International Giant Otter Studbook Husbandry and Management

Dietary Related Problems: Diarrhea and loss of appetite were caused by feeding fish in the
reproductive state (i.e. when they carried eggs) (Lazzrini 1998, pers. comm.; Dortmund Zoo,
pers. comm. 2001). (Fish eggs should be removed before feeding.) Giant otters have contracted
helminthes from live-fed fish (Flügger 1997).
When feeding giant otters “The fish has to be first quality, freshwater fish. Saltwater fish is
taken, but contains too much fat.” Wünnemann (1995 b ). Also Hagenbeck & Wünnemann
(1992) explain, “Marine fish, such as herring (Clupea harengus) and mackerel (Scomber
scombrus) are preferred by the otters but are not given as we consider them too oily to offer a
good balanced diet.” “Marine products contain high levels of poly- and mono-unsaturated fatty
acids.” (Reed-Smith 2001). Nutrient values vary between fish species and even within the same
species depending on age, sex and season of capture (Crissey 1998). Merck (1986) states
“Many fresh-water and salt-water fishes contain thiaminase, an enzyme that results in thiamine
[vitamin B 1 ] deficiency in animals fed exclusively on a diet of such fish.” Lewis (1995) states,
with regards to mustelids, “Diets high in polyunsaturated fat or fish may predispose vitamin E
deficiency.” The process of fish storage (freezing), thawing, and preparation causes fish
nutrient loss, particularly vitamins B 1 and E, and especially in fish with a high fat and/or high
thiaminase content (Crissey 1998, Merck 1986). Fish types containing high thiaminase and/or
high polyunsaturated fat levels should be avoided, as they can cause malnutrition, sickness and
even death (Merck 1986). Vitamin supplements, most especially vitamin B 1 (thiamine), vitamin
E, and a multivitamin, must be added when thawed frozen fish is the main diet. See Chapter 2
Section 19 for information on diets.
The following problems could be caused by feeding inappropriate diets, although these
problems have not been reported (see the paragraph below) to occur among giant otters:
(Following are excerpts from Reed-Smith, 1994-1995). “Thiamine (B1) - Thiamine deficiency
is also known as Chastek's paralysis. Clinical signs include, anorexia, salivation, ataxia,
incoordination, pupillary dilatation, and sluggish reflexes. Chastek's paralysis: "..a vitamin B1
deficiency induced by feeding certain types of raw fish that contain the enzyme thiaminase. "
(Merck, 1991) Early in the disease an abnormal gait, as if the hind legs were stiff, will be
observed. This leads (within 12 - 36 hours) to "extensive spastic paralysis" and the animal will
be unable to rise. It is treated by removing fish from the diet (then substituting fish that do not
contain thiaminase) and "daily injections of 100 u of thiamine..”. (Merck, 1991). “Vitamin E
Deficiency (yellow fat disease, steatitis) is produced by feeding high percentages of long-chain
polyunsaturated fatty acids provided in fish oils or horse fat." (Wallach & Boever 1983).
Clinical signs may include lethargy, lumpy subcutaneous fat, rear leg weakness and death.”
(End of excerpts.)
See under “Vomiting” and “Walking Difficulties Involving the Lower Back and Hind Legs”
(i.e. under “acute severe walking difficulties that occur suddenly and that last only for a brief
period of time”) below for more information about diets.
Excessive humming vocalizations: Otters have nine different vocalization types and many subcategories
exist for each type (Duplaix 1980). Normally humming is a positive contact
vocalization. Although when otters hum excessively (i.e. hum for an abnormally long time
or/and unusually frequently) this is not necessarily a positive sign and these sounds can mean
that the otters are stressed, nervous or anxious (Sykes-Gatz & Gatz pers. obs.).
43