"Tying Up" in Racing Pigeons

Imagine that near the end of a long, gruelling day when race birds have faced a headwind for much of the day, you have managed to clock two late arrivals, the last one just at dusk. Both birds are very tired and dehydrated, and have obviously lost some weight. You make sure they have a drink of water and some light feed before they settle in for the night. The next day, they seem a bit rested but there is no doubt that they are still tired, so you keep them in the loft for the remainder of the day. After that, because they continue to look and act tired, they are kept in the loft all the second day as well. When you enter the loft on the third morning, you find both birds on the floor, and as you approach them, they try to fly. You see that both are now very wobbly and stiff as they try to lift off the floor. One of them is finally able to fly to a low perch, but the other one remains on the floor with its wings raised, unable to fly. What is wrong?

Since the birds are so wobbly when they try to fly, one of your first fears is that they might have paramyxovirus (PMV) infection. After all, you did notice evidence of loose droppings on their perches the morning after they homed, and now they have trouble flying. You shake your head. How can this be PMV? You vaccinated all race and stock birds with an approved vaccine twice within five weeks before the birds were paired. In spite of the fact that the birds look bright, you continue to be concerned about PMV. The rest of the flock looks fine, but since you know that PMV spreads relatively slowly in an infected loft of birds, you wonder if this is the beginning of a major problem. On the other hand, could it be paratyphoid infection? The possibility that the birds picked up this organism during shipment, plus the stress of a tough race, and the presence of loose droppings a couple of days ago, along with wobbly, difficult flight might mean that paratyphoid organisms entered the bloodstream from the intestines and were spread to a number of tissues, including the wing joints, and maybe the brain. Wait though -- all birds were also vaccinated weeks ago against paratyphoid infection. Besides, these birds, along with the rest of the flock, don't look sick -- at least, not yet. What is wrong with these two birds?

Very worried, you decide to take one of the birds and some fresh droppings collected from both birds, to your veterinarian who is also a member of your Combine. You ask him to kill the bird if it's possible to avoid it. He agrees, then handles and examines the bird, draws a small blood sample, swabs its throat, and then cultures and examines the droppings for parasite eggs and coccidia. You contact him the next day for some early results, and he tells you that, so far, cultures are negative for paratyphoid organisms, but he needs another day or two to be more certain of today's result. He also tells you that in the samples of droppings there are a very few coccidia but no worm eggs, and that in the throat swab there are very few canker organisms. However, his laboratory work on the blood sample shows that the values of two enzymes that are associated with damaged muscle are elevated, and the value of one enzyme in particular, is very high. One of these enzymes, called aspartate aminotransferase (ASAT) has a high value of 147 compared with the normal range of 45-123.

The reading for the second enzyme, called creatine phosphokinase (CPK), is very high at 1004 compared with the normal range of 110-480. On the basis of the outward signs in these birds, coupled with the enzyme results and early negative bacteriology, he makes a presumptive diagnosis of "tying up". What is this disorder? Tying up is a condition involving the working muscles of an athletic animal after it has experienced a hard race or competition in which it has overexerted itself. It is seen in horses on the track, in human athletes, greyhounds and certainly, in pigeons, etc. One of the worst and most severe expressions of this problem that I have encountered in my professional experience is called capture myopathy or exert ional myopathy (myo = muscle; pathos = suffering; hence, the word refers to any disease or condition of muscle, in this case, degeneration), a condition which I was able to study extensively in wildlife at one point in my career. Capture myopathy occurs in various wildlife species, such as those that are captured either in baited traps or by driving them at high intensity into enclosures, often with ground vehicles and helicopters. Many more cases of this condition occur when these intense drives are held in hot weather compared with fewer cases when drives are held in cool weather.

Some of the key clinical signs of capture myopathy include marked muscular stiffness and associated pain, lethargy, depression, the passage of red or coffee-coloured urine, and sudden death if the heart muscle is affected. The urine is discoloured because of extensive damage to the muscle, from which the pigmented, oxygen-carrying, iron-containing compound called myoglobin (similar to haemoglobin which gives blood its red colour) leaks, enters the bloodstream and is filtered through the kidneys into the urine. At post mortem, significant changes are seen in the diaphragm and heart. These changes are seen as large, pale yellow or white streaks in the muscle, and indicate severe degeneration of the affected muscles.

Tying up is a much less severe expression of the whole process just described, and is characterized by stiffness and reluctance to walk, and in pigeons, inability to fly or difficulty in flying even to a low perch. Flight at this time is wobbly, and the fancier may well wonder about PMV or paratyphoid infection, or that the bird has hurt one or both wings. When the bird is held and examined, it was found that the breast muscles were swollen, making the bird feel large in the hand. However, closer attention to the breast muscles reveals that they are not supple but instead, they are swollen and hard, and to the inexperienced fancier, the may give the false impression that the bird is still in top physical condition. During handling, the affected bird often appears otherwise bright and normal. How has this condition occurred?

In my experience, the history given in the first paragraph is characteristic. A bird arrives home after a tough race, and because he is so tired, the concerned owner feels that he should have a good long rest. Result: the bird is left in the loft, undisturbed for several days. However, during this enforced period of rest, events are occurring within the breast muscles to create the clinical signs described previously. You may recall that in the large breast muscles of the pigeon there are two kinds of muscle fibres, one a narrow-diameter red fibre and the other, a broad-diameter white fibre. You may also recall too that the red fibres far outnumber the white fibres by about 14 to 1, and that these red fibres, fuelled primarily by fat, are utilized in the presence of oxygen, for prolonged, rapid flight. The lesser number of white fibres in the great breast muscles are able to operate normally and efficiently in anaerobic conditions (an = without; aerobic = oxygen; hence, these fibres operate effectively in very low levels of oxygen) in which they use glycogen as their major fuel. Importantly, it is also known that these white fibres are recruited at any time during flight when the rate of the wing beat, which is usually an average of 5.4 beats per second at cruising speed, is significantly altered, such as in situations that require dodging or explosive bursts of speed, or for example, if the bird has to pull hard against the wind. In our original example, since the race was tough, the birds had to pull strongly against the wind, and as a result, there were significant biochemical changes resulting from the anaerobic use of white fibres in the breast muscles.

