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At least 145 records · Page 8Linked to original sources
PubMed1985

The effect of marginal levels of calcium, fish meal, torula yeast and alfalfa meal on feed intake, hepatic lipid accumulation, plasma estradiol, and egg shell quality among laying hens.

In two 2 X 3 factorial-design experiments, Single Comb White Leghorn (SCWL) laying hens were fed either a corn-soy (CS) diet or one containing 5% each of fish meal, alfalfa meal, and torula yeast (FAY), each with 2.0, 2.75, or 3.5% calcium in Experiment 1 and 2.5, 3.5, or 4.5% in Experiment 2. Duration of the experiments were 6 and 8 weeks, respectively. Low dietary calcium resulted in decreased efficiency of energy utilization in both experiments and significantly elevated energy consumption in Experiment 2. Liver lipids and body weight were unaffected by dietary calcium level, and declines in both egg production and shell quality were observed in both studies. In Experiment 1, overall plasma estradiol and tibial bone ash were significantly reduced with lowered dietary calcium, but this was not observed in Experiment 2. Egg weight was significantly increased by decreased dietary calcium in Experiment 1. Plasma calcium was not affected by dietary calcium in either trial. Feeding FAY resulted in significantly lower liver lipid than feeding CS in both experiments, and similar but nonsignificant trends were realized for plasma estradiol. Tibial bone ash and egg-breaking strength were significantly higher for hens fed FAY in Experiment 1. In Experiment 2, plasma total calcium was lower and the percent shell was higher in hens fed FAY with 3.5% calcium than in hens fed CS with 3.5% calcium. No differences were observed between CS and FAY in feed consumption, body weight, or egg production. These studies indicate that feeding a more complex diet to laying hens may change calcium metabolism and improve shell quality at marginal levels of calcium compared with feeding a simplified CS diet.

Animal Feed↗
PubMed2026

Dietary L-Tyrosine Sustains Egg Production and Quality by Modulating Promoter CpG Methylation, Gene Expression, and Hormone Profiles in Reproductive Signalling Pathways of Aged Laying Hens.

Managing prolactin (PRL)-mediated reproductive suppression is critical for maintaining egg production in commercial laying hens. L-tyrosine (TYR), a precursor of dopamine (DA), may counteract age-related reproductive decline by suppressing PRL, thereby sustaining productivity and egg quality in late-phase laying hens. The present study evaluated the effects of dietary L-tyrosine supplementation on laying performance, egg quality, reproductive hormone profiles, gene expression, and promoter CpG methylation in aged laying hens. A total of 180 Atak-S laying hens (71 weeks old) were randomly assigned to three dietary treatments, each with six replicates of 10 hens, and were fed a basal diet without L-tyrosine (control) or the basal diet supplemented with 0.5&#x2009;g/kg (TYR0.5) or 1&#x2009;g/kg (TYR1) L-tyrosine for 12 weeks. Hens in the TYR1 group exhibited higher hen-day egg production, improved feed conversion ratio, and significantly greater eggshell weight, shell thickness, Haugh unit, yolk index, and albumen index than the control group (p&#x2009;<&#x2009;0.05). Dietary L-tyrosine increased plasma DA and serum estradiol while reducing serum PRL (p&#x2009;<&#x2009;0.05). L-tyrosine also upregulated the expression of key dopaminergic and reproductive signalling genes, with corresponding promoter hypomethylation (p&#x2009;<&#x2009;0.05), whereas PRL mRNA expression tended to decrease with concurrent promoter hypermethylation. A significant negative correlation was observed between target gene expression and promoter CpG methylation levels (p&#x2009;<&#x2009;0.05). These findings indicate that dietary L-tyrosine modulates reproductive hormone profiles and molecular responses within reproductive signalling pathways, resulting in improved laying performance and egg quality. Therefore, L-tyrosine may represent a promising nutritional intervention to sustain reproductive function and productivity in late-phase laying hens.

Animals↗
PubMed1992

Effects of age at lighting on reproduction of turkey hens.

