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Biomedical subjects

S Leeson

Publications and source records attributed to S Leeson.

At least 55 records · Page 3Linked to original sources
PubMed1999

The effect of feed deprivation and subsequent refeeding on the bone characteristics of aged hens.

In an attempt to improve skeletal integrity of older caged laying hens, birds were held without feed for 4 to 8 d and then refed. Feed deprivation caused an immediate loss in breaking force of the tibia (P < 0.05). Although bone strength increased during subsequent refeeding, values did not return to prefast levels (P < 0.05). Feed withdrawal did cause a reduction in modulus of elasticity of the tibia (P < 0.05), which is a potential benefit for bones that are more resilient to damage; this characteristic was maintained through 30 d of feeding. Histological examination of the tibia hinted at some bone remodelling during refeeding following withdrawal, although the magnitude of these changes was of limited biological significance. These data suggest that simple feed withdrawal for 4 or 8 d is insufficient to bring about a meaningful improvement in skeletal integrity of the older caged laying hen.

Aging↗
PubMed1999

Effect of phytase enzyme on dietary nitrogen-corrected apparent metabolizable energy and the ileal digestibility of nitrogen and amino acids in broiler chicks.

The effect of phytase on the performance, AMEn, and the ileal digestibility of N and amino acids was investigated in a 15-d trial using day-old male broilers with diets that were low in Ca (0.9% for control and 0.79% for phytase treatment) and available P (AP; 0.45% for control and 0.35% for phytase treatment). The assayed dietary phytase activity of crumble diet was 1,149 phytase unit (FTU)/kg. Chromic oxide was added to the diets to estimate ileal digestibility of N and amino acid. Excreta were collected from Day 12 to 15 to estimate AMEn. Weight gain, feed intake, and feed:gain of chicks fed phytase using diets with low Ca and AP were comparable with those observed for chicks fed more normal levels of Ca and AP. The diet with supplemental phytase had a higher AMEn (P< or =0.01) compared with the control diet. Chicks fed phytase had higher digestibilities for Val, Ile, nonessential amino acids (P< or =0.05), and total amino acids (P< or =0.01).

6-Phytase↗
PubMed1998

Nuclear magnetic resonance imaging as a tool to estimate the mass of the Pectoralis muscle of chickens in vivo.

1. Nuclear magnetic resonance imaging (MRI) was used to assess the advantages of the technique in determining the size (volume) and shape of the Pectoralis muscle (Pectoralis major and minor) in broiler chickens, non-invasively and in vivo. 2. The imaging was performed using a Spectroscopy Imaging System 2.0 Tesla/31 cm bore imaging spectrometer. Three-dimensional reconstruction of transverse images was used to estimate the size of the Pectoralis muscle of chickens ranging in body weight from 362 to 1643 g. 3. Regression analysis resulted in R2 values of 0.92 and 0.99 for the relationship between Pectoralis muscle weight, body weight and muscle volume, respectively. 4. It is concluded that MRI and 3-dimensional image reconstruction may be used to estimate the Pectoralis muscle size and shape. This may be readily extended to monitor the influence of various factors on the growth and development of specific organs and tissues in the body.

Animals↗
PubMed1998

Effect of housing birds in cages or an aviary system on bone characteristics.

Sixty-nine-week-old brown egg layers were either maintained in cages or moved to a litter-floored aviary system. After 10 or 20 d, birds were selected at random from within each environment, and their tibiae removed. After drying, bones were measured and then subject to various physical measurements of strength and elasticity. Bone ash and bone calcium content were also measured. Birds maintained in an aviary initially had stronger bones as measured by force (P < 0.05). After 20 d in an aviary, birds had stronger bones, as assessed by force, than their contemporaries maintained in cages. This same relationship was seen in measures of bone stress (P < 0.05). After 20 d in the aviary system, previously caged birds had bone ash values that were intermediate between birds held only in cages or the aviary (P > 0.05). Bone calcium content was not influenced by the bird's environment. It appears that the skeleton of caged birds can be affected by providing them with an environment that allows opportunity for increased static and dynamic loading of the bones.

