A series of articles published by the Newry City based Dr Philip Quinn from Blue Sky Pigeon products. Send orders to
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willie reynolds
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This article will discuss the origins of energy in the pigeon diet with particular reference to pigeon corn mixes and racing. The pigeon diet is very important all year round and fanciers have their own particular favourites. When it comes to getting the best race performances from the race team there are a wide choice of commercial corn mixes available. Some fanciers buy individual ingredients and make their own mixes. There are raw corn mixes available for all aspects of pigeon racing, breeding and the moult. I will present some background information to help you make an informed choice as to what and how you feed your pigeons.

I have found over the years, both from attending pigeon shows all over the British Isles and conversations with fanciers, that the pigeon world is awash with old wives’ tales. Unfortunately, there is a severe lack of specialist pigeon vets in the UK and Ireland. While there are some avian vets, specialist pigeon vets are a rarity. With over 40 years veterinary pharmaceutical research and product development experience I will present, in a simplified manner, some aspects of how the pigeon diet provides energy for both metabolism and for flight. As the racing season has now moved into full swing I hope that this article will prove helpful.

Corn Mixes
There are many different corn mixes available, but most are based on raw cereal grains (wheat, barley, corn, oats), raw legumes (peas, beans, peanuts) and raw seeds (sunflower, safflower). Plants produce grains, legumes and seeds (indeed they are just all seeds) for the sole purpose of growing new plants which were not intended to act as a feed for animals, birds or even humans especially in the raw form (unprocessed or uncooked). They are produced by the parent plants in such a way as to ensure their survival until the opportunity is favourable for germination and subsequent new plant growth.

The parent plants ensure that their seeds have sufficient “raw materials” stored so that they can grow into a small plant with green leaves that can then make their own food from carbon dioxide, water and sunlight. So, what did the parent plants store in these seeds? First, they made the germ or embryo (immature baby plant) and surrounded it with an energy reserve consisting of carbohydrates, fats/oils and proteins along with some enzymes, some minerals, some vitamins along with some simpler chemicals. They also included several anti-nutrients like phytate and digestive enzyme inhibitors.

But these stored carbohydrates, proteins and fats/oils are plant based. The seeds were provided with the necessary digestive enzymes and other raw materials to make big chemical changes to these ingredients during the first few days of germination to release the stored energy. So, what is the scientific basis underpinning the formulation of these various corn mixes? These corn mixes simply provide energy to all the body cells along with amino acids to make new proteins for many functions throughout the body. They provide only some minerals and a few vitamins.

Carbohydrates are composed of carbon, hydrogen and oxygen in very large complex molecules that need to be digested to the much smaller glucose molecules which are easily absorbed by the small intestine (upper gut) into the blood. Only some of these many different types of carbohydrates can be digested by the pigeon digestive enzymes. Glucose is taken up by all the tissue cells, including the brain cells (nerve cells) and excess is stored as glycogen as high blood levels are toxic. However, the pigeon body can only store a small amount of glycogen mainly in the liver, heart, kidney and a small amount in the wing muscles. The glucose is used by all cells to produce chemical energy in the form known as ATP. This chemical energy is used to power all the chemical reactions taking place in each cell (metabolism) and for limited flight.

So, what happens if you overfeed your pigeons with carbohydrates? Very simply, when the glycogen stores are full, excess glucose is converted by the liver into fatty acids and stored as triglycerides (fat) and your pigeons become overweight unless exercised. Pretty much the same mechanism operates in humans. So, you need to watch your own carbohydrate intake as well. The liver is the chemical factory in the body and excess digestible carbohydrate in the diet gives the already overworked liver extra work to do (uses energy) and introduces further stress. The liver can also convert amino acids to fatty acids when necessary (see below) but again with an energy and stress cost.

Some of the indigestible carbohydrate serves as an excellent food for the “good bacteria” that mainly reside in the lower part of the gut. These bacteria have the digestive enzymes necessary to break down this fibre for their own use and produce acidic by-products called short chain fatty acids. The physical presence of these good bacteria along with the acidity makes colonisation by pathogenic (disease causing) bacteria such as Salmonella typhimurium much more difficult.
Fats/oils are also composed of carbon, hydrogen and oxygen but combined in a totally different manner from carbohydrates. They have a 3-carbon backbone of glycerol (glycerine) with 3 long chains of fatty acids attached to each carbon. These fatty acids consist of a carbon-oxygen link to the backbone along with several carbons (usually 12-18) having hydrogen atoms attached. Fats/oils provide 9 calories per gram compared to 4 calories per gram for carbohydrates and proteins. Most fats/oils require digestion by digestive enzymes produced by the pancreas. This digestion requires prior emulsification by the bile acids which physically break the fats/oils into microscopic droplets in a manner like washing-up liquid on a greasy plate or pan. This creates a very large surface area for the fat enzymes to work on to release the fatty acids and glycerine (glycerol) which are absorbed by the gut lining and enter the lymph system before eventually entering the bloodstream near the heart.

