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Two experiments involving chicks fed a complete crystalline amino acid diet from day 8 to day 21 posthatching were employed to evaluate body composition changes and protein utilization as a function of dietary caloric density. In experiment 1 graded levels of corn oil from 5 to 25% of the diet were fed. Chicks gained as rapidly and utilized the dietary nitrogen as efficiently when 5% corn oil was fed as when higher levels were fed. As caloric density of the diet increased, chicks ate to meet their energy need and therefore cut back on feed (hence, protein) intake. Nonetheless, each increment of protein intake was used at the same efficiency. Body fat increased and body protein decreased with each incremental increase in dietary corn oil. In experiment 2 it was established that protein utilization remained constant over a wide range of protein intake (below the requirement for maximal protein retention), regardless of whether protein intake differences resulted from a change in caloric density of the diet or from a change in the dietary concentration of the complete amino acid mixture. Energy retention appeared to reach a maxima at a dietary concentration of 15% corn oil or 4.19 kcal. M.E./g. more...

SUMMARY The growth, body composition, cellular development and efficiency of dietary protein and energy utilization was measured in pigs given diets ranging from 0–15 per cent crude protein. The relationship of growth up to 49 days (y) and dietary protein concentration (x) up to 9 per cent was described by the linear regression y = 4 · 45 x + 17 · 3, but the growth response to protein plateaued at 9 per cent. Protein retention in the body was directly related to total protein intake. Energy retention was not consistently related to energy consumption particularly in pigs re-fed a 15 per cent protein diet following 0, 3 and 6 per cent protein intakes. Upon refeeding there was a considerable compensatory synthesis of DNA in many of the tissues studied. more...

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Nitrogen balance studies were performed with 12 normal full-term infants, 8 boys and 4 girls, during the first 4½ to 6 months of life. Three high-protein feedings were employed, supplying approximately 20% of the calories as protein from cow milk. Growth of the infants is interpreted as within normal limits. The concentration of total protein in the serum was not greater than that recorded in previous studies employing lesser dietary intakes of protein. The mean concentration of urea nitrogen in the serum was 21.8 mg/100 ml between 1 and 6 months of life and somewhat greater during the first month of life. A close relation between mean intake of protein in various studies and mean concentration of urea nitrogen was demonstrated. Intakes of protein were generally between 4.5 and 6 gm/kg/day, and retentions of nitrogen were, with few exceptions, between 200 and 300 mg/kg/day in the first 2 months of life and between 130 and 200 mg/kg/day from 4 to 6 months of age. The major sources of error in calculation of body content of protein on the basis of metabolic balance studies are mentioned. Metabolic balance studies are believed unsuitable for prediction of body composition. more...

The senescent leaf disks from Brassica rapa L. were floated on a medium containing 14C-L.-leucine in the presence or absence of kinetin. The increase in radioactivity in protein fraction of kinetin-treated disks was almost linear with time, while the increase in untreated disks incubated for 3 days started to slow down. The leaf disks were first incubated on the solution of 14C-L-leucine and then transferred to either kinetin solution or water in order to study whether the slower incorporation is due to the decreased rate of protein synthesis or that of protein retention. The decrease in radioactivity of disks floated on kinetin was slower than that of disks floated on water. The slower decrease in radioactivity caused by kinetin was not due to an increased turnover rate, since the same phenomena were observed in the presence of cold leucine or casein hydrolysate solution. These results suggest that kinetin retards the decomposition of protein in leaf disks and does not stimulate the synthesis of the bulk of protein. more...

An investigation has been made, by the method of balance trials, of the utilization of food protein, at different levels of protein intake, by bacon pigs throughout the period of growth from weaning to slaughter. Information has also been secured relating to the retention of lime, phosphoric acid and chlorine. The main conclusions are as follows:(1) The young pigs after weaning were able to digest their food with as high an efficiency as was displayed in the later stages of growth. The extra protein in the high-protein rations had little or no effect on the extent to which the food was digested.(2) No evidence was secured at any stage of the trials suggesting the presence of protein in the urine of the pigs subsisting on the high-protein diet.(3) The gilts showed a consistently higher rate of nitrogen retention than their brother-hogs. This behaviour was manifested even when the protein supply in the gilt's ration was lower than that in the ration of the hog with which it was compared. This more efficient utilization of food protein by the gilts is held to explain the tendency of gilts to give somewhat leaner carcasses than hogs.(4) Nitrogen retention from the high-protein diet was no higher than from the normal-protein diet, a rinding suggesting that the amount of protein in the normal rations is sufficient to meet the demands for the quick growth required by modern standards of bacon production. more...

SUMMARY1. The experiment was designed to investigate the effect of growth at a high ambient temperature, 33–35°C, on the protein and energy metabolism of pigs, compared with 25°C. The high temperature caused an increase in rectal temperature of 1·4° to 1·7°C. The animals were given two low levels of feeding while growing between 25 and 70 kg live weight; energy and nitrogen retention were measured periodically.2. The apparent digestibilities of the dietary dry matter and energy were decreased and urinary nitrogen losses were increased at the high temperature. Heat production was increased at the high temperature, by between 2% and 10%, the effect becoming more pronounced during the course of the experiment. Retention of energy and nitrogen was reduced at the high temperature.3. The net efficiency of utilization of metabolized energy above maintenance was between 63% and 67%, and was not significantly affected by live weight or temperature. The results suggested that maintenance requirement was increased at the high temperature.4. Analyses of sample joints indicated that the high temperature caused an increase in fat percentage only at the higher level of feeding; this result agreed with fat and protein retention calculated from the balances. more...

