The 70/30 Hypothesis in Living Color: How Feed and Care Unlock Genetic Potential

Photo Credit from Left to Right: Meyer Hatchery, American Poultry Association

This past weekend I attended the APA National Poultry Show in Fayetteville, Arkansas. It was my very first major poultry show, and one I was excited to attend for many reasons: It was the first time I would see some of the best birds in the country up close, and of course, meet the fantastic breeders behind the feathers. 

But, my main goal was to educate myself not only on the distinction between my own birds and theirs, but also to continue to collect data on my practices, confirm or disprove hypotheses, and bring back either corrections to implement, or confirmations to continue. 

One detail I had already noticed about my birds that was a deviation from other birds I have seen is their size. My birds are BIG. Not heavy, mind you.. but taller, longer, fuller, broader, with more complete and mature feathering at earlier ages. I have had a working hypothesis now for some time, and is not novel by any means, but perhaps should be revisited as we continue to push the margins of what is possible for heritage poultry. 

The 70/30 Hypothesis in Living Color: How Feed and Care Unlock Genetic Potential

In genetics, "nature plus nurture" means that genetics (nature) and environment (nurture) are inextricably linked and constantly interact to shape who we are. Genes provide a predisposition, but environmental factors can trigger or suppress those genes, a process known as epigenetics. This bidirectional relationship is so strong that it's often more helpful to think of it as a continuous, intertwined process rather than two separate forces. 

The interaction of nature and nurture

• Genes are not destiny: You can be genetically predisposed to a trait, but your environment determines if and how it develops. For example, a person can have genes for being tall, but their ultimate height will also be influenced by nutrition and health throughout their life.

• Environment impacts genes: External factors can actually change how your genes are expressed. For instance, diet and stress can influence epigenetic changes that can last for years and may even be passed down to future generations.

• Genetic influence on environmental response: A person's genetic makeup can also influence how they respond to environmental factors. For example, genetics can affect how an individual's body responds to certain medications.

• Active role in shaping environment: People often "niche-pick," meaning their genetic predispositions lead them to choose environments that are a good fit for them. For example, someone who is naturally more outgoing (nature) might choose to participate in more social activities (nurture). 

So how can we relate this to breeding poultry so that we can unlock our birds’ true potential? We have developed a working hypothesis called the 70/30 rule of epigenetics. 70% of what we have to work with is hard-coded into our birds’ DNA, and can and will be expressed to a certain degree of reality regardless of how we try to control it. This is especially true of dominant monogenic or polygenic traits that are simply going to “be”: high tail sets, feathered feet, number of comb points, etc. 

But, given a clean set of genetics, free from any major disqualifications, how can we unlock our bird’s potential through the 30% nurture theory? The answer is simple. While the blueprint is written in their DNA, it takes the right environment, nutrition, and management to turn those genes on. It’s the same principle in all living things: genetics loads the gun, environment pulls the trigger. When you get the balance right, you don’t just grow chickens - you reveal masterpieces.

Meet Major & Fleur – Proof of the Theory

These two are not just beautiful - they’re the physical manifestation of what happens when selective breeding meets targeted nutrition.

Major (Adam), our cock, is the model of Black Copper Marans excellence:

• Wide chest, balanced frame, and strong carriage

• Deep, lustrous copper hackles without brassiness

• True black plumage with a green iridescent sheen that shifts under light like oil on water

• Bright eye set, full comb symmetry, and overall presence that commands attention

Fleur-Juliette (Eve), his counterpart, embodies everything we breed toward in our hens:

• Compact, solid, and beautifully proportioned

• Even copper distribution in the hackle

• Perfectly rounded breast and tight feathering over the thigh

• Jet black sheen across the wing and back with a soft luster

Together, they’re not just a pairing - they’re the expression of years of genetic refinement activated by superior feed and environmental control. 

Feed as the Genetic Key

In our recent feed growth protocol, we focused on what we call nutrient unlocking - not just “feeding,” but activating metabolic efficiency and pigment pathways that enhance feather condition, immunity, and coloration.

Key findings and changes that drove growth and phenotype expression:

• Fermented whole-grain base: Increased nutrient absorption and gut flora balance, reducing total feed consumption while improving feather and egg quality.

• Raw probiotics + digestive enzymes: Improved amino acid uptake, translating to better feather regeneration and shine.

• Copper-rich greens and beetroot: Supported melanin synthesis and deepened both black and copper pigment.

• Natural fat sources (flax, BSFL, raw milk): Increased feather sheen and dermal health - essential for feather follicle hydration and reflective quality.

• Vitamin E and methionine balance: Resulted in tighter feather structure and more defined copper tone in the hackles.

• Consistent hydration & low-stress environment: Allowed hormonal stability that supports consistent copper distribution without “washout.”

The outcome? Within a single growth cycle, birds showed a marked difference in muscle density, feather condition, and sheen - but more importantly, their genetic potential was expressed at full fidelity.

Why 70/30 Works

Through observation and controlled feeding trials across multiple flocks, we’ve consistently found that 70% of a bird’s final phenotype expression is predetermined by genetics, but 30% is fully modifiable through environment - feed, stress levels, exposure, housing design, light cycles, and social structure.

That 30% isn’t the difference between good and bad - it’s the difference between average and exceptional.

Genetics may build the skeleton, but environment builds the soul.

The Takeaway

We can breed perfection on paper - the right pairings, the right lines, the right traits - but it’s only through intentional nutrition and care that those traits ever come to life.

Major and Fleur are proof that the 70/30 hypothesis isn’t just theory - it’s biology in motion.

Their glow, their balance, their composure - every feather tells the story of feed, light, minerals, and calm.

The next time someone tells you it’s “just genetics,” remind them: Even the finest blueprint needs the right builder.