Interactive Effects of Temperature and Dietary Carbohydrate to Lipid Ratios Supplemented With Star Anise Oil (Illicium verum) on the Growth and Organosomatic Indices of Marron (Cherax cainii Austin and Ryan, 2002)

A 90-day nutritional trial was conducted to evaluate the effect of two dietary carbohydrate to lipid ratios and an attractant, star anise oil (Illicium verum), on marron (Cherax cainii Austin and Ryan, 2002) growth and organosomatic indices at 18 and 22°C under laboratory conditions. Three isonitrogenous diets were formulated, with two different carbohydrate to lipid (CHO:L) ratios, each with a crude protein level of 35%: D1 (CHO:L of 3.32), D2 (CHO:L of 3.22 + star anise oil), and D3 (CHO:L of 5.77 + star anise oil). Protein sources were also adjusted in D3 to allow for the higher carbohydrate content. Marron were held in cages to prevent cannibalism and to allow for individual feeding. The marron cultured at 22°C and fed D1 produced the highest specific growth rate (SGR), weight gain (WG), lowest molt intervals (MIns), and the lowest feed conversion ratios (FCRs). At 18°C, the highest molt frequency (MF) was in marron fed D1. The apparent feed consumption was highest at 22°C, and was unaffected by any diet. The total meat yield of marron was higher at 22°C when fed D3. The condition factor (CF) and organosomatic indices were unaffected by the diet, except the tail muscle moisture content (TM%) which was highest in marron fed D3 at 22°C. The supplementation of star anise oil did not increase the ingestion rate, and therefore, did not increase growth rates under laboratory conditions. Furthermore, a dietary carbohydrate to lipid ratio of 3.32 produced the highest growth rate of juvenile marron at 22°C, whereas there was no significant effect of diet on the growth rates at 18°C.