Posted by Beth Anne Quinlan, PhD Avian Sciences on 7/15/2026 to
Companion Birds
...Continued from Part 1.
Vitamin B12
The primary function of Vitamin B12 is as a coenzyme in many enzyme systems. It is required to form one of the components of the citric acid cycle, succinate. Vitamin B12 is required for the synthesis of methionine in animal cells (Church, 1988).
A deficiency of Vitamin B12 produces anemia as well as skin, feather, and beak problems. There is a decrease in growth rate due to decreased appetite. Kidney damage, impaired thyroid function, and perosis (fully discussed in the section about manganese) all result from a deficiency of Vitamin B12. The hatchability of eggs is reduced. On necropsy, dead chick embryos have enlarged hearts and thyroids, fatty livers, and numerous hemorrhages (Church, 1988).
Cobalt
'The only known animal requirement for cobalt is as a constituent of Vitamin B12' (Church, 1988). Based on this, I wonder why I have seen cobalt on nutritional labels.
A deficiency of cobalt would produce the same signs as a deficiency of Vitamin B12, especially anemia. Details about these signs can be found in the section discussing Vitamin B12.
Iodine
Iodine is used by the thyroid gland to make thyroxine. This hormone regulates the metabolic rate of the body along with the hormone triiodothyronine. Thyroxine increases the metabolic rate.
A deficiency of iodine results in goiter which is quite common in budgerigars. Goiter is a condition in which the thyroid gland is enlarged. It contains inactive secretions which result in a sluggish bird. A loss of pigmentation is also a sign. In budgerigars, the characteristic sign is labored breathing along with squeaking noises. This is due to the pressure of the enlarged thyroid on the syrinx (Arnall, 1975).
Iron
The primary function of iron is a result of its presence in heme. Heme is present in hemoglobin among other compounds. Hemoglobin is the protein which combines with oxygen brought into the blood and later releases the oxygen. Myoglobin, found in muscles, also contains iron and is important for oxygen transport. Iron is also necessary for the function of ovotransferrin and several enzymes which are required primarily during egg production.
Iron deficiency in birds typically results from a mite or tick infestation. Anemia, a condition characterized by a sub-normal quantity of hemoglobin and smaller than normal red blood cells, is the result. Affected birds have a slower growth rate and appear depressed and are more susceptible to other diseases. The slower growth rate is because a lack of hemoglobin means that the blood cannot carry as much oxygen and subsequently it will not metabolize food as well.
Manganese
The primary function of manganese is to aid in bone and cartilage formation. Manganese is also important in carbohydrate metabolism as it is a component of one of the metalloenzymes, pyruvate carboxylase (Church, 1988). Manganese may also play a part in egg production.
In birds, a manganese deficiency is the primary cause of perosis. Deficiencies of chlorine, biotin, folic acid, niacin, and pyridoxine have also been determined to affect perosis, however the addition of manganese in the diet will minimize the problem in the flock (Whiteman, 1989). In perosis, the affected tendon, the gastrocnemius tendon at the hock, slips to the side of the hock joint (or joints) and the bird's leg is extended laterally from the body with the foot flexed.
On necropsy, the bird's hock is flattened, widened, and slightly enlarged (Whiteman, 1989). The leg bones of the affected birds tend to be shorter and thicker than those of normal birds.
In laying hens fed a diet deficient in manganese, production will drop. Egg shells will be thinner. If the produced eggs are fertile, the hatchability will be decreased due to a high incidence of embryonic death.
Calcium
Calcium has many important functions. Calcium is so important to birds that cuttle bones are often provided as a source of calcium for budgerigars.
Calcium is important in the mineralization of bone. It does so by being transported through the blood to the bone and deposited with the aid of hormones as osteoblast sites in the growth plates as well as deep within the bone (Church, 1988). In cases of high calcium concentration in the blood, the thyroid releases calcitonin which increases the storage of calcium in the bone. In cases of low calcium concentration in the blood, parathyroid hormone is secreted which stimulates the mobilization of calcium from bones and soft tissues (Firkins, 1993).
Producing hens require calcium for the formation of egg shells. The blood plasma levels of protein-bound calcium increase with an increase in estrogen (Sturkie, 1986). This calcium is deposited on the outer shell membrane as calcium carbonate under the control of hormones secreted by the parathyroid glands (Moreng, 1985).
Calcium is also important for the normal function of nerves and muscles, including the heart. Nerve cells communicate at synapses, the secretion of calcium causes the vesicles to fuse with the presynaptic membrane thus creating an action potential (the impulses which transmit information from the brain to the neuromuscular junctions elsewhere in the body or the reverse). During the contraction of muscles, ionic calcium is released when neural impulses reach the sarcoplasmic reticulum. These ions straighten the actin filaments in sequence and pull them inward. The relaxation of muscles is initiated by the return of calcium ions to the sarcoplasmic reticulum via active transport (Wallace, 1993).
In addition to rickets, which was discussed previously, a deficiency in calcium causes osteomalacia in producing hens. When a hen does not receive adequate calcium, she will take the calcium from her bones and make the egg shells anyway. Calcium mobilization from the bone is often increased due to a diet high in anionic salts. This makes the blood more acidic, probably through parathyroid hormone, thereby increasing the calcium mobilization from the bone (Firkins, 1993). As this situation continues, the bones become soft and the hens often have fractures, especially in the femur.
Finally, a deficiency in calcium can cause death since it is necessary for the proper regulation of heartbeat.
Conclusion
The most interesting thing I learned from the literary research I conducted was that vitamins and minerals usually require another vitamin or mineral in order to function properly. Therefore, I have to trust a specific brand and the scientists behind it when I make supplementation choices.
Acknowledgements
Arnall, L. and Keymer, I.F., Bird Diseases: An Introduction to the Study of Birds in Health and Disease. T.F.H. Publications, Neptune City, NJ 1975. pp. 71-74, 334-339.
Church, D.C. and Pond, W.G., Basic Animal Nutrition and Feeding. John Wiley & Sons, New York, New York, 1988. pp162-164, 182-184, 199-200, 224-225, 230-231, 246-248, 255-257.
Firkins, Jeff, lecture notes. 1993.
Moreng, Robert E. and Avens, John S., Poultry Science and Production. Reston Publishing Co., Inc., Reston, VA 1985. pp 71-71, 81-82.
Sturkie, P.D., Avian Physiology. Springer-Verlag, New York, New York, 1986. pp 44-45, 304-307, 419, 456-461.
Wallace, Robert A., Sanders, Gerald Pl, and Ferl, Robert J., Biology The Science of Life. HarperCollins Publishers Inc., New York, New York, 1993. pp 777-779, 797-801, 953-954.
Whiteman, C.E. and Bickford, A.A., Avian Disease Manual, third edition. Kendall/Hunt Publishing Company, Dubuque, IA, 1989. pp171-180.
