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At least 19 recordsLinked to original sources
PubMed1976

Effect of calcium propionate on performance of laying hens.

Laying hens kept in individual cages were fed a practical diet supplemented with 0, 0.1, 0.2., 0.4, or 0.8% calcium propionate for a six-week period. Rate of egg production, average egg weight, feed consumption, and body weight change during the experiment were not significantly affected by and dietary treatments. Liver weight, moisture content and fat content were also no significantly affected by dietary treatments. The results show that the performance of normal hens is not changed by calcium propionate supplementation.

Animals↗
PubMed1992

Calcium and phosphorus metabolism and eggshell thickness in laying hens producing thick or thin shells.

Two experiments were carried out to investigate the Ca and P metabolism of hens laying thick- (THK) or thin-shelled (THN) eggs on shell-forming days (SF) and days on which shell formation does not occur (NSF). In Experiment 1, 10 hens identified as producing THK or 10 hens producing THN eggs were offered a diet containing 3.5% Ca and .4% available P. Feed consumption, egg production, egg weight, egg deformation, and shell weight were recorded over 8 days. Shells and excreta were collected daily for Ca and P analysis. Feed, Ca, and P intake did not differ significantly (P greater than 0.5) between the two groups of hens, however, feed intake and Ca retention increased significantly (P less than .05) on SF compared with NSF days. The THK hens retained significantly (P less than .05) more Ca compared with THN hens. No differences (P greater than .05) were recorded for egg production, although there were differences (P less than .05) in egg weight and shell deformation between the two groups of hens. Increased egg weight did not account for differences (P less than .05) in eggshell deformation. Although percentage shell Ca was not significantly different (P greater than .05), total shell Ca was different (P less than .05) between the two groups. In Experiment 2, both groups of birds (THK and THN) were allowed simultaneous access to two different diets, a high-energy, high-protein diet low in Ca and P, and a low-energy, low-protein diet high in Ca and P.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Individual perching behavior of laying hens and its effects in cages.

1. ISA Brown hens were housed, from 18 to 71 weeks of age, as groups of 4 in cages with 675 cm2/bird. There were 7 treatments: control cages and 6 treatments with perches fitted across the rear of the cage. Five treatments had 450 mm wide cages, with perches made from hardwood, textured metal, smooth plastic, softwood and padded vinyl, and one treatment had a 600 mm wide cage, with a softwood perch. There were 4 cages in each of the first 6 treatments and 6 in the last. 2. Overall, birds spent about 25% of the day time on perches. Most time (28 to 41%) was spent perching on the 600 mm softwood perches. Among 450 mm perches, most time (25 to 30%) was spent on the softwood perch and least (13 to 23%) on the plastic; the results suggested that a slightly rough surface was preferred. Individual birds varied considerably in the proportion of day time they spent perching; this variation was relatively consistent over time. 3. Overall, the proportion of birds roosting on the perches at night was 85% in period 1; declined to 76% by period 6, probably because increased body size made it almost impossible for 4 birds to perch in the 450 mm cages. Birds roosting on the floor tended always to be the same individuals. 4. Damage to the soles of the feet was less in all treatments with perches than in control cages. It was least in 600 mm wide cages and showed a negative correlation with time spent perching, both within and between treatments. Long or twisted claws, in contrast, tended to be slightly worse in treatments where there was most perching. 5. Downgraded eggs tended to be slightly more frequent in cages with perches; the greatest proportion (cracked 1.4%, dirty 3.6%) was from the 600 mm wide cages, as a result of hens laying from the perch and a build-up of manure behind it. 6. Although problems remain the findings suggest that provision of perches is important for the welfare of hens; perch space should be sufficient to allow all birds to perch simultaneously.

Age Factors↗
PubMed1975

[Histological and electron microscopy studies on the adenocarcinomatosis of laying hens].

