Fish production

This invention is directed to the use of the compound ractopamine for improved production of fish.

BACKGROUND OF THE INVENTION 
Extensive fishing of natural waters has lead to a reduction in fish 
numbers. It is now recognized that fishing at a rate to sustain natural 
populations will not provide the world's needs for fish as a food. This 
has lead to the development of the aquaculture industry, in which fish and 
other aquatic species are produced in controlled bodies of water. Fish is, 
worldwide, the single biggest source of protein, and aquaculture is 
therefore an increasingly important means of producing food. Furthermore, 
since the fish are in a controlled body of water, means are being sought 
to control disease and maximize production. The present invention provides 
a new technique for improved fish production. 
BRIEF SUMMARY OF THE INVENTION 
The present invention is directed to a method for improved fish production, 
comprising the step of administering an effective amount of the compound 
ractopamine or a physiologically acceptable salt thereof. 
Ractopamine is the USAN name for the compound 
4-hydroxy-.alpha.-(((3-(4-hydroxyphenyl)-1-methylpropyl)amino)methyl)benze 
nemethanol, having the following structural formula: 
##STR1## 
Ractopamine is prepared by art procedures, see U.S. Pat. No. 4,690,951, 
which is incorporated herein by reference. In the present invention, it 
can be used as such or as a physiologically acceptable salt thereof, 
preferably the hydrochloride. The compound has two asymmetric carbon 
atoms. The R,R isomer is the most active but other isomers are also active 
and resolution is not necessary. Most preferably, a mixture of optical 
isomers is used. 
The use of ractopamine in fish production leads to numerous improvements, 
though not all such improvements will be obtained in every embodiment of 
the invention. In many instances, the practice of the present invention 
results in an improved growth rate and/or higher feed efficiency. The 
invention can also be used to reduce the percentage of fat in fish. The 
practice of the invention can also lead to improved flavor or texture, and 
other benefits. 
By "fish" is meant any member of the Phylum Chordata, Sub Phylum 
Vertebrata, and Super Class Pisces. The present invention can be practiced 
with any of the considerable variety of fish species. Representative 
species include the following: 
Catfish 
Channel Catfish (Ictalurus punctatus) 
Black Bullhead (Ictalurus melas) 
Yellow Bullhead (Ictalurus natalis) 
Brown Bullhead (Ictalurus nebulosus) 
Carp (Cyprinus carpio) 
Crucian Carp (Carassius carassius) 
Trout 
Rainbow (formerly called Salmo gairdneri, now called Oncorhynchus mykiss) 
Brown (Salmo trutta) 
Speckled brook (Salvelinus fontinalis) 
Salmon 
Atlantic (Salmo salar) 
Coho (Oncorhynchus kisutch) 
Chinook or King Salmon (Onorhynchus tshawytscha) 
Tench (Tinca tinca) 
Roach (Rutilus rutilus) 
Pike (Esox lucius) 
Pike-Perch (Lucioperca Iucioperca) 
Dover Sole 
Turbot 
Yellowtail (Seriola quinqueradiata) 
Bass 
Smallmouth (Micropterus dolomieui) 
Largemouth (Micropterus salmoides) 
Striped (Morone saxatilis) 
Milkfish (Chanos chanos) 
Tilapia (Sarotherodon sp.) 
Tilapia (Tilapia sp.) 
Gray Mullet (Mugil cephalus) 
Eels 
American (Anguilla rostrata) 
European (Anguilla anguilla) 
Japanese (Anguilla japonicus) 
Yet other species with which the present invention can be practiced will be 
apparent to those skilled in the art. 
In aquaculture, a practical mode of delivering a substance is in the feed. 
Indeed, fish feeds are a standard article of commerce, often tailored for 
an individual species. Typically, the feed is in the form of small 
pellets. Therefore, in practicing the present invention, while other 
routes of delivery can be employed, the preferred method of delivery is in 
a nutritionally balanced complete fish food. The ractopamine or 
physiologically acceptable salt is dispersed in the fish food by known 
techniques. 
The amount of ractopamine or salt to be employed will vary with the 
specific improvement desired, the fish species, the age of the fish, and 
other factors known to those in the field of aquaculture. In general, a 
concentration in the fish food of from 1 to 100 ppm will provide good 
results. In many instances, concentrations in the range of 5-20 ppm will 
suffice.

The invention is illustrated by the following examples. 
