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Biomedical subjects

L B Carew

Publications and source records attributed to L B Carew.

At least 19 recordsLinked to original sources
PubMed2003

Effects of methionine deficiencies on plasma levels of thyroid hormones, insulin-like growth factors-I and -II, liver and body weights, and feed intake in growing chickens.

We showed previously that Met deficiency at 0.25% of the diet causes elevations in plasma triiodothyronine (T3) in broilers. In the present study, plasma levels of thyroid hormones as well as insulin-like growth factors (IGF)-I and -II were measured in chicks fed 3 deficient levels of total Met. Control (0.5%) and Met-deficient diets (0.4, 0.3, and 0.2%) were fed to male broilers from 8 to 22 d of age. Additional groups of control chicks were pair-fed with the Met-deficient ones. Chicks receiving 0.4% Met increased feed intake by 10% with no significant change in body weight. The more severe Met deficiencies of 0.3 and 0.2% caused graded reductions in feed intake and weight gain. However, corresponding pair-fed control chicks were significantly heavier. These changes suggest more marked alterations in metabolic processes with 0.3 and 0.2% Met than with 0.4% Met. Liver weights were heavier in chicks fed 0.3 and 0.2% Met but not 0.4%. Plasma T3 was higher in all deficient chicks compared with the free-fed control, which was significant only with 0.3% Met. However, with 0.3 and 0.2% Met, plasma T3 was significantly elevated compared to pair-fed controls. Plasma thyroxine (T4) was lower in all deficient groups, which was significant only with 0.2% Met, whereas no significant differences occurred between deficient chicks and their pair-fed controls. Plasma IGF-I levels were not significantly different, but they were consistently lower in deficient chicks and deserve further study. Plasma IGF-II was significantly less in chicks fed 0.2% Met compared to pair-fed controls suggesting that Met deficiency interferes with IGF-II metabolism. We concluded that a deficit of dietary Met altered plasma T3 and IGF-II levels, but the effect was dependent on the degree of deficiency.

Animals↗
PubMed1999

Evaluation of raw and heated velvet beans (Mucuna pruriens) as feed ingredients for broilers.

Velvet bean plants (Mucuna pruriens) are used widely outside the U.S. as a cover crop. The beans (VB), high in protein, contain toxic substances that possibly can be destroyed by heating. Few data are available on the use of VB in poultry nutrition. We examined the effects of raw and dry-roasted VB on broiler performance in two experiments. In Experiment 1, 10, 20, and 30% raw VB were substituted into nutritionally balanced rations fed 0 to 42 d of age. Raw VB caused progressive reductions in growth; at 42 d of age, broilers fed 30% VB weighed 39% of controls. Feed intake declined significantly only with 30% VB. Feed efficiency decreased significantly with 20 and 30% VB. In Experiment 2, 10% raw VB and 10, 20, and 30% heated VB were fed 0 to 42 d. With 10% raw VB, broilers grew significantly slower but feed intake was unchanged. Inclusion of 10% heated VB allowed better growth than raw VB, and by 42 d of age, growth was not significantly different from that of controls. At 20 and 30%, heated VB promoted much better growth and efficiency than raw VB in Experiment 1, but values were significantly lower than those of controls. With 30% heated VB, broilers grew to 66% of control, a marked improvement over raw VB. Carcass yield was unaffected. Trypsin inhibitor activity but not L-3,4-dihydroxyphenylalanine (L-DOPA) in VB was destroyed by heating. We conclude that dry heating of VB partially destroys its growth-inhibiting factor(s), allowing successful use of 10% heated VB in broiler rations. Higher levels of heated VB reduced broiler performance, although results were much better than those of raw VB.

Animal Feed↗
PubMed1998

Growth, feed intake, and plasma thyroid hormone levels in chicks fed dietary excesses of essential amino acids.

