Biomedical subjects

S Leeson

Publications and source records attributed to S Leeson.

At least 109 records · Page 6Linked to original sources

PubMed1987

Effect of immature body weight on laying performance.

Two trials were conducted to note the effect of immature body size of leghorn pullets on subsequent laying performance, and in particular, egg size. In Trial 1, birds were classified as small, medium or heavy at 15 wk of age (997, 1,100, and 1,226 g, respectively). In Trial 2, segregation at 19 wk resulted in groups with mean weights of 1308, 1411, and 1564 g, respectively. In each trial, weight groups were represented by 40 replicate groups of four individually caged birds. Original weight groupings were maintained throughout the trials (P less than .05). In both trials, immature weight classification had a consistent effect on both feed intake and egg weight (P less than .05); larger birds consumed more feed while producing larger size eggs. In Trial 1, medium weight birds produced more eggs over the 52 wk. Similarly, smaller weight birds produced more eggs than did heavy birds (P less than .05). In Trial 2, weight grouping had no overall effect on egg production, although during the 19 to 23-wk period, heavy birds produced more eggs (P less than .05). It is concluded that immature body weight (15 to 19 wk age) can influence egg weight and that this relationship is linked to levels of nutrient intake. Each 100-g increase in body weight was associated with approximately 3.5 g increase in feed intake and 1.2 g increase in egg weight.

Age Factors↗

PubMed1986

Long-term toxicity of octachlorostyrene in the rat.

This study was designed to investigate the toxic effects produced by the long-term exposure to octachlorostyrene (OCS), a demonstrated environmental contaminant in the Great Lakes region of North America and the Norwegian Coast in Europe. Groups of 20 male and 20 female rats were administered OCS in diets at 0.005, 0.05, 0.5, 5.0, or 50 ppm for 12 months. Weight gain and food consumption were not affected. Increased liver weights were observed in the groups fed the highest dose of OCS. Hepatic microsomal aniline hydroxylase and aminopyrine demethylase activities were induced in male rats fed 5.0 ppm OCS and higher and in female rats fed 50 ppm of the chemical. Elevated serum cholesterol levels were seen in rats of both sexes fed the highest dose. Treatment-related histological changes occurred in the thyroid, liver, and kidney of rats. A dose-dependent accumulation of OCS in the fat and liver of the rats was found. Based on the data presented, it was concluded that the no adverse effect level of OCS was 0.5 ppm.

Aminopyrine N-Demethylase↗

PubMed1985

Response of laying hens to dietary saturated and unsaturated fatty acids in the presence of varying dietary calcium levels.

The response of 33-week-old White Leghorn laying hens to dietary palmitic, oleic, or a 50/50 mixture of oleic and palmitic acids at an 8% inclusion level in the presence of 3, 3.6, or 4.2% dietary calcium was investigated over a 7-week period. There was no significant effect of treatments on egg production and egg weight. Although birds on diets supplemented with oleic acid consumed less feed (P less than .01) than those on diets supplemented with palmitic acid (102 g vs. 114 g), they gained more weight (P less than .01) than birds on diets supplemented with palmitic acid (+105 g vs. -32 g) over the 7-week period. There was no significant effect of the fatty acid treatment on shell quality as estimated by shell deformation. However, increasing the calcium content of the diets reduced feed intake and weight gain (P less than .05) and improved egg shell quality (P less than .05). The fat content of diets supplemented with oleic acid was better utilized than that from diets with an oleic/palmitic mixture, which, in turn, was better utilized than fat from diets supplemented with palmitic acid (P less than .01). Metabolizable energy values of diets followed a trend similar to fat retention and were independent of dietary calcium levels. There were no significant effects of fatty acid supplementation on calcium and magnesium retention, although increasing the calcium content of the diet resulted in a decreased (P less than .01) percentage of calcium retention.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

Effect of nutrient intake on performance of dwarf broiler breeders.