Experiment 1 
Ractopamine hydrochloride in Catfish 
Full-sibling, year-2 channel catfish fingerlings averaging 91 g were 
stocked into nine 1-m.sup.3 circular raceways with continuously-flowing (6 
L/min) water supplied from an earthen reservoir. The fish were stocked at 
the rate of 50 fish per raceway and all fish were fed a high perfomance 
feed (36% crude protein, 3.2 kcal digestible energy/g) (Table 1) for 5 
weeks until the fish reached an average weight of 156 g. At this time, the 
raceways were randomly assigned to three experimental groups; one group 
continued to receive the control feed and the other groups were fed the 
control feed supplemented with 20 or 100 ppm of ractopamine. The feeds 
were prepared by regrinding the ingredients through a 2-mm diameter 
screen, mixing, and processing into 6 mm-diameter pellets with a 
laboratory pellet mill. The fish were fed the experimental diets to 
satiation two times daily, at 0900 and 1800 hours, for 4 weeks, then 
weighed and fed for an additional 2 weeks. At the end of the feeding 
period, 10 fish were randomly sampled from each raceway for measurement of 
dressing yield, mesenteric fat, and muscle composition. Minimum and 
maximum daily water temperatures during the first 4 weeks of the 
experiment averaged 29.degree. and 31.degree. C. and during the last 2 
weeks averaged 24.degree. and 26.degree. C. 
Analytical Procedures 
Skin, head and viscera were removed from each of the sampled fish and 
dressing yield (dressed weight as a percentage of whole fish weight) was 
determined. Mesenteric fat was separated from other viscera and weighed. 
Muscle from one side of each fish was removed for analysis of crude 
protein (Kjeldahl procedure), crude fat [Gerber procedure as described in 
Association of Official Analytical Chemists. (1984). Official methods of 
analysis. 14th edition. Arlington, Va.] and moisture. Differences among 
treatments in weight gain (4 weeks and 6 weeks), dressing yield, 
mesenteric fat, and muscle composition were tested by one-way analysis of 
variance and selected treatment comparisons (ractopamine versus control, 
high ractopamine versus low ractopamine) were made [Steel, R. G. & Torrie, 
J. H. (1980). Principles and procedures of statistics. A biomedical 
approach. 2nd edition. McGraw-Hill Book Company, New York]. Differences 
are considered significant at P&lt;0.05. Results are set forth in Tables 2 
and 3. 
TABLE 1 
______________________________________ 
INGREDIENT AND NUTRIENT 
COMPOSITION OF THE BASAL DIET 
Item Amount 
______________________________________ 
Ingredient (g/100 g): 
Menhaden fish meal 12.0 
Dehulled soybean meal 
53.5 
Wheat midlings 10.0 
Corn 21.2 
Dicalcium phosphate 
1.0 
Trace mineral premix.sup.1 
0.1 
Vitamin premix.sup.2 
0.2 
Menhaden oil 2.5 
Nutrient: 
Crude protein (%) 36.2 
Crude fat (%) 5.7 
Digestible energy (kcal/g) 
3.2 
P/E (mg protein/kcal DE) 
11 
______________________________________ 
.sup.1 Trace mineral mix was the same as described by Reis et al. [(1989) 
Proteinto-energy ratios in production diets and growth and body 
composition to channel catfish. Aquaculture, 77:21-27] and provided the 
following (mg/kg of diet): Zn, 150; Fe, 44; Mn, 25; I, 5; Cu, 3; Se, 0.25 
.sup.2 Vitamin premix provided the following (mg/kg diet): thiamin, 20; 
choline chloride, 2,000; niacin, 150; riboflavin, 20; pyridoxine, 20; 
folic acid, 5; calcium pantothenate, 200; cyanocobalamin, 0.06; retinol a 
(retinyl acetate) 4,000; allrac-alpha-tocopherol, 50; cholecalciferol 
(1,000,000 IU/g), 2; menadione, 10; biotin, 1; Lascorbic acid, 100; 
ethoxyquin (an antioxidant), 200. 
