The most intensive growth in large breeds continues until the puppies are 7 months. This is a crucial period when correct diet is essential for the puppy's health. Insufficient feeding inevitably causes growth and development disorders. The owners should remember that underfeeding is dangerous for the growing organism as well as overfeeding.
Vitamin D deficiency (hypovitaminosis D)
Lack of vitamin D, calcium and phosphorus cause rachitis (today this disease, to our delight, occurs quite rarely). One can indicate rachitis by troubles with general growth, crooked leg bones, thickening of joints, nodded ribs, flat and small ribcage, hollow chest, spinal curvature resulting from weak tendons and muscles, bloating caused by weak abdominal muscles, and retarded abnormal second dentition.
The roentgenological research reveals thickening of articular cartilages and metaphyses of leg bones.
To prevent rachitis the dog's food should include sufficient amounts of calcium and phosphorus in proper physiological ratio (1.2:1) and vitamin D. The daily demand for vitamin D is 20 units per 1 kg of bodyweight.
Timely treatment allows avoiding of dreadful after-effects of rachitis. Otherwise the bone deformation would be irreversible.
Calcium deficiency combined with surplus phosphorus
In young animals the most often consequence of breaking the physiological ratio of calcium to phosphorus is osteopathy.
When lacks calcium the organism produces excessive parathormone. It is secreted by parathyroid glands and regulates the calcium metabolism. Excess of parathormone leads to calcium "washing out" of bones, in such way the organism tries to make up the calcium deficiency in the blood. This results in general demineralization of bones.
The signs are: appetite loss, aggressiveness, painfulness, crooked fore and hindlegs (fiddle front/back, splayfeet, elbowing out, cow-hocks), the dog seems to be "plantigrade" because pasterns and hocks have excessive slope. The dog may get lame. In serious cases the walls of tubular bones become so thin that may break even at a slight tension.
The roentgenological research reveals the general lightness of skeleton, thin walls of bones and thickening metaphyses.
- not enough energy supply in the food, especially this regards to large breeds;
- diet consisting of pure meat (meat contains few calcium and much phosphorus).
Treatment: well-balanced diet, increase of calcium in food. But here one should avoid overdose of vitamin D, since this may aggravate the disorder.
Preventives: well-balanced calcium-phosphorus ratio in the diet; meat makes up no more than 33-40 % of daily ration, and 500 mg of calcium per 1 kg of bodyweight daily. It is better to use commercially prepared foods, which contain the complete complex of mineral and vitamin supplements.
The owners of the large breed puppies often overdose calcium, assuming they do right.
Surplus calcium in the presence of natural amount of vitamin D causes the metabolism disorders in the organism and hampers its' normal growth.
This effect was clearly demonstrated in the experiments of Dr. Hazenwinkel. He compared the development of Great Dane puppies at different amounts of calcium in their diet:
5 puppies received 1.1% calcium.
6 puppies received 3.3% calcium.
Puppies that had surplus calcium (3.3%) grew slower, had bad appetite and incorrect position of legs resulting from bones deformation.
Surplus calcium interferes with the absorption of zinc, and may cause skin troubles.
Moreover, overdose of calcium causes hypertrophy of mucous membrane of stomach and atony of pylorus - the risk factors for twisted bowels.
Preventive: do not exceed daily dosage of calcium (500 mg per 1 kg of puppy's bodyweight and 259 mg per 1 kg of adult dog bodyweight).
Surplus vitamin D (Hypervitaminosis D)
No doubt, that proper proportion of vitamin D and minerals is essential for the normal development of the young organism and also as a preventive measure of rachitis and osteofibromatosis. The dog's organism is unable to produce vitamin D under exposure to sunlight. That's why it should be added in food. However, one should consider the hypervitaminosis D is even more dangerous than the hypovitaminosis.
The risky is the dose larger than 100 units per 1 kg of bodyweight.
Treatment: changes in the organism are in most cases irreversible. The treatment may just stop the process, but not restore deformations of the bones. The dosage of vitamin D and calcium should be reduced and calcitonin prescribed. In some cases the surgical operation may be applied, especially for the correction of forelegs.
Preventive: do not admit overdose of vitamin D and calcium and refrain from overfeeding the dog.
Surplus vitamin D combined with calcium deficiency
- intensifies pathological changes caused by calcium deficiency and provokes severe demineralization of bones which results in crooked legs, lameness and fractures.
Surplus vitamin D combined with surplus calcium
- causes excessive mineralization of bones, which results in hypertrophic osteodystrophy.
Signs: depression, appetite loss, high temperature, articular pains bringing on lameness, and frequently, reluctance to move, symmetrical articular deformations, hot joints, splay feet.
The roentgenological research reveals hardening metaphyses, mineralization of epiphysis membrane that causes slow growth of bones and crook quarters. More serious cases involve accumulation of calcium inside large vessels, mitral valves, bronchial tubes, vocal chords and kidneys.
Causes: overdose of vitamin D and mineral supplements owing to extreme care of the owners about rachitis in their large breed pets. Instead of it they get osteodystrophy.
by Dr. Charrier, Translation from French into Russian - E. Pavlova
Consultant - Candidate of Biology Sciences, T. Mareeva
Translated by Tatiana Karpova (Moscow)
(MSU, Biology faculture, Dep. zoology and ecology).