Breeding Guide

Realistic Livestock RM replaces the base game's automatic reproduction with a realistic system requiring males and females, age requirements, health thresholds, and species-specific gestation periods. This guide covers everything you need to know about breeding.

Note: This documentation was generated with AI assistance and may contain inaccuracies. If you spot an error, please open an issue.

Requirements for Breeding

For reproduction to occur, ALL of the following must be true:

Male and female of the same species in the same pen (or artificial insemination)
Female has reached minimum breeding age
Male has not exceeded maximum breeding age
Female is not already pregnant
Female health is 75% or above
Female is not the daughter of that specific male (inbreeding prevention)

Breeding Ages & Gestation

Species	Female Breeds From	Male Breeds From	Male Breeds Until	Gestation	Female Fertility Ends
Cattle	12 months	12 months	132 months (11 yr)	10 months	132 months (11 yr)
Pigs	6 months	8 months	48 months (4 yr)	4 months	96 months (8 yr)
Sheep	8 months	5 months	72 months (6 yr)	5 months	120 months (10 yr)
Goats	16 months	5 months	72 months (6 yr)	5 months	120 months (10 yr)
Horses	22 months	36 months	300 months (25 yr)	11 months	264 months (22 yr)
Chickens	6 months	6 months	No limit	2 months	120 months (10 yr)

Critical insight: Males retire from breeding much earlier than females in some species! Boars stop at 4 years while sows breed until 8. Rams stop at 6 years while ewes breed until 10. Plan male replacements early.

Genetics matter: A male's maximum breeding age is scaled by his fertility genetics. A bull with high fertility may breed well beyond 11 years, while one with poor fertility may retire much sooner. The ages above assume average genetics.

Breed Restrictions

Most males can breed with any female of their species, with two important exceptions:

Male	Can Breed With
Water Buffalo Bull	Water Buffalo cows only
Ram Goat	Goats only
Any other Bull	Any cow breed (except Water Buffalo)
Any other Ram	Any sheep breed (except Goats)
All Boars	Any pig breed
All Stallions	Any horse colour
All Roosters	Any hen

Cross-breeding between different breeds of the same species is allowed (e.g., Angus bull × Holstein cow), except for breed-locked types. See Offspring Breed below for what breed the offspring will be.

Offspring Breed

When two different breeds produce offspring, each baby independently has a 50/50 chance of inheriting either parent's breed. There is no visual blending — the offspring will look exactly like one parent's breed or the other.

Breeding Pair	Possible Offspring
Angus bull × Holstein cow	Each calf: 50% Angus, 50% Holstein
Highland bull × Hereford cow	Each calf: 50% Highland, 50% Hereford
Landrace boar × Berkshire sow	Each piglet: 50% Landrace, 50% Berkshire
Landrace ram × Steinschaf ewe	Each lamb: 50% Landrace, 50% Steinschaf

Same-breed parents always produce same-breed offspring.

Litters and Twins

Each offspring rolls its breed independently. A Berkshire sow bred by a Landrace boar could produce a mixed litter — some piglets are Landrace, others are Berkshire. The same applies to sheep twins or cattle twins: each baby gets its own 50/50 roll.

Example: A Berkshire sow produces a litter of 12 piglets sired by a Landrace boar. On average, about 6 will be Berkshire and 6 will be Landrace — but any specific litter might skew 8/4 or even 10/2 by chance, just like flipping a coin 12 times won't always give exactly 6 heads.

Artificial Insemination

When using artificial insemination, offspring always inherit the mother's breed. The AI semen system doesn't carry breed information from a specific sire, so all offspring will be the same breed as their mother.

If breed consistency matters to you, AI is a reliable way to ensure it.

Breed vs Genetics

Don't confuse breed inheritance with genetic trait inheritance — they work differently:

Aspect	How It Works
Breed (appearance)	50/50 coin flip — one parent's breed or the other, no blending
Genetics (traits)	Always blended from both parents, regardless of breed outcome

A Holstein calf from an Angus bull × Holstein cow cross inherits its Holstein appearance, but its productivity, health, fertility, and other genetic traits are still a blend of both the Angus father and the Holstein mother. The same applies in reverse for an Angus calf from the same pairing.

In other words: cross-breeding doesn't affect genetic inheritance. Your offspring's traits are always influenced by both parents — only the visual breed is one-or-the-other.

Practical Tips

Want breed-pure offspring? Use same-breed parents, or use artificial insemination.
Cross-breeding for genetics? If the best bull in your pen is a different breed, the offspring will still inherit his genetic traits — they'll just look like one breed or the other.
Selling cross-bred litters? Breed affects sell price (e.g., Berkshire pigs sell for more than Black Pied). In a mixed litter, each piglet's value depends on which breed it inherited.

Offspring per Birth

Cattle

Cattle usually produce single calves. Twins and triplets are rare.

Cow Age	No Birth	1 Calf	Twins	Triplets
12–28 mo	Moderate	Most likely	Rare	Very rare
29–48 mo (prime)	Low	Most likely	Rare	Very rare
49–84 mo	Increasing	Most likely	Rare	Very rare
85–132 mo (old)	Very common	Less likely	Very rare	Extremely rare

Pigs

Pigs produce the largest litters. Healthy sows at prime age almost always deliver.

