Peas (Pisum sativum) are one of the four most important crops next to soybean, groundnut, and beans. It is a particularly important legume

in temperate areas with numerous food (dry seed, vegetable) and feed (seed, fodder) usages.

Field peas have attracted con-siderable attention as an animal feed due to increased produc-tion in Europe and Canada and thus reliable supply and com-petitive price. Peaseed meal has been trialed in Atlantic salmon, Rainbow trout and European sea bass with encouraging results.

Peas, when unprocessed, con-tain moderate levels of protein 22-25 percent but also several anti-nutritional factors (ANF); however, the levels of ANFs in peas are low compared with other legumes and peas did not induce enteritis in the distal intes-tine in Atlantic salmon as seen when feeding soybean meal.

New feed processing tech-nologies have provided more suitable products for use in high protein aquafeeds. Pea protein concentrate (PPC) is produced by fine grinding dehulled peas into pea flour, followed by air processing which separates the particles based on differences in size and density. The resulting concentrate has higher protein and lower carbohydrate and

ANF contents compared with unprocessed peas, and thus would be a promising protein source in aquaculture feeds.

The following study examined the efficacy and nutritional properties of peaseed protein concentrate as an alternative feed ingredi-

ent and protein source for all-male tilapia (Oreochromis niloticus) culture incorporating growth and digestibility trials.

Fish and rearing conditions Genetically male Nile tilapia (GMT) were

sourced as fry from Fishgen Ltd and raised at the Centre for Sustainable Aquaculture Research at Swansea University until they reached the appropriate sizes to be used in the trials. Fish were cultured indoors as part of a freshwater recirculation sys-tem, which included mechani-cal and bio-filtration units, a protein skimmer and a sand filter. Water temperature was kept at 27°C and pho-toperiod was set at 12 hours of light daily. Temperature and dissolved oxygen levels were measured daily, while total ammonia nitrogen, nitrite, nitrate and pH were measured weekly to assure optimum water quality.

Feed preparation Feeds were prepared

according to Table 1 by mix-ing the dry ingredients with a binder and water, extruded through a meat grinder and afterwards dried at 450C for 24 hrs. The resulting pellets had a diameter of 2.5mm and 3.5mm for growth and digest-

Pea Seed protein concentrate in Tilapia feeds

Table 1: Apparent digestibility coefficients (%) of fish meal and pea seed protein as determined in tilapia

Dry matter %

Protein%

Organic Matter%

Energy%

Fish meal* 72.1 ± 0.2 89.5 ± 0.2 82.7 ± 0.3 83.7 ± 0.4

Pea seed concentrate** 73.2 ± 0.1 88.4 ± 1.8 79.3 ± 2.2 80.3 ± 2.3

Table 2: Formulation and composition of experimental feeds (per kg as fed)

Ingredients Fishmeal 30% PPC 60% PPC 100% PPC

Formulation

Fish meal 605 410 210 -

Pea seed concentrate - 165 340 520

Corn Starch 325 340 320 310

Vegetable Oil 40 45 50 55

Vitamin &Mineral 5 5 5 5

Di-calcium- Phosphate - - 25 55

Calcium carbonate - - 25 55

Alginate 25 25 25 25

Composition

Dry matter, g 927 905 903 910

Ash, g 133 98.7 92.9 88.8

Lipid, g 86.6 85.6 84.9 83.6

Crude Protein, g 393 390 393 397

Gross Energy, MJ 17.90 18.00 18.08 18.32

Digestible Protein*, g 352 348 349 351

Digestible Energy*, MJ 14.79 14.76 14.67 14.82

DP/DE ratio g/MJ 23.8 23.5 23.8 23.7

* Incorporating results from digestibility trial

by Josh Cantril, Centre for Sustainable Aquaculture Research, Swansea University, Swansea, UK and Ingrid Lupatsch, Aqua Nutrition Manager, AB Agri Ltd

12 | INTERNATIONAL AQUAFEED | September-October 2015

FEATURE

ibility trial respectively and were stable up to 24 hours in water.

Sample preparation and chemical analyses

At the start of the growth trial samples of about 10 fish were taken and at the end 10 fish from each tank were sacrificed and blended to create homogenous samples. Sub-samples for estimation of dry matter were taken before the remaining homogenate was

oven-dried. The dried samples were once more mixed in a blender before all remaining analyses.

Identical analyses were applied for diets, faecal matter and body homogenates. Crude protein was measured using the Kjeldahl tech-nique and multiplying N by 6.25. Ash was cal-culated from the weight loss after incineration of the samples for 12h at 5500C in a muffle furnace. Gross energy content was measured by combustion in a Parr bomb calorimeter

using benzoic acid as the standard. Chromic oxide was estimated by wet digestion.

Feed and faeces containing Cr2O3 were digested in a mixture of perchloric acid, con-centrated sulphuric acid and Na-molybdate. The resulting dichromate was determined at 360 nm against Cr2O7 standard solutions.

Digestibility trial Digestibility of the pea seed protein con-

centrate was assessed by adding chromic oxide, an 0.8 percent inclusion, as the indi-gestible marker to the feed and collecting the faecal matter by siphoning. By assessing the ratio of marker to energy or nutrient in the feed compared to their ratio in faecal matter, digestibility of the nutrients can be established. Fishmeal was used as the reference ingredient and the test diet was mixed at a ratio of 50 percent fishmeal and 50 percent pea seed protein. Fifteen tilapia, weighing on average 400g, were stocked in 300L tanks to supply two replicates per treatment. Faecal matter from a given tank was pooled over the trial period until sufficient material was collected for subsequent analyses. Digestibility of ingre-dients were calculated using well established equations and are presented in Table 1.

