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The Evaluation of the Nutritional Value of Fish Meals and Meat Meals
T h e Evaluation of the Nutritional Value of Fish Meals and Meat Meals B. E. MARCH, D. STUPICH AND JACOB BIELY
(Received for publication March 7, 1949)
I
T HAS been shown (March and Biely 1948) that the nutritional value of fish meals and meat meals varies greatly according to the protein quality index method of evaluation (Almquist, Stokstad and Halbrook, 1935). Kokoski (1947) reported a similar range of variation in the protein index values of fish and animal products. Considerable differences have also been reported in the amino acid composition of these products (Block and Mitchell 1946, Schweigert 1947, Tarr 1948). Although protein quality index values have shown good correlation with chick growth response, no correlation has been shown between the protein quality index and the amount of any particular amino acid or combination of amino acids present in an animal protein concentrate. Almquist (1935) found no relationship between tryptophane or cystine content and protein index. Other investigators (Kraybill and Wilder 1947), using meat scrap in chick feeding tests, found some connection between total methionine and choline content and growth response. In experimental tests with rats, the tryptophane content of meat scrap appeared to be closely related to the growth response. In all these experiments, however, analyses for the amino acids were made on the total protein rather than on the digestible portion. Thus there is possibility of a relationship between the amount of
some of the amino acids in the digestible protein and the supplementary feeding value of fish meals and meat meals. The following experiments were conducted to determine if, on the basis of feeding tests, the variability of market samples of fish meals and meat meals as protein supplements was as great as their protein index values would indicate. Those essential amino acids in which poultry rations are most liable to be deficient (arginine, lysine, methionine, cystine, glycine and tryptophane) were determined with the object of ascertaining whether there was any correlation between the amount of any of the amino acids in a fish meal or meat meal and either the protein index value or the growth-promoting properties of the meal as a protein supplement. The amounts of each amino acid assayed were determined both on the basis of the total and the digestible protein. EXPERIMENTAL
Feeding Tests: Four feeding experiments were carried out with eight market samples of fish meals and meat meals. The meals were used as protein supplements to two types of basal ration, one containing wheat as the predominant grain, the other corn. The corn basal rations were used in feeding tests I and II and the wheat basal rations in tests III and IV. All the rations 718
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Poultry Nutrition. Laboratory, The University of British Columbia, Vancouver, Canada.
NUTRITIONAL VALUE OF FISH AND MEAT MEALS
In feeding tests I and III, day-old cockerel crossbred chicks (White Leghorn X New Hampshire) were used. In feeding tests I I and IV, day-old sexed New Hampshire chicks were used, the pullets and cockerels being equally divided among the lots. Each ration was fed to triplicate lots of chicks, eighteen chicks per lot in feeding tests I and I I I and twenty chicks per lot in tests II and IV. In all tests the chicks were reared to six weeks of age in Jamesway battery brooders. Throughout the tests the birds had free access to water and feed. They were weighed at weekly intervals. Protein Index Determination: The protein index values were determined on the meal samples according to Almquist's method (Almquist, Stokstad and Halbrook 1935). Before analysis the fish meals and meat meals were made up with bone meal in the same proportions as those used in compounding the feeding rations. The protein index values, there-
fore, represent the nutritive value of the protein of the fish or meat meal plus whatever protein was contributed by the addition of the bone meal. The bone meal analyzed 4.8 percent protein. Amino Acid Assays: Microbiological assays of the meals for amino acids were carried out using the media of Henderson and Snell (1947). Arginine, lysine, methionine, and tryptophane were determined using S. fecalis and glycine was determined using Leuc. mesenteroides. Cystine was determined chemically by Block and Boiling's modification of the Winterstein-Folin reaction (1945). Again the meals were balanced out with bone meal prior to analysis. Acid hydrolysates of the meals were used in the assays for the amino acids with the exception of tryptophane, for which an alkaline hydrolysate was used. The results of the assays have been expressed as percentages of the protein i.e., grams of the amino acid per 16 grams, of nitrogen. The results have been expressed in this way rather than as percentages of the whole meal in order that the relative merits of the samples per unit of protein might be compared, since it is on this basis that animal protein concentrates are fed. In addition to the analysis for the total amounts of the amino acids, analyses were made to determine the amount of each amino acid present in a form which is apparently digested by the chick. The indigestible fraction of the meal was separated out after a pepsin digestion similar to that used in the determination of the indigestible protein for protein index calculation. The indigestible material was analyzed for the various amino acids under consideration. As before, bone meal was added to the meals in order that the results of all parts of the experiment might
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were mixed to contain seventeen percent protein in such a way that, in any one test, the ratio of the amount of protein contributed by the grain to the amount from the animal protein concentrates was constant. Differences in weight were made up with granulated cane sugar. The percentage of ash in the rations was kept constant by the addition of bone meal. The amounts of calcium and phosphorus in the rations were excessive, but it was considered advisable to bring all rations up to the ash content of the ration containing the meat meal with the highest percentage of ash because, according to the findings of Heuser (1948) excess calcium may interfere with growth. Thus, poor growth might result from a protein concentrate in which the protein itself is of good quality but in which there is a high percentage of bone.
