Biomedical subjects

C C Whitehead

Publications and source records attributed to C C Whitehead.

At least 73 records · Page 4Linked to original sources

PubMed1989

Relation between some folate-dependent metabolic pathways and dietary folate content in chicks.

Responses of several folate-metabolizing pathways to dietary folic acid were studied in 2-week-old chicks. Oxidation of a histidine load to carbon dioxide was impaired in folate-deficient chicks. There was a curvilinear relation between oxidation and dietary folate, and maximum oxidation occurred with 2 mg supplemental folic acid/kg. Hepatic activities of glutamic acid formiminotransferase (EC 2.1.2.5) and glycine N-methyltransferase (EC 2.1.1.20) were not affected significantly (P greater than 0.05) by dietary folic acid. The activity of dihydrofolate reductase (EC 1.5.1.3) in erythrocytes was elevated in folate-deficient chicks. These studies show that the activities of two folate-dependent pathways can be used as biochemical criteria of folate status in chicks.

Animal Nutritional Physiological Phenomena↗

PubMed1989

Responsiveness to dietary cholesterol in the domestic fowl is not related to the degree of body fatness.

The hypothesis that chickens of a lean rather than a fat line are hyperresponsive to dietary cholesterol was tested. Birds of the fat line showed higher initial plasma total cholesterol levels. The addition of 1% (w/w) of cholesterol to the diet significantly increased plasma cholesterol concentrations but there was no difference in response between the two lines. Dietary cholesterol increased liver cholesterol in both lines, the effect being more pronounced in birds of the lean line. It is concluded that the responsiveness of plasma cholesterol to dietary cholesterol in chickens is not related to the degree of body fatness.

Adipose Tissue↗

PubMed1988

Haematological and tissue abnormalities in chicks caused by acute and subclinical folate deficiency.

1. Haematological, histological and ultrastructural findings in young chicks fed on a purified diet severely deficient in folate are reported. 2. Growth of the birds was greatly depressed and they had a macrocytic anaemia. Other haematological changes included abnormal nuclear formations in erythrocytes, numerous mitoses and hypersegmented granulocytes. 3. Megaloblasts were observed in bone marrow and their fine structure is described for the first time in an avian species. 4. Morphological changes occurred also in the liver. The parenchyma had damaged sinusoidal endothelium, inflammatory cells and no glycogen. Mitochondria were damaged and many were associated with unusual crystalline structures. 5. Chickens fed on a semi-purified diet of low folate content showed no growth depression or clinical signs of deficiency but had abnormal haematological values and morphological changes that resembled those seen in birds fed on the purified diet. 6. These abnormalities responded to dietary supplements of pteroylmonoglutamic acid in a dose-related manner and may be useful in diagnosing subclinical folate deficiency.

Animals↗

PubMed1988

Effects of age and of early lighting on ovarian function in breeding turkeys.

1. Yellow follicle numbers and production of defective egg shells were greater in the early part of the laying period in conventionally-reared turkeys photostimulated at 24 rather than 30 weeks of age. 2. The number of yellow follicles declined with age and were similar in both groups at 40 weeks of age. 3. At 55 weeks of age more birds photostimulated at 24 weeks were out of lay and birds in lay had fewer yellow follicles and more atresia compared with turkeys photostimulated at 30 weeks of age. 4. The numbers of white follicles in the 1 to less than 2 mm size were similar in the two groups at each age. The proportion of white follicles which were atretic was negatively related to the number of yellow follicles, particularly in follicles 5 to less than 8 mm diameter.

Age Factors↗

PubMed1988

Energy and nitrogen retention and loss in broiler chickens genetically selected for leanness and fatness.

1. A breeding programme based on the assessment of the body fat content of broilers by measurement of plasma very low density lipoprotein concentration has resulted in 2 lines with significantly different body fat contents. 2. Energy and nitrogen intake and retention were measured in 63- to 70-d-old females from each line during 5-d periods of indirect chamber calorimetry. Results obtained by this technique were compared with results from a previously published growth trial incorporating carcase analysis at 49 d. 3. Body weight, metabolisable energy intake, heat production, energy retention and efficiency of energy retention did not differ significantly between the fat and lean lines. 4. The proportion of energy retained as crude protein and the efficiency of crude protein retention were significantly greater in the lean line. 5. In terms of whole-body energy and nitrogen exchanges, the essential difference between the lines was therefore in the partition of the same quantity of retained energy between fat and protein deposition. 6. The results were consistent with a higher rate of breakdown of amino acids in the fat line; because heat production did not also increase, a greater proportion of retained energy therefore became available for storage as fat.

