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Effect of soybean antitrypsin on growth of the chick
Effect of Soybean Antitrypsin on Growth of the Chick H. J. Almquist and J. B. Merritt From the Grange Company, Modesto, California Received July 31, 1951 INTRODUCTION
In a previous paper (1) we reported that as little as 5% of raw soybean meal protein in the diet of the chick was associated with an effective level of antitrypsin. We have made further studies of the relation between the quantity of soybean antitrypsin in the diet and the growth rate of the chick. EXPERIMENTAL All protein in the chick diets was furnished as either raw solvent-extracted soybean flakes or as solvent-extracted commercial soybean meal or combinations of these. The total level of protein was 20%. The remainder of the diet was composed of DLmethionine 0.3%, and vitamin supplements, minerals, and glucose as used in the previous studies (1). TABLE I
Effect of Various Levels of Raw Soybean Meal on the Growth of Chicks Raw soybean meal protein
Cooked soybean meal protein
Average weights of duplicate chick groups at 14 days
% 0 5 10 15 20
% 20 15 10 5 0
g. 182.0 152.5 154.5 154.5 143.0
In the first experiment the proportions of raw to cooked soybean meal protein in the diets were varied by 5% increments, from 20% raw to 20% cooked protein. Barred Rock-New Hampshire cross chicks in duplicate groups of six were fed these diets. The growth of the chicks is indicated in Table I. These results seemed to indicate t h a t nearly all of the growth inhibitory effect had been attained at the 5 % raw protein level. Little further effect was attained until the diet contained only raw meal as a source of protein. 352
353
EFFECT OF SOYBEAN ANTITRYPSIN
TABLE Ii Effect of Various Levels of Raw Soybean Meal and of Trypsin ~ on the Growth of Chicks Raw soybean meal protein %
0 2.5 5.0 7.5 10.0 Pfanstiehl, 1-110.
Cookedsoybean meal protein
Average weights of duplicate chick groups at 12 days Without trypsin. With 0.1% trypsin in diet in diet
%
g.
g.
20 17.5 15.0 12.5 10.0
152.8 145.0 134.3 136.2 132.3
156.5 156.5 145.7 138.8 138,2
A repetition of this experiment was conducted, in this case by varying the amount of raw protein from 0 to 10% in steps of 2.5%. In addition, each diet was also fed with a supplement of trypsin (Pfanstiehl, 1-110) at 0.1% of the diet. Duplicate groups of eight chicks each were placed on each diet. The results are given in Table II. DISCUSSION
These results agree with our previous statement that nearly maximal growth inhibition was attained when the diet contained enough raw soybean meal to furnish 5 % protein in the diet. I t is apparent from the data in both Tables I and II t h a t a plateau in the inhibitory effect was reached at the 5 % raw protein point, and little or no increase in this effect was observed at higher levels of raw protein. Such a result m a y be explained b y assuming t h a t one component of the proteolytic enzyme system in the chick, such as trypsin, was almost completely inactivated by a substance, such as the antitrypsin, at the 5 % raw protein stage, leaving the remainder of the enzyme system to function, but at a reduced efficiency. The remaining enzymes were, obviously, not appreciably hampered by larger amounts of the antitrypsin until, perhaps, all the meal was in the raw state. The results with and without trypsin in the diet (Table II) showed t h a t the added trypsin was beneficial in overcoming the antitrypsin until the 5 % raw protein stage was exceeded, after which a plateau of growth rate was apparently reached. Such results suggest t h a t there exists an approximately quantitative and specific interaction between the antitrypsin and the trypsin available in the chick. This relation is in h a r m o n y with the i n vitro observation b y Kunitz (2) t h a t crystalline soybean antitrypsin and crystalline trypsin combine in definite proportions into a relatively nondissociable compound,
354
H. J. ALMQUIST AND J. B. MERRITT SUMMARY
Chicks were fed complete diets containing protein exclusively from soybean meal, either cooked or raw or in combinations, at a total of 20% protein. As little as 5% of raw protein was accompanied by nearly maximal growth retardation due to the tryptic inhibitor in raw soybean meal. The growth inhibition was overcome by adding trypsin to the diet. REFERENCES 1. ALMQUIST~H. J., AND MERRITT, J. B., Arch. Biochem. Biophy~. 31, 450 (1951). 2. KVNITZ, M., J. Gen. Physiol. 29, 149 (1946).
