Effect of Feeding Different Carbohydrates to Rats on Low Protein Diet S. 1. Ette, 0. Bassir, and E. A. Bamgboye Ibadan, Nigeria

The experimental results to be presented here do not demonstrate any significance among the means of the values obtained for the various carbohydrate diets, except for lactose. The results will suggest that the differences between the values for lactose and other diets are significant (PLO.05). No definite trend in the biological value (BV), the net protein utilization (NPU), and the true digestibility (TD) which can be attributed to the influence of the carbohydrates are shown by these results. The various dietary manipulations produce no results significantly different than the values for starch, the exception being lactose. The values for lactose are more than for other sugars. However, the results will show a relationship between a mixture of protein in the diet with the values of the individual protein sources if determined separately. Evidently, the values of each protein in any mixture can be predicted by measuring its TD in the mixture. In this study of the effects of feeding different carbohydrates to rats on low protein diets, it has been observed that the response of these experimental animals to diets containing one source of protein varies between the individual rats. While some of the rats may dislike eating diets containing only one protein source, nearly all of them tend to enjoy the same diets if more than one source of protein has been added, suggesting that the animal response may depend either on a particular or mixture of proteins, or upon the nature of the carbohydrate in the diet. Hankes et all suggested that complex carbohydrates are preferable to simple sugars in studies where the growth rate is one of the parameters investigated. Harper and Katayama,2 and Chang,3 agreed with this observation while other investigators, Spivey et al,4 differed in their conclusions.

Supported by the Senate Research Grant of the University of Ibadan, Ibadan, Nigeria. Requests for reprints should be addressed to Dr. S.l. Ette, Department of Biochemistry, University of Ibadan, Ibadan, Nigeria.

It has, however, been reported by

Buraczewski5 that when proteins

are

offered in a diet with carbohydrates, the digestibility was determined by the protein. Egum reported a beneficial effect on protein retention in rats by adding lacose to the meal. Rolls et al6 suggested that the hydrolysis rate of lactose may be a critical factor in protein absorption. Wiener et a17 and Glen Hansen,8 seem to agree that dietary carbohydrates given to rats had no effect on protein digestibility and nitrogen retention. True protein digestibility (TD) and biological value (BV) were not dependent on the nature of the carbohydrate. We have found that a higher lactose level in the diet causes diarrhea. The present experiment was designed to test the influence of carbohydrates on protein utilization and we used starch, glucose, sucrose, and lactose. Our sources of protein were (a) fish (b) calcium caseinate (Casilan) (c) meat (d) crab and periwinkle (e) skim milk from the local store and (f) soybean from Federal Agriculture Research Station, Moore Plantation, Ibadan.

JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 69, NO. 1, 1977

Experimental Procedure Sixty Wistar strain (male and female) rats from our animal inbred colony were used for these experiments. They were fed for an initial period of seven days, after which they were randomly grouped. There were 10 rats in each group, caged individually, and each group fed the experimental and control diets, respectively. The feeds were weighed each day, and the body weight of the rats, every other day. To demonstrate the effect of carbohydrate on protein utilization, the test diet contained 220 gm of the appropriate protein material per kg dry matter and either 110, or 220 gm of starch, glucose, sucrose, or lactose per kg diet. Changes in true protein digestibility, biological value, and net protein utilization were calculated and recorded. Starch meals were used as the control diet. Many experiments had been performed in which the feeds were offered to the animals separately or together. But with our procedures, it was possible to assess protein digestibility of mixtures of two or more proteins given together or separately.

Analysis The regression equation:

TDcalc = 0.0084 + 0.99 x TD measured. was obtained by calculated true digestibility. The values obtained are given in Table 2.

Results True digestibility: The test did not demonstrate any significance among the means of the values obtained for the various carbohydrate diets except for lactose. The results suggest that the 53

differences between the values for lactose and the other diets are significant (PLO.05). Biological value: The test did not show any significance at all in all the diets, including lactose. Net protein utilization: The "t" test had indicated absence of any significance among the means of all the other carbohydrate diets, except lactose, where a comparison with other diets demonstrates significance

among the means (PLO.00 1). Regression analysis of calculated true digestibility gave the following means: R = 0.98; Regression coefficient standard deviation 0.17 and intercept of 0.1352.

