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Why do chickens eat?

Published: February 11, 2025
Summary
All commercial poultry eat with reasonably good precision to balance nutrient intake with requirements. Short term, there can be some variation in feed intake related to local situations, but long-term, the mechanisms of feed intake regulation are quite precise. Matching nutrient needs with intake is an obvious inherent evolutionary necessity to ensure survival and reproduction. A bird’s da...
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Mentioned in this news release:
Steve Leeson
Poultry Health Research Network
Poultry Health Research Network
Influencers who recommended :
E. Ernest M. Pierson, George Entz
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Kevin Stickney
Harbro Limited
24 de febrero de 2025
An excellent presentation. At what stage do you think that a laying hen would be able to self-select for calcium intake by taking oyster-shell or granular limestone from pan feeder? Would it make sense to offer such a mineral supply alongside a Pre-Lay ration, with ~2% calcium, in order to prevent any immediate shell quality issues when the first eggs are aid?
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Steve Leeson
Poultry Health Research Network
Poultry Health Research Network
24 de febrero de 2025

@Kevin Stickney In theory, yes. You could offer feed and oyster shell, etc., and they would balance their nutrient needs. The practical issue is that birds invariably take too much oyster shell because of its novel texture. We see this in small flocks where a calcium feeder is set up. Birds consume 8-10g/d of oyster shell and then soft shelled eggs appear because of an induced P deficiency. You could give two diets, High and Low in Ca, and they would balance themselves, but that becomes a logistics challenge. A pre-lay diet with most Ca as large particle will work, assuming it’s a mash diet.

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Dr Kotaiah Talapaneni
Indbro Research & Breeding Farms
Indbro Research & Breeding Farms
25 de febrero de 2025
Excess calcium is consumed by birds which are on controlled feed (feeders are empty) when grit is offered on free choice basis. Layer hens which are on full feed (feeder has feed) the hens eat as they need. They don't over consume the grit
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Bob J. Brill
Brilliant Alternatives
1 de marzo de 2025
Hi Dr. Leeson, I enjoyed reading your detailed post about feed intake, bird growth and all of the other great information you provided. As i was reading your article, i was reminded of the many lectures that you and Dr. Somers gave a few years back. Thanks for my updated course on Why Chickens Eat.
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Daniel Carlos Besso
CADIA - Centro Argentino de Ingenieros Agrónomos
CADIA - Centro Argentino de Ingenieros Agrónomos
19 de abril de 2025

I disagree with you Steve.
Generaly animals are like children.
candy or soup, children chooze candy.
So we give a mix with all feedstuffs they need. and give this mix in peels. So they cannot choose.
I apologise for my English. Sorry.

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Tuvi Soreq
Sorpol
7 de mayo de 2025
Dear Sirs and Ladies
Many thanks
Pls email the actual report
regards
tuvi
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Nuhad Daghir
American University of Beirut
American University of Beirut
15 de mayo de 2025

Many thanks, Dr. Leeson, for an excellent article. I have only one comment regarding ideal temperature for layers. I agree with you that 26 degrees is ideal for layers in post-peak production but before peak production a lower temperature is desirable to stimulate them to eat more to meet adequate production and desirable body weight. I enjoyed your article immensely. Best regards

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Mirzaasad Baig
19 de mayo de 2025
Chickens eat to get the energy and nutrients they need to survive, grow, lay eggs, and stay healthy—just like all animals. Their diet typically includes grains, seeds, insects, greens, and sometimes small animals like worm
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M.C. Fernando R. Feuchter A.
2 de junio de 2025
Just remember that chickens do not have AMYLASE in their saliva. So feed digestion is not immediately as other animal species. As an adult, they love to have GRIT on their CROP and many of the stone pieces will stay for days in there. So soluble calcium will be released at different concentrations each day.
Calcium grit is usually provided at molt time rather than as calcium supplement.
So regulation of GRIT intake from layers would take a few days to be constant.
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Dr Pragati Salutgi
ABTL Advanced Bio-Agro Tech Ltd
ABTL Advanced Bio-Agro Tech Ltd
1 de julio de 2025

@M.C. Fernando R. Feuchter A. What is the first enzyme that acts on the feed once it enters the digestive system in chickens and what is the location?

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M.C. Fernando R. Feuchter A.
2 de junio de 2025
A good search on this topic is Dr. Kenneth Anderson of North Carolina Univ.
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Dr Pragati Salutgi
ABTL Advanced Bio-Agro Tech Ltd
ABTL Advanced Bio-Agro Tech Ltd
18 de junio de 2025
Thank you Dr Leeson, this reading has revised most basic concepts while answering the most basic questions- Why chickens eat? Now we know!
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Antônio Mário Penz Junior
Cargill
Cargill
17 de agosto de 2025

Dear Steve, one more article of yours that recicle knowledge and brings new information to add to our understanding. Regarding pellet and mash diets, there are differences in this main energy feed consumption regulation?