Adipose Tissue↗

PubMed1988

Fatty acid requirements of breeding turkeys.

1. Turkey hens were fed during the breeding period on 5 diets containing different amounts of linoleic acid and total fat provided by varying supplements of maize or olive oils. 2. Reproductive performance of the turkeys increased in response to dietary linoleic acid. Eleven g linoleic acid/kg diet gave optimum poult production. 3. Egg weight did not show a significant response to dietary fat content. 4. Adipose tissue fatty acid composition of the hens was influenced by dietary oleic and linoleic acid content.

Adipose Tissue↗

PubMed1987

Role of avidin and other biotin-binding proteins in the deposition and distribution of biotin in chicken eggs. Discovery of a new biotin-binding protein.

In addition to the previously characterized egg-yolk biotin-binding protein (BBP-I), we have discovered another BBP (BBP-II) in the plasma and yolk from laying hens. BBP-I is stable to 65 degrees C, whereas BBP-II is stable to 45 degrees C. Both proteins are normally saturated with biotin and together they account for most, if not all, of the biotin in hen plasma and yolk, except in hens fed excessive amounts of biotin (greater than 1 mg of biotin/kg of feed). The maximal production of BBP-I is attained at lower levels of dietary biotin (approximately 50 micrograms/kg) than for BBP-II (approximately 250 micrograms/kg); however, the maximal production of BBP-II is severalfold greater than for BBP-I. Consequently, as dietary biotin increases, the ratio of BBP-II to BBP-I increases and becomes constant at dietary intakes of biotin above 250 micrograms/kg. The observation that the amounts of these proteins are limited by biotin in the normal dietary range (less than 250 micrograms/kg) suggests that biotin is required for the synthesis, secretion or stability of these proteins. Although both plasma vitamin-protein complexes are transported to the oocyte and concentrated in the yolk, BBP-II is transferred more efficiently. Thus biotin deposition in the yolk is a function of the amounts and relative concentrations of the two proteins. Dietary biotin above 250 micrograms/kg exceeds the transport capacity of BBP-I and BBP-II in the plasma; however, unbound biotin does not accumulate. Rather it is efficiently scavenged by avidin in the oviduct and transferred to the egg albumen. Only when avidin becomes saturated at high dietary intake does free or weakly bound biotin accumulate in plasma and yolk. The synthesis of avidin is independent of dietary biotin. Small amounts of BBPs with the heat-stability of avidin or BBP-I respectively are present in the plasma of adult males or immature chickens. BBP-II, the major BBP in the plasma and yolk of laying hens, was not detected in the plasma of non-laying chickens.

Animals↗

PubMed1987

N tau methyl histidine excretion and [U-14C]amino acid oxidation in fully chickens from two lines selected for high and low body fat contents.

Protein turnover and amino acid oxidation were examined in two lines of domestic broiler chicken selected for high (fat) and low (lean) plasma very low density lipoprotein levels. Protein turnover was assessed by comparing N tau methyl histidine excretion in two lines. No differences between the fat and lean birds were found. Oxidation of [U-14C]amino acids in vivo was measured in birds of both lines which had been fed ad lib. The lean birds oxidized significantly less of the administered [U-14C]amino acids to 14CO2 than their fat counterparts during the first 90 min following administration. Lean birds also excreted significantly less 14C than fat birds from [U-14C]amino acids.

Amino Acids↗

PubMed1987

Reproductive performance of dwarf broiler breeders given different allowances of food during the rearing and breeding periods and two lighting patterns.

1. Dwarf broiler breeders were either fed ad libitum or restricted to allow growth to mean body weights of 1.4 or 1.8 kg at 20 weeks of age. During the breeding period these birds were fed ad libitum, or food was restricted to different degrees and the birds subjected to two different incremental lighting patterns. 2. Egg production of birds fed ad libitum during the breeding period increased with the degree of food restriction during rearing. 3. Food restriction during the breeding period increased the egg production of birds weighing 1.8 kg at 20 weeks but decreased that of birds weighing only 1.4 kg. 4. Fertility was relatively low and inversely related to body fatness of females. 5. The differences in lighting pattern did not influence performance. 6. For optimum reproductive performance during the rearing period dwarfs should not be restricted so severely as conventional breeders. Best chick production was obtained from birds with a bodyweight of 1.8 kg at 20 weeks of age, which were subjected to a 10% restriction of food during the breeding period.