Animals↗
PubMed1998

Size and components of poult yolk sacs.

An experiment was designed to examine the effects of strain of turkey, size of egg, and stage of embryonic development on yolk and yolk sac utilization. Sixty eggs from Nicholas and British United Turkeys of America (BUTA) breeders were selected within each of the weight categories 70 to 76, 80 to 86, and 90 to 96 g. These eggs were incubated under commercial conditions, and eggs selected at 0 or 25 d incubation, at hatch, and 24 h posthatch and yolk and embryos were weighed and assayed for fat, protein, or fatty acids. Yolk weight declined from 23.7 g at setting to 4.66 g at hatch and subsequently to 2.87 g, 24 h posthatch. Yolk weight was affected by strain and egg weight and a number of significant (P < 0.05) interactions were observed. Nicholas strain birds yielded the largest yolks, with the strain difference being most pronounced for the largest egg weight category. Larger turkey eggs contained more water, such that at 24 h posthatch there was double the amount of residual water in the yolk sac. At 24 h posthatch, the Nicholas poults had more water available in the residual yolk. Egg weight had little effect on lipid reserve in the yolk or yolk sac after 25 d incubation. Fatty acid profile of yolk lipids changed little throughout incubation. A number of strain differences are seen in fatty acid profile in the yolk during utilization, although these are quite small and may not be of sufficient magnitude to account for any strain differences seen in early poult viability or growth. Data suggests that the poult and chick may be different in metabolism of various lipid fractions, although in general nutrient utilization by the poult follows a fairly well established sequence of events.

Animals↗
PubMed1998

Organoleptic evaluation of eggs produced by laying hens fed diets containing graded levels of flaxseed and vitamin E.

Eighteen-week-old laying hens were fed diets containing 0, 10, or 20% ground flaxseed and 10 or 100 IU vitamin E/kg diet, in a factorial arrangement. When birds were 60 wk of age, eggs were collected from various treatments and used in taste panel studies. All studies involved freshly boiled eggs. In Experiment 1, four separate panels were conducted to obtain information on egg aroma, egg flavor, presence of any off-flavor, and overall acceptability of the egg. Pooled data showed a very significant difference among panelists for all attributes tested (P < 0.01) and off-flavors were detected in eggs from hens fed 10 and 20% flaxseed with 10 mg vitamin E/kg. In Experiment 2 panelists were asked to evaluate egg aroma, yolk flavor, and overall acceptability in eggs from birds fed the lowest level of vitamin E with 0 or 10% flaxseed, and birds fed 20% flaxseed and 10 or 100 mg vitamin E/kg. The highest ratings for egg aroma, yolk flavor, and overall acceptability were for the control eggs. There was a significant reduction in overall acceptability as flaxseed concentration increased (P < 0.05) and an interesting and significant (P < 0.05) decline in overall acceptability for birds fed 100 vs 10 IU vitamin E/kg diet in eggs for birds fed 20% flaxseed. In a third study, there was an indication of preference for eggs from birds not fed flaxseed, when the diet contained 10, rather than 100 IU vitamin E/kg diet. These data suggest that high (> 10%) levels of flaxseed used in the bird's diet will result in some decrease in overall egg acceptability as assessed by aroma and flavor. These effects seem to be accentuated by using high levels of vitamin E in the bird's diet.

Animals↗
PubMed1997

Layer performance of four strains of Leghorn pullets subjected to various rearing programs.

Two experiments were conducted using four strains of Leghorn pullets, namely Babcock, DeKalb, H & N, and Shaver. Pullets were grown on conventional or low protein diets fortified with additional amino acids. At 18 wk of age, 64 pullets from each strain and diet treatment were transferred to individual laying cages, using eight replicate groups of four adjacently caged birds. In a second experiment, pullets from the four strains were selected based on body weight at 18 wk of age (approximately 1,270 vs 1,650 g). Each weight group and strain was again represented by eight replicate groups of four birds. In Experiment 1, there were no strain or rearing diet effects on egg production (P > 0.05). Rearing diet had little long-term effect on any adult characteristics. There were significant (P < 0.01) strain effects on body weight, feed intake, and egg weight, although these were independent of rearing diet. In Experiment 2, regardless of bird strain, the pullets with smaller body weight matured more slowly (P < 0.01) and produced less total egg mass to 70 wk age (P < 0.05). These smaller birds ate less feed and produced smaller eggs (P < 0.01). There were strain effects, independent of 18-wk body weight, for egg weight and eggshell quality (P < 0.01). It is concluded that minor strain differences exist with respect to response to juvenile nutrition, although such effects are only evident in early lay. All strains of bird remain small, 18-wk body weight is reduced, and these birds subsequently eat less feed and produce smaller eggs.