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Steve Leeson
Poultry Health Research Network
Poultry Health Research Network
18 de agosto de 2025

Mario, always good to talk to you.

Mash vs. pellets adds another dimension to feed intake. For broilers, it’s obvious that the physical density of a pelleted feed allows for faster intake of a given quantity of feed. Pellet size likewise influences time spent feeding. Both these factors greatly impact intake and growth after about 25d at higher stocking densities, when we invariably see slowing of growth rate that is usually blamed on formulation or sub-clinical disease challenges. We can’t increase feeder space, so maximise pellet dimensions!!

Mash diets allow for some self-selection of ingredients, and so this can cause temporary shift in nutrient intake. But birds still eat to energy needs. Mash feeds work better than most of us expect, but there is always more variation in individual birds growth rate and in carcass yield of individual birds. Mash feeds, on the other han,d usually result in drier litter and better liveability, especially beyond 2.5kg live weight.

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George Entz
20 de agosto de 2025
@Steve Leeson

I agree that in mash feeds that the g/ bird/day decreases after day 25, but are there not ways we can get around that, by increasing density of the mash feed, particles size of feed, ingredient selection...etc?

I'm curious what you think the GMD of finisher feeds for broilers should be?
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Emile Haasbroek
19 de agosto de 2025
Good evening Dr Leeson.

I have a question regarding broilers.

I see in your article that for fully feathered layers the ideal temperature is 26 degrees C.

What would the ideal temperature be for fully feathered broiler grown to 32 days taking humidity into consideration?

Most broiler handbooks and articles says between 21 and 23 degrees.
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Steve Leeson
Poultry Health Research Network
Poultry Health Research Network
20 de agosto de 2025
At 21c you may get faster growth rate (0.2-0.3d) but inferior feed efficiency (+0.01-0.02) depending on efficiency of ventilation system
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Eugeni Roura
University of Queensland
University of Queensland
22 de agosto de 2025

Hi Dr. Leeson, thanks for your interesting paper. In my view, there is one topic that is misunderstood: the role of taste and smell in feed intake. Evolution has kept roughly 250 genes in the chicken genome for these 2 systems. Claiming these are not well-developed is probably inaccurate. For example, chickens have a very fine taste system, including roughly several fold more taste buds in the oral cavity than humans (relative to volume). The main taste ligands are nutrients (sugars, amino/fatty acids, calcium…) or toxins / antinutritional factors all potentially powerful feed intake drivers. They involve ca 12 well-characterized taste receptors which are present in the oral cavity, gut and brain, orchestrating short-term (within meal) and mid/long-term (between meals) feed intake through the gut-brain axis. In my view, it is not possible to understand feed intake mechanisms in birds (or mammals) without understanding the taste system.

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Dr Kotaiah Talapaneni
Indbro Research & Breeding Farms
Indbro Research & Breeding Farms
23 de agosto de 2025
Very good observations. Chicken feed intake is regulated by
1. Requirement for maintainace
2. Requirement for Growth and productio.
3. Energy content of the feed.
4. Environment temperature
5. Texture of feed, grain/pellet size.
6. Taste, colour and smell of the feed.
7. Appetite of the birds.
8. light and visibiity which creates appetite
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Reza Abdollahi
Massey University
Massey University
24 de agosto de 2025

@Antônio Mário Penz Junior
@George Entz

Thank you all for this very interesting and important topic. Feed intake is the major factor driving the growth rate of meat chickens. The modern broilers and Turkeys are more susceptible than ever to feed intake stressors, and to achieve their genetic potential, it is vital to recognize, minimize or even eliminate feed processing-related factors inducing feed intake suppression. Feed consumption can be affected by particle size and degree of grinding, feed form (mash, crumble, pellet), pellet size (diameter and length), pellet quality (percentage of intact pellets vs fines, hardness, and durability), and whole grain feeding (type of grain, barley vs wheat, inclusion rate, Introduction age, and grain hardness). An important point regarding the particle size is that the effect of particle size on the feed intake of broilers could be different in mash diets from the pelleted diets. if you are interested to know more about the feed processing and its impact on feed intake, you could have a look at the following review article from Massey University, New Zealand:
Feed intake response of broilers: Impact of feed processing
M.R. Abdollahi, F. Zaefarian, V. Ravindran

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dan hofer
28 de agosto de 2025
Pallet Feed is good, but sometimes there’s more dust than pellets that’s where mash feeds shines
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dan hofer
28 de agosto de 2025
Another big factor is Feeder heights to lift them so they are standing and eating, not downsitting when eating
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Antônio Mário Penz Junior
Cargill
Cargill
31 de agosto de 2025
Fully agree, Dr. Dan Hofer. Feeder and drinker height are important observation when we get into a chicken house. Also, how much feed there is in the feeders.
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