Histological examination of 187 tumours from 98 hens (laying hybrids of various lines, age 80-123 weeks) showed that highly-differentiated tubulo-alveolar adenocarcinoma was present in 95% of the birds; in 20% it had a scirrhus structure. Histological and ultrastructural features of these carcinomas and their tendency to form secretory granules pointed to an origin from the protein-secreting part of the oviduct (magnum). In the remaining 5% of birds there were non-specific adenocarcinomas (probably ovarian carcinoma) and mesotheliomas.

Adenocarcinoma↗
PubMedDate not supplied

Bone histomorphometry in 1,25(OH)2D3- and vitamin D3-treated aged laying hens.

Aged laying hens at oviposition were given four levels of dietary vitamin D3 and three levels of 1,25-dihydroxyvitamin D3 (1,25[OH]2D3) to determine the effects of the additives on the medullary and endosteal bone. Oxytetracycline hydrochloride labeling and histomorphometry of undecalcified sections were used in the determination of changes in medullary bone and endosteal surface of mid-diaphyseal tibiotarsal bones. Treatment with 1,25(OH)2D3 increased mineralized medullary bone area, endosteal surface length, amount of tetracycline labeling in medullary and endosteal bone, total number of osteoclasts on endosteal and medullary bone, and appositional rate of mineralizing bone. Vitamin D3 increased mineralized medullary bone area and total tetracycline labeling in endosteal bone but decreased endosteal mineral apposition rate. Medullary bone matrix with no mineral was observed only in the group receiving neither supplement. These areas were much larger than typical osteoid seams usually seen in trabecular bone. Both 1,25(OH)2D3 and vitamin D3 were effective in stimulating bone formation and retention of mineral within medullary bone matrix at oviposition.

Aging↗
PubMed1976

Susceptibility of chickens to avian encephalomyelitis virus. IV. Behavior of the virus in laying hens.

Some laying hens 6 months of age were inoculated subcutaneously or orally with a chick embryo--adapted strain of avian encephalomyelitis virus and examined for propagation of the virus in the body. When inoculated subcutaneously, the virus appeared in liver, spleen, ovarian follicle, and muscle at the site of inoculation 1 day, in kidney and lumbar part of the spinal cord 3 days, in the pancreas 5 days, in heart, duodenum, and cervical part of the spinal cord 7 days, and in the brain 11 days after inoculation. After its appearance, it increased gradually in amount in liver, spleen, pancreas, muscle at the site of inoculation, and cervical and lumbar parts of the spinal cord, but remained at a low level in any other organ. When examined 14 days after inoculation and later, it was distributed mainly in the central nervous system. It was detected from 12 of 16 organs examined. The highest virus level in each organ was 10(2.6)/0.1 g in pancreas and lumbar part of the spinal cord, which were followed by muscle at the site of inoculation (10(2.0)/0.1 g), spleen (10(1.8)/0.1 g), cervical part of the spinal cord, heart, and liver in the order listed. When inoculated orally, the virus was found sporadically in spleen, pancreas, kidney, cecum, ovarian follicle, and lumbar part of the spinal cord. The virus level was low in these organs, of which pancreas, kidney, and lumbar part of the spinal cord showed the highest virus level, or 10(1.3)/0.1 g.

Administration, Oral↗
PubMed1975

The influence of intestinal (ceca) flora on serum and egg yolk cholesterol levels in laying hens.

Normal and cecectomized laying hens were used to study the influence of intestinal (ceca) flora and the implantation of Lactobacillus acidophylus on the levels of serum and egg yolk cholesterol. The ceca had been surgically removed when the experimental birds were 16 months of age. Serum cholesterol levels of cecectomized laying hens were higher than that of normal birds; the Lactobacillus acidophylus implantation resulted in a significant decrease in serum cholesterol levels in both normal and cecectomized birds. The normal intestinal (ceca) flora and Lactobacillus acidophylus implantation did not influence fat digestibility. Egg yolk cholesterol levels were higher for cecectomized birds. A constant relationship between serum and egg yolk cholesterol was not observed.

Animals↗
PubMed1992

Plasma 1,25 dihydroxycholecalciferol and its free index are potentiated by ovulation dependent factors and shell formation induced hypocalcemia in the laying hens.