The consequences of dietary excesses of 10 essential amino acids, His, Ile, Phe, Trp, Val, Arg, Leu, Lys, Met, Thr, on growth, feed intake and plasma levels of triiodothyronine (T3) and thyroxine (T4) in growing chicks were investigated. Each amino acid was added to a starter ration to bring it to a level 2.84x above the National Research Council (1984) requirement. Excesses of all amino acids except His and Leu caused significant reductions in weight gain. Of the amino acid excesses that reduced growth, only Trp and Val did not also reduce feed intake. Gain:feed decreased significantly only in chicks consuming excess Arg, Lys, Phe, and Trp. Chicks fed excesses of Ile and Val had plasma T3 levels that were statistically higher than control levels; none of the other amino acid excesses significantly altered blood concentrations of this hormone. Compared to the control, plasma T4 levels were not significantly altered by the amino acid excesses, but there was a significant difference between Trp and Val, the latter being lower. This study shows that high dietary levels of essential amino acids cause depressions in weight gain and feed intake, and, with Ile and Val, these depressions are accompanied by elevations in plasma T3 levels. Otherwise, the amino acid excesses had little effect on plasma levels of thyroid hormones.

Amino Acids, Essential↗
PubMed1997

Growth and plasma thyroid hormone concentrations of chicks fed diets deficient in essential amino acids.

Consumption of low protein (10%) diets is known to produce elevations in plasma triiodothyronine (T3) in growing chickens. Therefore, we evaluated the effect of individual essential amino acid deficiencies on plasma thyroid hormone concentrations. For 13 to 15 d, chicks were fed either a control diet free-choice, one of six amino acid-deficient diets free-choice, or the control diet, pair-fed at the level consumed by chicks fed each of the deficient diets. The control diet was a 50/50 mixture of broiler starter and purified amino acid diets. The amino acids, fed at the indicated percentages of National Research Council recommendations, were: arginine, 60%; lysine, 60%; threonine, 60%; leucine, 75%; isoleucine, 75%; and methionine, 50%. Feed consumption and weight gain were significantly lower in all deficient groups than in the free-choice control group. In all cases except leucine, deficient chicks also gained less weight than their pair-fed controls. Plasma T3 levels in the groups deficient in arginine, lysine, isoleucine, or methionine were higher than in their respective pair-fed controls. However, only with the isoleucine deficiency did T3 levels exceed those of control chicks given free access to feed. Thyroxine levels were significantly lower than control levels only with the lysine deficiency. These results suggest that changes in circulating levels of thyroid hormones in a protein deficiency may be a consequence of selected amino acid deficits, because individual essential amino acids, when deficient in the diet, do not exert the same effect on circulating levels of thyroid hormones.

Amino Acids, Essential↗
PubMed1997

Dietary carbohydrate and fat do not alter the thyroid response to protein deficiency in chicks.

Consumption of low-protein diets consistently causes elevations in circulating levels of triiodothyronine (T3) in several species of animals. In chicks this is often accompanied by lower levels of circulating thyroxine (T4). Since low-protein diets are usually formulated by replacing the detected protein with carbohydrate, the question arises as to whether the changes in thyroid hormones are a result of the lower protein or higher amounts of carbohydrate in such diets. Male broiler chicks, 13-26 days of age, were fed experimental diets that contained either an adequate level of protein (24%) or levels that were slightly (17%) or moderately (10%) deficient in protein. The deleted protein was replaced, isocalorically, with either glucose, soybean oil, or hydrogenated coconut fat. Though the level of protein and source of energy differed among diets, all diets contained identical amounts of all nutrients and energy, and were of similar weight densities. Circulating levels of thyroid hormones were measured from blood samples taken at the end of the study. Plasma T3 was elevated to a similar degree in all protein-deficient animals compared with control. Plasma T4 decreased in all protein-deficient chicks and was lowest with 10% dietary protein. Changes in circulating levels of thyroid hormones occurred independently of the source of dietary energy. Therefore, it is concluded that alterations in circulating levels of thyroid hormones that occur in chicks fed low-protein diets are a specific effect of the protein deficit and are not a related to the amounts of carbohydrate or fat present in the diet.

Animals↗
PubMed1992

Growth, thyroid function, and serum macromineral levels in magnesium-deficient chicks.

Growth and thyroid function were studied in Mg-deficient chicks. Dietary levels of 80 to 315 ppm Mg were compared with control levels of 578 to 787 ppm Mg. Signs of Mg deficiency appeared rapidly and acutely within 2 to 5 days at dietary levels of 250 to 260 ppm or lower. Growth and feed intake decreased progressively as the deficiency became more severe. Control chicks pair-fed with the deficient chicks gained significantly more weight. Serum Mg decreased at all levels of Mg below control, but at 260 and 315 ppm it returned to control values after 21 days on treatment. Serum Ca diminished only when dietary Mg was 250 ppm or less. Serum K increased in severely deficient chicks but decreased over time in milder deficiencies. Thyroid gland weights were unchanged. However, very young chicks fed a Mg-deficient diet had lower serum 3,5,3'-triiodothyronine (T3) whereas serum thyroxine (T4) was generally unaffected. Beyond 1 wk of age chicks that had prior access to a Mg-sufficient diet had low serum T4 levels whereas serum T3 was unchanged. Therefore, peripheral thyroid hormone metabolism is altered in a Mg deficiency, but this effect is dependent on the age at which the deficiency occurs.