An experiment was undertaken to test the response of dwarf broiler pullets when fed on two planes of nutrition in the growing period and fed either a 17 or 19% protein diet in the breeder house. Pullets offered 20% more feed in the growing period were heavier at 21 weeks of age and reached 50% egg production 2 weeks earlier than birds fed the regular diet. Pullets fed 20% more feed in the growing period and full-fed to 26 weeks in the laying house, gained appreciably more weight, and although they came into production faster, were less persistent in lay than birds fed the regular diet. There was no difference in egg production, egg size, or body composition of dwarfs fed 17 or 19% breeder diets.

Animals↗

PubMed1985

Influence of age, dietary cholic acid, and calcium levels on performance, utilization of free fatty acids, and bone mineralization in broilers.

The effects of age on the utilization of dietary palmitic or a 50/50 mixture of palmitic and oleic acid at the 8% inclusion level in the absence or presence of .2% cholic acid and also in the presence of low (.8%) or high (1.2%) calcium were investigated using broiler chicks from 1 to 56 days of age. Significant interactions (P less than .01) were observed between the type of fatty acid supplemented and the presence or absence of cholic acid on weight gain and feed efficiency. Supplementing diets with a mixture of equal weights of palmitic and oleic acid, reduced feed intake relative to control diets and diets supplemented with palmitic acid alone. There was an interaction between the age of the bird and the type of fatty acid supplemented on fat retention and metabolizable energy (ME) of diets (P less than .01). There was also a significant interaction between the type of fatty acid supplemented and the addition of cholic acid on fat retention and ME of diets. While cholic acid reduced soap formation during the process of digestion (P less than .05), increasing dietary calcium level increased the proportion of the digesta fat that was present as soap (P less than .01). The proportion of digesta and excreta fat, present as soap, depended on the type of fatty acid supplemented. The addition of free fatty acids to broiler diets resulted in a decrease in bone ash and bone calcium content relative to those birds fed the control diet. It is concluded that the ability of broilers to utilize dietary free fatty acids depends on the age at which they are fed, although in all cases supplemental cholic acid enhances fatty acid utilization.

Aging↗

PubMed1985

Effects of dietary fat level on laying hens fed various concentrations of calcium.

The effects of supplementing laying hen diets with 0, 5, or 10% fat in the presence of 3.0, 3.6, or 4.2% dietary calcium was investigated using laying hens over a 7-week period. There was no significant effect of the fat or calcium treatments on laying hen performance as judged by feed intake, weight gain, egg production, egg weight, and egg shell deformation. Although there was an increase in fat retention with an increase in dietary fat level (P less than .01), a larger proportion (P less than .05) of unabsorbed fat was present as soap in the excreta of birds on these diets relative to those fed the control diet. There was evidence to indicate that most of the soap observed in the excreta of laying hens was formed in postabsorptive areas of the gut, thereby explaining why the detrimental effects of soap formation were not seen in the laying hen. Increasing the dietary calcium level reduced both percentage calcium (P less than .01) and magnesium (P less than .05) retention. There were no significant effects of the treatments on nitrogen and phosphorus retention. There were also no significant effects of the treatments on shell ash, shell calcium, magnesium, and phosphorus content. Increasing the dietary calcium level increased bone ash (P less than .05) while reducing bone magnesium content (P less than .05). There were no significant effects of the fat and calcium treatments on bone calcium and phosphorus content.

Animals↗

PubMed1984

Effect of heat stress and diet composition on performance of White Leghorn hens.

A total of 192 Single Comb White Leghorn pullets were divided into three groups to study the effect of heat stress and diet composition on feed intake and laying performance at 21, 25, and 33 weeks of age. For each age group all birds were fed a control diet [17.1% crude protein (CP), 2770 kcal metabolizable energy (ME)/kg] for a 7-day period. During this time they were kept at a temperature of 18 C. The temperature was then immediately increased to 35 C, and groups of 16 birds offered either the control diet, a high protein diet (43.5% CP), a high energy diet (3371 kcal ME/kg), or a diet of high nutrient density (28.3% CP, 2842 kcal ME/kg, and 6.5% Ca) for a 3-day period. After the 3-day test period, temperature was returned to 18 C, although birds were still offered the experimental diets for an additional 4 days prior to returning to the control diet. Production parameters were measured for individual birds. Feed consumption, egg production (except for the 21-week-old birds), egg weight, and egg shell thickness decreased (P less than .05) with heat stress. Increases in energy and calcium intake helped partially to maintain normal egg production, egg weight, and egg shell deformation. Egg weight and egg shell deformation returned to pretest levels within an 8-week postexperimental period. With the exception of those birds receiving the control and high nutrient density diets at 21 weeks of age, data collected over the test periods showed that heat stress caused a significant reduction (P less than .05) in liveweight birds.