Six semi-synthetic diets with a casein and corn-starch base, containing 10 to 60% protein were fed for 4 months to young gilthead breams (Chrysophrys aurata, of average initial weight 2.6 g). The object of the study was to determine the optimum amount of protein necessary for growth. The daily intake of the gilthead breams was 5.2 to 2.3% of their live weight. The less protein the diet contained, the more feed the fish consumed. The conversion factor decreased regularly as protein percentage increased. The most favourable conversion rate was 1.4, noted for the group receiving 60% protein. The less protein in the diets, the better the protein efficiency for weight gain and body protein retention. Growth of gilthead breams was proportional to protein content of the diet up to an incorporation rate of 40%. Beyond this, no significant difference in final average individual weight was observed. These results are discussed in relation to those reported for other species of fishes. They show that the gilthead bream requires about 40% protein in its diet, as do most fresh-water species. more...

1. Reduced intake of energy or protein per se decreased riboflavin requirement of the chicks under restricted feeding regimens.2. In severe riboflavin deficiency (2·26 mg/kg diet), efficiency of utilization of both energy and protein was decreased significantly under ad lib. conditions of feeding.3. Efficiency of utilization of energy (but not protein) was decreased significantly in border-line riboflavin deficiency (3·02 mg/kg diet), when chicks were fed ad lib.4. Efficiency of protein utilization was decreased significantly in severe riboflavin deficiency when chicks received an energy-restricted diet supplying 80, 70 or 60 yo of the energy intake of the controls.5. Neither energy nor protein utilization was affected by riboflavin deficiency when both energy and protein were restricted to 70 yo of that consumed by chicks fed ad lib. However, the riboflavin deficiency produced characteristic deficiency symptoms, namely heterophilia, curled-toe paralysis, and reduction in concentration of liver riboflavin. more...

As an extension of investigations of the endocrine control of fasting metabolism (White and Dougherty, 1947; Szego and White, 1949; White, Hoberman and Szego, 1949), a study has been conducted of the role of the gonads in the mobilization of tissue constituents during fasting. This approach appeared of interest in view of the implication of androgenic hormones in net protein anabolism (cf., Kochakian and Murlin, 1935; Kenyon et al., 1944; Kochakian, 1946; White, 1948) together with the observation that it was possible to demonstrate relative protein retention under the influence of growth hormone during total inanition (Szego and White, 1949). Moreover, since it appears that gonadal hormones exert an influence upon the size and enzymic activity of specific organs (cf. Korenchevsky, 1939; Korenchevsky and Ross, 1940; Korenchevsky and Hall, 1941; Ross and Korenchevsky, 1941; Kochakian, 1946), it was of interest to localize further, if possible, certain of the metabolic influences more...

Protein quality of five Middle Eastern meals was evaluated by using simplified chemical score (SCS), protein efficiency ratio (PER), net protein ratio (NPR), protein retention efficiency (PRE), and net protein utilization (NPU). The meals consisted of Arabic bread in combination with sesame (Halaweh), with sesame and chickpea (Hommos tehineh), with rice and lentil (Rice Mujaddarah), with parboiled wheat and lentil (Burghul Mujaddarah), or with parboiled wheat, yoghurt, and meat (Kishk). Halaweh, Hommos tehineh, and Kishk were limiting in lysine, while the other two meals were limiting in methionine. Lysine and methionine appeared to be fully available in all meals with the exception of Halaweh, in which lysine was partially unavailable. All methods ranked the meals in the same order, with Halaweh as the poorest, Hommos tehineh the best, and the other three meals slightly inferior to Hommos tehineh in quality. Methods for determining the protein contribution of meals which took into account both quantity and quality of protein, i.e., net dietary protein calories per cent (N.D-p. Cals %), protein rating (PR), and per cent complete protein (% CP), were also tested. Values for N.D-p. Cals % and PR correlated closely with each other and relatively poorly with % CP. Values for SCS × % protein calories correlated closely with N.D-p. Cals % and PR. more...

An evaluation of the protein and energy value of wheat, barley and maize when fed in conjunction with wheat offals was made. The Gross Protein Value test, and two methods of estimating protein and energy retention, one the conventional balance technique and the other body analysis, were used. For protein and energy provision, the cereals were of equal value when fed in this way. The values obtained by the two methods of determining protein retention varied significantly and this is discussed. The relative accuracy of the several methods is also discussed together with the validity of the Gross Protein Value test. more...

Summary Three types of milk diet were tested in balance experiments using premature infants. They were: breast milk, “humanized” milk and half skimmed cow's milk containing more protein and less fat than the other' two milks. It was ascertained that protein retention was about the same on all three diets, while nitrogen elimination via the urine was much higher on the half skimmed milk. Fat retention was lowest on half skimmed milk, but this may have been due to the low fat content of that milk. more...

SummarySimultaneous administration of testosterone propionate and growth hormone to castrated rats resulted in a summation of their respective effects on body weight and nitrogen retention even at maximal doses. more...

with the amount of paraquat applied (Table 2). Grasses were not seriously affected by the fungus. These unseasonably late rains also resulted in prolonged growth of the unsprayed clover and an increase in total production up to three times that of the sprayed clover. The amount of paraquat necessary to desiccate the different species within 6 days of the early spraying varied with species and year (Table 3). The grasses were desiccated by lower rates than were the clovers. Subclover was the most resistant, never drying greater than 50% even with 2 lb./acre. Earlier studies also showed subclover very resistant to damage from paraquat (Kay, 1964 and 1968). This report indicates that complete desiccation of the plants studied is not necessary for protein retention. While more than 1 lb./ acre was required for complete desiccation of any of the species tested, protein was retained with much lower rates. This was also noted in the work on curing range forage (Kay and Torell, 1970). Literature Cited more...