The time-course of the changes in blood ionized calcium, and in plasma 1,25 dihydroxycholecalciferol (1,25(OH)2D3) concentrations and its free index were studied in hens following suppression and resumption of shell formation and throughout the laying cycle in hens laying hard-shelled eggs, in hens fed a low or normal calcium diet and in hens laying shell-less eggs. The respective roles of the calcium needs for shell formation and of the reproductive status in regulation of 1,25(OH)2D3 production were analysed. Plasma 1,25(OH)2D3 decreased 3 hr after suppression of shell formation following premature egg expulsion and remained lower than that of hens laying hard-shelled eggs when premature expulsion of the eggs was continued for several days. Circulating 1,25(OH)2D3 tended to increase progressively when shell formation was resumed. Ablation of the parathyroid glands abolished this increase. In hens laying hard-shelled eggs, the plasma 1,25(OH)2D3 was higher during the period of shell secretion. Feeding hens a low calcium diet (1.2%) caused a marked increase in the plasma 1,25(OH)2D3. Ionized calcium levels tended to show reciprocal changes to plasma 1,25(OH)2D3 decreasing when calcification took place and increasing after its suppression. In hypercalcemic hens laying shell-less eggs and fed a 3.5% Ca diet, the plasma 1,25(OH)2D3 was at a high level 4 hr after ovulation and diminished thereafter. This additive stimulation does not, therefore, involve the parathyroid gland and may involve hormonal changes induced by ovulation. Vitamin D binding protein (DBP) in the plasma was at a high level in mature hens and was not affected by shell formation. Consequently, the free 1,25(OH)2D3 index fluctuated in parallel with total level of this hormone in mature hens. It is concluded that the calcium demand for shell formation modulates, in the short term, plasma 1,25(OH)2D3, via the homeostatic regulation of blood calcium by PTH, but that a large part of its increase is independent of PTH and is associated with the endocrine events concomitant with ovulation.

Animals↗
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↗
PubMed1978

Metabolism of linoleate versus linoelaidate in the laying hen.

The metabolic fate in the laying hen of linolaidic acid, the trans,trans-geometric isomer of linoleic acid, was compared to that of the naturally occurring cis,cis linoleate. In two experiments, mixtures of radioisotope-labeled linoleate and linoelaidate were orally administered to a set of three laying hens. A third mixture consisting of linoleate-3H and linoleate-14C was fed to three hens to measure biological isotope effects. Isotopic ratios (3H/14C) of the neutral lipid and phospholipid fractions isolated from egg yolks and of the octadecadienoic acids from these fractions were compared to those of the administered mixtures. The 3H/14C ratios indicate that linoelaidic acid and linoleic acid are equally incorporated into egg yolk neutral lipids and phospholipids. Arachidonic acid was found exclusively in the phospholipid fraction and was radiolabeled with the isotope from the cis,cis octadecadienoate isomer only. Further detailed analysis of individual neutral lipid components indicated: (a) discrimination against the trans,trans isomer in cholesteryl esters and (b) no discrimination against either isomer in triacylglycerols.

Animals↗
PubMed1978

Effect of dietary fiber on egg yolk, liver, and plasma cholesterol concentrations of the laying hen.

Two experiments were conducted to determine the effect of dietary fiber source and level on egg yolk, liver, and plasma cholesterol concentrations of White Leghorn laying hens. Initially, dietary fiber levels of 2.05, 4.41, 6.68, and 8.79% furnished mainly by sunflower meal were fed to laying hens for 140 days. In the second experiment, alfalfa meal, ground whole oats, sunflower meal, rice mill feed, or wood shavings was added to a corn-soybean meal basal diet to furnish 2.00% added crude fiber and fed to laying hens for 84 days. Yolk cholesterol decreased 4.39, 10.38, and 13.29% by feeding crude dietary fiber levels of 4.41, 6.68, and 8.79%, respectively, to hens as compared to a corn-soybean meal basal diet containing 2.05% crude fiber. Egg yolk cholesterol was significantly decreased by feeding alfalfa meal, oats, sunflower meal, rice mill feed, or wood shavings to laying hens when compared to yolk cholesterol of hens fed the basal diet. The greatest reduction in egg yolk cholesterol was found by feeding either oats or wood shavings. No significant differences were found in plasma cholesterol due to dietary fiber level. Plasma triglycerides decreased and liver cholesterol increased as dietary fiber level increased in diets fed to laying hens. When laying hens were fed alfalfa meal, oats, rice mill feed, or wood shavings, plasma cholesterol significantly decreased. Liver cholesterol increased when hens were fed either alfalfa meal or rice mill feed as the primary fiber source.