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B. E. MARCH, D. STUPICH AND JACOB BIELY
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PROTEIN
INDEX
FIG. 1. Feeding Test I : Growth response to samples 1, 2, 3, and 4 with corn basal ration.
The feed utilization of the various rations, calculated as grams of feed
be compared on a single basis. The results of the assayswere expressed as percentages of the indigestible protein itself and of the total protein present in the sample. The difference between the total amount of an amino acid present and the amount in the indigestible protein has been taken to represent the amount of that amino acid available to the chick. RESULTS AND DISCUSSION Differences in growth response to the various rations were evident as early as the second week of the experiments and by the end of the sixth week these differences had become very pronounced (Figures 1, 2, 3, 4). The relative supplementary effect of the meals was practically the same regardless of the grain in the basal ration. In feeding tests II and IV, however, a reversal can be seen in the relative growth response to samples 5 and
PR
OTEIN
FIG. 2. Feeding Test I I : Growth response to samples 5, 6, 7, and 8 with corn basal ration.
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6. If the results obtained with sample 5 are eliminated, the ratio of the chick weights at six weeks on the corn rations to those on the wheat rations range from 1.09 to 1.26 with samples 1 and 8 respectively. It will be noticed that, in general, meals of high quality lowered the ratio. The samples which were quoted above as producing the extremes in ratio had the highest and lowest protein index values (Table 1) as well as the extremes in available tryptophane-digestible protein-nitrogen product (Table 2). In both feeding tests I and III the difference in growth response to protein concentrates of the same protein index value is interesting. The meat meal (sample 3) gave a much lower growth response than the fish meal (sample 2) although both meals had the same protein index value.
NUTRITIONAL VALUE OF FISH AND MEAT MEALS
50 PROTEIN
FIG
70
80 INDEX
3. Feeding Test III: Growth response to samples 1, 2, 3, and 4 with wheat basal ration.
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FIG. 4. Feeding Test IV: Growth response to samples 5, 6, 7, and 8 with wheat basal ration. protein index values of the meat meals compared to the fish meals were due mainly to a greater percentage of collagen. Of the amino acids determined (Table 2) arginine showed the least variation, both in the amount present in the total crude protein and the amount present in the digestible protein. The ratio of the lowest to the highest available arginine content was 0.76. Lysine was present in the meals in somewhat higher than average percentages. The ratio of the lowest to the highest available content of this amino acid was 0.69. The meat meal protein was also found to contain about double the amount of glycine found in the fish meal protein. The difference between the glycine content of fish meals and meat meals was to be expected because of the larger amounts of collagen present in the meat meal. There was an inverse relationship between the glycine and the tryptophane
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required to produce 100 grams gain in weight, varied considerably. In the first place the corn rations were more efficiently utilized than the wheat rations. Secondly, the rations containing the protein supplements of high nutritional value were those which were most efficiently utilized. The protein index values of the protein concentrates were widely divergent (Table 2). The four samples of fish meal ranged from 69 to 83 and the four meat meals ranged from 50 to 71. This range of values coincides very closely with the range obtained previously with market samples of fish meal and meat meal. Contrary to the results obtained previously, a marked difference in protein index value was apparent between a flame-dried and a vacuum-dried fish meal (samples 1 and 2). The low protein index of the flame-dried meal was the result of large amounts of indigestible protein material. The low
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TABLE 1.—Protein index analyses offishmeals and meat meals Percentage of total nitrogen Sample no.