Aging↗
PubMed1997

Influence of dietary levels of fat, fiber, and copper sulfate and fat rancidity on cecal activity in the growing turkey.

Two experiments were conducted with 6- to 10-wk-old turkeys. In Experiment 1, 6-wk-old turkeys were fed diets varying in level of fat (4.4 to 10%) or fiber (2.5 to 9.0%). The diets also contained extra copper as copper sulfate at either 0.1 or 0.2% of the diet. At 8 wk of age, 15 replicate birds were housed in individual cages and all excreta was collected. Excreta was separated as being "regular" or "cecal" in origin based on appearance. At 10 wk of age, 10 birds per treatment were killed and cecal contents removed under anaerobic conditions. Cecal contents were assayed for various nutrients and viscosity was measured. In a second comparable study, turkeys were fed animal-vegetable fat or regular or rancid canola oil (60.25 vs 120.24 ng/g malonaldehyde, respectively). In Experiment 1, feeding copper sulfate had the most noticeable effect on various cecal parameters. There was an increase (P < 0.01) in dry matter cecal droppings produced and the cecal contents were of increased viscosity (P < 0.05). Copper had no effect on pH or microbial colony count of the cecal contents. Feeding copper resulted in a significant increase in the high molecular weight (> 300,000) fraction of cecal contents and this fraction was of higher viscosity. Feeding copper sulfate resulted in a dramatic increase in copper content of cecal contents (280 to 11,848 ppm), although the copper content of regular excreta was also increased (17 to 1,008 ppm). The various levels of fiber and fat generally had no effect on cecal parameters. Feeding rancid canola oil did result in increased viscosity of cecal contents, compared to the situation seen with fresh canola oil. Fat rancidity per se, however, failed to influence other parameters such as total mass of cecal material produced and composition of cecal material. Feeding copper sulfate or rancid fat will increase the viscosity of cecal material, which may contribute to litter management problems.

Animals↗
PubMed1997

A problem with characteristics of the thin albumen in laying hens.

Industry observations indicate that a proportion of shell eggs exhibit an uncharacteristic spreading of the thin albumen when they are broken-out for fast-food preparation. Because the height and characteristics of the thick albumen are unaffected, the eggs are classified as Grade A. Preliminary observations discounted effects of egg storage or contaminated feed. Two experiments were conducted with Leghorn hens over a full laying cycle, and involved different levels of protein (14, 16, 18, or 20%) and associated amino acids, or different degrees of acid-base balance (150, 200, 250, or 300 mEq/kg). In each trial, treatments were represented by eight replicate groups of four adjacently and individually caged birds. Diet treatment had some effects on conventional production parameters, although there were no major effects on the area of the thin albumen produced when eggs were broken out. In Experiment 1, birds fed the highest level of protein produced eggs with the smallest thin albumen area; however, there was considerable bird to bird variation with thin albumen area varying from 69 to 122 cm2. Ten birds with compact (x 69 cm2) and 10 birds with spreading thin albumen (x 112 cm2) were inseminated with semen from a single, unrelated rooster. Offspring from these hens had significantly (P < 0.01) different thin albumen characteristics corresponding to those of their dams. Offspring producing eggs with the spreading thin albumen had the thickest eggshells as assessed by deformation measurement (P < 0.05). It is proposed that the excessively large spreading thin albumen area is caused by eggs spending more time in the shell gland.

Acid-Base Equilibrium↗
PubMed1997

Nutrition of the broiler chicken around the period of compensatory growth.

