AHPS weeks 9 and 10 Flashcards
(36 cards)
What are the three factors that mean FCE in fish can be close to 1?
- don’t thermoregulate (poikilotherms)
- ammonia secretion via the gills is more effective
- don’t support their bodies against gravity
At what stage of development are salmon transferred to salt water? What is an indicator that they are ready for this to happen?
Smolt
- they turn silver
Would test a group in saline water first anyway to be sure
How old are salmon when they are usually harvested for meat? How heavy?
2 - 2.5 years, 4 - 4.5 kg
What is the optimum temperature range for Atlantic salmon?
15.9 degrees - 17.5 degrees
Problems arise above 18
What is the optimum temperature range for
ocean trout?
10 - 22 degrees C
What is the optimum temperature range for yellowtail kingfish?
22 degrees C
What is the optimum temperature range for Southern bluefin tuna?
19 - 21 degrees C
What is the optimum temperature range for Barramundi?
26 - 28 degrees C
Do barramundi require salt or fresh water?
Both - young in salt, mature in fresh
What effect can non-optimal water temperatures have?
Reduce fertility
Increase susceptibility to disease
What determines water ‘quality’? Does this vary with temperature?
Amount of dissolved O2 - warmer water holds less oxygen
What is desirable level of O2 dissolved in water? What happens if this is too low?
75 - 80%
Fish can vomit
How much protein does a growing salmonid require? Is there a limiting amino acid?
400g/kg
Yes - lysine
Why include CHO in salmonid feed?
Acts as an alternative energy source which spares dietary protein for muscle growth
What management strategy is used to ensure salmon availability year round?
Manipulate the photoperiod in smolts
What are two advantages of total destocking?
Low supp feed cost
Good preservation of pasture and soil
What are three disadvantages of total destocking?
Lose genetic progress
High cost to buy more stock after drought
Risk introduction of disease with new stock
What are two disadvantages of partial destocking?
High cost supp feed
Damage to pasture (unless use SCA)
What stock would you sell if partial destock?
Less productive stock
- wethers in merino system
- old cows in dairy or beef system
What roughage percent should be provided when feeding grain ration?
20%
What health concerns do you need to address when feeding a grain-based ration to your SCA stock?
Ca:P ratio - grain is high in P, so add 1.5% CaCO3 to feed to balance
Vitamin E deficiency - comes from green feed - supplement stock every 6 weeks
How many MJ ME per DSE per day is recommended for maintenance during a drought?
5 MJ ME / DSE
How much bare ground needs to be exposed before risk of soil erosion is high?
20 - 30%
What is the stocking rate of a SCA?
1000 sheep/0.5Ha
