Medium Protein Diet Research Articles

Effect of feeding restricted amounts of a medium‐ and high‐protein diet on growth and body composition of ducklings

AbstractA total of 216 ducklings of mixed sex were fed diets containing either 19.5 or 24.7% crude protein, either to appetite or to 85% of appetite, from 1 to 21 or 24 days of age.There were no significant interactions between dietary protein content and level of feeding. At 21 days ducklings fed the high‐protein diet were 28% heavier than those fed the medium‐protein diet and birds fed the higher level of intake were 17% heavier than restricted groups. At 24 days the body weight of restricted ducklings was similar to that of those fed the higher level of intake at 21 days. From 1 to 21 days efficiency of food utilisation was better for ducks fed the high rather than the medium protein diet, but similar for the two levels of food intake. Efficiency of the restricted groups in the 1 to 24 days period was slightly worse than that of groups of similar body weight fed the higher level of intake from 1 to 21 days.At 21 days carcasses of ducklings fed the high protein diet contained 31% dry matter, of which 34% was fat and 53% was protein, compared with 34% dry matter in the carcasses from the medium protein groups, of which 41% was fat and 48% was protein. Feed restriction had no effect on carcass dry matter and the reduction in percentage ether extract was only about half the magnitude of the reduction due to dietary protein level. Dietary treatments had no significant effect on percentage protein in fat‐free dry matter. At 24 days carcasses of restricted ducklings contained more dry matter but the proportions of ether extract and crude protein were similar to those in younger (21 days) ducklings of similar body weight fed at the higher level of food intake.

The performance of calves given concentrate diets treated with formaldehyde

Five groups of Friesian bull calves were given concentrate diets containing 70 % barley in which low (12 %), medium (15 %), and high (19%) protein levels were obtained by varying the amount of peanut meal included. The effects of protein level and of formaldehyde treatment of the complete diet at the low and medium protein levels were studied in terms of liveweight gain, voluntary food consumption, digestibility of the diet, ammonia nitrogen in rumen fluid, and urea and a-amino nitrogen in blood plasma. Observations were begun when the calves reached 70 kg liveweight and continued until they reached 130 kg liveweight. The calves given the low protein diets grew more slowly than those given the higher protein diets. The calves given the high protein diet grew no better than those given the medium protein diets. Formaldehyde treatment was associated with an increase in the rate of liveweight gain of 9% (P = 0.11) at the low protein level but had practically no effect at the medium protein level. The treatment did not adversely affect voluntary food consumption but was associated with decreases in the digestibility of nitrogen and in rumen ammonia levels and small increases in plasma urea levels.

Calcium Retention in the Adult Human Male as Affected by Protein Intake

The effect of level of protein intake on the excretion and retention of calcium in the adult human male was studied. Nine young men given 800 mg calcium daily were fed 47, 95 and 142 g protein each for 15 days. Subjects retained an average of 12 and 1 mg calcium, respectively, when fed 47 and 95 g protein but lost 85 mg when fed 142 g. There was a highly significant difference in urinary calcium at each level of protein intake, the respective values being 217, 303 and 426 mg calcium when the subjects were fed the low, medium and high protein diet. Fecal calcium was significantly decreased as the protein intake was increased from 47 to either 95 or 142 g daily but not when it was increased from 95 to 142 g. Protein intake had no effect on serum calcium.

The nutrition of the early weaned lamb:III. The effect of ad libitum intake of diets varying in protein concentration on performance and on body composition at different live weights