One very interesting fact is that there are only 2 species of birds that do not have a gall bladder to store bile acids --- pigeons and parrots. This means that there is continuous release of bile acids from the liver via the bile duct into the upper gut. Even birds with a gall bladder, have a second bile duct that goes direct from the liver to the upper gut to also provide a continuous supply of bile acids. This fact alone tells us that fats/oils must play a central role in the diet of all birds and especially pigeons. The bile acids are reabsorbed by the lower gut and recycled to the liver. The free fatty acids and glycerol released by digestion are parcelled up with blood proteins and deposited in many cells including the liver, kidney, heart and especially in the wing muscles.

Plant proteins are very large molecules consisting of one or more very long chains of small amino acid units. The amino acids consist of carbon, hydrogen, oxygen, nitrogen and a few also contain sulphur. Digestive enzymes release amino acids from plant proteins for building new tissue and can under certain conditions (see below) also serve as a source of energy. The protein profile of the corn mix is chosen so that at least all 9 or so of the essential amino acids are present. Essential amino acids must be supplied in the diet as pigeons are unable to make them from other chemicals.
While the protein content of grains is high what is important is their digestibility by the pigeon digestive enzymes. Protein digestibility is a very complex problem and in raw unprocessed grains the protein digestibility depends on many factors including the carbohydrate-protein interactions, presence of other chemicals including tannins and other polyphenols.
The digestibility of raw cereal proteins in pigeons is around 70-80% while the digestibility of raw legume proteins is very much lower at around 20%. So, depending on the ratio of cereal grains to legumes the protein digestibility of a corn mix may just be around 50-60%. The proteins in legumes (peas and beans) contain certain amino acids present in higher amounts than those in cereal grains so that by selecting a mixture the pigeons will have a balanced amino acid diet. Blending the various components of the corn mixes in certain ratios is meant to ensure that the pigeons will receive a balanced diet.

Balanced Diet?
Well this presents a problem. Firstly, pigeons are very selective eaters and given a choice they will individually eat the ingredients in the corn mix for which they have a preference (see quote 3 at the end of this article). This means that some of the pigeons at the communal feeder do not get a balanced diet and more importantly do not get all the essential amino acids. All 9 or so essential amino acids must be supplied in the diet as the pigeon metabolism is unable to manufacture these from simpler chemicals. During the moult this lack of amino acids becomes apparent from the presence of stress bars on the feathers. Second, 40-45% of the proteins in typical raw corn mixes are indigestible by the pigeon.

The small intestine in pigeons is relatively short and so the residence time of partially digested feed in the gut is short leading to even further protein indigestibility. The undigested proteins are excreted in the droppings. This high protein content in pigeon droppings is one of the 3 reasons why pigeon droppings are an excellent fertiliser due to the nitrogen content of the protein. The second reason is the poor absorption of minerals by the small intestine and the third reason is due to the presence of anti-nutrients in corn mixes particularly in raw legumes. For example, one anti-nutrient present, phytate, binds with minerals such as iron, copper, zinc, magnesium, calcium and cobalt forming large complexes which are excreted in the droppings. Other anti-nutrients include digestive enzyme inhibitors which interfere with protein digestion. So just because you feed your pigeons with a wide range of corm mixes and supplements it does not mean that these are totally digestible or that they are fully absorbed through the small intestine into the bloodstream.

Flight Energy
First, I will address the use of carbohydrates ie glucose, as a source of limited flight energy in the pigeon breast muscles. Muscles cells can only contract (shorten) and relax when they receive electrical signals via their nerve cells. Pigeon breast muscle consists of approximately 85-95% slow twitch muscle cells and 5-15% fast twitch muscle cells. Muscle cells are sometimes referred to as muscle fibres. The slow twitch muscle cells have a small diameter and have a rich capillary blood supply as evidenced by the pink/red colouration of breast tissue while the fast twitch muscles are much thicker and stronger with a much poorer blood supply.

