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OCR for page 18
Feec! Aciclitives
Feed. additives are considered as nonnutritive substances
added' in small amounts to the diet to improve animal per-
formance. No requirements are listed for them.
ANTIBIOTICS
Antibiotics are substances that when fecal at Tow levels modify
bacterial populations ire. the digestive tract in favor of d'esir-
able microorganisms, while at higher levels they tend to sup-
press disease-producing organisms.
The response of mink and foxes to dietary antibiotics has
been variable and may depend upon the quality of the diet and
the health of the animal. Increased growth rate of: weaned kits
and improved pelt. quality have been attributed to the feeding.
of' aureomyc~n, zinc bacitracin (Bassett and Warner, 1962),
and terramycin (Luther,. 1952; Warner et al., 195~8~. Anti-
bitotics fed to female breeders have also been. reported to in
crease weaning weights; and reduce kit mortality. Wood
(1963) and Admix (1955:), however, observed no significant im-
provement in growth or- fur quality of mink from feeding
several different antibiotics at levels ranging from 0.4 mg to
110' mg per kilogram of diet:. Swedish anti Norwegian. ~;~n-
vestigators were also unable to confirm any growth improve-
ment: from feeding terramycin, penicillin, or bacitracin from
weaning- to pelting, but did note a. growth response in kits
where the feed was supplemented with bacitracin during the
lactation period (Glen,-lIansen, 1911~.
In studies with. foxes (Breirem et al., 1955), aureomycin and
penicillin. were found to have no effect on. reproduction or pup
growth where fed to vixens, nor did these antibiotics, or terra-
mycin, improve growth of' young foxes from weaning to peit-
~ng. According to NorUfeldt et al. (as reported by AitLen,
19~), the- addition of 10 mg aureomycin per kilogram of dry
matter of diet frotn weaning to pelting failed to enhance the
growth of young foxes, although the growth of nursing pups of
vixens given 10 mg penicillin per kilogram of dry matter of'
diet was improved.
Russian investigations, reported by Aitken (1963), showed
that au:reomycin, penicillin, or l:evomycetin fed to foxes en-
hanced breeding performance, pup growth, and pelt value
and reduced mortality due to digestive disorders. A study by
Petersen (1953) also showed improved growth and pelt quality
of young foxes by the additions of penicillin (2S,000' IU per
kilogram dry matter) tot the diet.
There is presently some concern that the continuous feed~.n.g
of' low levels of antibiotics to animals may enhance the pro-
liferation of resistant strains of microorganisms and thereby
reduce the effectiveness of antibiotics in disease outbreaks.
Therefore, ~regulations- governing the use of antibiotics in
animal feeds are subject to change.
ANTIOXII)'ANTS
Antioxidant- are adder! to feeds to preserve nutrients and help
prevent oxidation of' fat. Horse meat and fish Improperly stored,
or stored for prolonged periods, are especially prone to oxida-
tion and when fed to mink may cause steat~tis (yellow fat
disease). ~
Studies by teekley et al. (1962') have shown that butylated' hy-
droxytoluene (BHT), 2,4,5-trihydroxy butyrophenone (THBP),
or dehydroethoxy trimethylquinoline (ethoxyquin) when added
at a level of 123 mg per kilogram of wet diet were effective in
preventing steatitis in mink fed diets that contained high levels
of' fish waste. Travis and Schaibl'e (1961) found no adverse ef-
fects on reproduct~or>, growth, or fur quality from feeding 0.2
percent BHT or 0.12S percent ethoxyquin (10 times the allow-
able level in reedy to mink. Di.phenyI-p-phenylene diamine
(DPPD) added to mink diets at 123 ma; per kilogram of wet
feed was effective in controlling steatit~s but had a detri.mer~tal
effect on reproduction (Leekley and Cabell, 1959~.
lg
Representative terms from entire chapter:
russian investigations
