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A limited survey of published reports on dietary nutrient requirement estimates for ®sh (three journals, 46 papers) indicates that broken-line analysis and analysis of variance (ANOVA ANOVA) are often used to estimate nutrient requirements from dose±response data. The application of regression models using published treatment mean values to re-evaluate estimates was possible using 33 of these reports. Re-evaluation suggests that the broken-line method and ANOVA ANOVA frequently underestimate the requirement. Regression produced estimates that averaged approximately twice, but were up to ®ve times the published requirement. Additional problems that prevented re-evaluation or produced errors in the original estimates were: failure to include nutrient levels high enough to produce a maximum response, failure to space nutrient input levels closely enough to adequately model the dose±response relationship, an apparent failure to screen data before analysis, and insucient model diagnosis. Examples from the literature are presented to illustrate how design, method of analysis and the choice of model aect the requirement estimate. The eects of measurement frequency and the experiment duration on the resulting requirement estimate are discussed. A set of protocols is presented to help improve nutrient requirement estimates.KEY WORDS analysis problems are shown and protocols for preventing these problems are presented. The approach taken is conceptual rather than computational, and references discussing pertinent topics in detail are provided to aid in rectifying speci®c problems.

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A pathological condition was induced in Atlantic salmon, Salmo salar L., by feeding a diet severely deficient in phosphorus. Parallel results were obtained in two consecutive experiments, one in fresh water and one in sea water. The deficiency condition was first manifest as a reduction in whole‐body calcium (Ca) and phosphorus (P) levels and the development of abnormally soft and malformed bones. In later stages, growth was severely impaired and there was elevated mortality compared with fish fed a diet with sufficient phosphorus. Two semipurified casein‐based test diets were used in the experiments. The low‐P diet contained only the P from casein, 3.5 g kg−1 or 0.35%, whereas the reference diet was supplemented with P and contained 9.0 g kg−1 or 0.9%, The diets were fed to salmon parr in fresh water (initial weight 4.7 g) and to post‐smolts in sea water (initial weight 113 g) for 12 and 15 weeks, respectively. In both experiments, the fish grew adequately for a prolonged period, whereas the whole‐body Ca and P levels declined almost immediately. Within a few weeks, the whole‐body P content was reduced to ≊ 65% of the initial value, and Ca to 40%. The reductions in mineral content were most severe in the mineral‐rich tissues, bones and scales. On gross examination, all bony structures were abnormally soft. The ribs were wrinkly, and the spine displayed scoliotic changes. These changes were correlated to the reduction in bone mineralization, and were manifest at the time when reductions in growth rate could be noted. After the deficient fish were fed adequate levels of P for 9 weeks, their whole‐body mineral levels returned to normal. The bone lesions did not heal completely during the same period of time.