Animals↗
PubMed1987

Thyroid function, energy balance, body composition and organ growth in protein-deficient chicks.

Protein-deficient diets (17, 10, 6.5 or 3% protein) and a 24% control diet were fed to growing chicks. A control group was pair-fed daily with each deficient group. Energy intake was lower in the 6.5 and 3% protein groups than in the other groups. However, weight gain, bone growth and feed conversion efficiency were lower with 10% protein or less. Relative thyroid weights were unaffected by dietary protein. Plasma T3 (3,5,3'-triiodothyronine) levels were significantly higher in all deficient groups, whereas plasma T4 (thyroxine) was lower. Plasma rT3 (reverse T3) was unaffected by the protein deficiencies, suggesting that enhanced conversion of T4 to T3 rather than to rT3 had occurred. Hepatic alpha-glycerol-3-phosphate dehydrogenase (alpha-GP) shuttle activity increased markedly in protein-deficient chicks. Efficiency of energy utilization was unaltered in chicks fed 17 or 10% protein but was higher in chicks fed 6.5 and 3% protein than in controls. All deficient chicks had more fat and less protein and water in the tissues. The lower feed conversion efficiency therefore represents almost entirely a shift in body composition toward fat and does not reflect a loss of energy as heat. We conclude that elevations in plasma T3 and in thyroid-controlled alpha-GP shuttle activity, although sensitive indicators of protein deficiencies, are not good predictors of altered thermogenic activity in protein-deficient chicks.

Animals↗
PubMed1987

Thyroid function, growth hormone, and organ growth in broilers deficient in phosphorus.

The effects of a dietary P deficiency on thyroid function, serum growth hormone, and growth parameters in 10 to 29-day-old broiler cockerels was determined. Chicks fed severely P-deficient diets (.05% or .10% available P) grew more slowly and ate less feed than controls fed .65% P. The deficiency was also accompanied by hypercalcemia, hypophosphatemia, and decreases in percent bone ash, fat-free tibial weight, and tibial length and width. Increases in the relative weights of kidneys, hearts, and pituitary glands (.05% P only) occurred as well. Most of these changes occurred to a lesser extent or not at all in pair-fed controls, showing that they resulted specifically from the P deficiency and were not simply a result of reductions in feed intake. Phosphorus deficiency also was accompanied by peripheral edema and hydropericardium. Relative thyroid weight was unaffected. Serum triiodothyronine was consistently lower in the P-deficient chicks, although effects were significant only in one experiment. Thyroxine levels tended to be low also, but not consistently so. Serum growth hormone in P-deficient chicks in both studies was consistently lower than that in pair-fed controls, but this was significant only when .10% but not .05% available P was fed. The findings suggest that serum levels of both thyroid hormone and growth hormone are altered by P deficiency, but the results were not clearly definitive.

Animals↗
PubMed1985

Effect of phosphorus deficiency on thyroid function and growth hormone in the white Leghorn male.

Leghorn males, 66 to 96 days of age, were fed a diet marginally deficient in phosphorus (.14% nonphytate). Growth and feed intake were significantly reduced, but plasma calcium and phosphorus were unchanged. Bone ash was significantly reduced compared to pair-fed controls but not ad libitum-fed controls. Thyroid size increased and plasma growth hormone (GH) levels decreased with the deficiency, apart from any effect attributable to the lower food intake and weight gain. Plasma 3,5,3'triiodothyronine (T3) and thyroxine (T4) were not significantly changed, although there was a tendency for T4 to be lower in the deficient chickens. As both thyroid size and plasma GH are regulated partly by pituitary function, dietary phosphorus may alter endocrine function through changes in pituitary metabolism.

Animals↗
PubMed1984

Purification of chick nuclear thyroid-hormone-receptor protein.

