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Mortality rates of wild spiny lobster seed Panulirus ornatus are typically high, with losses of 40–60% occurring within 30 days of capture. Mortality appears symptomatic of a micro-nutrient deficiency or captivity related stressors. Cholesterol is a micro-nutrient essential for healthy ecdysis, growth and survival in crustaceans. This paper reports a 7-week study examining the growth, survival and tissue cholesterol responses of juvenile P. ornatus lobsters fed a low cholesterol basal diet that was serially supplemented with cholesterol at 0.75 g kg − 1 increments from 1.25 to 4.25 g kg − 1 dry matter (DM). The basal diet contained 45 g kg − 1 phospholipid (from natural ingredients and supplemented soybean lecithin) and this was fed to all lobsters for 2 weeks prior to commencement of the experiment to reduce cholesterol reserves in the lobsters. A sixth diet comprising equal amounts of green-lipped mussel ( Perna canaliculus ) and whiting fillet ( Silago ciliate ) was included in the treatment array as a reference diet. One hundred and fifty lobsters were blocked by initial weight into five groups and then from within these groups they were equally distributed to 30 tanks (n = 5 tanks per treatment). There was no significant difference in survival, daily growth coefficient or tissue dry matter cholesterol content between lobsters fed the lowest and highest cholesterol diets: 55%, 349%, 243 mg 100 g − 1 and 70%, 456%, 253 mg 100 g − 1 respectively. However, there was a trend (P = 0.065) for lobster percentage weight gain to increase linearly with dietary cholesterol. There was a significant relationship between the starting weight of the lobsters and subsequent survival, with only 43% of the smallest lobsters (0.2 to 0.5 g block) surviving compared to 90% for the largest lobsters (2.71 to 3.40 g block). No specific dietary cholesterol requirement for small P. ornatus was determined. Feeds which contain practical marine proteins require no supplementary cholesterol, a significant cost saving in feed formulation. Feeds which contain high levels of plant proteins may require supplementary cholesterol to provide at least 4.0 g kg − 1 DM dietary cholesterol.

In recent years, new cultivars of lupins have largely replaced the cultivars that were studied in previous research with shrimp. There was a need to establish if the breeding programs had introduced changes in the new lupin cultivars that would affect the nutritional value of the kernel meal for shrimp. We have determined the apparent dry matter digestibility (ADMD), apparent crude protein digestibility (ACPD) and apparent digestibility of energy (ADE) of the yellow lupin Lupinus luteus cv. Wodjil, as well as of six of the new cultivars of Lupinus angustifolius when used in diets for the black tiger shrimp, Penaeus monodon . The L. angustifolius cultivars represent about 80% of Australia's lupin production. We have also determined the apparent digestibility (AD) of the amino acids of five of the new cultivars of L. angustifolius, and of L. luteus , cv. Wodjil. Ytterbium acetate was used as an inert digestibility marker at a concentration of 0.5 g kg − 1 in the diets. During the periods when faeces were collected, the shrimp were fed every 6 h and faeces were collected within 3 h of being passed. Six replicate tanks were assigned to each treatment. The kernel meal from L. luteus cv. Wodjil had the highest ADMD (70.0%) and ADE (79.9%) but its ACPD was mid-range at 93.8%. The ADMD of the L. angustifolius kernel meals varied between 56.5% and 66.3% with the mean (± s.e.m.) of 62.6% (± 0.95%), and the ADE varied between 69.6% and 77.2% (mean ± s.e.m. = 74.0% ± 0.72%), whereas the ACPD varied between 92.7% and 96.8% (mean ± s.e.m. = 94.3% ± 0.48%). The AD of the amino acids was similar to the ACPD value. Though there were significant differences among the ADs of the new cultivars of L. angustifolius , their values are similar to, though slightly lower than the AD reported for the older cultivar, Gungurru. The general consistency of the L. angustifolius AD results suggests that nutritionists and feed formulators can confidently use mean AD values for dry matter, protein and energy for kernel meals comprising of random mixtures of cultivars.

The essentiality of marine invertebrate meals in diets for marine shrimp is unresolved. Three experiments were carried out with juvenile Penaeus monodon of 3–6 g initial weight to address this issue. In a 6-week growth experiment, shrimp head meal (SHM) or whole dried krill Euphausia spp. were included in a basal diet at 5% increments from 0 to 15% without altering the gross nutritional specification of the diet and fed to five tank replicates of shrimp. Shrimp daily growth coefficient (DGC) improved curvilinearly (P 3.5 kDa or