Postprandial nutrient dynamics and their implications for formulated feed development for the ornate spiny lobster (Panulirus ornatus)

Crustacean feeding morphology and postprandial nutrient processing is a highly size-selective procedure. The digestive system of lobsters is predicated on grinding feed to a fine particle size before digestion. Therefore, fine pregrinding of raw materials may bypass the need for extensive grinding in the proventriculus and expedite digestive and absorptive processes. Panulirus ornatus juveniles (N = 56) were allocated to four feed groups (n = 14). Groups A, B and C were fed nutritionally identical feeds featuring raw materials ground to 1000 µm (Feed A), 500 µm (Feed B) and 200 µm (Feed C) while the fourth group (Group S) acted as a 24-h nonfeeding baseline control group. Sequential postprandial haemolymph extractions were performed at 0.5, 1, 1.5, 2, 3.5, 5.5 and 24 h across treatment groups. Haemolymph samples were assessed and analysed for brix (%), total proteins (g L^–1), glucose (mmol L^–1) and cholesterol (mmol L^–1). Brix was found to have significant positive correlations with all the haemolymph biochemical properties while no significant correlations were identified between individual lobster size and haemolymph properties. Analysis of deviance applied to mixed effects models did not identify significant differences in haemolymph properties across feed groups. Trends identified here are indicative of diurnal rhythm patterns, likely orchestrated by the release of the crustacean hyperglycaemic hormone (CHH) when anticipating a meal. Additionally, the use of brix values, may not be optimal for identifying postprandial trends, yet could remain a valid indicator of longer-term nutritional status.