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 91
2.2. Chemical analysis and water stability tests
Proximate analysis of ingredients and diets were determined according to the
following procedures: crude proteinCP Ž Tecator, 1987 ., moisture ŽA.O.A.C., 1990, No.
929.36 ., ash Ž A.O.A.C., 1990, No. 942.05 ., lipid Ž Tecator, 1983.
and crude fiber
Ž A.O.A.C., 1990, No. 962.09 .. The gelatinization of starch that resulted from the
processing of the peas was measured as glucose released by digestion with amyloglucosidase
Ž Bjork et al., 1987 ..
Water stability tests, replicated five times per diet, were performed with synthetic
marine water at a salinity of 34‰ and temperature between 288C and 298C according to
the method of Aquacop Ž 1978 .. Five-gram samples of the pellets Žspaghetti-like strands,
1.6-mm diameter and approximately 1-cm length.
were gently shaken in wire-mesh
baskets submersed in seawater for 1 h, in order to simulate the conditions on the bottom
of the experimental tanks. The percent dry matter loss Ž %DML.
was calculated as:
%DMLs100= Ž DWdyDWwid.
rDWd; where DWd and DWwid are the dry matter
weights in the diet before and after immersion, respectively. The percent crude protein
loss Ž %CPL. was calculated as follows: %CPLsŽ100=CPdyŽ 100yDML . =
CPwid. rCPd; where CPd and CPwid are the crude protein concentrations Ž% of dry
matter.
in the diet and water immersed diet, respectively.
2.3. Growth trial
The growth trials and digestibility bioassays were conducted at the facilities of the
Programa Maricultura in Monterrey, using a closed recirculating system containing
synthetic marine water with a salinity of 34‰. The shrimp were held in 60-l fiberglass
culture tanks equipped with aeration and constant water temperature control at 288C.
The shrimp for the growth study were selected in a weight range between 200 and
310 mg and distributed, 10 per tank, in four replicated blocks of seven dietary
treatments. A similar weight distribution pattern in each tank was achieved by allotting
the shrimp according to their individual weight. Treatments were randomly assigned to
the tanks within each block. The shrimp were weighed again at 14 and 28 days to obtain
mean body weights for each tank.
Dry feed intake was determined by feeding to satiation. The shrimp were initially fed
a ration of 10% of biomassrday in two feedings daily at 10:00 and 17:00 h. The
following morning leftover feed, which could be readily identified by its swollen pellet
shape, was removed and quantified by estimating the amount in its original dry form,
and the ration adjusted accordingly to minimize the amount of uneaten feed.
The following response variables were determined for each experimental tank: mean
body weight; growth rate expressed as percent weight gain Ž %WG. s100= Žinitial
weightyfinal weight. rŽ initial weight .; dry food intake per shrimp Ž DFI.
was estimated
Ž .
28
from the sum of average daily food intake for each tank DFI sÝ wŽ
is1 intake on ith
day. rŽ number of shrimp on ith day .x; food conversion ratio Ž FCR. sŽfood intake per
shrimp. rŽ average weight gain per shrimp .; protein efficiency ratio Ž PER. sŽweight