Age Factors↗

PubMed1987

Relationship of biotin deposition in turkey eggs to dietary biotin and biotin-binding proteins.

The biotin and biotin-binding protein contents of egg yolk, egg albumen, and hen plasma were determined on eight groups of four turkey hens each that had been fed diets ranging from less than 10 to 3,475 micrograms available biotin per kilogram. Biotin deposition in the yolk was strongly dependent upon available dietary biotin below 100 micrograms/kg. Between 100 and 1,000 micrograms/kg the amount of biotin deposited in the yolk increased slightly and was directly related to and limited by a biotin-binding protein that transferred biotin from the plasma to the yolk. Over the entire dietary range, biotin deposition in yolk was proportional to the total biotin concentration in the plasma. In contrast, biotin deposition in the albumen, which was proportional to dietary biotin, increased several-fold over a very narrow range of plasma biotin concentration (56 to 62 micrograms/L). When dietary available biotin exceeded 160 micrograms/kg, there was more biotin deposited in the albumen than in the yolk. Although the concentration of unbound biotin in plasma is low, it appears to be the component of plasma biotin that is rapidly scavenged by avidin in the oviduct. It seems likely that avidin-bound biotin is available to the turkey embryo.

Animals↗

PubMed1986

Riboflavin-binding protein. Concentration and fractional saturation in chicken eggs as a function of dietary riboflavin.

The concentration of riboflavin and riboflavin-binding protein were determined in the plasma, egg yolk and albumen from hens fed a riboflavin-deficient diet (1.2 mg/kg) supplemented with 0, 1, 2, 3, 10 and 40 mg of riboflavin/kg. We observed that the deposition of riboflavin in egg yolk and albumen is dependent on dietary riboflavin and reaches half-maximal values at about 2 mg of supplemental riboflavin/kg. The maximal amount of riboflavin deposited in the yolk is limited stoichiometrically by the amount of riboflavin-binding protein, whereas the maximum amount of riboflavin deposited in albumen is limited by other factors before saturation occurs. The amount of riboflavin-binding protein in yolk and albumen is independent of dietary riboflavin. If there is a specific oocyte receptor for riboflavin-binding protein, it cannot distinguish between the apo and holo forms of the protein. Riboflavin-binding protein is about six times more concentrated in yolk than in plasma.

Animals↗

PubMed1986

Development of divergent lines of lean and fat broilers using plasma very low density lipoprotein concentration as selection criterion; results over the fourth generation and lack of effect of dietary fat on performance and carcase fat content.

Comparisons were made of the performance and carcase composition of lean and fat broilers from the 4th generation of a breeding experiment which were fed diets containing 25 or 80 g fat/kg. Selection over the 4th generation resulted in continued divergence in the selection trait and the correlated responses of total body lipid and protein contents and the efficiencies of conversion of food and dietary protein. In both lines body weight, efficiency of food utilisation and total body lipid and protein contents were unaffected by dietary fat content. Tissue fatty acid composition was influenced by dietary and genetic factors: dietary fat increased the proportions of linoleic and oleic acids at the expense of palmitic, palmitoleic and stearic acids whilst greater body fatness increased the proportion of palmitoleic at the expense of linoleic acid.

Adipose Tissue↗

PubMed1985

Biotin requirements of broiler breeders fed diets of different protein content and effect of insufficient biotin on the viability of progeny.

Production of eggs or normal chicks was depressed when practical diets containing 168 g or 137 g of crude protein (CP)/kg were not supplemented with synthetic biotin. Overall egg production and hatchability of fertile eggs was significantly (P less than 0.05) higher with the diets containing 137 g CP/kg. Biotin requirement was higher with the diet containing 168 g CP/kg and was estimated to be about 100 micrograms of available biotin/kg, equivalent to a daily intake of 16 micrograms for food-restricted hens. Biotin concentrations in egg yolk and chick plasma were related to maternal intake and increased with maternal age. The minimum yolk biotin concentration indicative of adequate maternal status was about 550 micrograms/g. Chicks from young hens fed insufficient biotin had the poorest biotin status at hatching and their growth potential and viability were reduced.

