Animal Feed Science and Technology 107 (2003) 117–128 Evaluation of the variability in chemical composition and digestibility of different lupin (Lupinus angustifolius) kernel meals when fed to rainbow trout (Oncorhynchus mykiss) Brett Glencross a,∗ , John Curnow a , Wayne Hawkins b a Mariculture Research and Advisory Group, Research Division, Department of Fisheries, P.O. Box 20, North Beach, WA 6020, Australia b Pulses and Oilseeds Program, Department of Agriculture, Baron Hay Court, South Perth, WA 6150, Australia Received 13 December 2001; received in revised form 18 February 2003; accepted 18 February 2003 Abstract The study examined the influence of variability in the chemical composition of lupin (Lupinus angustifolius) kernel meals on their digestibility when fed to rainbow trout. A range of lupin kernel meals were included into separate diets fed to rainbow trout and the feces collected by stripping. Comparison of the composition of feed and feces was undertaken to assess the extent of nutri- ent and energy digestibility. There was a strong correlation between protein content of a lupin kernel meal and the digestibility of that protein. Notably, the strongest correlation was that be- tween kernel meal protein content and nitrogen digestibility (y = 0.001(±0.00007)x - 0.473, R 2 = 0.981, P = 0.0011). The identification of this relationship allowed the calculation of equations to predict the digestible protein content of lupin kernel meals based on their crude protein content (y = 1.202(±0.032)x - 149.118, R 2 = 0.998, P = 0.00004). The strong correlation between kernel meal protein content and its nitrogen digestibility had a direct ef- fect on the relationship with energy digestibility. Notably, the kernel meal protein content had more influence on its energy digestibility (y = 0.002(±0.000314)x - 0.274, R 2 = 0.927, P = 0.0086) than that of the nitrogen digestibility. This is likely to be related to the relatively large contribution that protein makes to the dietary energy content of the lupin kernel meal relative to that of the carbohydrate content. The demonstrated relationship, between lupin kernel meal ∗ Corresponding author. Tel.: +61-8-9239-8103; fax: +61-8-9239-8105. E-mail address: bglencross@fish.wa.gov.au (B. Glencross). 0377-8401/03/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0377-8401(03)00067-1