Three experiments were conducted with cage-reared broilers to 21 d following nutrient restriction from 6 to 12 d age. In Experiment 1, birds were full-fed from 6 to 11 or given 50% of ad libitum intake on a daily basis, or 100% of ad libitum intake on a daily basis when the diet was diluted 50% with oat hulls. Birds were not able to fully recover body weight depression by 21 d, although birds previously restricted, by whatever method, were more efficient (P < 0.01) in overall energy intake:body weight gain. Prior feed restriction had no effect on ability to metabolize diet energy (P > 0.05), although these birds did exhibit increased nitrogen retention compared to birds full-fed from 6 to 11 d. In a second experiment, birds were fed diets with 1.25, 1.38, 1.51, 1.63, 1.76, or 1.88% lysine in the realimentation diet from 12 to 21 d. Lysine level had no effect on growth rate or feed efficiency (P > 0.05) for full-fed birds; however there was a linear (P < 0.05) decline in growth rate from 12 to 21 d in response to extra dietary lysine for the birds previously feed restricted from 6 to 12 d. In a third experiment, birds were fed diets varying in energy (3,000 to 3,300 kcal/kg) or protein (22 to 29% CP) from 12 to 21 d following ad libitum vs 50% feed restriction from 6 to 11 d age. Protein level of the diet had little effect on performance traits to 21 d, although there was an indication of improved growth in response to the higher energy concentration. Birds full-fed from 6 to 11 d showed increased liver size at 21 d when fed more protein, although the converse was true for the restricted birds (P < 0.05). The growth response to diet energy was associated with increased carcass fatness. In general, there does not seem to be any advantage to manipulating diet formulation during realimentation of birds previously nutrient-restricted.

Abdomen↗
PubMed1996

Broiler response to energy or energy and protein dilution in the finisher diet.

Two experiments were carried out with male broiler chickens in which diets from 35 to 49 d of age were diluted by oat hulls and sand. In one experiment only energy was diluted; in the second experiment, both energy and protein (amino acid) levels were affected. Each diet was tested with four replicate floor pens each containing 25 1-d-old birds. All birds received a standard starter diet to 16 d and then grower diet to 35 d. In Experiment 1, dilution of only energy resulted in a significant linear (P < 0.01) reduction in body weight at 42 d, although there was growth compensation after this time such that all birds weighed the same at 49 d. Diet energy dilution resulted in increased feed intake, although energy intake was not maintained (P < 0.01). Diet energy dilution generally had little effect on carcass weight or yield of breast meat, although there was less abdominal fat (P < 0.01). In Experiment 2, dilution of both energy and protein had a comparable effect on growth rate as described in Experiment 1; however, in this study there was a linear decrease in carcass weight and breast meat yield as the diet was diluted. These results suggest that the male broiler chicken can grow quite well on very low energy diets but that a period of at least 7 d is required for adjustment to feed intake. Even with compensatory increase in feed intake, however, the bird is unable to maintain its energy intake when fed such diluted diets.

Amino Acids↗
PubMed1996

Broiler response to diet energy.

Male broiler chickens were fed corn-soybean diets providing 2,700, 2,900, 3,100 or 3,300 kcal ME/kg. In all experiments, each treatment was tested with three replicate groups of 30 birds grown to 49 d of age. In Experiment 1, birds consumed the various diets ad libitum whereas in Experiment 2, all birds received identical and restricted quantities of feed so as to ensure variable intakes of energy. In a third experiment, after 7 d of age, broilers had access to feed in two feeders that contained only the highest level of energy, or the 3,300 kcal ME/kg diet in combination with one of the other diets previously described. Providing diets of 2,700 to 3,300 kcal ME/kg for ad libitum consumption had no effect on growth rate (P > 0.05) and energy intake was constant; however, reducing the energy level of the diet did result in reduced carcass fatness (P < 0.01). When feed intake was controlled in Experiment 2, there was reduced growth (P < 0.01) rate as energy level of the diet was reduced. This reduced growth was associated with dramatic reduction in carcass fatness (P < 0.01), although breast meat yield was not affected. When broilers were offered a choice of diets, they showed remarkably precise control of intake, such that energy intake was again constant across all treatments. However, even though energy intake was constant, broilers consuming the choice diets involving the lower energy content diets tended to have less carcass fat. It is concluded that the broiler still possesses a good ability to control its feed intake based on desire to normalize energy intake. As energy intake is decreased, or there is increased protein intake, the bird deposits less carcass fat.

