
I have heard that some kibbles have a high calcium content. So thought you might like this information, gathered from a number of sources.
The borzois club did a study of other effects of feeding young dogs too much calcium, some years ago and the results were that these dogs then became more prone to bloat (torsion).
Actual calcium levels are important....an adult has an active
mechanism by which to regulate calcium uptake, so can more easily get rid of
excess by means of the kidneys. A pup relies almost entirely on passive
means so cannot actively excrete excess calcium; if there is excessive
calcium in the diet, it will be absorbed and not excreted. This goes whether
it be from raw bones or calcium supplementation, because of the form of
calcium in which uptake occurs - calcium is taken up in its ionic form,
vitamin D metabolites act as a carrier across the gut wall. All this stuff
about it being impossible to overdo calcium from a natural source doesn't
hold weight scientifically - the body doesn't make any distinction between
calcium ions from a bone and calcium ions from commercial food or
supplements.
http://www.petsvetsandyou.com/pcl/articles/c100010/q10000064.htm
"Immature dogs do not appear to be able to effectively limit intestinal
absorption of dietary calcium. Because of this inability, the higher the
calcium level in the diet, the more calcium that will be absorbed and
incorporated into developing bone. The resulting disturbances of
endochondral ossification can lead to the characteristic skeletal and joint
lesions."
http://www.speedyvet.com/NIP/CALCIUM/default.htm
"Calcium is absorbed in the ionised form, so the absorption is directly
related to the amount that is soluble and ionised in the small intestine.
Between 25 and 90 % of dietary calcium is absorbed from the intestine, by a
combination of passive (uncontrolled) and active (controlled) mechanisms.
Passive diffusion is the more important route in growing animals. Dogs have
the ability to adapt to long term calcium-deficient diets by increasing
calcium utilisation from the diet to over 90 %.
**(Which implies to me that it's better to be light on the bony offerings
than heavy!)
......Chronic overfeeding of calcium increases calcitonin secretion and
decreases PTH secretion. This decreases the activity of the osteoclasts
which are important for bone remodelling during growth. Young dogs do not
have the mechanisms to protect themselves against excessive calcium intake,
since the major route of calcium uptake is uncontrolled passive absorption.
The excess calcium is mainly deposited in the skeleton, which together with
reduced bone turnover, results in pathological changes in the growing
skeleton."
http://www.msu.edu/~silvar/hips.htm
"Plasma calcium concentration is tightly regulated by the body. This
regulation is needed for the many calcium-dependent biologic processes, such
as muscle contraction, hormonal release, and blood coagulation. The release
of calcium-regulating hormones (parathyroid hormone [PTH], calcitonin [CT],
and 1,25- dihydroxycholecalciferol [1,25 vitamin D]) is influenced by plasma
calcium concentration. These hormones regulate calcium dynamics in the
intestine, kidneys, and bone.
Calcium excess is routed primarily to bone through the influence of the
calciotropic hormones on target organs. Chronic, high intake of calcium in
large breeds has been associated with hypercalcemia, concomitant
hypophosphatemia, rise in serum alkaline phosphatase, retarded bone
maturation, higher percentage of total bone volume, retarded bone
remodeling, decrease in osteoclasts, and retarded maturation of cartilage.
These changes cause disturbances in endochondral ossification (articular and
epiphyseal).(6) When high calcium intake (calcium excess) is coupled with
relatively little absorption from bone, severe pathologic changes occur in
the young, growing skeleton that is unable to respond by normal remodeling
and endochondral ossification. The clinical diseases associated with these
changes are osteochondrosis, retained cartilage cones, radius curvus
syndrome, and stunted growth.(1,6) Therefore, calcium excess is a major
causative or contributing factor in the pathogenesis of skeletal disease in
the growing giant-breed dog.(3-6)
It is the absolute level of calcium, rather than the calcium/phosphorus
ratio, that most influences skeletal disease.(11) Young, giant-breed dogs
fed a diet containing 3.3% calcium (dry matter basis) and 0.9% or 3%
phosphorus have significantly increased incidence of developmental bone
disease. These dogs seem to be unable to protect themselves against the
negative effects of chronic excess levels of calcium.(26) "