Description
Copper precipitable
73.8 75.0 50.8 49.7 67.0 58.3 57.1 49.7
Herring meal vacuum dried Herring meal flame dried Meat and bone meal Meat and bone meal Herring offal meal Salmon offal meal Meat and bone meal Meat and bone meal
PhosphotU C ^acid^ ' Indjjrestprecipitable
93.3 91.2 90.0 87.1 95.2 94.8 88.1 73.9
7.2
0.4 0.6 5.0 4.5 0.9 4.9 7.6
19.5 11.6 9.6
15.8
11.1 13.8 10.2 16.4
Hot water soluble
Nonprotein
6.2 5.4
6.3 8.2 7.0 8.4 3.9 3.0 4.3
17.8 20.1 5.1 6.2
16.9 22.4
Protein index
Percentage of total nitrogen present in digestible protein** 86.5 72.3 81.4 82,0 85.0 83.2 85.5 73.3
83 69 69 67 81 79 71 50
10.3
* From the filtrate left after copper precipitation. ** 100% minus percentage of total nitrogen which is in the form of indigestible protein minus percentage of total nitrogen which is non-protein.
content of the meals. This is logical since collagen is high in glycine and deficient in tryptophane. There was also a relationship between the glycine content of the meals and growth response. Here again, the relationship was inverse and was probably the result of a decrease in tryptophane content with an increase in the amount of collagen present. Methionine was found in fish meals in almost double the amount present in the meat meals. There was, however, very little difference among the fish meals or among the meat meals. The cystine content of the meals varied considerably, with a ratio of 0.56 between the lowest and the highest available cystine content. No correlation was evident between the cystine content of the meals and growth response. When, however, methionine and cystine were
considered together, there was a relationship between the sum of the available methionine and cystine contents of the meals and growth response (Fig. 5). Tryptophane showed considerable variation not only between fish meals and meat meals, but also among the fish meals and among the meat meals. The ratio of the lowest to the highest available tryptophane content was 0.39. The percentages of available tryptophane in the crude protein of the meals showed some relationship with the growth response of the meals. It was found that the available tryptophane, when considered in conjunction with the digestible protein nitrogen content of the crude protein, gave a better correlation with growth response than did the protein index values. The
TABLE 2.—The amino acid content offish meals and meat meals (Calculated to 16.0 grams of nitrogen) Arginine Sample no.
1 2 3 4 5 6 7 8
Total
9.2 7.8 7.8 8.2 8.5 8.7 8.9 8.7
Lysine
Methionine
Cystine
AvailAvailAvailAvailable Total able Total able Total able 8.9 7.0 6.8 7.6 8.2 8.1 8.4 8.3
8.8 9.4 11.2 12.1 9.1 12.7 12.8 11.4
8.6 8.6 10.3 11.6 8.8 12.1 12.4 11.1
2.5 2.5 1.4 1.3 2.5 2.6 1.3 1.3
2.3 2.0 1.1 1.2 2.3 2.3 1.2 1.2
1.16 1.26 1.57 1.05 1.48 1.34 1.32 1.19
1.03 1.03 1.16 0.73 1.31 1.08 1.06 1.03
Avail able
Glycine
Tryptophane
Cystine AvailAvailplus methi- Total able Total able onine 3.33 3.03 2.26 1.93 3.61 3.38 2.26 2.23
8.0 7.3 15.9 17.7 7.4 8.6 13.4 11.6
7.8 6.8 15.2 17.3 7.1 7.8 13.0 11.3
.87 .94 .62 .44 1.09 .80 .56 .54-
.80 .93 .52 .39 .99 .69 .50 .48
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1 2 3 4 5 6 7 8
Percent crude protein
NUTRITIONAL VALUE OF FISH AND MEAT MEALS
AVAILABLE C Y S TIN E + M E T H I O N I N E X AVAILABLE PROTEIN NITROSEN
FIG. 5. The effect of the available cystine methionine-available protein nitrogen product on growth response.
AVAILABLE
TRYPTOPHANE
AVAILABLE
PROTEIN
X
NITROSEN
FIG. 6. The effect of the available tryptophaneavailable protein nitrogen product on growth response.
fed. If the rations had been made up to a higher protein content, it is reasonable to suppose that the optimum percentage of tryptophane in the supplementary protein would likewise have been increased. The available tryptophane-digestible protein nitrogen product gave a better indication of the supplementary value of the protein of fish meals and meat meals than did the protein quality index. Since submission of this paper for publication, Clandinin has reported on the effect of processing temperature on the nutritive value of herring meal. His results show that meals which have been scorched may be expected to be inferior in nutritive value, and further, that the liberation of lysine, arginine and possibly threonine by acid hydrolysis is decreased and the liberation of all essential amino acids by enzymatic hydrolysis greatly depressed. From our data and those of Clandinin (1949) it would appear that a satisfactory evaluation of an animal protein concentrate might be obtained from the amino acid content based on acid hydrolysis of the total protein corrected for the indigestible and non-protein fractions.