Animals↗
PubMed1996

Changes in body composition and adipocyte cellularity of male broilers subjected to varying degrees of early-life feed restriction.

Three experiments were conducted to determine growth performance, body composition changes, and adipocyte characteristics of male broilers subjected to early-life feed restriction. The purpose of Experiment 1 was to determine 42-d growth performance and body composition changes. Treatments used were full-fed control and 50% physical feed restriction during the period 6 to 12 d of age. Experiment 2 was conducted to determine the adipocyte characteristics during and after feed restriction to 42 d of age. An additional treatment involved gradual refeeding following the feed restriction period. Experiment 3 was designed to test the effect of feeding different types of dietary fat during realimentation on the abdominal fat pad (AFP) size, and lasted until 18 d of age. Three types of fats were tested, namely animal-vegetable (A-V) blend, flax oil, and animal tallow, each represented by full-fed and feed-restricted treatments. Complete compensatory growth by feed-restricted birds relative to controls was not achieved by 42 d in either Experiments 1 or 2. Early feed restriction resulted in lower body fat percentage at 12 d (P < 0.05), although by 42 d a higher rate of fat deposition mainly by hypertrophy of adipocytes resulted in no difference in fatness. Gradual reintroduction into ad libitum feeding did not alter such adipocyte hypertrophy nor improve compensatory growth response during refeeding. There was consistent improvement in feed efficiency associated with early-life feed restriction (P < 0.05). The use of different types of dietary fat did not effect the AFP when expressed as percentage body weight. Birds that were fed A-V blend during the refeeding period had bigger AFP (grams per bird), a situation that is attributable to differences in body weight. Attainment of growth compensation by the feed-restricted broilers apparently requires a more prolonged growth period or a less severe feed restriction program than that used here. Saturation of dietary fat has no effect on realimentation characteristics of the broiler.

Adipocytes↗
PubMed1996

Effect of dietary fat, fiber, and monensin on cecal activity in turkeys.

Two experiments were conducted to determine the physical, chemical, and microbial properties of turkey cecal droppings and relate them to intake of common dietary components, namely fat, fiber, and the anticoccidial, monensin. Experiment 1 involved collection and analysis of physical and chemical properties of cecal and regular droppings from commercial turkey flocks. Experiment 2 tested the effect of dietary fat, fiber, and monensin on growth performance and cecal activity in male turkeys. Compared to regular excreta, cecal droppings analyzed in Experiment 1 were higher in viscosity and fat content, and lower in dry matter, nitrogen, and fiber content (P < 0.05). High dietary fiber and fat significantly (P < 0.05) improved growth performance in Experiment 2. Prolonged feeding of monensin significantly (P < 0.05) reduced cecal evacuation. Results of chemical composition showed that higher dietary fat and fiber significantly (P < 0.01) reduced the fat percentage of cecal contents, whereas prolonged feeding of monensin increased the fat in both cecal contents and droppings. There was no significant effect of any of the treatments on pH, viscosity, and microbial counts of cecal contents. There is the need to identify and characterize the compound responsible for the high viscosity of cecal droppings.

Animals↗
PubMed1995

alpha-Linolenic acid- and docosahexaenoic acid-enriched eggs from hens fed flaxseed: influence on blood lipids and platelet phospholipid fatty acids in humans.

