.

Inspect both values with the gene scanner and use blue labels to track animals or containers. Distinguish a high displayed value from carrying a useful inherited value, so you do not accidentally harvest valuable breeding stock.

3. Select offspring, then backcross to preserve the advantage

Backcrossing means pairing a selected offspring with the original parent carrying the desired value. In this game, the practical sequence is:

1. Identify and label a parent with a useful growth value; keep it out of the harvest group.
2. Breed it and check which offspring inherited that value.
3. Retain a suitable opposite-sex carrier and pair it with the original parent.
4. Inspect the next generation for animals carrying the target value on both sides, then establish a consistent line.

The video illustrates H/L × H/X. Ignoring mutation and assuming equally likely inheritance, H/H is one of four combinations: about 25% per offspring. That does not mean one guaranteed success per litter or a guaranteed result from one backcross. Inspect the offspring rather than counting nights alone.

4. After establishing a line, look for improvements through mutation

The initial random-generation range is not necessarily a permanent inheritance ceiling. The creator separates early selection and backcrossing from later attempts to find better mutations through more effective breeding.

When a better single value appears, retain its carrier and work toward preserving it in both copies. A 2.2 / 1.5 pair still displays around 1.85. One exceptional inherited value is not yet a consistently high-value line.

Do not expect every generation to improve. The model includes unfavorable changes and resistance at higher values. Expanding beyond what you can feed while waiting for a breakthrough may cost more than it returns.

5. Organize cages around effective breeding

The creator’s simulated comparison recommends three breeding cages with two males and four females each, with more females retained in the candidate pool—roughly one male to three females. This depends on the modeled growth trait, candidate pool and management conditions; it is not the only valid setup for every save.

Start at a scale you can feed. Know which animals are parents, candidates and harvest stock. Doubling the candidate pool also increases food and management costs without necessarily doubling improvement speed.

What does “six times in one night” mean?

The video describes an order-dependent case: place six females first and one male last, potentially allowing six passive-plus-active mating checks. The creator recommends testing the behavior.

Six checks do not guarantee six pregnancies. Processing-order behavior can change with versions and is not a production promise. Likewise, the earlier introductory claim about three females should not be read as an absolute cap.

6. A kilogram rat is a long-term target

The later model begins with an established 1.5 / 1.5 growth line and focuses on growth alone. It does not solve early selection, simultaneous improvement of all traits and every care condition as one problem.

The kilogram target also depends on high inherited growth on both sides, sufficient food, avoiding hunger penalties and appropriate harvest timing. A displayed arrival-day estimate does not establish when your own colony will reach it.

If food and crowding are still daily problems, improve the care and harvesting routine first. A simple record of parents, both target values, offspring and retention reasons is more useful than expanding blindly.

Credits

The breeding material follows He Xiaolu’s rat genetics and breeding tutorial, which combines game-mechanic analysis and simulations. This page distinguishes practical steps from model results; we have not reproduced every experiment in our own save.