Discussion of Results No definite trends in the BV, NPU, and TD, which can be ascribed to the influence of the carbohydrate sources, have been demonstrated by these re-

Table 1

Effect of Feeding Different Carbohydrates on Protein Utilization* Digestibility (TD)

Carbohydrate Sources

TD

BV

NPU

Starch (corn), control

0.88 ± 0.07

0.82 ± 0.04

0.83 ± 0.05

Starch (glucose 3:1)

0.87 ± 0.06

0.84 ± 0.06

0.81 ± 0.02

Starch (glucose 11:9)

0.86 ± 0.05

0.88 ± 0.66

0.84 ± 0.06

Starch (sucrose 3:1)

0.88 ± 0.07

0.83 ± 0.05

0.85 ± 0.06

Starch (sucrose 11:9)

0.86 ± 0.05

0.86 ± 0.06

0.85 ± 0.06

Starch (lactose 3:1)

0.77 ± 0.05

0.79 ± 0.03

0.77 ± 0.03

Starch (lactose 11:9)

0.65 ± 0.04

0.79 ± 0.04

0.65 ± 0.05

*As measured by true digestibility (TD), biological value (BV), and net protein utilization (NPU).

Table 2. True Digestibility*

Measured TD

Calculated TD

Soybean

0.88

0.88

Smoked fish (edible portion) only

0.86

0.86

Casilan (calcium caseinate) B.D.H.

0.91

0.91

Meat

0.86

0.86

Crab

0.86

0.86

Smoked fish + meat

0.86

0.86

0.88

0.88

0.87

0.87

0.90

0.90

crab

0.88

0.88

Soybean + crab + meat

0.84

0.84

Casilan + meat + fish

0.80

0.80

Protein Source

Soybean

+

smoked fish

Smoked fish

+ meat +

soybean

Soybean + meat

Soybean + meat

*TD

54

=

0.0084

+

+

0.99 X Measured TD.

sults. The various dietary manipulations have produced no results significantly different from the values for starch, except for the lactose results which in all respects, are lower than other sugars. It is observed that separately determined results demonstrate a relationship between a mixture of proteins in the diet with the values of the individual protein sources. The differences are not statistically significant. It follows that the values of each protein in any mixture can be safely predicted by measuring the TD of the mixture. This implies that each source of protein will contribute equally to the animal protein requirement. If, however, the substitution of any one carbohydrate in the diets had any effect on protein utilization, such effects are neither specific nor conclusive. The same observations using cod meal, peas, soybean meal, and wheat were made by others, whereas Porter and Rolls9 suggested a reduced protein digestibility for heat-damaged protein. We believe that the nature of the carbohydrate has very little or no appreciable or significant influence on protein utilization by these rats. Acknowledgment The assistance of Mr. Augustine Ukut and the cooperation of Professor Turner T. Isoun is appreciated.

Literature Cited 1. Hankes LV, Henderson LM, Brickson WL, et al: Effect of amino acids on growth of rats in niacin-tryptophon-deficient rations. J Biol Chem 174:873-881, 1948 2. Harper AE, Katayama MC: Influence of various carbohydrates on utilization of low-protein rations by white rat: Comparison of sucrose and cornstarch in nine percent casein rations. J Nutr 49:261-275, 1953 3. Chang VO: Effect of carbohydrates on utilization of protein and lysine by rats. J Nutr 78: 21-27, 1962 4. Spivey HE, Katayama MC, Yoshida M, et al: Significance of the protein-sparing effect of dextran. Am J Physiol 193:479482, 1958 5. Buraczewski O, Porter JW, Rolls BA, et al: The course of digestion of different food proteins in the rat: 2. The effect of feeding carbohydrate with proteins. Br J Nutr 25:299-306, 1971 6. Rolls BA, Porter JWG, Westgraph: The course of digestion of different food proteins in the rat: 3. The absorption of proteins given alone and with supplements of their limiting amino acids. Br J Nutr 28:283-293, 1972 7. Weiner RP, Yoshida M, Harper AE: Influence of various carbohydrates on the utilization of low-protein rations by the white rat: 5. Relationships among protein intake, calorie intake, growth, and liver content. J Nutr 80:290-297, 1963 8. Hansem NG: Yearbook. Copenhagen, Agricultural Research Laboratory, 1972, p 231 9. Porter JW, RollIs BA: Some aspects of the digestion of proteins. Proc Nutr Soc 30: 17-25, 1971

JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 69, NO. 1, 1977

Effect of feeding different carbohydrates to rats on low protein diets.

Effect of Feeding Different Carbohydrates to Rats on Low Protein Diet S. 1. Ette, 0. Bassir, and E. A. Bamgboye Ibadan, Nigeria The experimental resu...
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