The amino acid requirements of growing turkeys. 1. Model construction and parameter estimation.

A model has been formulated to calculate the protein and amino acid requirements for growing turkeys. A requirement was taken as the sum of the needs for maintenance, for gain in carcass weight without feathers, and for the feathers. Parameters used in the model were obtained from a study of carcass composition along the growth period and from two balance trials with adult turkeys. The maintenance requirement was considered to be the sum of the needs for replacing skin and intestinal protein losses and for the obligatory creatinine excretion in the urine. Nitrogen retention was determined at 2.3 g/day in protein-fed adult (17 kg) male turkeys as an estimate for the replacement needs for skin protein loss. Creatinine excretion in these birds was 123 mg/day. When fed an N-free diet, 16.5 kg adult turkeys excreted a total of 3.5 g/day amino acids as a result of intestinal losses. The protein requirement for maintenance was estimated at 32 mg/day/g2/3 of body weight by summing up the different needs and dividing by .85, the coefficient of protein absorption. Protein and amino acid analyses of nude carcass and feathers and the growth curve were used to calculate the requirements for growth. These were then related to energy intake predicted by equations, which included previously determined coefficients for maintenance and growth (Hurwitz et al., 1980a), and the results of carcass lipid analysis. The calculated amino acid requirements were similar to those of the National Research Council (1977).

Handling of water and dietary monovalent ions by the young turkey.

Sodium and water turnover rates were measured in young turkeys fed diets with three concentrations of NaCl and kept at 12, 18 or 30 degrees C. Sodium absorption averaged approximately 60% and was unaffected by temperature. Water and sodium pools were affected by temperature and sodium intake. Water turnover was linear to sodium turnover at the lower two temperatures. No significant relationship was apparent in birds kept at 30 degrees C. The reciprocal of the slope of the function of water turnover on sodium turnover was 125-170 mM, suggesting an increase in isotonic urine excretion with sodium intake and a corresponding increase in water intake. Dietary sodium and potassium stimulated water turnover similarly. Dietary chloride concentration did not affect water turnover. In the turkey plasma pH and pCO2 were unaffected by a wide range of the anion-cation balance. It is concluded that excess sodium or potassium intakes is handled effectively in the turkey by increased water intake and excretion.

Cholecalciferol requirements of young turkeys under normal conditions and during recovery from rickets.

Day-old turkeys fed vitamin D-deficient diets became rachitic within 17-24 days. The symptoms included reductions in body weight, plasma calcium and inorganic phosphorus, plasma and intestinal calcium-binding protein (CaBP), plasma 25-hydroxycholecalciferol [25(OH)D3], bone ash, and kidney 25(OH)D3-24-hydroxylase and a rise in kidney 25(OH)D3-1-hydroxylase activity. Supplementation of the diet with 12.5 micrograms cholecalciferol per kilogram was sufficient to promote maximal body weight and normal plasma calcium, Plasma calcium, plasma phosphorus and bone ash. Feeding diets containing 250 or 1250 micrograms cholecalciferol per kilogram resulted in a reduced body weight. An increased in the concentration of plasma 25(OH)D3 with increasing dietary cholecalciferol concentration was observed. Feeding vitamin D-deficient rachitic birds for 4 days a diet containing 50 micrograms cholecalciferol per kilogram restored plasma calcium and phosphorus and bone ash. Body weight remained lower than that of the control for an additional 6-day period. Additional cholecalciferol, 25(OH)D3 or 1 alpha-hydroxycholecalciferol in the diet, intramuscular injection of the vitamin D derivatives, or a high-calcium, high-phosphorus diet did not accelerate the recovery from the rachitic state.

Glucose absorption and starch digestion in the intestine of the chicken.

Starch digestion and glucose absorption were determined in vivo along the chick's (Gallus domesticus) intestine, using 91Y and 51Cr-EDTA as unabsorbed reference substances. About 65% of the ingested starch was digested up to the end of the duodenum, 85% up to the end of the jejunum and about 97% at the terminal ileum. A fraction of about 97% of the glucose, ingested or released from ingested starch, was absorbed. The duodenum was the major site of glucose absorption which continued at a decreased rate down the small intestine. Glucose absorption increased linearily with luminal concentration with no indication of saturation. The apparent permeability for glucose was similar for the jejunum and ileum.

Phosphate absorption and excretion in the young turkey, as influenced by calcium intake.

Phosphorus absorption in the young turkey, measured with the aid of yttrium-91 as a reference substance, was linear with phosphorus intake. This observation suggested the lack of adaptation of the phosphorus transport mechanism to changes in the phosphorus needs. Phosphorus retention and bone ash initially increased with increased intake to plateau at a dietary phosphorus concentration of about 0.8%. The excess phosphorus absorbed from diets higher in phosphate, was eliminated in the urine. Plasma inorganic phosphate was linear with absorbed phosphate. The apparent phosphorus absorption from the basal vegetable diet was 45% of the intake and that of the inorganic supplement, sodium phosphate and calcium monophosphate, was about 100%, at low calcium intakes. Increasing the calcium intake above 440 mg/day progressively depressed the absorption of phosphate. This inhibitory action of calcium on phosphate absorption was resolved into a linear coefficient.

