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276 Hand-Rearing Birds

problems at all stages of rearing, and may enter care with MBD or develop it during care. In grow-
ing wild birds, MBD typically manifests as a malformation of growing long bones and is almost
always caused by a deficiency of dietary calcium during the rapid growth phase. In affected chicks,
the bones may palpate soft or rubbery, the chick may have trouble standing when old enough to do
so, or it may develop folding fractures of the long bones. Radiographs are helpful to ascertain
whether the problem is limited to one long bone or to the entire body. Chicks with only one or two
affected bones may recover well but chicks with multiple or all long bones affected hold a poor
prognosis. Chicks with spinal deformities also hold a poor prognosis; those not able to normally
ambulate or fly when old enough to do so should be humanely euthanized. For mild to moderately
MBD‐affected chicks, administration of additional amounts of calcium or a vitamin D supplement
may be helpful in assisting the chick with rapid mineralization of the skeleton. If a chick enters
care with the problem, feeding a diet with a calcium‐to‐phosphorus ration of 3 : 1 during the rest of
growth will provide additional calcium to help make up the deficit. Some fish species used to feed
piscivores in captivity have been found to have low calcium to phosphorus ratios (Table 17.1) or to
be deficient in vitamin D 3 (Hoopes and Clauss 2016).
For chicks with questionable (e.g. rubbery) bone quality at arrival, supplemental calcium is rec-
ommended in the form of calcium carbonate (CaCO 3 ) pills, usually 500–600 mg tablets, being sure
to avoid those containing vitamin D 3 , unless the primary food items are known or suspected to be
deficient (e.g. capelin, Hoopes and Clauss 2016). Vitamin D may be given separately orally or intra-
muscularly to assist with uptake of the calcium supplementation if the diet is known or suspected
to be deficient. Consult your avian veterinarian for species‐appropriate doses and combinations of
supplements to assist bone development. Excessive vitamin D supplementation can result in min-
eralization of soft tissues and other problems; hence, it is prudent to know the content of foods
before assuming more is better.

Table­17.1­ Calcium and phosphorus content of commercially available feeder fish, with calcium
supplement amounts needed to support skeletal growth of piscivorous chicks.

Calcium Phosphorus­ Calcium Calcium­supp.­needed­(mg/100g­
Species (mg/100­g­fish) (mg/100­g­fish) Phosphorus­ratio fish)­to­have­Ca : P = 1.5­:­1

Atlantic 392 389 1.01 191.5
Herring
Atlantic 137 255 0.54 245.5
Mackerel
Capelin 352 400 0.88 248
Finger Mullet 1040 764 1.36 106
Lake Smelt 301 202 1.49 2
Night Smelt 557 473 1.18 152.5
Pacific 644 528 1.22 148
Herring
Peruvian 479 393 1.22 110.5
Smelt
Pink Salmon 280 364 0.77 266
Silversides 752 510 1.47 13
Source: data from McRoberts Sales Inc., 2015–2016 catch analyses.