SUMMARY1. Fifty lambs weaned at about 5 weeks of age were fed ad libitum on mixtures of barley and fish meal containing either 11·0, 15·7 or 19·4% crude protein in dry matter. Male and female lambs on each diet were killed at intervals, starting after they had been on the diets for 3 weeks. The last to be killed had attained a live weight of about 55 kg.2. The mean rate of voluntary feed consumption was less at all live weights for the lambs on the diet containing 11·0% crude protein than for those on the other diets and the difference was statistically significant at live weights of 30 and 35 kg. Mean rates of live-weight gain on the low, medium and high protein diets were respectively 191, 270 and 330 g per day for the male lambs and 177, 225 and 301 g per day for the females, the increase with protein concentration being highly significant. Feed conversion rate (kg feed/kg gain) over the whole experiment increased with increasing weight at slaughter. After adjustment for this effect the mean values showed significant dietary effects, and were least on the highest protein concentration.3. The percentages (y) of nitrogen or of ether extract in the dry matter of the carcass or of the whole empty body were found to be related non-linearly to the empty-body weight (x) at time of slaughter. The relationships were satisfactorily described by equations of the form y = A + Be-Cx, where A, B and C were fitted constants. The relationships for males and females had to be fitted separately, but a common value of A could be used with each of the three groups of male lambs and similarly for the three female groups.4. These relationships were used to obtain estimates of the nitrogen, ether extract and energy content of empty-body gain per unit live-weight gain. The estimated percentages of energy retained as fat were of the order of 76–83%, in agreement with ARC estimates (1965), except for male lambs between 14 and 20 kg live weight on medium or high-protein diets, for which the estimates were only 62 and 63%.5. The implications of these relationships are discussed with particular reference to the finding of dietary effects on body composition during the growth period of the lambs and to the tendency for these differences in body composition to diminish as mature live weight was approached. The differences in body composition between male and female lambs showed no such tendency to diminish.

Efficiency of conversion of food to wool. IV. Comparison of sheep selected for high clean wool weight with sheep from a random control group at three levels of dietary protein

An experiment is described in which ewes from a flock selected for a number of years for high clean wool weight per head (S) are compared with ewes from a random control flock (C) under ad libitum feeding of three diets differing in crude protein content but not in gross energy. Differences between the S and C groups were significant for clean wool weight (W), efficiency of conversion of gross energy to wool (W/I), fibre number per unit area of skin (N), and mean body weight (B), the S group having higher values for W, W/I, and N but being lighter in B. Differences between the means of ewes fed on the high and medium protein diets (H and M groups) and the means of those fed on the low protein diet (L group) were highly significant for Wand each of its physical and physiological components. The H and M groups had higher values for W, W/I, B, intake per unit body weight (I/B), fibre cross-sectional area (A), staple length (L), and smooth body surface area (S) but lower values for N. The mechanisms of these differences are discussed in relation to other published work. Differences between ewes fed on the H and M diets were significant for Wand W/I, the H groups having the higher value in each case. These responses are contrasted with those reported by other workers and the possible mechanisms are outlined. When differences between the S and C groups on the H and M diets were averaged and contrasted with the differences between them on the L diet, there were significant group x diet interactions in W and W/I and appreciable but not significant interactions in N, A, and L. Taking the value for the C group as 100 in each case, the values for the S group on the L, M, and H diets respectively were: W, 97, 125, 129;W/I, 92,129,132; N,129,110,111; A, 74,114,110; L, 92,109,110. The possible mechanisms for these changes in the differences between the S and C groups are discussed. The group x diet interaction was not significant for any character when the difference between S and C groups on the H diet was contrasted with the difference between them on the M diet, though there were slight increases in the differences in Wand W/I on the H diet.

Nutritional factors affecting lean meat production in cutting pigs

A series of trials were designed to determine the slaughter weight of cutting pigs at which lean meat production is most economical, and to investigate nutritional factors which affect lean meat onput in cutting pigs of about 260 lb. live-weight. The trials involved about 1100 pigs and ad lib. feeding was adopted from weaning to slaughter.In the first trial, pigs were fed on various diets to 300 lb. live-weight. The diets differed in the amount of protein fed during the 90–180 lb. growth period, and the most economic growth was made by feeding a high protein (17 %) diet to 140 lb., or a medium protein (14 %) diet to 180 lb. followed by a cereal-mineral diet thereafter to 300 lb.Animals were slaughtered and dissected at various live-weights between 90 and 300 lb. and it was found that killing-our percentage, the percentages of usable meat (lean plus fat) and of fat, increased with carcass weight. The increase in fat deposition was mainly at the expense of the non-edible parts of the carcass. Onput of lean and increase in area of eye muscle occurred throughout the range.Total food requirements, expressed as pounds of food, calories of gross energy or pounds of protein, per pound of usable meat produced decreased as slaughter weight increased. The cost of food required to produce a given quantity of lean meat was least when pigs were slaughtered between 240 and 260 lb. when the commercial value of the remainder of the carcass was taken into account.The second trial investigated the effect of two levels of protein and mineral supplementation of cereals during the 140–260 lb. growth period of heavy pigs. Correct mineral supplementation of cereals was essential because, although lean meat production was not increased, the cost of food required to produce it was less. The lower protein diet had no effect on growth or carcass composition, but the higher protein diet increased the lean meat content of carcasses and decreased the amount of food required to produce it. The production of the extra lean meat, however, was not economical because of the cost of the high protein diet.The third trial showed that replacement of barley by wheat during the 140–260 lb. growth period led to carcasses having less lean meat and to higher feed requirements. This is probably connected with the high energy content of wheat as compared to barley.