Two experiments were conducted to evaluate age at photostimulation on subsequent reproductive performance of Large White turkey hens. All hens were exposed to short daylengths [8 h light (L):16 h dark (D)] for a minimum of 8 wk immediately prior to photostimulation with long day-lengths (16L:8D). Photostimulation started at either 24, 26, 28, or 30 wk of age during January and February (Experiment 1) or July and August (Experiment 2). Data were collected for body weight, time to onset of lay, egg production, and livability in both experiments. In addition, egg quality, broodiness, floor egg production, and poult weight data were obtained in Experiment 2. An inverse relationship occurred between initiation of egg production and the age at lighting up to 30 wk of age. However, peak egg production level and the number of eggs produced per hen during the first 20 wk of egg laying were similar among treatment groups in both experiments. The number of soft-shelled or shell-less eggs produced was also similar among treatment groups. Hens photostimulated at 30 wk of age in Experiment 2 laid the heaviest eggs throughout 20 wk of egg production. Poult weight was reduced when hens were photostimulated at 24 or 26 wk of age, but this only occurred in the first 11 wk of lay. Even though Large White hens responded to photostimulation at 24 wk of age, the results do not support advancing the age at photostimulation to 28 wk or earlier.

Aging↗
PubMed2006

Early maternal, genetic and environmental components of antioxidant protection, morphology and immunity of yellow-legged gull (Larus michahellis) chicks.

Maternal effects mediated by egg quality are important sources of offspring phenotypic variation and can influence the course of evolutionary processes. Mothers allocate to the eggs diverse antioxidants that protect the embryo from oxidative stress. In the yellow-legged gull (Larus michahellis), yolk antioxidant capacity varied markedly among clutches and declined considerably with egg laying date. Analysis of bioptic yolk samples from clutches that were subsequently partially cross-fostered revealed a positive effect of yolk antioxidant capacity on embryonic development and chick growth, but not on immunity and begging behaviour, while controlling for parentage and common environment effects. Chick plasma antioxidant capacity varied according to rearing environment, after statistically partitioning out maternal influences mediated by egg quality. Thus, the results of this study indicate that egg antioxidants are important mediators of maternal effects also in wild bird populations, especially during the critical early post-hatching phase.

Animals↗
PubMed2005

Digestibility, retention and incorporation of low-level dietary PCB contents in laying hens.

Polychlorinated biphenyls (PCBs) are persistent and hazardous environmental contaminants, which tend to bioaccumulate in the food chain. In the present report the long-term effect of low-level dietary PCB concentrations was studied on performance, egg quality, apparent PCB digestibility, apparent PCB retention and PCB accumulation in laying hens that were fed experimental diets for 41 weeks. The tested dietary concentrations of supplemented PCBs, based on the sum of seven reference congeners, were 0, 1.5 and 6 ng/g. PCB ingestion did not significantly affect performance or egg quality parameters. The PCB concentration in egg yolk reached a nearly constant level after approximately 40 and 70 days of consumption of the diets containing 1.5 and 6 ng PCBs/g, respectively. Apparent faecal PCB digestibility and apparent retention were not influenced by dietary levels of added fat varying between 1.5% and 4.5%, but were significantly higher in hens fed diets containing added PCBs. Moreover, apparent PCB digestibility and retention increased significantly with age. Among the seven individual PCB congeners, no systematically significant differences with regard to apparent faecal digestibility were observed throughout the experiment. Accumulation of PCBs in the fat fraction of egg yolk, abdominal adipose tissue and thigh and breast muscle greatly depended upon PCB intake, but never exceeded the maximally allowed concentration of 200 ng/g. As PCBs 52 and 101 were hardly found in egg yolks and hen tissues, it was concluded that both congeners were greatly metabolised. Comparison of relative contents of individual PCB congeners revealed that PCBs 118, 138 and 153 were preferentially incorporated in yolk and body tissues.

Animals↗
PubMed2004

Effects of housing system (outdoor vs cages) and age of laying hens on egg characteristics.

1. Effects of two housing systems (cages vs outdoor) on external and internal egg characteristics were investigated. 2. In total 785 eggs from three different lines in cages and 268 eggs from outdoor-housed layers were examined for egg weight, albumen, yolk and shell content, albumen height and pH, and albumen and yolk dry matter content. 3. Interactions between layer age and housing systems were found for egg weight, eggshell content, albumen height, albumen pH, and dry matter content of the albumen and yolk. This was mainly due to the greater variation with age in the outdoor layers, compared to the caged layers. 4. Irrespective of age eggs from outdoor layers were relatively broader than eggs from the caged layers. Yolk colour was considerably darker in the outdoor group (11.0 vs 9.3). 5. We concluded that it is more difficult to maintain constant external and internal egg quality in an outdoor housing system than in a battery cage system. Factors that determine the greater fluctuations in internal egg quality need to be investigated.