Animals↗

PubMed1984

Effect of skip-a-day feed restriction on the jejunal mucosa of broiler breeder pullets.

Jejunal tissue was taken from 18-week-old broiler breeder pullets previously reared on a daily or skip-a-day feed restriction system. Light and scanning electron microscopy revealed no changes in mucosal appearance or structure related to feeding system. Comparable duodenal samples all revealed extensive desquamated epithelial damage possibly related to postmortem change.

Animals↗

PubMed1984

Effects of cage density and diet energy concentration on the performance of growing Leghorn pullets subjected to early induced maturity.

Leghorn pullets of a commercial strain were cage-reared at densities of 293 or 586 cm2/bird. Diet treatments consisted of a control step-down protein program, a reverse-protein program, and two treatments involving 18% crude protein throughout rearing with modification of texture and energy concentration according to bird age. Thus, one treatment involved a crumbled low-energy diet to 10 weeks, followed by a crumbled high-energy diet to 16 weeks, while the alternate series involved a mash low-energy diet to 10 weeks followed by the crumbled high-energy diet to 16 weeks. Birds were weighed periodically throughout rearing and, when they were subsequently moved to laying cages, light was immediately increased from 8 to 14 hr. Irrespective of diet treatment, the more liberal density of 586 cm2/bird resulted in a 5 to 8% increase in feed intake (P less than .01). However, this increased intake was not associated with increased body weight (P greater than .05), and as confirmed by carcass analysis, it is assumed that this increased nutrient intake relates to increased maintenance requirement associated with bird activity. Birds offered the crumbled vs. mash high-energy diet to 10 weeks of age, consumed more feed (P less than .01), although change of diet texture from mash to crumble at 10 weeks failed to stimulate appetite. Also, birds reared on either the step-up energy programs were similar in weight to control-reared birds at 16 weeks of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Influence of vitamin deficiency and level of dietary protein on the incidence of leg problems in broiler chicks.

Diets containing either 22 or 30% protein were supplemented with a vitamin mix where one of 11 added vitamins were singly eliminated from the mix. Male, day-old broilers were fed these diets to 3 weeks of age, and weight gains, feed utilization, and leg problems were recorded. In general, the higher protein diet did not result in a greater incidence of leg problems; however, it did alter performance of several of the vitamin-deficient diets as compared to the lower protein diet. Of the 11 vitamins studied only nonsupplementation of riboflavin markedly reduced weight gain and feed utilization during the 3-week feeding period. However, deletions of vitamin D3 and niacin also resulted in reduced performance. Riboflavin deficiency resulted in paralysis in a high percentage of the birds while the niacin-deficient diet gave a high percentage of birds with deformed legs and problems of mobility. The results demonstrate that a high incidence of leg problems may be present in a flock with little or no signs of reduced gain or feed utilization. The data suggest that under practical conditions the elimination of a particular vitamin from a diet for a short period of time would probably have a negligible effect on performance.

Animals↗

PubMed1984

Influence of nutritional modification on skeletal size of Leghorn and broiler breeder pullets.

Two trials were undertaken to study the effect of nutrient intake on skeletal size in growing pullets. Leghorn chicks at 28 days were smaller in weight and shank and keel length when fed 16% as compared to 22% crude protein. Increasing the energy or mineral-vitamin concentration of the diet had no effect on skeletal parameters. Increased skeletal size of pullets in response to increased diet protein was associated with reduced (P less than .01) tibial ash content. In a subsequent trial, broiler breeder pullets were fed, ad libitum, starter diets (0 to 21 days) containing graded levels of protein from 20 to 13%. Reducing protein level had a consistent negative effect on body weight, shank length, and keel length at 21 days. When birds were subsequently fed restricted quantities of a common grower diet, no differences in body weight and skeletal parameters were evident at maturity. It is concluded that although early body weight and skeletal size can be markedly influenced by diet protein level, such effects are subsequently nullified by conventional restricted feeding programs.