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product of the percentage available tryptophane in the crude protein and the percentage of digestible protein nitrogen (i.e. 100 percent minus the percentage of total nitrogen which is non-protein in nature) gave good correlation with chick weights at six weeks of age. A correlation was evident also between growth and the product obtained by multiplying the available methionine-cystine sum by the digestible protein nitrogen. The latter correlation was not so good, however, as that with the available tryptophanedigestible protein nitrogen product. As can be seen from Fig. 6, the available tryptophane-digestible protein nitrogen product plotted against the average chick weights resulted in a straight line. Furthermore, the graphs for each feeding test were nearly parallel. Any percentage of available tryptophane greater than 0.75 was reduced to this figure before the product was calculated (Table 3) since in a ration containing seventeen percent protein this amount of tryptophane in the protein supplement supplied enough of this amino acid to balance out the protein
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B. E. MARCH, D. STUPICH AND JACOB BIELY and cystine considered in conjunction TABLE 3.—Available tryptophane, with digestible protein nitrogen 1
2
3
4
5
6
7
8
% Available cystine and methionine X % digestible protein nitrogen
288
219
184
158
307
281
193
163
% Available tryptophane X % digestible protein nitrogen
69.2
67.2
42.3
32.0
84.2
57.4
42.8
35.2
% Available tryptophane (with 0.75 max.) X % digestible nitrogen
64.9
54.2
42.3
32.0
63.8
57.4
42.8
35.2
SUMMARY
The supplementary protein value of four market samples of fish and four market samples of meat meal was investigated by the protein quality index method (Almquist); microbiological assays for arginine, lysine, methionine, cystine, glycine, and tryptophane; and chick feeding tests. 1. According to the results of all three methods there was considerable variation in the nutritive value of the fish meals and meat meals. 2. The relative supplementary feeding values of the different meals were much the same regardless of whether corn or wheat was the principal grain in the basal ration. 3. None of the amino acids that were studied gave a satisfactory correlation with the growth response of the chicks to the meals. The amount of available tryptophane present in the protein of the meals showed some relationship with growth, as did the sum of the available methionine and cystine contents. 4. A correlation was found between the product of the available methionine + cystine and the digestible protein nitrogen and chick growth. 5. A linear correlation was established between the available tryptophanedigestible protein nitrogen product and chick growth. 6. It is suggested that an amino acid
analysis based on acid hydrolysis of the total protein corrected for the indigestible and the non-protein fractions would indicate the biological value of animal protein concentrates. REFERENCES
Almquist, H. J., E. L. R. Stokstad and E. R. Halbrook, 1935. Supplementary values of animal protein concentrates. J. Nutrition 10: 193-211. Block, Richard J. and Diana Boiling, 1945. The amino acid composition of proteins and foods. Charles C Thomas, Springfield, 111. Block, Richard J. and Harold H. Mitchell, 1946-47. The correlation of the amino acid composition of proteins with their nutritive value. Nutr. Abst. and Rev. 16: 243-278. Clandinin, D. R., 1949. The effects of processing on the nutritive value of herring meals. Poultry Sci. 28: 128-131. Henderson, L. M. and Esmond E. Snell, 1948. A uniform medium for determination of amino acids with various microorganisms. J. Biol. Chem. 172: 15-29. Heuser, G. F., 1948. The effect of excess calcium rations. Feedstuff s, Feb. 7: 39. Kokoski, F. J., 1947. Protein evaluation in fish and animal products. J. of Assoc. Off. Agr. Chemists 30: 609-613. Kraybill, H. R. and O. H. M. Wilder, 1947. The nutritive value of meat scraps and tankages. A report by the American Meat Institute. Tarr, H. L. A., 1948. Pacific Fisheries Experimental Station, Vancouver, B. C. Private communication. March, B. E. and Jacob Biely, 1948. Nutritional value of British Columbia fish and meat meals. Canadian Chem. and Process Industries, 32: 447-448, 451-452. Schweigert, B. S., 1948. The value of various feeds as sources of arginine, histidine, lysine and threonine for poultry. Poultry Sci. 27: 223-227.