Sow Age	Chance of No Birth	Small (1–6)	Medium (7–10)	Typical (11–13)	Large (14–16)
6–12 mo (young)	Low	Rare	Uncommon	Most likely	Possible
13–36 mo (prime)	Very low	Rare	Uncommon	Most likely	Possible
37–60 mo	Low–moderate	Rare	Uncommon	Most likely	Possible
61–80 mo	Moderate	Uncommon	Possible	Most likely	Less likely
81–96 mo (old)	High	Possible	Possible	Less likely	Rare

Most pig litters are 11–13 piglets. Older sows may produce smaller litters of 1–10 piglets. Low health significantly reduces litter size.

Sheep & Goats

Sheep and goats have high twin rates at prime age. First-time mothers usually have singles.

Ewe/Doe Age	Singles	Twins	Triplets
First-time mother	Most likely	Uncommon	Rare
18–36 mo	Common	Common	Rare
36–72 mo (prime)	Less common	Most likely	Uncommon
72–120 mo (old)	Uncommon	Most common	Rare

At prime age, twins are more common than singles! Goats follow the same pattern but start breeding later (16 months vs 8 months for sheep).

Horses

Horses almost always produce a single foal.

Outcome	Likelihood
1 foal	Almost always
Twins	Rare
Triplets	Very rare

Horse fertility declines gradually with age through to 264 months.

Chickens

Chickens have large but unreliable hatches. The chance of no offspring is always significant.

Hen Age	No Hatch	Small Brood (1–5)	Medium Brood (5–7)	Large Brood (7–12)
6–12 mo	Common	Uncommon	Most likely	Possible
12–24 mo	Common	Rare	Most likely	Possible
24–48 mo	Frequent	-	Most likely	Possible
48–84 mo	Very common	-	Uncommon	Rare
84–120 mo	Almost always	-	Very rare	Very rare

Unlike other animals, hens never die during hatching.

Lactation

Cows and goats enter a lactation period after giving birth. This has major effects on both production and consumption.

Parameter	Value
Duration	10 months after birth
Milk production	Only during lactation (zero otherwise)
Food consumption	Noticeably higher during lactation
Water consumption	Considerably higher during lactation
Sell price	Small bonus while lactating

Lactation Phase Curve

Milk output varies within the lactation period:

Months Since Birth	Milk Output
0–1	Ramping up (below full potential)
2–3	Peak production
4–9	Gradually declining
10+	Lactation ends (zero milk)

Peak milk production occurs around month 2–3 after birth. See the cattle and sheep factsheets for specific breed output ranges.

Mermaid Diagram

Chart shows the lactation factor as a percentage of peak output (month 3). Production starts at ~62% of peak at birth and declines gradually, dropping to zero at month 10. Actual litres depend on breed and genetics - see the cattle factsheet for specific ranges.

Pregnancy Complications

Breeding is not without risk. Low health significantly increases complications:

Parent Health	Risk Level
90%+	Very low risk of complications
75–90%	Low risk
60–75%	Moderate risk, fewer offspring
Below 60%	High risk, mother may die during birth

If the mother dies during birth, offspring may still survive. Low health also reduces the chance of multiple offspring.

Freemartin Effect (Cattle Only)

When a cow gives birth to twins where one is male and one is female, the female calf has a 97% chance of being infertile (a "freemartin"). This is a real biological phenomenon. The male twin is unaffected.

Freemartins can still be raised for milk or sold, but they will never breed. This only affects mixed-sex cattle twins - same-sex twins are not affected.

Pen Capacity

If a pen is at maximum capacity when offspring are born, excess newborns are automatically sold. Make sure your pens have room for new arrivals, especially:

Pig pens (litters of 11–16)
Sheep pens at prime age (frequent twins)
Any pen during peak breeding season

Artificial Insemination

If you don't want to keep males, artificial insemination (AI) is available through the livestock menu. Press I on a female animal to open the insemination dialog.

Breeds your female without needing a physical male in the pen
Uses an AI animal pool (can be refreshed in settings)
Same breed restrictions apply (Water Buffalo and Goats need breed-specific AI)
Same health and age requirements apply
The insemination button is automatically disabled when the female is ineligible (pregnant, too young, or recovering from birth)

Breeding Calendar

Plan your breeding based on gestation periods:

Species	Breed	Birth	Next Possible Breeding
Cattle	Month 0	Month 10	~Month 12 (after lactation)
Pigs	Month 0	Month 4	~Month 5
Sheep	Month 0	Month 5	~Month 6
Goats	Month 0	Month 5	~Month 6
Horses	Month 0	Month 11	~Month 12
Chickens	Month 0	Month 2	~Month 3

Cows have the longest cycle - roughly one calf per year at best. Pigs can produce 2–3 litters per year, making them the fastest-reproducing large animal.

Tips

Track male ages. The #1 surprise is boars stopping at 4 years. Set up reminders or check your boar ages regularly.
Actively manage your breeding stock. Offspring inherit from parents, but individual calves can be worse than either parent due to natural genetic variation. Pair your best animals, sell or castrate underperformers, and don't let a herd breed unchecked through generations - genetics will drift towards average without active culling. See the FAQ for why this happens.
Keep health above 75%. Below 75%, breeding fails entirely. Below 60%, the mother risks death. Good food, water, straw, and medical treatment are essential.
Budget for lactation costs. Lactating cows eat noticeably more food and considerably more water. Plan your feed budget for the 10-month lactation window.
Use pen capacity wisely. A pig sow can produce 13 piglets at once. If your pen only has 5 spaces, 8 piglets get auto-sold at newborn prices. Expand pens before breeding season.