Animal Feed↗
PubMed1992

Wheat middlings as an alternative feedstuff for laying hens.

Three long-term experiments were conducted to evaluate the possibility of using wheat middlings (WM) for laying hens and to study the responses of six strains of commercial laying hens fed WM diet. In Experiment 1,320 layers maintained in floor pens were fed diets containing 45% WM with .25 or .75% salt, or 89% WM with .25% or 1.5% salt. Salt supplementation did not show any beneficial effect on egg production. Hen-day egg production by hens fed the 45% WM diet was significantly higher for hens fed 45% WM than for those fed the 89% WM diet (79 versus 67.5%, 44-wk period). Feed, limestone, and water intakes were increased by the 89% WM diet. Yolk color, Haugh units, hen livability, and reproductive parameters were not different among the dietary treatments. In Experiments 2 and 3, laying hens from six commercial strains (four strains each experiment, 240 hens per strain) were maintained in laying cages in each year, and fed either a corn and soybean meal (CSM) or a 25% WM diet. Results show that neither diet nor strain had effects on hen-day egg production; however, egg weights from Strains A, C, and F were heavier than those from Strains B, D, and E. Feed intakes and feed utilizations were similar among the s trains. The 25% WM diet increased egg weight, feed intake, and feed utilization compared with the CSM diet. Livability of hens was 93.8 to 97.5% and was not affected by either strain or diet. It is concluded that commercial strains of laying hens can be fed diets containing 25 to 45% WM and still have normal hen-day egg production although feed utilization will be poorer.

Analysis of Variance↗
PubMed1992

Evaluation of a chick mortality model for predicting the consequences of Salmonella enteritidis infections in laying hens.

The effects of four domestic Salmonella enteritidis (SE) isolates were compared in experimentally infected chicks and laying hens. The pathogenicity of each strain for 1-day-old chicks was determined by recording postinoculation mortality. The effects of the SE strains on adult hens were measured in terms of changes in total egg production, the frequency of production of SE-contaminated eggs, the dissemination of SE to internal organs, and the elicitation of a specific antibody response. Significant differences in the consequences of infection with different SE strains were observed in mortality rates among chicks and in total egg production, the frequency of production of contaminated eggs, and the serum antibody response among laying hens. The usefulness of a chick mortality model for predicting the probable frequency of production of contaminated eggs by laying hens infected with particular SE strains was then further evaluated by infecting chicks and laying hens with four other field isolates of SE. Although significant differences between SE strains were observed in both chick mortality and the frequency of production of contaminated eggs by hens, a strong correlation between these two parameters was not evident.

Animals↗
PubMed1992

Short-term reduction in egg production in laying hens treated with an agonist of GnRH.