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Sample no.
(Received for publication March 7, 1949)
I
T HAS been shown (March and Biely 1948) that the nutritional value of fish meals and meat meals varies greatly according to the protein quality index method of evaluation (Almquist, Stokstad and Halbrook, 1935). Kokoski (1947) reported a similar range of variation in the protein index values of fish and animal products. Considerable differences have also been reported in the amino acid composition of these products (Block and Mitchell 1946, Schweigert 1947, Tarr 1948). Although protein quality index values have shown good correlation with chick growth response, no correlation has been shown between the protein quality index and the amount of any particular amino acid or combination of amino acids present in an animal protein concentrate. Almquist (1935) found no relationship between tryptophane or cystine content and protein index. Other investigators (Kraybill and Wilder 1947), using meat scrap in chick feeding tests, found some connection between total methionine and choline content and growth response. In experimental tests with rats, the tryptophane content of meat scrap appeared to be closely related to the growth response. In all these experiments, however, analyses for the amino acids were made on the total protein rather than on the digestible portion. Thus there is possibility of a relationship between the amount of
some of the amino acids in the digestible protein and the supplementary feeding value of fish meals and meat meals. The following experiments were conducted to determine if, on the basis of feeding tests, the variability of market samples of fish meals and meat meals as protein supplements was as great as their protein index values would indicate. Those essential amino acids in which poultry rations are most liable to be deficient (arginine, lysine, methionine, cystine, glycine and tryptophane) were determined with the object of ascertaining whether there was any correlation between the amount of any of the amino acids in a fish meal or meat meal and either the protein index value or the growth-promoting properties of the meal as a protein supplement. The amounts of each amino acid assayed were determined both on the basis of the total and the digestible protein. EXPERIMENTAL
Feeding Tests: Four feeding experiments were carried out with eight market samples of fish meals and meat meals. The meals were used as protein supplements to two types of basal ration, one containing wheat as the predominant grain, the other corn. The corn basal rations were used in feeding tests I and II and the wheat basal rations in tests III and IV. All the rations 718
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Poultry Nutrition. Laboratory, The University of British Columbia, Vancouver, Canada.
NUTRITIONAL VALUE OF FISH AND MEAT MEALS
In feeding tests I and III, day-old cockerel crossbred chicks (White Leghorn X New Hampshire) were used. In feeding tests I I and IV, day-old sexed New Hampshire chicks were used, the pullets and cockerels being equally divided among the lots. Each ration was fed to triplicate lots of chicks, eighteen chicks per lot in feeding tests I and I I I and twenty chicks per lot in tests II and IV. In all tests the chicks were reared to six weeks of age in Jamesway battery brooders. Throughout the tests the birds had free access to water and feed. They were weighed at weekly intervals. Protein Index Determination: The protein index values were determined on the meal samples according to Almquist's method (Almquist, Stokstad and Halbrook 1935). Before analysis the fish meals and meat meals were made up with bone meal in the same proportions as those used in compounding the feeding rations. The protein index values, there-
fore, represent the nutritive value of the protein of the fish or meat meal plus whatever protein was contributed by the addition of the bone meal. The bone meal analyzed 4.8 percent protein. Amino Acid Assays: Microbiological assays of the meals for amino acids were carried out using the media of Henderson and Snell (1947). Arginine, lysine, methionine, and tryptophane were determined using S. fecalis and glycine was determined using Leuc. mesenteroides. Cystine was determined chemically by Block and Boiling's modification of the Winterstein-Folin reaction (1945). Again the meals were balanced out with bone meal prior to analysis. Acid hydrolysates of the meals were used in the assays for the amino acids with the exception of tryptophane, for which an alkaline hydrolysate was used. The results of the assays have been expressed as percentages of the protein i.e., grams of the amino acid per 16 grams, of nitrogen. The results have been expressed in this way rather than as percentages of the whole meal in order that the relative merits of the samples per unit of protein might be compared, since it is on this basis that animal protein concentrates are fed. In addition to the analysis for the total amounts of the amino acids, analyses were made to determine the amount of each amino acid present in a form which is apparently digested by the chick. The indigestible fraction of the meal was separated out after a pepsin digestion similar to that used in the determination of the indigestible protein for protein index calculation. The indigestible material was analyzed for the various amino acids under consideration. As before, bone meal was added to the meals in order that the results of all parts of the experiment might
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were mixed to contain seventeen percent protein in such a way that, in any one test, the ratio of the amount of protein contributed by the grain to the amount from the animal protein concentrates was constant. Differences in weight were made up with granulated cane sugar. The percentage of ash in the rations was kept constant by the addition of bone meal. The amounts of calcium and phosphorus in the rations were excessive, but it was considered advisable to bring all rations up to the ash content of the ration containing the meat meal with the highest percentage of ash because, according to the findings of Heuser (1948) excess calcium may interfere with growth. Thus, poor growth might result from a protein concentrate in which the protein itself is of good quality but in which there is a high percentage of bone.