Aging↗

PubMed1984

Effects of dietary saturated or unsaturated fatty acids and calcium levels on performance and mineral metabolism of broiler chicks.

The effects of inclusion of 8% oleic, palmitic, or a 50/50 mixture of oleic and palmitic acids as the major source of fat in the presence of .8, 1.2, or 1.6% calcium in broiler diets was investigated using broiler chicks from day-old to 3 weeks of age. Supplementation of broiler diets with oleic acid reduced feed intake (P less than .05) and improved feed efficiency (P less than .01) compared to other treatments. Chicks fed diets supplemented with oleic acid or a mixture of oleic and palmitic acid gained more weight (P less than .01) over a 3-week period. Significant interactions were observed between type of dietary fatty acid and calcium level on metabolizable energy of diets (P less than .01), magnesium retention (P less than .05), calcium and fat retention (P less than .01), and proportion of excreta fatty acid that was present as soap (P less than .01). Although all fatty acids tested formed soap in the small intestine, soaps of oleic acid were efficiently utilized as opposed to soaps of palmitic acid. There was a significant (P less than .05) reduction in bone ash and bone calcium content of chicks fed diets supplemented with palmitic acid. There was a significant interaction (P less than .05) between type of fatty acid and calcium level on bone magnesium content. Increasing the calcium content of diets aggravated the decrease in calcium retention and bone calcium content associated with addition of fat.

Animals↗

PubMed1983

Consequence of increased feed allowance for growing broiler breeder pullets as a means of stimulating early maturity.

Two hundred and forty Hubbard X Hubbard breeder pullets, 3 weeks of age, received conventional quantities of feed according to the breeder's recommendation or 5, 10, or 20% extra feed allowance. On reaching an average weight of 2.1 kg, birds were moved to laying cages, subjected to 14 hr of light per day, and offered a breeder diet at the breeder's recommended allowance. Increased feed intake resulted in increased growth rate such that control, +5, +10, and +20% groups reached 2.1 kg liveweight at 20, 18, 18, and 16 weeks, respectively. Total feed intake was significantly less to 2.1 kg liveweight for the younger birds. The early move to the laying house subsequently resulted in early maturity. However, these birds failed to show persistency of production after peak, there being a 10% decline within a 4-week period. Control reared birds, starting production at 23 weeks, exhibited a more conventional and persistent peak egg production. There was an indication that early maturity adversely affected egg size. The significant saving in pullet feed cost warrants further trials aimed at elucidating the mechanisms affecting persistency of production in early maturing broiler breeders.

Animals↗

PubMed1983

Influence of increasing the calcium and magnesium content of the drinking water on performance and bone and plasma minerals of broiler chickens.

Calcium and magnesium contents of drinking water for broiler chicks were adjusted by additions of calcium and magnesium to provide levels of 0, 25, 50, 75, or 100 ppm Mg and 0, 50, or 100 ppm Ca, arranged in a factorial design. During a 3-week trial, increasing the water magnesium concentration significantly (P less than .05) improved feed efficiency and significantly (P less than .05) increased the incidence of swollen hocks and shortened tibia but had no effect on other measures of performance. Bone ash and bone mineral content were not significantly affected by the calcium treatment. However, increasing magnesium level to 100 ppm significantly (P less than .05) increased bone magnesium and phosphorus levels. Plasma minerals were not affected by these same water treatments.

Animals↗

PubMed1983

Effects of feather cover and insulative jackets on metabolic rate of laying hens.

Two experiments were conducted to determine the influence of feather cover and newly-devised insulative jackets on the heat production in Single Comb White Leghorn laying hens at 20 C. An open-circuit calorimeter was used to measure the gaseous exchange of the birds. With ad libitum feeding, birds with clipped back and breast feathers produced 6% more heat than did normally feathered hens. This difference was removed by placing jackets on the defeathered birds. The jackets also decreased the surface temperature of the feather-clipped areas, indicating an effective insulation. When the jackets were applied to naturally poor-feathered hens, fasting heat production decreased significantly, but not to the base level of that of normally feathered hens.

