Digestibility of lupin kernel meals in feeds for the black tiger shrimp, Penaeus monodon

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 (ADNID), apparent crude protein digestibility (ACPD) and apparent digestibility of energy (ADE) of the yellow lupin Lupinus litteus cv. Wodjil, as well as of six of the new cultivars of Lupinits angustifolizis 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. litteus 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. angustifolitis, 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.