Aging↗
PubMed2004

Effects of supplemental vitamin E during the laying period on the reproductive performance of Taiwan native chickens.

1. One-day-old Taiwan Native Breeder female chicks were fed on maize/soybean growing diets without supplemental vitamin E from hatch to 17 weeks of age. After 17 weeks the birds (n = 300) were randomly assigned to 5 dietary treatments and fed on maize/soybean laying diets supplemented with 0, 40, 80, 120 and 160 mg/kg of vitamin E (dl-alpha-tocopherol acetate), respectively, until 46 weeks of age. The variates measured included: age at first egg, feed consumption (FC), feed efficiency (FE), egg production (EP), egg weight (EW), egg specific gravity (ESG), eggshell strength (ESS), fertility and hatchability. 2. The addition of 120mg/kg of vitamin E lowered the first EW (P<0.05); however, there was no significant difference in the age or body weight (BW) of pullets at first egg or mortality rate to 46 weeks of age among the treatments. FE and egg mass were improved (P<0.05) in pullets fed 80 mg/kg of supplemental vitamin E. A significant increase in EP was observed after peak EP in pullets given 80 mg/kg of supplemental vitamin E. However, this favourable effect decreased as supplemental vitamin E exceeded 80 mg/kg. 3. From 17 to 46 weeks of age, egg quality (ESG and ESS) decreased with age. However, there was no correlation between age and fertility or hatchability during the experimental period, suggesting that egg quality is more age-sensitive than reproductive performance for breeder pullets. 4. Compared with the control, fertility and hatchability of all eggs set for the treatment with 80 mg/kg supplemental vitamin E increased by 7.7 and 13.4%, respectively. There was no difference in the hatchability of fertile eggs. 5. These results suggest that using supplemental vitamin E during the laying period can improve the reproductive performance of breeder pullets. The addition of 80 mg/kg of vitamin E obtained the best performance in EP, egg mass, FE (feed/egg), hatchability and fertility.

Aging↗
PubMedDate not supplied

Effects of an S6 strain of Mycoplasma gallisepticum challenge before beginning of lay on various egg characteristics in commercial layers.

Mycoplasma gallisepticum (MG) is a reproductive/respiratory disease in poultry implicated in suboptimum egg production and decreased hatchability. Commercial layer hens raised in a controlled environment were inoculated with the S6 strain of MG at 10 wk of age. Egg production and selected egg and egg quality parameters were quantitated over the entire lay cycle for inoculated and control birds. The S6 inoculation had no effect on bird weight, egg production, associated egg quality parameters, or histopathologic lesion scores. This study shows that in the absence of environmental stressors a prelay S6 MG inoculation does not produce detrimental effects on layer hen performance.

Animals↗
PubMed1984

Egg shell quality, medullary bone ash, intestinal calcium and phosphorus absorption, and calcium-binding protein in phosphorus-deficient hens.

The effect of dietary phosphorus deficiency on the performance and on various parameters of calcium, phosphorus, and vitamin D metabolism was studied in laying hens. Phosphorus deficiency resulted in a decline in rate of production and egg weight, probably through appetite depression. The latter, or any secondary calcium deficiency, does not appear to cause the observed reduction in shell quality due to the deficiency. Similar to the response in the chick, phosphorus deficiency resulted in an increase in calcium-binding protein in intestine and kidney, there was no change in the activity of kidney 25-hydroxy-vitamin D3-1-hydroxylase. Percentages of calcium and phosphorus absorption were also higher during phosphorus deficiency. Medullary bone ash, decreased during phosphorus deficiency, was probably due to a reduction in the rate of bone formation.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed2004

Modest follicle-stimulating hormone elevations in younger women: warn but don't disqualify.

Markers of quantitative defects in egg production (low ovarian reserve) have often been used to exclude patients from treatment, even when egg quality is apt to be satisfactory. Women younger than 38 years of age with modest FSH elevations (10-15 or even 20 IU/L) have acceptable pregnancy rates despite their limited production of eggs ("quality matters more than quantity") and so should be given the opportunity to try IVF.

Adult↗
PubMed1988

Further studies of effects of sodium aluminosilicate on egg shell quality.