Animals↗

PubMed1983

Influence of increasing dietary calcium and magnesium levels on performance, mineral metabolism, and egg mineral content of laying hens.

The effects of increasing dietary magnesium level from .17 to .77% and calcium level from 3 to 4.2% for laying hens over a 7-week period was investigated. Increasing either dietary magnesium or calcium level had no significant effect (P greater than .05) on feed consumption, egg production, egg weight, or egg shell deformation. Increasing dietary magnesium level had no significant effect on calcium retention, although there was a significant (P less than .01) reduction in the percentage of magnesium retained. Egg shell calcium content was significantly (P less than .01) reduced and shell magnesium significantly (P less than .05) increased in response to increase in dietary magnesium content. Increasing dietary magnesium level also significantly (P less than .01) reduced bone calcium and zinc contents while concomitantly increasing bone magnesium levels. Bone ash and calcium were significantly (P less than .05) increased and bone magnesium reduced when the calcium content of the diet was increased. Plasma calcium was significantly (P less than .01) increased in dietary calcium level and significantly decreased with increased dietary magnesium. The converse was true for plasma magnesium in response to increases in dietary calcium and magnesium. Significant positive correlations were observed between mineral contents of diet and bone, bone and plasma, and plasma and shell. A negative correlation was observed between shell magnesium level and egg shell quality as assessed by deformation. An antagonistic relationship seems to exist between calcium and magnesium, and this is discussed in relation to skeletal integrity and egg shell quality.

Animals↗

PubMed1983

Residues of polychlorinated phenols and anisoles in broilers raised on contaminated woodshaving litter.

Broilers were raised for 8 weeks on litter made up of woodshavings containing high (700 micrograms/g) levels of contamination with polychlorinated phenols (PCP). The PCP levels declined in the litter over the test period while polychlorinated anisoles (PCA) increased in the highly contaminated litter. Final weights of the birds was only slightly different; however, feed conversion was slightly higher for those birds raised in the highly contaminated pens. Panelists rated the cooked samples from the birds raised on highly contaminated litter significantly lower for flavor and overall acceptability than either of the lower PCP level treatments. Residues of the odiferous pentechloroanisole were present in muscle and fat of the birds raised on the highly contaminated litter; however, residues in muscles of the birds on low level contaminated litter could not be detected. Polychlorinated anisoles were present in the fat of birds raised on normal litter but adjacent to the contaminated pens.

Animals↗

PubMed1983

Effects of dietary levels and types of fat on performance and mineral metabolism of broiler chicks.

Two experiments were conducted to investigate the effects of increasing dietary fat level from 0 to 9.0% and sources of supplemental fat (animal-vegetable fat or corn oil) on the performance and mineral metabolism in broiler chicks from day-old to 3 weeks of age. In experiment 1, increasing dietary fat level significantly (P less than .05) increased 3-week body weight and significantly (P less than .01) improved feed efficiency. There was no significant effect of the treatments on bone ash, bone magnesium, phosphorus, manganese, or zinc, although bone calcium content was significantly (P less than .01) reduced with increase in dietary fat level. Plasma minerals were not significantly affected by the diet treatments. In Experiment 2, neither source of fat, dietary calcium, nor vitamin D3 had any significant effect on performance parameters. Calcium and magnesium retention were significantly (P less than .05) reduced by dietary corn oil. Bone ash and magnesium were significantly (P less than .01) reduced when corn oil was the source of dietary fat, and there was a significant interaction between source of fat and dietary calcium level on bone calcium content. Increasing the dietary vitamin D3 from 1600 to 3200 IU/kg significantly (P less than .05) increased bone calcium content. Bone phosphorus, manganese, and zinc content were not significantly affected by the diet treatments. Plasma magnesium, phosphorus, and zinc content were not significantly affected by the diet treatments. It is concluded that increasing dietary fat, although beneficial for growth, was detrimental to calcium retention and bone calcification. Increasing dietary calcium does not seem to alleviate this problem.

Animals↗