A crude nuclear thyroid-hormone-receptor protein preparation from chick liver (an ammonium sulfate fractionation of high-ionic-strength-solubilized chromatin proteins) binds both triiodothyronine and thyroxine with high affinity. This crude preparation has characteristics similar to preparations from a variety of animal tissues, reported by several different laboratories, and is used for the further purification of the receptor protein. For this purification an affinity chromatography medium, 4-[N-(3,5,3'-triiodothyronine)-2-amino-3-hydroxypropoxy]-butylpropoxy -Sepharose ether, is used to take advantage of the observation that hydroxymercuribenzoic acid causes a reversible dissociation of the complex between triiodothyronine and the receptor protein. The hydroxymercuribenzoate treatment greatly increases this rate of dissociation at low temperatures compared with other methods, such as free triiodothyronine competition or an increase in ionic strength or pH. This procedure results a in purified fraction (1000-10000-fold with respect to binding triiodothyronine), which has a molecular mass of approximately 65 kDa and which retains a high degree of the original thyroid-hormone-binding activity.

Animals↗
PubMed1984

Effects of selected wavelengths of light on reproductive development in cockerels.

This study examined the effects of light from different portions of the spectrum on reproductive development in Leghorn cockerels. Chicks were distributed among six identical chambers. One was illuminated with broad spectrum white light; the other five were equipped with filter systems designed to provide approximately 100-nm bandwidths of light of similar intensity. All treatment groups were synchronized to a 14L:10D photoperiod. Plasma concentrations of LH and testosterone were measured by radioimmunoassay in 15- and 18-week-old cockerels. Body weights and testes weights were obtained from 18-week-old birds. Statistically significant (P less than 0.05) differences in plasma LH concentrations due to lighting could not be detected at either age. However, at 15 weeks, circulating testosterone levels were significantly higher in the groups exposed to red or white light. Three weeks later, testosterone was also elevated in cockerels grown under green light, while testes weights were heavier only in birds kept under white or red.

Animals↗
PubMed1983

Effect of a tryptophan deficiency on thyroid gland, growth hormone and testicular functions in chickens.

Broiler chicks from 2 to 4 weeks of age were fed control (0.23%) and deficient (0.115, 0.058%) levels of L-tryptophan. Separate groups of control chicks were pair-fed daily with the deficient chicks. Deficient chicks grew less efficiently than did pair-fed controls. Plasma triiodothyronine (T3) was elevated in deficient chicks, especially compared to pair-fed controls, and this was accompanied by lower reverse T3. Plasma thyroxine (T4) was also reduced with 0.059% tryptophan. However, thyroid weights and follicle diameters were unchanged. Reductions in weight gain and bone growth, increases in pituitary and pineal weights, and elevations in plasma GH occurred in the tryptophan-deficient chicks apart from any effect due to reductions in feed intake. Comb and testis size, and plasma testosterone were little affected by the deficiency. Based on changes in plasma T3 levels and feed conversion efficiencies, we conclude that tryptophan-deficient chicks show signs of relative hyperthyroidism and energy wastage compared to pair-fed controls. The elevations in plasma growth hormone and T3 support the concept that serotonin is a negative modulator of the synthesis or release of these hormones in chickens.

Animals↗
PubMed1982

The effects of pre- and postweaning dietary protein levels of mitochondrial metabolism in developing liver and interscapular brown adipose tissue (IBAT) in rats.

Isoenergetic diets containing casein:carbohydrate:fat, 22:59:10% (control protein, CP), or 8:73:10% (low protein, LP), were fed to female rats during gestation and lactation and to offspring postweaning. Control fed rats were pair-fed to the LP-fed group. In the LP-fed group, body and liver weights were similar at birth but decreased at 10, 21, and 42 days, while intercapsular brown adipose tissue (IBAT) weight decreased from birth to 10 and 21 days but increased at 42 days compared to controls. Hepatic mitochondrial oxygen consumption (OC) with pyruvate + malate as substrate was similar at 21 and 42 days, whereas OC in state 3 and 4 with succinate was decreased at 42 days, only in the LP-fed group. In IBAT, OC was similar in each group at each age. In the LP-fed group, hepatic glycerolphosphate (GP) shuttle activity was the same as in controls at birth but increased progressively from 10 to 21 and 42 days, whereas malate-aspartate (M-A) shuttle activity was not substantially changed during development. In IBAT, shuttle activities were similar in both groups during development with M-A shuttle activity increased in the LP-fed group at 21 days. Serum triiodothyronine (T3) levels in the LP-fed group were increased at 10 and 42 days but decreased at 21 days after birth. These results suggest a role for both pre- and postweaning diet composition as a regulator of hepatic metabolism during development. The deficit in IBAT weight in the LP-fed group during early postnatal development indicates a decreased capacity for heat production in the neonate caused by maternal protein undernutrition.

