level protein and ammonia production

7/29/2019 Level Protein and Ammonia Production

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aquaculturalengineeringELSEVIER Aquacultural Engineering 16 (lYY7) 161-166

The influence of feed protein intake on tilapia ammoniaproduction

J.L. Brunty, R.A. Bucklin, J. Davi$, C.D. Baird, R.A. Nordstedt Agricultural und Biologicul Enginruri ng Drpartmmt , Uni w rsi~ o f Florida. Gai nrs~il lr . FL 3261 I. USA

72hnology Group. EPCOT Cent er: Luk e Bw na Vist a. FL 32830. U SA

Received 5 September 1996; accepted 8 November 1996

AbstractBiological filters designed to remove toxic amm onia excreted as fish wastes a re an integral

part of any recirculating aquac ultural system. The quantity of ammo nia excreted by fish isrelated to the quantity of nitrogen supplied by the protein contained in feed. Thisexperiment evaluated short term Total Amm onia Nitrogen (TAN ) production by juveniletilapia fed rations w ith six different protein contents. Five feeds composed using soybeanmea l as their protein source and one feed deriving most of its protein content from fishmeal were tested. Statistically significant increases (P~0.10 ) in TA N production wereobserved as protein content increased during the 24 h period following feeding. Fish mealand soybean meal did not produce statistically different TA N production rates. 0 lYY 7Elsevier Science B.V.ki~~orrls: Feed protein; Tilapia: Ammonia

1. IntroductionAquacu lture is becoming an increasingly important source of fish products as

harvests from natural waters decline worldw ide due to overfishing and pollution.Currently, most fish are grown in outdoor pond systems whe re w ater is divertedfrom a nearby lake or river for a single p ass through the pond system and thenreleased again to the environment. The quality and the quantity of water u sed arebecoming an increased concern and efforts are being made to develop production0 144~X609/97/$17.00 0 1997 Elsevier Science B.V. All rights reserved.P/I SOl44-X~O9(9h)OlOl9-9


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162 J. L. Brunty rt al .lA yuaculi ural Engineeri ng 16 (1997) 161-166

systems wherein the water is at least partly recycled. The quantity of nutrientsadded by fish wastes is a major concern when designing systems to reuse water.Total amm onia nitrogen (TAN) levels can be a limiting factor for the reuse ofwater because high levels can reduce fish vitality and/or growth or cause death inextreme cases. Protein in fish food is the primary source of nitrogen that isexcreted through fish gills as amm onium ions. Knowledge of protein utilizationrates w ill allow selection of the most econom ical feed m ix to minimize proteinwastes and reduce both costs and amm onia production. This study attempted toevaluate the relative levels of TAN produ ction that resulted from varied sourcesand levels of feed protein.

2. BackgroundProtein within the fish feed is the source of amm onia introduced into production

systems and higher levels of the nitrogen source should result in higher levels ofTAN production. However, different species of fish and fish at different life stageswithin the sam e species a re differentially able to utilize the protein in feed, an d therelationship between protein levels and TAN p roduction for all species and all lifestages may vary (Begum et al., 1994). Proteins are generally considered to contain16% N (Overton, 1993).

The reason for quantifying protein requirements is to develop the lowest costfeed that provides adequate or maxim um g rowth. Anima l sources of protein aretypically more expensive than plant sources (Wee and Shu, 1989). Fish meal istypically composed of 25-65% protein, while plant sources only contain 5-15%protein, therefore necessitating the use of fish meal as a protein base.

Speece (1973) observed that from 0.026 to 0.032 lb NH3-N was produced per lbof feed at temperatures from 49 to 62F (26 to 32 g of NH 3-N per k g of feed at9.4 to 16.7 C). Several studies (Khan et al., 1993; Tucker and Boyd, 1979; San-tiago and R eyes, 1991; Watanabe et al., 1993; Reigh and Ellis, 1992; Wu et al.,1994 have investigated the effects of feed source and protein content on thequantity of amm onia eventually released by the fish into production water, but didnot report amm onia levels in terms of feed protein content.

Studies relating amm onia levels to feed protein content are not in close agree-ment. Masser et al., 1992; Meade (1985); Mires and Amit (1990); Rychly (1980)and Wright (1993) report that fish excrete from 60 to 95% of feed nitrogen asammonia and that 1 kg of feed w ill produce 19.5 g of NHX -N and possibly as muchas 300 g NH4-N.

3. Materials and methodsThis study was conducted in the Structures and Environment Lab of the Agri-cultural an d Biological Engineering Department at the University of Florida overa 4 week period during the fall of 1994. Two grou ps of young hybrid tilapia were


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.I. L. Brmt y rt al .lA cpacult ural Engi nerr i ng 16 (1997) 161-166 163

Table IFeed composition

Feed

Factor

32%)proteinArkatMinnowMeal

34%proteinZieglerCichlidDiet

36%proteinArkatMinnowMeal

38%proteinZieglerTropicalFishFeed

42%proteinArkatMinnowMeal

55%proteinZieglerSalmonStarter

Crude proteinCrude fatCrude fiberProtein source

> 32?+>;3.5%5 0%Soybeanmeal

2 34%)2 696

Soybeanmeal

z 36% > 38%235% 2 10%55%Soybean Soybeanmeal meal

> 42%2 7%239;Soybeanmeal

> 5S%,2 15%< 2%Soybeanmeal

placed in two separate 37.9 L tanks, w ith 21 fish (160 g total weight) in Tank 1 and20 fish (99 g total w eight) in Tank 2. Fish were fed the feed type to be tested for24 to 48 h prior to the beginning of each feed test. The co mposition of the feedstested, as described on the manufacturers label for each feed, are listed in Table1.