Differential response of calcium transport systems in laying hens to exogenous and endogenous changes in vitamin D status.

Changes in intestinal calcium absorption, calcium deposition into egg shell, and intestinal, renal and uterine calcium-binding protein (CaBP) in laying hens were related to changes in 25 hydroxycholecalciferol-1-hydroxylase activity (1-hydroxylase), or to the supplementation of 1alpha-hydroxycholecalciferol (1alpha-OH-CC). The onset of egg production resulted in an increased kidney 1-hydroxylase activity and intestinal and uterine CaBP. Renal concentrations of CaBP remained unchanged. Intestinal calcium and phosphorus absorption, during the period of egg shell formation, and duodenal calcium-binding protein (CaBP), were higher in 1alpha-OH-CC-fed than in cholecalciferol-fed hens. Renal or uterine CaBP and calcium deposition into the egg shell did not fluctuate with the vitamin D source or concentration. 1alpha-OH-CC injection into non-laying Nicarbazinfed hens resulted in an increase in intestinal but not renal or uterine CaBP concentrations. It is suggested that (a) CaBP in various organs responded independently to the same stimuli; and (b) calcium deposition into egg shell and uterine CaBP level are not related to kidney 1-hydroxylase activity or concentration of 1,25 dihydroxycholecalciferol.

Regulation of intestinal calcium absorption in the laying quail: independent of kidney vitamin D hydroxylation.

Two experiments were carried out with laying quail (Coturnix coturnix japonica) fed either cholecalciferol (40 mug/kg) or 1 alpha-hydroxycholecalciferol (8 mug/kg). Recovery following vitamin D depletion, as indicated by egg production and shell deposition, was faster in quail fed 1 alpha-hydroxycholecalciferol than in those fed cholecalciferol. Overall intestinal calcium absorption was higher in the 1 alpha-hydroxycholecalciferol-fed quail due to a higher absorption in the middle parts of the small intestine. This was associated with corresponding differences in the concentration of calcium binding protein. Intestinal calcium absorption was markedly higher during periods of shell formation than during periods of uterine inactivity in quail fed either cholecalciferol or 1 alpha-hydroxycholecalciferol. It is suggested, therefore, that the mechanism responsible for this difference is independent of vitamin D hydroxylation in the kidney.

Calcium-binding protein and calcium absorption in the laying quail (Coturnix coturnix japonica).

A vitamin D3-dependent calcium-binding protein (CaBP) has been found in the intestinal mucosa of Japanese quail (Coturnix coturnix japonica). This protein is similar, if not identical to that of the chick (Gallus domesticus). A similar protein fraction appears also in uterine mucosa of laying quail. Both intestinal and uterine CaBP levels are higher in laying than in non-laying quails. Uterine CaBP was higher during egg shell formation than during uterine inactivity. The slight corresponding difference in the intestinal CaBP was not significant. Intestinal calcium absorption measured with 91Y as a reference substance was higher in birds during formation of egg shell than in those with inactive uteri. The possible role of CaBP in calcium translocation is discussed.

51Cr-EDTA, 91Y and 141Ce as nonabsorbed reference substances in the gastrointestinal tract of the chicken.

The use of 91Y, 51Cr-EDTA, and 141Cr as nonabosrbed reference substances in the gastrointestinal tract of the chick was examined. In single oral dose experiments, more than 95% of the isotopes administered was recovered from the gastrointestinal tract 3 hours after dosing. 51Cr was higher in blood than the other isotopes tested. When the isotopes were fed continuously, the ratio of 91Y to 141Cr changed little throughout the gastrointestinal tract. However, the ratio of 91Y to 51Cr was higher in the crop and gizzard and lower in the duodenum than in the feed. Thus, passage time was shorter for 51Cr in the crop and gizzard and longer in the duodenum than that of 91Y. On the basis of distribution between solid and liquid phases in the intestinal contents, 91Y or 141Ce appears to be a suitable reference substance for studying the absorption of nitrogen and fatty acids, wheras 51Cr-EDTA would be preferable for bile acid absorption studies.

Semipermeable ion-exchange membranes as a preconcentration matrix for trace analysis by electrochemical and neutron-activation techniques.

Ion-exchange membranes were used in conjunction with neutron-activation analysis and anodic stripping voltammetry for the determination of certain trace metal ions. The various parameters which govern the applicability, limitations and sensitivity of the methods were investigated. A new membrane "barrier" electrode assembly was introduced and found to be useful for the anodic stripping determination of trace metal ions in the presence of surface active materials.