Five experiments were conducted using 36 dietary treatments to compare chloride salts and HCl as chemical sources of Cl for the adjustment of dietary Cl when using sodium aluminosilicate (SAS), to compare SAS to natural zeolites (clinoptilolite and mordenite), and to determine the appropriate level of dietary SAS for optimum egg specific gravity. The methods of Na and Cl correction used in the various treatments included altering the levels of NaCl, calcium chloride (CaCl2), potassium chloride (KCl), magnesium chloride (MgCl2), iron chloride (FeCl3), or hydrochloric acid (HCl). Experimental diets were fed for 6 to 8 wk. Results of all experiments (except Experiment 2) indicated that the addition of SAS to layer diets improved egg specific gravity and that correction for Na by removal of NaCl and the addition of HCl was not necessary for SAS to be effective. No beneficial effects of dietary SAS on egg specific gravity were observed when Na and Cl corrections were made using CaCl2, KCl, MgCl2, or FeCl3. The feeding of SAS has no influence on egg production in Experiments 1 and 3 but significantly improved egg production in Experiment 4, when it was added to diets containing 2.75% Ca. An adverse effect on production of feeding SAS was observed, especially at the higher levels of SAS in Experiments 2 and 5. In general, SAS tended to reduce feed consumption, with no effect on egg weight. It was concluded that .75% SAS will improve egg specific gravity approximately 1 to 3 units and that correction for Na was not necessary for SAS to be effective.

Aluminum Silicates↗
PubMed1988

Egg shell quality and cholecalciferol metabolism in aged laying hens.

Calcium-binding protein D28K (calbindin) synthesis, vitamin D metabolism and shell quality were investigated in young and aged laying hens fed diets containing either cholecalciferol (CC) or its 1-hydroxylated derivatives. Duodenal calbindin concentration was similar in the young and in the aged laying hens. Exogenous 1-hydroxylated CC derivatives increased duodenal calbindin concentration, regardless of age. Shell weight and shell density (mg/cm2) were significantly lower (P less than 0.01) in the aged than in the young hens. Egg shell weight and density tended to decrease along the clutch. The rate of decline was higher in aged than in young hens. Feeding aged hens a diet containing 5 micrograms 1,25-dihydroxycholecalciferol [1,25(OH)2CC] or 1 alpha-hydroxycholecalciferol per kilogram improved shell quality, slowed down the progressive reduction in shell quality during the clutch and increased culling and mortality. The results indicate a) that the capacity for expression of 1,25(OH)2D3 in the intestine is not altered by age and b) that prolonged feeding of 1-hydroxylated derivatives of vitamin D3 improves shell quality in aged laying hens and increases culling and mortality.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed2000

[Effect of blood concentrations of preovulatory estradiol on the quality of eggs and pre-embryos in patients treated with fertilization in vitro].

The objective was to investigate if the preovulatory estradiol concentrations obtained during controlled ovarian hyperstimulation (COH) have effect on reproductive outcome. The study included a total of 198 in vitro fertilization (IVF) cycles. Patients were divided into four groups according to serum preovulatory estradiol concentrations. In low responder patients was observed significantly decreased oocyte and preembryo quality compared with normal or high responders (P < 0.01). In this work high response do not have effect on IVF outcome. The clinical results indicate that low estradiol levels the day of hCG administration are apparently correlated with poor oocyte and embryo quality.

Adult↗
PubMed1984

Physiological profile of caged layers during one production year, molt, and postmolt: egg production, egg shell quality, liver, femur, and blood parameters.

A longitudinal study of a flock of Single Comb White Leghorn pullets was initiated at 19 weeks of age (preproduction) and continued through a production year, a forced molt, and for 4 months of postmolt production. A representative sample of hens was obtained at 12-week intervals during the first year and at subsequent selected times. Liver lipid, femur weight, femur volume, femur density, egg weight, shell weight, percent shell, milligrams shell/square centimeter of shell surface area, serum calcium, serum phosphorus, and serum alkaline phosphatase were determined. Percent hen-day production peaked at 90% and then declined by .6 to .7% each week during the first production year. After molting, percent hen-day egg production peaked at 80% and declined .9% per week over the subsequent 20 weeks. Egg weight increased continually during the first production year. Shell weight was greatest immediately postmolt; thereafter it declined. Shell thickness was greatest at 31 weeks of age and declined throughout the first year. After molting, the shell thickness of 83-week-old hens was similar to values of hens about 37 weeks of age. Serum calcium and phosphorus of laying hens were influenced by age, feed intake and environmental temperature. The lowest values occurred during hot weather. Liver lipid was lowest in nonlaying hens (17 to 20%) and was approximately 42% of dry weight in laying hens. Femur density was greater in laying than nonlaying hens.

Alkaline Phosphatase↗