The influence of protein deficiency and excess in diet on immunity response. II

After the long-term administration (eight months) of a low protein, medium and high protein diet in rats, no significiant differences were found in the formation of specific antibodies following immunisation and in natural and acquired resistance to Salmonella paratyphi B. The differences obtained by the short-term administration of the diets were not accentuated on long-term administration; on the contrary, these differences were effaced. Four months after commencing the diets the level of complement was determined. The group of rats with protein deficiency had a significantly smaller amount of complement as compared with the groups of rats fed on a high protein and medium protein diet. In the group of rats fed on a low protein diet, a significant number of deaths occurred from spontaneous infection in the course of the experiment, resulting in natural selection of the more resistant individuals. The possibility of adaptation to long-term administration of the diet is discussed. При долговременном (8-м есячном) низкобелков ом, высокобелковом и ура вновешенном в смысле содержания б елков рационе у крыс н е наблюдалось сколько-нибудь значительной разницы в образовани и специфических анти тел после иммунизации и в естес твенной или приобрет енной устойчивости по отно шению к Salmonella paratyphi В. Разницу, полученную при кратковременной диэ те, не только не удавал ось увеличить в результа те длительного рацио на, а напротив, эта разниц а стиралась. Уровень к омплемента определялся через 4 ме сяца после начала опыта с диэтой. У группы крыс, получав ших бедную белками пищу, количес тво комплемента было значительно мен ьше в сравнении с крыс ами, получавшими богатый белком или нормальный корм. В течение опыта в групп е крыс с низкобелковой пищей наблюдался значительный падеж в результате спонтанн ых инфекций, так что осуществлялс я естественный отбор наиболее устой чивых особей. Обсуждается возможн ость приспособления к длительной односторонней диэте.

Potassium, Sodium and Chlorine Balances of Pre-School Children Receiving Medium and High Protein Diets

Potassium, Sodium and Chlorine Balances of Pre-School Children Receiving Medium and High Protein Diets

THE EFFECT OF DIETARY PROTEIN ON THE COURSE OF NEPHROTOXIC NEPHRITIS IN RATS

Acute nephritis of medium severity, affecting both glomeruli and tubules, was produced in rats by injections of anti-rat-kidney serum, given on 3 consecutive days. The course of the nephritis was markedly influenced by the type of diet which was fed. Rats tended to recover promptly from the induced nephritis when a low protein-high carbohydrate diet was given. On the other hand, in nephritic rats maintained on a medium protein diet the nephritis almost invariably became chronic and half the animals died of renal insufficiency during the 10(1/2) months of observation. Finally none of the rats which received a high protein-low carbohydrate diet recovered from the acute renal injury; all developed chronic progressive nephritis and the majority died of renal failure after some months.

The Influence of Diet on the Nitrogen Balances of Pre-School Children: Two Figures

Five children received constant diets containing 3 gm. of protein per kilogram. They all excreted the same proportion of the nitrogen intake, but the urine figures fluctuated according to intake variations while the feces values remained constant for each child and were proportional to the dry weight of the feces. The ratio of fecal nitrogen to dry matter consumed remained fairly constant for each child but varied between children according to the character of the stools. For individual children the coefficient of digestibility varied between 86.0 and 92.7%, while the retention values remained more constant but both values fluctuated in proportion to the period by period variation in the diet. Immediately following the change to a 4-gm. protein diet, the excretion values were irregular, but after 9 days they had apparently reached an equilibrium. A comparison of the data following the preliminary period with that on the medium protein diet indicated the effects of protein on the metabolism. The percentage of the intake excreted did not vary, but the total grams increased, practically all of the increase occurring in the urine. The small fecal nitrogen increase was proportional to the increase in dry weight of the feces. The ratio of fecal nitrogen to dry food eaten increased slightly for each child but there was no correlation between the two factors. The coefficient of digestibility was higher for each child. The percentage of the intake nitrogen retained was practically the same, but the total grams increased. The average of the retention and intake values per kilogram for all children for each separate period showed that the children retained nitrogen in relation to the period by period variations except immediately following the change in diet.