Optimisation of diets for Atlantic cod (Gadus morhua) broodstock: effect of arachidonic acid on egg & larval quality

Transcription

1 Optimistion of diets for Atlntic cod (Gdus morhu) roodstock: effect of rchidonic cid on egg & lrvl qulity Dr Gordon Bell, Ms. An Blnco, Dr Bill Roy, Dr Derek Roertson, Dr Jim Henderson nd Mr Richrd Prickett, Institute of Aquculture, University of Stirling, Stirling FK9 4LA, Scotlnd, UK & Mchrihnish Mrine Frms Ltd., Mchrihnish, Argyll PA28 6PZ, Scotlnd, UK.

2 Cod: The pros nd cons Cod frming hs gret potentil due to the decline in cpture fisheries nd the high mrket vlue of frmed cod. However, inconsistent egg nd lrvl qulity, coupled with poor survivl rtes, could limit the growth in production. Currently there is hevy relince on wild cught roodstock to mintin high levels of lrvl production. To provide future growth in the industry frmrered roodstock must e developed to provide consistently high egg nd lrvl qulity.

3 Cod: Egg nd lrvl qulity Essentil ftty cids (EFA) hve een linked with reproductive performnce in terms of fecundity, egg qulity, htch rte, numers of norml lrve nd incidence of deformity. Although provision of optiml 22:6n-3 (DHA) nd 2:5n-3 (EPA) re importnt supplementtion with 2:4n-6 (ARA) hs improved egg nd lrvl qulity in hliut, se ss nd Jpnese flounder. Wild cught cod tend to produce lrger, etter qulity eggs thn cptive roodstock. Is this linked to nutrition in generl nd ARA in prticulr?

4 Lipids nd ftty cids in wild, cptured nd frmed cod roodstocks (Slze et l. 25) E g g lip id c o n te n t (% w e t weight) nd rchidonic cid c o n te n t (% T F A ) in d iffe re n t roodstocks. 4 3 W ild W ild - c p tive Frmed 2 1 % to tl lip id A R A Broodstock origin C olum ns ssigned different letter re significntly different, (P <.5) E g g e i c o s p e n t e n o i c c i d ( % T F A ) n d E P A / A R A r t i o i n d i f f e r e n t r o o d s t o c k s. 2 W i ld W i ld - c p t i v e F r m e d 1 E P A E P A / A R A r t i o B r o o d s t o c k o r i g i n C o lu m n s s s i g n e d d i f f e r e n t le t t e r, w i t h i n e c h f t t y c i d, r e s i g n i f i c n t ly d i f f e r e n t, ( P <. 5 )

5 Experimentl roodstock nd husndry conditions Experimentl roodstock were second yer spwners of n F1 genertion derived from eggs otined in fish of initil weight 2.32 kg were plced in 4 circulr tnks of 4m dimeter nd 1.2m depth in Octoer 24. The sex rtio ws ~1:1 nd fish were fed the two experimentl diets, in duplicte, etween Dec 24 nd June 25 t.33% ody weight/dy. The experimentl diets were sed on 12 mm pellets of Ewos Mrine 15. The ws produced y coting with 11.4g/kg of Vevodr oil (DSM Food Specilities BV, Hollnd) to provide.6% ARA y dry weight. The control feed ws coted with similr quntity of fish oil.

6 Diet proximte nd ftty cid composition Component (%) Protein 5 5 Oil Totl sturtes Totl monoenes :4n :5n :6n :5n-3/2:4n

7 Fertilised egg production on dily sis in ech tnk (4.1 & 4.3, control; 4.2 & 4.4, Dily fertilised egg production y tnk Tnk 4.1 Tnk 4.2 Tnk 4.3 Tnk 4.4 no fertilised eggs /4/25 19/4/25 26/4/25 3/5/25 1/5/25 17/5/25 24/5/25 31/5/25 7/6/25 14/6/25 dte

8 Cumultive production of fertilised eggs Cumultive no of fertilised eggs ARA +ARA /4/25 14/4/25 16/4/25 18/4/25 2/4/25 22/4/25 24/4/25 26/4/25 28/4/25 3/4/25 2/5/25 4/5/25 6/5/25 8/5/25 1/5/25 12/5/25 14/5/25 16/5/25 18/5/25 2/5/25 22/5/25 24/5/25 26/5/25 28/5/25 3/5/25 1/6/25 3/6/25 5/6/25 7/6/25 9/6/25 11/6/25 13/6/25 15/6/25 17/6/25

9 Percentge of fertilised eggs surviving until dy 5 nd % htch in incutors survivl (dy 5) htching rte

10 Comprison of egg dimeter etween dietry tretments

11 Egg lipid (%) nd ARA content (% TFA) in control nd ARA tretments vs wild nd frmed eggs from Slze et l. (25).75.5 Wild Frmed Wild Frmed

12 Egg EPA/ARA nd DHA/EPA rtios in control nd ARA tretments vs wild nd frmed eggs from Slze et l. (25) d c Wild Frmed 3 2 Wild Frmed 1

13 Effect of diet on milt qulity nd ftty cid composition Effects of diet on milt qulity hve een much less studied thn egg qulity. In hliut, supplementing with.4% ARA produced more stle spermtocrit vlues nd extended milt production through the spwning period. In cod spermtocrit vlues were 56.3 ± 4.4% in control fish nd 66.7 ± 2.7% in ARA supplemented fish nd were not different. In cod there were no significnt differences in spermtozo motility durtion ut ARA supplemented sperm showed stronger motility following sewter ctivtion

14 ARA nd EPA content (% TFA) & EPA/ARA nd DHA/EPA rtios in milt ARA EPA EPA/ARA DHA/EPA Columns ssigned different letters re significntly different, P <.5).

15 Summry There were no differences etween tretments in egg viility in terms of survivl nd htching rte. However, survivl nd htching rtes were very low, in oth groups, compred to norml commercil production. Egg dimeter ws significntly greter in the ARA supplemented group. The ftty cid profile of the eggs ws closely relted to diet with ARA vlues nd EPA/ARA rtios eing similr to those seen in wild eggs fter feeding the tril diets for round 12 weeks efore spwning.

16 Summry continued No significnt differences were seen in milt qulity etween tretments, lthough this my hve een prtly due to smll smple sizes (n = 6). As with eggs, milt ftty cids were closely correlted to diet ftty cids with ARA significntly incresed nd EPA nd EPA/ARA rtio significntly reduced in fish fed the. Clerly improvements in egg nd lrvl qulity in frmed roodstock cnnot e chieved y ARA supplementtion lone. It is likely tht the poor qulity of eggs from frmed roodstock is linked to numer of fctors in ddition to nutrition. Future studies with ARA supplementtion re likely to focus on cptured wild stocks where roodstock qulity is currently more relile.

17 Acknowledgements Mchrihnish Mrine Frms Ltd for supply of experimentl roodstock. DSM Food Specilities for supplying the Vevodr oil for ARA supplementtion. Ewos Ltd for supply of sl feed.