Digestive tract health in Yellowtail Kingfish

Immerse yourself in research into the digestive tract health of yellowtail kingfish, fed diets with different energy level, with and without an emulsifier at winter water temperatures.

In fish, dietary energy is the second growth limiting factor, after dietary protein, which should ideally be satisfied by dietary lipids. Yellowtail Kingfish grow out diets previously containing 20% crude lipid (Stone and Bellgrove, 2013).

Based on recent research however, Stone et al. (2016) suggested that Yellowtail Kingfish may be fed a higher lipid (~30-35%) diet during summer water temperatures to improve growth.

Temperate water marine fish species, including Yellowtail Kingfish, may be less tolerant to high lipid diets when exposed to low water temperatures.

To improve lipid digestion and absorption in the gastrointestinal region of Yellowtail Kingfish, an emulsifier may be included in the diet. However, the effect of different energy levels (lipid levels) and emulsifiers on the digestive tract health of Yellowtail Kingfish is unknown.

Key methodology:

Investigating two factors (2 × 2):

• Factor one, emulsifier (no emulsifier and emulsifier)
• Factor two, lipid level (high [30%] and low [20%]).

Twenty fish will be measured, weighed and stocked into one of the three replicate 5000 L tanks treatment combination-1 (n = 4 treatments; n = 12 tanks). Tanks will be supplied with partial flow-through/recirculating (100% system water exchange d-1), sand filtered, UV treated sea water at ambient temperature.

Fish will be fed to apparent satiation at 9:00 h daily for a total of 84 days. At the conclusion of the study, the hind gut of fish will be sampled to investigate digestive tract health of Yellowtail Kingfish.

Funding for sample analysis is provided by SARDI. Samples will be collected from a larger industry funded project.