TABLE 2 
______________________________________ 
AVERAGE WEIGHT INCREASE BY YEAR-2 
CHANNEL CATFISH FED RACTOPAMINE FOR 4 WEEKS 
AND FOR AN ADDITIONAL 2 WEEKS 
______________________________________ 
Dietary Percentage 
Ractopamine 
Fish Weight (g) Weight Increase 
(ppm) Initial 4 Week 6 Week Wk 0-4 Wk 4-6 
______________________________________ 
0 146 265 325 81.5 22.6 
20 163 318 373 95.0 17.3 
100 168 319 377 89.8 18.1 
______________________________________ 
F test: 
Contrast 0-4 Weeks 4-6 Weeks 
______________________________________ 
Control vs ractopamine 
p&lt;0.05 NS 
Low ractopamine vs 
NS NS 
high ractopamine 
______________________________________ 
NS = not statistically significant 
TABLE 3 
__________________________________________________________________________ 
MESENTERIC FAT, MUSCLE COMPOSITION AND DRESSING 
PERCENTAGE FOR YEAR-2 CHANNEL CATFISH FED 
RACTOPAMINE FOR 6 WEEKS IN RACEWAYS 
__________________________________________________________________________ 
Mesenteric 
Dietary 
fat Muscle 
ractopamine 
(g/100 g 
Fat Protein 
Moisture 
Dressing 
(ppm) body wt.) 
(%) (%) (%) Percentage 
__________________________________________________________________________ 
0 3.2 .+-. 0.4a 
8.4 .+-. 1.4 
16.8 .+-. 2.2 
73.7 .+-. 6.1 
66.8 .+-. 0.5 
20 2.6 .+-. 0.2b 
6.3 .+-. 1.3 
16.6 .+-. 0.6 
76.0 .+-. 6.9 
65.5 .+-. 0.1 
100 2.6 .+-. 0.1b 
5.6 .+-. 0.3 
16.4 .+-. 0.6 
76.8 .+-. 7.1 
66.0 .+-. 0.3 
__________________________________________________________________________ 
F. test: Mesenteric 
Muscle 
Muscle 
Muscle 
Dressing 
Contrast fat fat protein 
moisture 
percentage 
__________________________________________________________________________ 
Control vs 
P&lt;0.05 
P&lt;0.05 
NS P&lt;0.05 
P&lt;0.05 
ractopamine 
Low ractopamine 
NS NS NS NS P&lt;0.05 
vs high 
ractopamine 
__________________________________________________________________________ 
a,b: different letters indicate a statistically significant difference. 
NS = not statistically significant 
Discussion 
During the initial 4-week period, the fish fed ractopamine gained 
significantly more weight than the control (Table 2). There was no 
difference in weight gain between 20 and 100 ppm of ractopamine. During 
the following 2-week period there was no difference in weight gain among 
treatments. Water temperature in the outdoor raceways had begun to 
decrease at the beginning of the second feeding period and could have been 
a factor. 
Feeding ractopamine significantly reduced the amount of mesenteric fat in 
the fish; however, there was no effect of increasing ractopamine from 20 
to 100 ppm (Table 3). Feeding ractopamine also significantly reduced 
percentage of fat in the muscle of the fish (Table 3). Increasing 
ractopamine from 20 to 100 ppm effected a slight further decrease in 
percentage muscle fat (which, however, was not statistically significant). 
Moisture content of the muscle increased as fat decreased. Protein 
percentage of the wet muscle was not different among treatments; however, 
on a moisture-free basis there was a significantly higher percentage of 
protein in muscle of the ractopamine fed fish. Dressing percentage was 
significantly higher in the control fish. Feed efficiency was not 
calculated because accurate measurement of food consumed could not be made 
since the pellets sank to the bottom of the raceways when fed. 
Experiment 2 
Ractopamine in Rainbow Trout at 5-40 ppm in Diet 
Rainbow trout were sorted into groups weighing 150-200 g. Thirty-two fish 
were randomly assigned to each of 20 experimental tanks (capacity 60 L 
water). Fish weights per tank were then balanced prior to initiation of 
the trial in order to minimize between tank variation. The tanks were 
aerated and maintained on a single pass, flow-through system with flow 
rate set at 2.5 L/min. Water temperature was continuously electronically 
monitored. Five diets with levels of ractopamine at 0, 5, 10, 20 and 40 
ppm were formulated using a previously pelleted, commercial diet, steam 
pelleted to 4.0 mm, and dried for 24 hours. The diets were sieved and 
stored at 5.degree. C. until fed. Fish were fed to near satiation, twice 
daily for 12 weeks. Feed consumption and water quality (dissolved oxygen, 
total gas pressure, pH and ammonia) were recorded weekly. Fish were 
weighed and feed conversion was calculated every four weeks. Daily 
behavioral and health/morbidity/mortality records were also kept. Results 
were as set forth in the following tables. 
