Oils ain’t oils.

The ornamental fish keepers have been advocating avoiding the use of fats other than those that originate from fish and invertebrates in the diets of their fish. But in the food fish industry, this can be very expensive and so alternatives are being sought. The issue I have with this study is that the trial only goes for 5 weeks and the normal production for the kingfish would be in the vicinity of 2 years. Is growth the only parameter that we should be looking at? What about disease resistance?

Aquaculture
Volume 357, Number 3 (August 2012)
Replacement of fish oil by poultry oil and canola oil in yellowtail kingfish (Seriola lalandi) at optimal and suboptimal temperatures
Authors: J.N. Bowyer, J.G. Qin, R.P. Smullen, D.A.J. Stone
Author Affiliations:
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Source: Aquaculture, Volume 357, Number 3 (August 2012)
Page Numbers: 211 – 222
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Abstract: Fish oil has been replaced by alternative oils to reduce the cost of aquaculture diets, but fish growth may be compromised when fish are fed these oils at suboptimal temperatures. A 5-week feeding trial was conducted to examine the interactive effects of water temperature and the partial or total replacement of fish oil with poultry oil and canola oil on the performance of yellowtail kingfish (YTK, Seriola lalandi), in the early stages of the production cycle. Practical diets were identical in composition, except the dietary lipid component was supplemented with 100% lipid as either poultry oil (PO), canola oil (CO), a blend of fish oil and poultry oil (FO/PO; 50:50) or a blend of fish oil and canola oil (FO/CO; 50:50). A control diet was included and the dietary lipid component contained 100% fish oil (FO). Fish fed the CO diet at 18°C had inferior growth performance, feed efficiency and nutrient retention, and showed higher incidences of green liver and lower plasma cholesterol levels than those fed the other diets. Whole body proximate composition was influenced by water temperature, but not diet, except moisture content which was highest in fish fed CO. The fatty acid composition of fillet lipid correlated with the PO and CO inclusion, in that the proportions of 18:1n-9, 18:2n-6 and 18:3n-6 all increased with increasing dietary PO and CO. The concentrations of 20:5n-3, 22:6n-3 and 20:4n-6 in the fillet lipid were reduced with increasing contents of dietary PO and CO. Our results confirmed that 100% poultry oil and 50% canola oil can replace fish oil in diets without reducing growth, but 100% canola oil results in poor fish growth compared with the FO control, regardless of water temperature. These findings are useful in dietary formulation to reduce feed costs without compromising yellowtail kingfish growth.
Citation: J.N. Bowyer, J.G. Qin, R.P. Smullen, D.A.J. Stone . Replacement of fish oil by poultry oil and canola oil in yellowtail kingfish (Seriola lalandi) at optimal and suboptimal temperatures. Aquaculture, Volume 357, Number 3 (August 2012), pp. 211-222, <http://ejournals.ebsco.com/direct.asp?ArticleID=4F078538461BA51F37FC&gt;
URL: http://ejournals.ebsco.com/direct.asp?ArticleID=4F078538461BA51F37FC

Mental health check.

It’s that gloomy winter time again and we should be keeping ourselves well and looking out for our neighbours.

Check out these useful sites on mental health:

Australian Veterinary Association

Vetlife

Onelife

Reach Out for the youth.

 

Please share this information with your family, friends and colleagues.

Temperature changes should be gradual.

Following on from my last post about goldfish preferring the warmer water and people rushing out to buy a heater, I should add that any changes should be done gradually. See also attached, a page from my recently published book (orders can be made via my website – http://www.thefishvet.com.au) about temperature.

Geriatric goldfish needs this winter.

Very often people think of goldfish as cold water fish. They are in fact, subtropical fish that are tolerant of cold water for periods. The optimal water temperature for this species is in the vicinity of 22-24 degrees Celsius. So, if you find your goldfish are not coping so well this winter, you may introduce a heater and bring the water temperature up slowly at about 1-2 degrees Celsius per day until you reach the optimal temperature. If your fish’s health doesn’t improve, consult your fish vet.

Tips on choosing fresh healthy fish for the fork.

Check out my latest post on my Facebook Fanpage.

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Yours sincerely,

Dr Richmond Loh
BSc BVMS MPhil MANZCVS (Aq & Pathol)
The Fish Vet, Perth, Western Australia.
Veterinary Medicine for fish.
http://www.thefishvet.com.au
Ph: +61 (0)421 822 383

At first there was Aquavet…

AquaVet I and II completed, AquaVet III starts Monday 9th July, 2012 for the first time. This will have a marine mammal focus with hands on clinical experience.

Dr Loh will be consulting in Melbourne.

Dr Loh will be at Boronia Aquarium this Saturday, 7th July. Please call Boronia Aquarium to book an appointment.

Please note that the management subsidises Dr Loh’s professional fees significantly for their customers.