Processed feed pea and canola meal for blue shrimp diets

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L.E. Cruz-Suarez et al.rAquaculture 196 2001 87–104 99
3.4. Analysis of the effects of dehulling and extrusion
Factorial ANOVA of the results for diets 1, 2, 3 and 4 showed that the effects from
extrusion were generally higher than from dehulling. No significant effects on performance
were observed as a result of dehulling, although a higher feed consumption and
lower PER approached significance Ž Ps0.121 and Ps0.073, respectively ..
Extrusion reduced feed intake Ž P-0.001 ., improved feed conversion Ž Ps0.009 .,
increased PER Ž Ps0.006.
and tended to improve dry matter digestibility of peas
Ž Ps0.192 .. Extrusion had no effect on growth Ž Ps0.44 ., survival Ž Ps1.
and protein
digestibility Ž Ps0.751 .. These results again can be explained by improved digestibility
of gelatinized over native starch.
4. Discussion
The impact of dry matter and protein losses due to leaching before ingestion has been
evaluated through the calculation of corrected values, which take into account the losses
that occurred in the diets after 1 h. This simple correction seems justified by considering
that most of the losses occur during the first hour of immersion ŽRomero-Alvarez,
1995 ., and that the average interval time of feed consumed was generally noted to be
approximately 1 h after offering the feed. Corrected values showed the same relative
positions as standard values, even in the case of the WEX treatment, which stability in
water was significantly better than that of other diets. The corrected values are of
interest because they indicate the true biological values of feed intake, conversion ratio
and PER as a more accurate measurement of the crustacean’s metabolic response to the
dietary treatments. They also allowed a truer estimation of the carbohydrate digestibility
of the experimental ingredients. The uncorrected values on the other hand reflect the
results of a practical significance, which can be compared with other studies using
standard calculations.
The results of this study show that raw peas, and peas processed by dehulling,
extruding and micronizing, have a nutritional value similar to that of a mixture Ž 1:3.
of
soybean meal and wheat flour Ž 80% hard–20% soft varieties, Table 2.
in shrimp diets.
Also, substituting a portion of the soybean meal, fish meal and wheat Ž1:2:3 parts,
respectively.
with extruded canola meal did not affect shrimp performance. Our results
corroborate the reports by other authors cited in the introduction that pea seed meal and
canola meal can be successfully included in practical aquaculture feeds. When alternate
plant origin ingredients are used in diets containing the same concentration of digestible
energy and digestible protein, and meeting nutrient requirements, similar performance
can be expected. However, Gomes et al. Ž 1995.
found that voluntary food intake of trout
fed diets including coextruded peas and canola was depressed due to inherent factors
present in the plant ingredients Ž Novoa and Castillo, 1998 .. Therefore, similar growth
was not obtained. In the present study, no adverse response to raw whole peas was
observed. Studies with trout Ž Kaushik et al., 1993. and European sea bass ŽGouveia and
Davies, 2000.
have emphasized the requirement for dehulling and extrusion cooking
under conditions that would be more severe than they would during complete feed