In a previous paper (1) we reported that as little as 5% of raw soybean meal protein in the diet of the chick was associated with an effective level of antitrypsin. We have made further studies of the relation between the quantity of soybean antitrypsin in the diet and the growth rate of the chick. EXPERIMENTAL All protein in the chick diets was furnished as either raw solvent-extracted soybean flakes or as solvent-extracted commercial soybean meal or combinations of these. The total level of protein was 20%. The remainder of the diet was composed of DLmethionine 0.3%, and vitamin supplements, minerals, and glucose as used in the previous studies (1). TABLE I
Effect of Various Levels of Raw Soybean Meal on the Growth of Chicks Raw soybean meal protein
Cooked soybean meal protein
Average weights of duplicate chick groups at 14 days
% 0 5 10 15 20
% 20 15 10 5 0
g. 182.0 152.5 154.5 154.5 143.0
In the first experiment the proportions of raw to cooked soybean meal protein in the diets were varied by 5% increments, from 20% raw to 20% cooked protein. Barred Rock-New Hampshire cross chicks in duplicate groups of six were fed these diets. The growth of the chicks is indicated in Table I. These results seemed to indicate t h a t nearly all of the growth inhibitory effect had been attained at the 5 % raw protein level. Little further effect was attained until the diet contained only raw meal as a source of protein. 352
353
EFFECT OF SOYBEAN ANTITRYPSIN
TABLE Ii Effect of Various Levels of Raw Soybean Meal and of Trypsin ~ on the Growth of Chicks Raw soybean meal protein %
0 2.5 5.0 7.5 10.0 Pfanstiehl, 1-110.
Cookedsoybean meal protein
Average weights of duplicate chick groups at 12 days Without trypsin. With 0.1% trypsin in diet in diet
%
g.
g.
20 17.5 15.0 12.5 10.0
152.8 145.0 134.3 136.2 132.3
156.5 156.5 145.7 138.8 138,2
A repetition of this experiment was conducted, in this case by varying the amount of raw protein from 0 to 10% in steps of 2.5%. In addition, each diet was also fed with a supplement of trypsin (Pfanstiehl, 1-110) at 0.1% of the diet. Duplicate groups of eight chicks each were placed on each diet. The results are given in Table II. DISCUSSION
These results agree with our previous statement that nearly maximal growth inhibition was attained when the diet contained enough raw soybean meal to furnish 5 % protein in the diet. I t is apparent from the data in both Tables I and II t h a t a plateau in the inhibitory effect was reached at the 5 % raw protein point, and little or no increase in this effect was observed at higher levels of raw protein. Such a result m a y be explained b y assuming t h a t one component of the proteolytic enzyme system in the chick, such as trypsin, was almost completely inactivated by a substance, such as the antitrypsin, at the 5 % raw protein stage, leaving the remainder of the enzyme system to function, but at a reduced efficiency. The remaining enzymes were, obviously, not appreciably hampered by larger amounts of the antitrypsin until, perhaps, all the meal was in the raw state. The results with and without trypsin in the diet (Table II) showed t h a t the added trypsin was beneficial in overcoming the antitrypsin until the 5 % raw protein stage was exceeded, after which a plateau of growth rate was apparently reached. Such results suggest t h a t there exists an approximately quantitative and specific interaction between the antitrypsin and the trypsin available in the chick. This relation is in h a r m o n y with the i n vitro observation b y Kunitz (2) t h a t crystalline soybean antitrypsin and crystalline trypsin combine in definite proportions into a relatively nondissociable compound,
354
H. J. ALMQUIST AND J. B. MERRITT SUMMARY
Chicks were fed complete diets containing protein exclusively from soybean meal, either cooked or raw or in combinations, at a total of 20% protein. As little as 5% of raw protein was accompanied by nearly maximal growth retardation due to the tryptic inhibitor in raw soybean meal. The growth inhibition was overcome by adding trypsin to the diet. REFERENCES 1. ALMQUIST~H. J., AND MERRITT, J. B., Arch. Biochem. Biophy~. 31, 450 (1951). 2. KVNITZ, M., J. Gen. Physiol. 29, 149 (1946).