Because the white fibres function in the absence of oxygen or in very low levels of oxygen, one of the biochemical by-products of their work is lactic acid, which can build up, in the overworked system.

This build up of lactic acid can damage not only internal organs, but also both types of fibres -- red and white -- in the breast muscles where it is first produced. Under these acidic conditions, the muscle fibres become damaged and they react by swelling to cause the hard, board-like feel noted when affected birds are handled. The rise in the values of the two serum enzymes mentioned helps to tell the story.

Characteristically, CPK values rise very quickly following injury to muscle, and indicate very recent, on-going damage to the muscle, whereas ASAT values rise more slowly and indicate earlier damage, in this case, damage that likely began soon after the bird arrived home.

Now, what about the treatment of birds already affected by the tying up problem? At this somewhat late stage of the condition, exercise is out of the question for obvious reasons: the bird is too tied up and in pain because of the lactic acidosis that has caused the damaged muscles to swell. All that the fancier can really do at this stage is to wait for the situation to return to normal, perhaps with the use of light feed such as barley and a little support. In theory, alkaline powders such as baking powder could neutralize the generalized acidity but there is the risk that overdosing could shift the system from acidic side to the alkaline side. It would be best to err on the side of caution by relying on rest and time to resolve this problem.

Can anything be done to prevent the condition in the long run?

In my experience, exercise is unquestionably the best and most practical preventive measures by far. To me, the biggest single contributing factor to the problem after birds return home is enforced prolonged rest. Yes, the birds are tired after a hard fly, but I feel very strongly that it is critical after any race, and definitely after a hard race, to let all race birds out of the loft for light exercise, even for a few minutes, at the next exercise period that day or certainly, the following day and beyond. The effect of this mild exercise is to metabolise or "burn off" any build up of lactic acid that has occurred during the race. Note that human sprinters, thoroughbreds, greyhounds, etc. all routinely walk for 15-30 minutes after a race, and for the same reason: to metabolise the lactic acid that has accumulated during the race.

For race birds, a few minutes of free exercise -- not forced exercise -- each day after the race is an excellent preventive strategy, even for tired birds. Dim ethyl glycine (DMG) known commercially as Spur in North America, is said to be helpful in preventing lactic acidosis in horses on the track, and may also be similarly helpful in racing pigeons. As well, in Belgium, carnitine was shown to have some effect in decreasing lactic acid levels in blood. However, in my experience, light exercise beginning as soon as possible after any race, but especially after a tough one, is a simple and very practical therapy.

Although the key triggering conditions that set the problem in motion seem to be days of prolonged rest immediately after a race, especially a long or tough one, there are other management factors that may contribute to the development of tying up. Vitamin E and the trace mineral selenium are both highly important in the maintenance of normal muscle structure, and both act to protect muscle fibres against degenerative changes that can occur with intensive work.

For this reason, a water-soluble multivitamin mix containing vitamin E, and to which vitamin C can also be added, one to two days each week, is very useful on a routine basis throughout the year. Both vitamins C and E are antioxidants that help to prevent the damaging effects of oxygen in the form of peroxides, in tissues. As well, at all times of the year, fanciers should provide a loose, wide-ranging mineral mix that also contains selenium, which add to the protective insurance provided by vitamin E. Because there is a very fine line indeed between normal and toxic levels of selenium, it is important NOT to add extra selenium to the mineral mix. Stay with the legal limits of selenium included in the mineral mix you buy.

In my experience, in selenium-deficient areas, one result of that deficiency in livestock such as cattle and sheep grazing these areas, often foothills and mountainous terrain, can be sudden death of newborn animals when the heart is severely affected, or sudden paralysis because of degeneration of muscles in the limbs very soon after these young animals become active after delivery. In these areas of low selenium status, regular supplementation with mineral mixes containing selenium is generally preventive.

Why raise the point about affected calves and lambs in an article on racing pigeons? Well, simply to explain that not only the forages eaten by livestock, but also the grains grown in these selenium-deficient areas and fed to our birds, are also likely to be very low in selenium. Thus there is value in the routine use in racing pigeons, of a loose wide-ranging mineral mix containing legal levels of selenium.

Before closing, I feel that a final couple of explanatory notes might be useful. Firstly, enzymes, mentioned earlier, are compounds, often proteins, that are capable of producing or accelerating some change in a specific chemical substance on which they act. Characteristically, the names of enzymes end in "ase". The enzymes ASAT and CPK are found in normal muscle. If the muscle is damaged, as it was in this case, these enzymes leak out of the muscle and circulate in the bloodstream where their levels can be measured and interpreted. In order to function properly, enzymes often require a helper chemical known as a co-enzyme. It is in the role of co-enzymes that many of the B vitamins function most effectively.

Secondly, the enzyme values reported here were taken from an actual case of tying up in one of two racing pigeons (affected at different times) from the same loft.

I am grateful to my veterinary colleague Dr Paul Miller (PA Veterinary Laboratory, Harrisburg, Pennsylvania, USA) who asked me to comment on this case at the time it occurred, for his courtesy in allowing me to use these values in this otherwise fictional account of tying up.

By Dr. Gordon A Chalmers, DVM

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