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PROTEIN
INDEX
FIG. 1. Feeding Test I : Growth response to samples 1, 2, 3, and 4 with corn basal ration.
The feed utilization of the various rations, calculated as grams of feed
be compared on a single basis. The results of the assayswere expressed as percentages of the indigestible protein itself and of the total protein present in the sample. The difference between the total amount of an amino acid present and the amount in the indigestible protein has been taken to represent the amount of that amino acid available to the chick. RESULTS AND DISCUSSION Differences in growth response to the various rations were evident as early as the second week of the experiments and by the end of the sixth week these differences had become very pronounced (Figures 1, 2, 3, 4). The relative supplementary effect of the meals was practically the same regardless of the grain in the basal ration. In feeding tests II and IV, however, a reversal can be seen in the relative growth response to samples 5 and
PR
OTEIN
FIG. 2. Feeding Test I I : Growth response to samples 5, 6, 7, and 8 with corn basal ration.
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6. If the results obtained with sample 5 are eliminated, the ratio of the chick weights at six weeks on the corn rations to those on the wheat rations range from 1.09 to 1.26 with samples 1 and 8 respectively. It will be noticed that, in general, meals of high quality lowered the ratio. The samples which were quoted above as producing the extremes in ratio had the highest and lowest protein index values (Table 1) as well as the extremes in available tryptophane-digestible protein-nitrogen product (Table 2). In both feeding tests I and III the difference in growth response to protein concentrates of the same protein index value is interesting. The meat meal (sample 3) gave a much lower growth response than the fish meal (sample 2) although both meals had the same protein index value.
NUTRITIONAL VALUE OF FISH AND MEAT MEALS
50 PROTEIN
FIG
70
80 INDEX
3. Feeding Test III: Growth response to samples 1, 2, 3, and 4 with wheat basal ration.
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PROTEIN
FIG. 4. Feeding Test IV: Growth response to samples 5, 6, 7, and 8 with wheat basal ration. protein index values of the meat meals compared to the fish meals were due mainly to a greater percentage of collagen. Of the amino acids determined (Table 2) arginine showed the least variation, both in the amount present in the total crude protein and the amount present in the digestible protein. The ratio of the lowest to the highest available arginine content was 0.76. Lysine was present in the meals in somewhat higher than average percentages. The ratio of the lowest to the highest available content of this amino acid was 0.69. The meat meal protein was also found to contain about double the amount of glycine found in the fish meal protein. The difference between the glycine content of fish meals and meat meals was to be expected because of the larger amounts of collagen present in the meat meal. There was an inverse relationship between the glycine and the tryptophane
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required to produce 100 grams gain in weight, varied considerably. In the first place the corn rations were more efficiently utilized than the wheat rations. Secondly, the rations containing the protein supplements of high nutritional value were those which were most efficiently utilized. The protein index values of the protein concentrates were widely divergent (Table 2). The four samples of fish meal ranged from 69 to 83 and the four meat meals ranged from 50 to 71. This range of values coincides very closely with the range obtained previously with market samples of fish meal and meat meal. Contrary to the results obtained previously, a marked difference in protein index value was apparent between a flame-dried and a vacuum-dried fish meal (samples 1 and 2). The low protein index of the flame-dried meal was the result of large amounts of indigestible protein material. The low
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TABLE 1.—Protein index analyses offishmeals and meat meals Percentage of total nitrogen Sample no.