Growth trialFour experimental diets were formulated

Table 3: Performance parameters of tilapia after 35 days of growth at 27oC (mean ± SD)

Treatment Fishmeal 30% PPC 60% PPC 100% PPC

Initial weight (g) 32.2 ± 1.0 32.5 ± 0.6 32.7 ± 1.2 33.4 ± 0.6

Final weight (g) 97.8 ± 2.2 105.7 ± 1.0 100.9 ± 4.1 65.7 ± 3.2

Weight gain g/fish/day 1.88 ± 0.03 2.09 ± 0.01 1.95 ± 0.08 0.92 ± 0.07

Feed intake g/fish/day 2.06 ± 0.05 2.23 ± 0.12 2.09 ± 0.06 1.07 ± 0.02

FCR 1.10 ± 0.05 1.06 ± 0.06 1.07 ± 0.02 1.16 ± 0.08

Survival (%) 97 ± 4 100 ± 0 97 ± 4 82 ± 8

Table 4: Composition of tilapia per g live weight (mean ± SD)

Initial Fishmeal 30% PPC 60% PPC 100% PPC

Dry Matter, mg 230 248 ± 0.7 274 ± 0.4 266 ± 1.2 247 ± 0.2

Crude Protein, mg 127 139 ± 0.4 150 ± 4.0 149 ± 12.1 133 ± 2.1

Lipid, mg 43.1 65.3 ± 4.0 80.9 ± 1.0 77.0 ± 1.0 63.7 ± 0.4

Ash, mg 59.2 43.6 ± 2.4 43.2 ± 0.8 40.1 ± 1.1 50.4 ± 0.8

Gross Energy, kJ 4.52 5.59 ± 0.18 6.63 ± 0.24 6.37 ± 0.37 5.29 ± 0.0

September-October 2015 | INTERNATIONAL AQUAFEED | 13

FEATURE

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to contain 40 percent protein and nine percent lipid and to gradually include pea seed concentrate at the expense of fishmeal (Table 2). Seventeen tilapia of 35g initial size were stocked in 150L tanks provid-ing two replicates per treat-ment. The trial lasted 35 days and fish were fed manually to apparent satiation up to 4 times daily. Any uneaten pel-lets were collected at the end of the day and accounted for.

Thus feed intake was quantified and evaluated in relation to growth response. Through comparative body composition of fish carcass the relationship between dietary protein and energy intake and pro-tein and energy deposition was assessed, which allowed estimation of the utilisation efficiency of the feeds.

Results and DiscussionComparison of growth performance

among fish showed no difference when PPC supplied up to 60 percent of the protein in the diet. But growth obviously deteriorated in tilapia fed the 100 percent

pea seed diet compared to the other three feeds. Survival was also slightly reduced (Table 3).

Despite the poorer growth performance, results in Table 3 indicate that FCR was not different among the treatments (Table 3). Furthermore a trend can be inferred that fish performance improved with the inclusion of the pea seed concentrate. This differ-ence was not proven to be significant, but nevertheless higher weight gain, improved FCR (Table 3) and increased energy content (Table 4) can be described which ultimately resulted in improved energy and protein

retention efficiencies (Table 5).

The reduced weight gain was thought to be correlated with reduced feed intake in fish fed the 100 percent pea seed feed as indicated in Table 3.

Conclusions Tilapia performed on

feeds with pea seed pro-tein of up to 35 percent dietary inclusion very well. At this level - equiv-alent to 65 percent of

fishmeal protein replacement - performance of tilapia was equivalent to fish when fed the all fishmeal feed.

The reduced growth of tilapia fed the 100 percent pea seed feed was mainly due to decreased feed intake and palatability might have been an issue. No significant differences were found with regards to FCR, energy and protein retention efficiency values. This fact supports the notion that whichever pro-tein source the fish consumed they utilised equally well.

References available on request

Table 5 : Energy and protein retention efficiency (mean ± SD) in tilapia fed pea seed meal at increasing inclusion levels.

Fishmeal 30% PPC 60% PPC 100% PPC

Digestible Energy intake (kJ / fish /day)

30.5 ± 0.8 32.9 ± 1.7 30.7 ± 0.9 15.9 ± 0.2

Energy gained(kJ / fish /day)

11.5 ± 0.3 15.8 ± 0.6 14.1 ± 1.7 5.6 ± 0.3

Digestible Energy retention efficiency (%)

37.7 ± 0.0 47.2 ± 0.7 46.0 ± 4.2 35.4 ±1.5

Digestible Protein intake(g / fish /day)

0.73 ± 0.02 0.77 ± 0.04 0.73 ± 0.02 0.38 ± 0.01

Protein gained(g / fish /day)

0.27 ± 0.00 0.34 ± 0.01 0.31 ± 0.05 0.13 ±0.01

Digestible Protein retention efficiency (%)

37.5 ± 1.5 43.4 ± 1.0 42.7 ± 5.4 34.4 ±1.0

14 | INTERNATIONAL AQUAFEED | September-October 2015

FEATURE

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