TABLE 4 
__________________________________________________________________________ 
EFFECTS OF RACTOPAMINE (LEAST SQUARE 
MEANS .+-. SEM) ON ABSOLUTE WEIGHT GAIN/FISH (G) 
DURING THREE TREATMENT PERIODS 
Level in Diet 
Weeks Ave. Over 
(ppm) 1-4 4-8 8-12 Weeks 
__________________________________________________________________________ 
0 86.80 .+-. 2.32 
74.51 .+-. 2.67 
92.13 .+-. 5.24 
85.02 .+-. 2.21 
5 87.86 .+-. 2.29 
.sup. 82.00 .+-. 2.65.sup.b 
89.70 .+-. 5.99 
87.45 .+-. 2.27 
10 .sup. 93.83 .+-. 2.51.sup.a 
80.57 .+-. 2.21 
92.66 .+-. 5.30 
89.82 .+-. 2.26 
20 83.44 .+-. 2.58 
74.10 .+-. 2.21 
96.93 .+-. 5.55 
85.49 .+-. 2.39 
40 87.55 .+-. 2.28 
79.71 .+-. 2.21 
99.22 .+-. 5.20 
89.32 .+-. 2.27 
__________________________________________________________________________ 
.sup.a Within the same column, different from controls (p.ltoreq.0.05) 
.sup.b Within the same column, different from controls (p.ltoreq.0.1) 
TABLE 5 
__________________________________________________________________________ 
EFFECTS OF RACTOPAMINE (LEAST SQUARE MEANS .+-. SEM) 
ON FEED INTAKE/FISH (G) OVER 
THREE TREATEMENT PERIODS 
Level in Diet 
Weeks Ave. Over 
(ppm) 1-4 4-8 8-12 Weeks 
__________________________________________________________________________ 
0 107.89 .+-. 1.78 
111.75 .+-. 2.55 
144.40 .+-. 3.39 
121.09 .+-. 1.50 
5 108.76 .+-. 1.75 
107.13 .+-. 2.48 
145.77 .+-. 3.79 
.sup. 120.77 .+-. 1.51.sup.a 
10 .sup. 101.86 .+-. 1.74.sup.b 
107.16 .+-. 2.41 
138.75 .+-. 3.38 
115.89 .+-. 1.46 
20 .sup. 112.81 .+-. 1.73.sup.c 
113.83 .+-. 2.75 
146.02 .+-. 3.45 
.sup. 124.78 .+-. 1.51.sup.c 
40 107.65 .+-. 1.74 
108.80 .+-. 2.83 
137.74 .+-. 3.31 
118.80 .+-. 1.51 
__________________________________________________________________________ 
.sup.a Within the same column, different from controls (p.ltoreq.0.01) 
.sup.b Within the same column, different from controls (p.ltoreq.0.05) 
.sup.c Within the same column, different from controls (p.ltoreq.0.1) 
TABLE 6 
__________________________________________________________________________ 
EFFECTS ON RACTOPAMINE (LEAST SQUARE MEANS .+-. SEM) 
ON FEED CONVERSION (G FEED/G GAIN) 
OVER THREE TREATMENT PERIODS 
Level in Diet 
Weeks Ave. Over 
(ppm) 1-4 4-8 8-12 Weeks 
__________________________________________________________________________ 
0 1.25 .+-. 0.03 
1.49 .+-. 0.06 
1.58 .+-. 0.09 
1.44 .+-. 0.04 
5 1.23 .+-. 0.03 
.sup. 1.33 .+-. 0.06.sup.b 
1.61 .+-. 0.1 
1.38 .+-. 0.04 
10 .sup. 1.15 .+-. 0.03.sup.a 
1.39 .+-. 0.06 
1.56 .+-. 0.09 
1.37 .+-. 0.04 
20 1.28 .+-. 0.03 
1.47 .+-. 0.07 
1.46 .+-. 0.09 
1.40 .+-. 0.04 
40 1.23 .+-. 0.03 
1.37 .+-. 0.07 
1.45 .+-. 0.09 
.sup. 1.35 .+-. 0.04.sup.b 
__________________________________________________________________________ 
.sup.a Within the same column, different from controls (p.ltoreq.0.05) 
.sup.b Within the same column, different from controls (p.ltoreq.0.1)