Description
Copper precipitable
73.8 75.0 50.8 49.7 67.0 58.3 57.1 49.7
Herring meal vacuum dried Herring meal flame dried Meat and bone meal Meat and bone meal Herring offal meal Salmon offal meal Meat and bone meal Meat and bone meal
PhosphotU C ^acid^ ' Indjjrestprecipitable
93.3 91.2 90.0 87.1 95.2 94.8 88.1 73.9
7.2
0.4 0.6 5.0 4.5 0.9 4.9 7.6
19.5 11.6 9.6
15.8
11.1 13.8 10.2 16.4
Hot water soluble
Nonprotein
6.2 5.4
6.3 8.2 7.0 8.4 3.9 3.0 4.3
17.8 20.1 5.1 6.2
16.9 22.4
Protein index
Percentage of total nitrogen present in digestible protein** 86.5 72.3 81.4 82,0 85.0 83.2 85.5 73.3
83 69 69 67 81 79 71 50
10.3
* From the filtrate left after copper precipitation. ** 100% minus percentage of total nitrogen which is in the form of indigestible protein minus percentage of total nitrogen which is non-protein.
content of the meals. This is logical since collagen is high in glycine and deficient in tryptophane. There was also a relationship between the glycine content of the meals and growth response. Here again, the relationship was inverse and was probably the result of a decrease in tryptophane content with an increase in the amount of collagen present. Methionine was found in fish meals in almost double the amount present in the meat meals. There was, however, very little difference among the fish meals or among the meat meals. The cystine content of the meals varied considerably, with a ratio of 0.56 between the lowest and the highest available cystine content. No correlation was evident between the cystine content of the meals and growth response. When, however, methionine and cystine were
considered together, there was a relationship between the sum of the available methionine and cystine contents of the meals and growth response (Fig. 5). Tryptophane showed considerable variation not only between fish meals and meat meals, but also among the fish meals and among the meat meals. The ratio of the lowest to the highest available tryptophane content was 0.39. The percentages of available tryptophane in the crude protein of the meals showed some relationship with the growth response of the meals. It was found that the available tryptophane, when considered in conjunction with the digestible protein nitrogen content of the crude protein, gave a better correlation with growth response than did the protein index values. The
TABLE 2.—The amino acid content offish meals and meat meals (Calculated to 16.0 grams of nitrogen) Arginine Sample no.
1 2 3 4 5 6 7 8
Total
9.2 7.8 7.8 8.2 8.5 8.7 8.9 8.7
Lysine
Methionine
Cystine
AvailAvailAvailAvailable Total able Total able Total able 8.9 7.0 6.8 7.6 8.2 8.1 8.4 8.3
8.8 9.4 11.2 12.1 9.1 12.7 12.8 11.4
8.6 8.6 10.3 11.6 8.8 12.1 12.4 11.1
2.5 2.5 1.4 1.3 2.5 2.6 1.3 1.3
2.3 2.0 1.1 1.2 2.3 2.3 1.2 1.2
1.16 1.26 1.57 1.05 1.48 1.34 1.32 1.19
1.03 1.03 1.16 0.73 1.31 1.08 1.06 1.03
Avail able
Glycine
Tryptophane
Cystine AvailAvailplus methi- Total able Total able onine 3.33 3.03 2.26 1.93 3.61 3.38 2.26 2.23
8.0 7.3 15.9 17.7 7.4 8.6 13.4 11.6
7.8 6.8 15.2 17.3 7.1 7.8 13.0 11.3
.87 .94 .62 .44 1.09 .80 .56 .54-
.80 .93 .52 .39 .99 .69 .50 .48
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1 2 3 4 5 6 7 8
Percent crude protein
NUTRITIONAL VALUE OF FISH AND MEAT MEALS
AVAILABLE C Y S TIN E + M E T H I O N I N E X AVAILABLE PROTEIN NITROSEN
FIG. 5. The effect of the available cystine methionine-available protein nitrogen product on growth response.
AVAILABLE
TRYPTOPHANE
AVAILABLE
PROTEIN
X
NITROSEN
FIG. 6. The effect of the available tryptophaneavailable protein nitrogen product on growth response.
fed. If the rations had been made up to a higher protein content, it is reasonable to suppose that the optimum percentage of tryptophane in the supplementary protein would likewise have been increased. The available tryptophane-digestible protein nitrogen product gave a better indication of the supplementary value of the protein of fish meals and meat meals than did the protein quality index. Since submission of this paper for publication, Clandinin has reported on the effect of processing temperature on the nutritive value of herring meal. His results show that meals which have been scorched may be expected to be inferior in nutritive value, and further, that the liberation of lysine, arginine and possibly threonine by acid hydrolysis is decreased and the liberation of all essential amino acids by enzymatic hydrolysis greatly depressed. From our data and those of Clandinin (1949) it would appear that a satisfactory evaluation of an animal protein concentrate might be obtained from the amino acid content based on acid hydrolysis of the total protein corrected for the indigestible and non-protein fractions.