1. In two experiments laying hens were treated with an agonist of gonadotrophin releasing hormone (GnRH) to induce a reduction in the secretion of luteinising hormone (LH) and a pause in egg production. 2. In experiment 1, 70-week-old laying hens were either given daily subcutaneous injections of saline for 7 d, offered whole oats for 7 d (nutrient restriction), given daily injections of the GnRH agonist [D-Trp6-Pro9 N-ethyl amide]GnRH for 7 d at 50 micrograms/kg or 100 micrograms/kg or administered 4 biocompatible implants each containing 120 micrograms of the GnRH agonist. 3. Weekly egg production was monitored for 7 weeks and blood samples were taken at weekly intervals and assayed for plasma LH and oestradiol. Egg production was reduced in the birds treated with the agonist (28 to 46% reduction) but not to the same extent as in the birds offered whole oats (92.3% reduction). 4. The treatments also reduced plasma LH and oestradiol in treated hens but again to a greater extent in the birds offered whole oats than the birds treated with the agonist. Egg production and plasma LH and oestradiol increased following the termination of the treatments. 5. The birds fed whole oats suffered a reduction in weight of 16.7% over the treatment period whereas there were increases in the weights of the birds treated with saline, 50 micrograms of GnRH agonist and the implants of GnRH agonist, but no change in birds treated with 100 micrograms of GnRH agonist. 6. The birds fed oats lost feathers over the treatment period but the birds in the other treatment groups suffered no loss. 7. In experiment 2 laying hens were either injected daily with saline or 200 micrograms GnRH agonist and weekly egg production and plasma LH and oestradiol were measured. As egg production was reduced by almost 60% in the birds treated with the agonist but did not completely cease. Reductions in plasma LH and oestradiol were also observed. All variables increased to pretreatment levels once treatment ceased. 8. These data confirm the effects of severely depriving hens of nutrients on egg production and the secretion of LH and oestradiol.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Feed↗
PubMed1978

Copper deficiency in the laying hen.

Copper deficiency in the laying hen resulted in anemia and the production of eggs which were abnormal in size and shape. Many of the eggs had shells which were wrinkled and rough in texture. There was also an increase in the number of shell-less eggs. Examination of malformed egg shells using the scanning electron microscope revealed ultrastructural changes in the mammillary layer of the shell. The effect of copper deficiency on shell formation was attributed to the shell membranes which were altered in color, appearance, and physical consistency. Amino acid analysis of the membranes indicated that the membranes from copper deficient hens were characterized by an increase in lysine content. This suggests that copper is necessary for the formation of lysine derived cross-links in a manner similar to that which occurs in connective tissue. The exact nature of these cross-links is unknown at this time.

Amino Acids↗
PubMed1977

Dietary sodium for laying hens.

Dietary sodium requirements of laying hens in open type and evaporatively cooled housing were determined to be 0.126 and 0.145% of the diet, respectively. The lowest level of 0.04% sodium supported average rates of production of 49.1 and 60.3% in the two houses for the 28 weeks of the study.

Animal Feed↗
PubMed1992

Effect of duration of fasting on postmolt laying hen performance.

Two experiments were conducted to examine the effects of varying length of feed withdrawal on postmolt laying hen performance. Commercial laying hens (65 wk of age) were fed continuously or fasted for 4 or 10 days in Experiment 1 and fed continuously or fasted for 4, 7, or 14 days in Experiment 2. Egg production performance was evaluated for 35 wk of production following initiation of fasting. Hen-day egg production (Weeks 1 to 35) and egg weight (Weeks 5 to 35) did not differ between treatments in Experiment 1; however, in Experiment 2, egg production was depressed for the 14-day fasted hens compared with the fed hens. Lower egg weight also occurred for the 14-day fasted hens compared with the fed, 4-, or 7-day fasted hens in Experiment 2. Egg yield (grams of egg per hen per day) for Weeks 5 to 35 was lower for fed hens versus the 4- or 10-day fasted groups in Experiment 1, but no treatment differences occurred in Experiment 2. Feed efficiency (grams of egg per gram of feed) for Weeks 5 to 13 was not affected by length of fasting in Experiment 1, but feed efficiency of hens fasted for 14 days was lower (P less than .05) than that of hens on other treatments in Experiment 2. Egg specific gravity was highest for hens fasted for 10 or 14 days and was lowest for fed hens, with egg specific gravity for hens fasted for 4 or 7 days being intermediate (P less than or equal to .05). The results indicated that fasting periods of less than 10 days may yield satisfactory egg production and egg weight but that eggshell quality may be enhanced by using fasting periods of 10 days or longer.

Animals↗