Animals↗

PubMed1985

Influence of egg storage on hatchability, embryonic development and vitamin status in hatching broiler chicks.

Storage of eggs for 14 d prior to incubation depressed hatchability by 10%. Most of the increase in embryonic mortality (64%) occurred during the first week of incubation, with a further 30% taking place during the third week. Chicks hatching from stored eggs did not show any increased incidence of physical abnormalities characteristic of vitamin deficiencies. Chicks from stored eggs showed haematological abnormalities characteristic of mild macrocytic anaemia. Such changes can result from deficiencies of folic acid or cobalamin. Biochemical and haematological data did not suggest impairments in the status of the chicks with respect to a range of other vitamins.

Animals↗

PubMed1985

Assessment of biotin deficiency in animals.

Biotin deficiency can be induced readily in monogastric animals and is accompanied by characteristic abnormalities. These include dermal lesions involving hyper- and parakeratosis and, in fur-bearing animals, alopecia and achromatricia. Biochemical changes include depressions in the activities of biotin-dependent enzymes and the metabolic pathways in which they are involved. However, it has been shown in chickens that the relative changes in the activities of these enzymes and the resultant manifestations of the deficiency can be markedly influenced by the dietary content of other nutrients such as protein or fat. Biochemical criteria are required for the diagnosis of subclinical deficiency and these are best-established for poultry. Blood pyruvate carboxylase activity is a good criterion in young birds. Biotin-responsive disorders have been identified in several species. The etiology of fatty liver and kidney syndrome in chickens is now largely understood and is an interesting example of how a combination of nutritional and environmental factors can result in sudden death in, until then, apparently healthy animals.

Acetyl-CoA Carboxylase↗

PubMed1984

Lipogenic enzyme activity and fructose 2,6-bisphosphate concentration in livers of two lines of domestic fowl (Gallus domesticus) selected for different body fat content.

Livers were obtained from two lines of domestic broiler which had been selected for low (lean) and high (fat) plasma very-low-density lipoprotein concentration over three generations. The fat line possessed significantly higher hepatic specific activities of malate dehydrogenase (NADP), ATP citrate lyase and fatty acid synthase, and lower glucose bisphosphatase than the lean line. The glycolytic enzymes, pyruvate kinase and phosphofructokinase, were similar and so was the concentration of fructose 2,6-bisphosphate. This recently discovered metabolic regulator was present at somewhat higher concentrations than previously reported in rats or mice. It exhibited a positive correlation with phosphofructokinase activity (only data for the fat line are shown), and stimulated enzyme activity when added to crude preparations.

ATP Citrate (pro-S)-Lyase↗

PubMed1984

Comparison of plasma very low density lipoproteins and lipogenic enzymes as predictors of fat content and food conversion efficiency in selected lines of broiler chickens.

Activities of lipogenic enzymes and plasma very low density lipoprotein (VLDL) concentrations were measured in lines of chickens with large differences in food conversion efficiency (FCE) and body fat. Hepatic activities of malate dehydrogenase [EC 1.1.1.40 (MD)] and ATP citrate lyase [EC 4.1.3.8 (CL)] were correlated with the proportion of both abdominal and total body fat (r = 0.50) but were poorly correlated with gain: food ratio. Activities of MD and CL in plasma were low and variable and were not correlated with any other characteristics. Plasma VLDL concentration was significantly correlated with the proportion of abdominal and total body fat (r = 0.59), and gain: food ratio (r = 0.36).

ATP Citrate (pro-S)-Lyase↗

PubMed1984

Biotin intake and transfer to the egg and chick in broiler breeder hens housed on litter or in cages.

Biotin concentrations in the plasma of hens and chicks and in egg yolk were measured at different ages in broiler breeder hens housed on litter or in cages and fed restricted amounts of diets containing different concentrations of biotin. In the caged groups, biotin concentrations in these fluids increased with increasing maternal biotin intake over the range of intakes studied. Biotin concentrations in hen plasma and yolk were linearly related and increased with age. Biotin concentration in chick plasma was highly correlated (r = 0.93) with yolk concentration. The poorest biotin status was predicted for chicks from young hens. There was no evidence that ingestion of excreta contributed substantially to the biotin status of hens housed on deep litter.

Aging↗