This study was undertaken to examine the effects that consumption of eggs from hens fed diets containing flaxseed would have on plasma and platelet lipids of male volunteers. Feeding diets containing 0%, 10%, and 20% ground flaxseed to Leghorn pullets provided a marked progressive increase in n-3 fatty acid content as alpha-linolenic acid (alpha-LNA) (28, 261, and 527 mg/egg) and docosahexaenoic acid (DHA) (51, 81, and 87 mg/egg) but no alteration in the cholesterol concentration of the egg yolk. Twenty-eight male volunteers, divided into three groups, were fed four eggs per day for 2 wk according to a cyclic Latin-square design. No statistically significant changes were observed in total cholesterol, high-density-lipoprotein cholesterol, or plasma triglyceride concentrations. Significant increases in total n-3 fatty acids and in DHA content (which rose from 1.5 to 2.0% by wt or 33% overall), and a significant decrease in ratio of n-6 to n-3 fatty acids were found in platelet phospholipids of subjects consuming eggs from flaxseed-fed hens. Health and Welfare Canada in 1990 set recommended intakes for dietary n-3 fatty acids and for the ratio of n-6 to n-3 fatty acids, which are not being met currently by the overall population. Eggs modified by the inclusion of flaxseed in the laying hens' diet could provide an important nutritional source of n-3 fatty acid.

Adult↗
PubMed1995

Relation between functional deficit and intraneural local anesthetic during peripheral nerve block. A study in the rat sciatic nerve.

BACKGROUND: During peripheral nerve block, local anesthetic (LA) penetrates within and along the nerve to produce the observed functional deficits. Although much is known about the kinetics and steady-state relation for LA inhibition of impulse activity in vitro in isolated nerve, little is known about the relation between functional loss and intraneural LA content in vivo. This study was undertaken to investigate the relation of functional change to intraneural LA. METHODS: A sciatic nerve block was performed in rats with 0.1 ml 1% lidocaine radiolabeled with 14C. The total intraneural uptake of LA was determined at different times after injection, and the distribution of lidocaine along the nerve was assayed at different stages of functional block. Drug content was also compared with equilibrium lidocaine uptake in the isolated rat sciatic nerve. RESULTS: Total intraneural lidocaine in vivo increased to near steady-state in about 3 min, stabilizing at approximately 14.3 nmol/mg wet tissue for about 12 min before decreasing to zero at 70 min after injection. Although intraneural lidocaine was 1.6% of the injected dose during full block, only 0.3% was left when deep pain sensation returned and 0.065% was still detected when functions fully recovered. Despite these large differences in total lidocaine content, the longitudinal distribution remained constant. Intraneural lidocaine concentrations obtained at full block and partial recovery could be achieved in vitro by equilibration in 0.7-0.9 and 0.2-0.3 mM lidocaine, respectively. CONCLUSIONS: During peripheral nerve block only a small amount of injected LA penetrates into the nerve. The intraneural content of LA correlates with the depth of functional block.

Animals↗
PubMed1995

D-arabitol metabolism in Candida albicans: construction and analysis of mutants lacking D-arabitol dehydrogenase.

Candida albicans produces large amounts of the acyclic pentitol D-arabitol in culture and in infected animals and humans, and most strains also grow on minimal D-arabitol medium. An earlier study showed that the major metabolic precursor of D-arabitol in C. albicans was D-ribulose-5-PO4 from the pentose pathway, that C. albicans contained an NAD-dependent D-arabitol dehydrogenase (ArDH), and that the ArDH structural gene (ARD) encoded a 31-kDa short-chain dehydrogenase that catalyzed the reaction D-arabitol + NAD <=> D-ribulose + NADH. In the present study, we disrupted both ARD chromosomal alleles in C. albicans and analyzed the resulting mutants. The ard null mutation was verified by Southern hybridization, and the null mutant's inability to produce ArDH was verified by Western immunoblotting. The ard null mutant grew well on minimal glucose medium, but it was unable to grow on minimal D-arabitol or D-arabinose medium. Thus, ArDH catalyzes the first step in D-arabitol utilization and a necessary intermediate step in D-arabinose utilization. Unexpectedly, the ard null mutant synthesized D-arabitol from glucose. Moreover, 13C nuclear magnetic resonance studies showed that the ard null mutant and its wild-type parent synthesized D-arabitol via the same pathway. These results imply that C. albicans synthesizes and utilizes D-arabitol via separate metabolic pathways, which was not previously suspected for fungi.

Alleles↗