Adipose Tissue, Brown↗
PubMed1982

Effect of selected light treatments on pineal weight and lipid content in the cockerel (Gallus domesticus).

The effect of early and prolonged exposure of growing cockerels to selected photoperiods and wavelengths of light on pineal gland weight and lipid composition was investigated. The six treatments included 14L:10D white (control), 24L:OD white, OL:24D dark, and 14L:10D narrow-band blue, green or red light. Pineal gland fresh and dry weights were greatest under the white light treatment and least under the dark and red treatments. Examination of histological preparations and biochemical analysis both indicated that the absence of light depleted pineal lipid. When expressed as a percent of dry tissue weight, lipid from the colored light treatments was significantly greater than from the control. We conclude that both the photoperiod and the wavelength of light are capable of influencing pineal gland lipid metabolism in the cockerel.

Animals↗
PubMed1980

Dietary phosphorus levels during growth of brown egg type replacement pullets.

Caged Sex-Sal (DeKalb Warren) replacement pullets were fed diets containing .30%, .35%, or .41% available phosphorus from 0 to 20 weeks of age; in a second study pullets were fed the above levels plus a level of .25% available phosphorus from 2 to 20 weeks of age. Some of the pullets were fed diets restricted by 11 to 16% from 8 weeks of age. Reducing the dietary phosphorus did no harm weight gain, feed intake, feed conversion efficiency, bone ash or total calcium and inorganic phosphorus levels in plasma. There was a very small but significant reduction in weight gain and feed intake when .30% or .35% available phosphorus was fed from 0 to 4 weeks of age, but this difference disappeared at the later ages. With the nonstimulatory lighting schedule used, plasma phosphorus decreased markedly in the latter phase of the studies at all levels of dietary phosphorus and thus represented a nondietary age effect. These results show that dietary available phosphorus for cage, brown egg type pullets on full or restricted feeding programs can be decreased to a level as low as .25% from 2 to 20 weeks, and .30% from hatching to 20 weeks without adverse effect.

Animal Nutritional Physiological Phenomena↗
PubMed1980

Pinealectomy and light environment effects on testicular and comb development in the 46-day-old broiler cockerel.

Four replicate experiments were conducted to determine the effects of pinealectomy and environmental lighting on testes and comb weights in the broiler cockerel. Birds were housed in brooder batteries under a 14L:10D fluorescent white light regime for 2 weeks and then allotted to light-controlled chambers. Surgery was performed when the chicks were 3 to 5 days old. The fluorescent light treatments were 14L:10D green (narrow-band, 545 nm peak), 14L:10D cool white, and constant darkness. At the end of the 46-day experimental period, testes weights were determined and comb weight recorded. Pinealectomy did not affect testes weights or comb development. Darkness significantly (P less than .05) depressed testes and comb weight. This suggests that lack of light, but not pinealectomy, affects circulating hormone levels and/or tissue responsiveness in the young cockerel.

Animals↗
PubMed1980

Pineal gland lipid characterization in the seven-week-old cockerel (Gallus domesticus).

The composition of pineal gland lipid was characterized in young cockerels. The total pineal lipid was 159.7 microgram, which was equivalent to 3.0 and 14.1% of fresh and dry tissue weight, respectively. The major phospholipids were phosphatidyl choline (63.1%), phosphatidyl ethanolamine (16.1%), and sphingomyelin (14.7%). Palmitic, stearic, oleic, and arachidonic acids composed 27.9%, 19.4%, 15.8%, and 13.7% of the phospholipid fatty acid fraction, respectively. Free fatty acids (38.4%), cholesterol (17.6%), and cholesterol ester (17.2%) comprised the major fraction of neutral lipids, while the predominant neutral lipid fatty acids were palmitic (26.0%) and oleic (23.8%). The percentage of wet tissue weight that is lipid in the pineal is considerably less when compared to brain cortex or retina. When chickens are compared to several mammalian species, there is little difference in percent lipid per milligram pineal tissue, but definite differences exist in the percentage of various lipid classes.

Animals↗