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97
LIPID AND FATTY ACID COMPOSMONAL DIFFERENCES BETWEEN
EGGS OF WILD AND CAPTIVE BREEDING ALLIGATORS
(Alhgotot mississiwiens&): AN ASSOCIATION WITI{ REDUCED
IIATCHABILITY
Mark W.J, Fergusonr, R.C. Noble'? and R. McCartnef
rDepa metrt of Cell and Structural Biology, University of Manchester,
Stopford Building,Odord Road, Matrchester, M13 9PT, Enlland
'Department of Biochemical Scieoces, The Scottish Agricultural College,
Auchincruive, Ayr, KA6 5IIW. Scotland
A common problem in crocodilian farming is the reduced hatchability of eggs from
captive breeding programmes. In the Amedcan alligator, the typical hatchability of
eggs ftom captive breeding females is 507a, compared with 947o amongst wild eggs.
The major problem is ea y €mbryonic death. We perfomed detailed aoalysis of the
lipid and fatty acid compositions of the yolks of eggs from wild and captive breeding
alligators from the Rockefeller Wildlife Refuge l.ouisiana. There were extensive
differences between the wild and captive bred egg yolks. The lipid of the yolks from
the captive bred eggs displayed considerably lower levels of C20 aud C22
po\unsatunted fatty acids atrd higher levels of C18 polyunsaturates, compared to
the wild eggs. More specifically, overall levels of N6 polyunsaturates were increased
at the expetrse of N3 acids in the captive eggs. C20 al'd C22 polynsaturated fatty
acids play a key role in enbryonic development, e.g. of the newous system. It is
therefore likely that the yolk fatty acid compositional differences and the differences
in hatchability between captive bred and wild eggs are associated. We therefore
aualysed the lipid and fatty acid compositions of typical alligator diets, iDcluding
nutria, crocker fish and 3 commercial ratiotrs. The nutria and all 3 commercial
rations were deficient in C20 and C22 polynsaturated fatty acids and had high levels
of C18 polJrunsaturates; the levels bearing an uncanny resemblance to those found in
the captive bred eggs! Fish on the other hand, had higher levels of C20 arLd C22
pollunsaturates. It is therefore proposed that tle dies of breeding alligators need to
be supplemented (or the commercial composition of the rations altered) to itrclude
specific species ftom the C20 aad C22 polyumaturated fatty acids. However, these
fatty acids will need to be adequately protected with s€letrium aDd vitamin E, as
occurs in natural fresh fish. Preliminary analysis of the captive eggs for seleuium
ard_vitamin E sho*s that they are also deficietrt in these compounds which may
further potentiate the problem. Subtle dietary differences may be tle cause of
reduced hatchability in eggs from captive breedhg programm€s.