Each group w as placed in a tank of fresh tapwater dechlorinated through the useof NovA qua Tapwater Conditioner and fed 2% of the overall average body weightto begin the test. The fish were then left in a lighted room overnight. Am mon iameasu rements were taken at four separate times the next day. At the end of theday, the fish were placed in another clean tank an d again fed 2% of the overallbody weight of the same feed and the process w as repeated. The fish were fed thenext feed type to be tested for l-2 days before the next feed test began. Am mon ialevels were measured using Nesslers Reagent and Hach Company Nessler Method(Hach, 1993) on a Milton Roy spectrometer. The method measured total amm onianitrogen (TAN) including both NH 3 and NH,+.

The relationship between amm onia production levels and the nitrogen contentsof the different fish feeds was statistically analyzed using the Regression Procedureof the SAS System (Statistical Ana lysis Systems Institute Inc., 1990). An analysis ofvariance was conducted using the General Linear M odels Procedure of SAS toevaluate time effects an d differences in dissolved oxygen, water temperature andwater pH . Differences at the 90% probability level or greater were considered tobe statistically significant.

4. ResultsWater temp eratures ranged between 24.0 and 25.2 C, with fluctuations occurring

at approximately the same time in both tank s. Dissolved oxygen levels throughout


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16 4 J. L. Brunty et al.lAquacultural Engineeri ng 16 (1997) 161-166

the study were above 5 ppm in both tanks w ith the exception of Day 1 of the 32%protein feed in Tank 2 when dissolved oxygen m easured 4.3 ppm . The fish grewfrom initial weights of 7.6 g per fish in Tank 1 and 4.9 g per fish in Tank 2 to finalweights of 11.1 g per fish in Tank 1 and 14.7 g per fish in Tank 2. No fish diedduring the study, a nd the final total weights w ere 233 g in Tank 1 and 294 g inTank 2. No statistically significant differences related to treatments were observedin pH. The average pH was 7.04 with a standard deviation of 0.12.

Resu lts of the regression of observed TAN versus nitrogen content of feedindicated that amm onia levels increased with significant (P ~0.10) linear trends asprotein levels increased. The linear increase in TAN p roduction as a function feednitrogen content (FEED-N) is expressed by Eq. 1 where TAN and FEED-N areexpressed in gram s per kilogram of feed. The coefficient of determination (?) forthis relationship is 0.68.

TAN = 0_604*FEED-N+3&3 (1)The experimental observations for all feed trials and the values predicted by eqn(1). are shown in Fig. 1. Statistical analysis determined that there was significant

MEAN TAN+/- ONE STANDA RDDEVIATION

TAN = 0.604*FEED-N 3.88

0

FEED-N, grams per kilogram of eedFig. 1. Observed TAN levels.


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J. L. Brunty et al .lA quacult urul Engineeri ng 16 (1997) 161-166 165

TableObserved TAN levels

Feed protein contentGrams of nitrogen per

kilogram of feedGrams of TAN measured

per kg of feed(SD)

32c7r 34% 36% 38% 424 5SCiSl.1 54.4 58.7 h@X 67.2 884

35.1 40.x 34.1 39.7 44.9 57.4

(1.1) (4.1) (2.1) (4.2) (24) (?4)

variability in TAN levels as a result of the various feed treatments. Table 2 lists thefeed N contents and the observed TAN levels.

5. DiscussionAm monia levels increased linearly as protein co ntent increased, without regard

to protein source. The coefficient of determination of 0.68 indicates that a linearmodel can explain 68% of the relationship between TAN a nd feed protein content.Am monia levels were expected to increase w ith feed protein content because thenitrogen content of feed increases as the feed protein content increases. Increasednitrogen content results in increased potential for amm onia formation because ofthe increased presence of the nitrogen atoms required to form amm onia. Increas-ing amm onia levels as a result of increased feed protein content agrees w ith thefindings of Wright (1993) Meade (1985), and Rychly (1980). Feed protein sourcehad no significant effect on amm onia production in this study. Am mon ia produc-tion from fish meal proteins were w ithin the limits of the linear m odel developedby the statistical analysis. The re sults m ay differ for long term feeding effectsbetween fish meal and soybean m eal proteins. Brunty (19 95) found tha t over an8-week period, the 40% Silver Cup an d 42% Arkat feeds used in this experimentresulted in significantly different TAN , pH, and nitrate levels. Because the proteinlevels in Brunty (199 5) were nearly equivalent, these differences were attributed tothe source of the protein content.Because the fish were fed a minim al percent of their body w eight (20/o), all ofthe feed was consumed. The average percentage of nitrogen excreted for all feedtypes was 66% comp ared with the value of 80% found by Mires an d Am it (1990).Nitrogen excretion levels observed in this study ranged from 34.2 to 57.4 g of TANper k g of feed compared to the values of 19 .5 g of NH3-N per k g of feed reportedby Meade ( 1985) and 2 6 to 32 g of NH3-N per kg of feed reported by Speece(1973). Many factors that may affect TAN production, such as temperature, salin-ity. alkalinity, fish species, dissolved oxygen, etc. were not considered in thisexperiment. These factors alone or in combination with other factors may cause adifferent protein content/TAN level relationship when the factors are differentfrom those found in this study.


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166 J. L. Brunt y et al.i Aquacul t ural Engi neeri ng 16 (1997) 161-166ReferencesBegum . N.N., Chakrabo rty, SC. and Zaher, M., 1994. Replacement of fishmeal by low-cost animal

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