When pigeons want to take off, land or engage in short in-flight avoidance manoeuvres (electricity pylons/cables, tall buildings or birds of prey) then the fast twitch muscles spring into action. The glucose store is rapidly converted to pyruvate and a small amount of chemical ATP energy which quickly provides the rapid and very powerful muscle cell twitch flight energy. This glucose metabolism is anaerobic (does not require oxygen) but is only possible for a short time as muscle fatigue soon sets in as the glucose store is depleted. During these “short sprint” activities the wing beat is 10-12 beats/second while during normal flight it is 5-6 beats per second. The glucose store in the fast twitch muscle cells is restored with existing or newly generated glucose from the liver for use later. Most of the pigeon flight fuel energy does not come from carbohydrates. Read on.
Fats and oils (triglycerides) are an essential part of the pigeon diet. Fats are simply larger oil molecules which are solids at room temperature and on digestion supply fatty acids and glycerol. These fatty acids are transported to all cells where they enter “small energy converters” called mitochondria. These mitochondria are present in all cells, except red blood cells, and they remove the hydrogen atoms from the fatty acids and glucose which then react with oxygen molecules in a specially controlled way to produce ATP energy and water. The carbon atoms are converted to carbon dioxide. This ATP chemical energy drives all the metabolic processes (chemical reactions) as well as producing the wing muscle cell twitches for flight. It should not come as a surprise to learn that the heart muscle cells, wing muscle cells and liver cells contain many more mitochondria than other tissue cells as these must produce much more energy. The formation of ATP is a very complicated process and is known as the citric acid cycle or Krebs cycle named after Dr. Hans Krebs who published his great work in 1937 while working at Sheffield University. He received the Nobel Prize in 1953 and was knighted in 1958.

Race Training
When fanciers are “training” their pigeons they are doing 4 things:
(1) Increasing the exercise regime causes the muscle cells (heart and wing) to manufacture a lot more mitochondria;
(2) Improving the muscle cell chemistry (metabolism) so that fatty acids are transported faster from the outer muscle cell into the mitochondria – this explains the use of L-carnitine in some pigeon race supplements as carnitine is naturally present in muscle cells;
(3) Improving the chemistry (metabolism) within the mitochondria so that the fatty acids are broken down faster to supply the chemical energy ATP for muscle twitch;
(4) Improving the transmission of electrical signals along the nervous system for both muscle cell twitching and wing feather twisting during wing movements. Calcium is extremely important for such nerve signalling.

Poor Race Fuelling
When pigeons are not properly fuelled for races especially in tough flying conditions they undergo “self-cannibalism”. When the fatty acid stores are depleted enzymes break down the breast protein to amino acids which are transported by the blood to the liver. Here they are converted to fatty acids and these return to the flight muscle cells to fuel flight. Eventually pigeons arrive home with much breast muscle loss. That fatty acids serve as the fuel for endurance (see quote 1 below) from the following research article provides the necessary proof:
Effect of endurance training on fatty acid metabolism during whole body exercise MARTIN, WADE H. III
Medicine & Science in Sports & Exercise: May 1997, Vol 29, Issue 5, p 635-639

Quote 1
“….. a variety of species of migratory organisms (fish, birds, insects) amass vast amounts of triglycerides within skeletal muscle fibers prior to their journey, and these deposits are absent or severely depleted following arrival. Several studies in mammals, including humans, have provided good evidence that triglycerides are broken down in slow-twitch and fast-twitch oxidative skeletal muscle fibers during prolonged exercise”
For fanciers who want more expert detail on feeding pigeons then I highly recommend the research paper below (highly readable for those with a limited scientific background). The paper describes actual diets fed to farmed pigeons. I think the 2 quotes I have selected from this recent paper should make you think much more about what you feed your pigeons.
The Journal of Applied Poultry Research, Volume 24, Issue 3, 1 September 2015, Pages 371–379, Published: 15 August 2015

Quote 2
“Despite being widely kept for nearly 1,000 yr for meat, as messengers, and experimental animal models, the nutrient requirements of pigeons are still largely undefined”.
Quote 3
“Unfortunately, in the majority of the farms in China, pigeons are still fed a mixture of whole grains (corn, wheat, sorghum, and so on) and a high-protein formula feed that was described 20 yr ago. A nutritional imbalance and feed wastage are likely inevitable because of the idiosyncratic patterns of the pigeon's food selection when they are fed the mixture”.
The take home message from this article is that there is only one form of energy in living cells and it is called ATP and it is produced mainly from oils/fats with a smaller amount coming from carbohydrates. Fatty acids from fats/oils is the pigeon flight fuel.
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