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300 Hand-Rearing Birds

Table­18.3­ Recommended nutritional supplements for fish eaters.

Nutrient Indoors Outdoor­Exposure

Vitamin A No supplement No supplement
Vitamin E 100 IU/kg of fish 100 IU/kg of fish
Vitamin D 15–20 min/day of sunlight or UV full-spectrum No supplement
lights during daylight hours
Thiamine 25–35 mg/kg of fish 25–35/kg of fish
Calcium In chick formula In chick formula

Ibis are nomadic species that forage on a variety of animal and insects. A variety of protein
sources are beneficial as a nutritional source because these sources vary in their fatty acid, vitamin,
and carbohydrate contents. Nutritional values vary in feeder prey based on the age, species, and
season caught, among other variables. For piscivorous feeders, the main nutrients of concern are
vitamin E, vitamin B (thiamine), vitamin D, and calcium in growing chicks (Table 18.3).
Vitamin A is the most toxic of the fat-soluble vitamins and is already found in high concentra-
tions in fish livers. Vitamin A levels are very high in some commercial nutritional supplements.
Additionally, high doses of vitamin A have been shown to decrease vitamin E absorption in many
species including humans and chickens, suggesting the need for vitamin interaction awareness.
Birds ingesting whole fish probably do not need Vitamin A supplementation.
Vitamin E is of concern in fish-eaters and supplementation is recommended to prevent deficien-
cies. Vitamin E oxidizes easily (peroxidation) and may be lost prior to the thawing process (Bernard
and Allen 1997); 100 IU vitamin E/kg of fish is recommended (Geraci 1972). Vitamin E deficiency
may lead to electrolyte imbalances, irregular molts, steatitis, muscular degeneration, liver necrosis,
or anemia (Geraci and St. Aubin 1980).
Thiamine (B 1 ) supplementation is critical in birds with diets largely composed of fish. The pro-
cess of thawing fish in running water depletes the fish of water-soluble vitamins. In addition, many
fish species contain thiaminase, an enzyme that destroys thiamine (B 1 ). Thiaminase is not
destroyed by the freezing process and thiamine continues to break down while frozen. Thiamine is
important for the nervous system and also for conversion of carbohydrates to glucose. Feeding a
variety of fish and limiting the consumption of fish containing thiaminase prevents thiamine defi-
ciency syndrome. Syndrome symptoms manifest in paralysis, anorexia, “star-gazing,” or death.
Star-gazing is often one of the first recognized symptoms. Take immediate action if neurological
issues are noted. When recognized early, thiamine deficiency can be reversed with supplementa-
tion of B 1. The recommended routine supplementation is 25–30 mg of thiamin per kg of fish (wet
basis) (Bernard and Allen 1997).
Vitamin D supplementation is not usually needed for ibis with access to direct sunlight.
Windows interfere with UV light and do not provide adequate intensity. It is recommended to
provide a full-spectrum UVB artificial light source during daylight hours if ibis cannot be housed
with natural lighting.
Calcium concentrations in whole fish and krill are typically 0.9–6.4% of dry matter, and may
need supplementation as growing chicks need a calcium to phosphorus ratio of 2 : 1 to support
rapid skeletal growth (Klasing 1998). The concentrations of calcium, phosphorus, and vitamin D
in dietary items and the calcium : phosphorus ratio can negatively affect metabolism when out of
balance (Bernard and Allen 1997). Ibis likely need calcium supplementation during growth stages.