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product of the percentage available tryptophane in the crude protein and the percentage of digestible protein nitrogen (i.e. 100 percent minus the percentage of total nitrogen which is non-protein in nature) gave good correlation with chick weights at six weeks of age. A correlation was evident also between growth and the product obtained by multiplying the available methionine-cystine sum by the digestible protein nitrogen. The latter correlation was not so good, however, as that with the available tryptophanedigestible protein nitrogen product. As can be seen from Fig. 6, the available tryptophane-digestible protein nitrogen product plotted against the average chick weights resulted in a straight line. Furthermore, the graphs for each feeding test were nearly parallel. Any percentage of available tryptophane greater than 0.75 was reduced to this figure before the product was calculated (Table 3) since in a ration containing seventeen percent protein this amount of tryptophane in the protein supplement supplied enough of this amino acid to balance out the protein
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724
B. E. MARCH, D. STUPICH AND JACOB BIELY and cystine considered in conjunction TABLE 3.—Available tryptophane, with digestible protein nitrogen 1
2
3
4
5
6
7
8
% Available cystine and methionine X % digestible protein nitrogen
288
219
184
158
307
281
193
163
% Available tryptophane X % digestible protein nitrogen
69.2
67.2
42.3
32.0
84.2
57.4
42.8
35.2
% Available tryptophane (with 0.75 max.) X % digestible nitrogen
64.9
54.2
42.3
32.0
63.8
57.4
42.8
35.2
SUMMARY
The supplementary protein value of four market samples of fish and four market samples of meat meal was investigated by the protein quality index method (Almquist); microbiological assays for arginine, lysine, methionine, cystine, glycine, and tryptophane; and chick feeding tests. 1. According to the results of all three methods there was considerable variation in the nutritive value of the fish meals and meat meals. 2. The relative supplementary feeding values of the different meals were much the same regardless of whether corn or wheat was the principal grain in the basal ration. 3. None of the amino acids that were studied gave a satisfactory correlation with the growth response of the chicks to the meals. The amount of available tryptophane present in the protein of the meals showed some relationship with growth, as did the sum of the available methionine and cystine contents. 4. A correlation was found between the product of the available methionine + cystine and the digestible protein nitrogen and chick growth. 5. A linear correlation was established between the available tryptophanedigestible protein nitrogen product and chick growth. 6. It is suggested that an amino acid
analysis based on acid hydrolysis of the total protein corrected for the indigestible and the non-protein fractions would indicate the biological value of animal protein concentrates. REFERENCES
Almquist, H. J., E. L. R. Stokstad and E. R. Halbrook, 1935. Supplementary values of animal protein concentrates. J. Nutrition 10: 193-211. Block, Richard J. and Diana Boiling, 1945. The amino acid composition of proteins and foods. Charles C Thomas, Springfield, 111. Block, Richard J. and Harold H. Mitchell, 1946-47. The correlation of the amino acid composition of proteins with their nutritive value. Nutr. Abst. and Rev. 16: 243-278. Clandinin, D. R., 1949. The effects of processing on the nutritive value of herring meals. Poultry Sci. 28: 128-131. Henderson, L. M. and Esmond E. Snell, 1948. A uniform medium for determination of amino acids with various microorganisms. J. Biol. Chem. 172: 15-29. Heuser, G. F., 1948. The effect of excess calcium rations. Feedstuff s, Feb. 7: 39. Kokoski, F. J., 1947. Protein evaluation in fish and animal products. J. of Assoc. Off. Agr. Chemists 30: 609-613. Kraybill, H. R. and O. H. M. Wilder, 1947. The nutritive value of meat scraps and tankages. A report by the American Meat Institute. Tarr, H. L. A., 1948. Pacific Fisheries Experimental Station, Vancouver, B. C. Private communication. March, B. E. and Jacob Biely, 1948. Nutritional value of British Columbia fish and meat meals. Canadian Chem. and Process Industries, 32: 447-448, 451-452. Schweigert, B. S., 1948. The value of various feeds as sources of arginine, histidine, lysine and threonine for poultry. Poultry Sci. 27: 223-227.
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Sample no.