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PubMed1995

Effects of population density on layer performance.

Four experiments were conducted to study the effects of population density on layer performance. in each experiment, 20-wk--old White leghorn pullets were housed in 30.5 x 50.8 cm cages at the rate of one, two, three, and four birds per cage for Treatments 1, 2, 3, and 4, respectively. in Experiment 4, there were three additional treatments: for Treatments 5, 6, and 7, birds were placed into identical cages (30.5 x 50.8 cm) at the rate of three, two, and three birds per cage, respectively, at 20 wk of age. At 28 wk of age, one bird was removed from each cage in Treatment 5, and one bird was added to each cage in Treatments 6 and 7. In the first three experiments, all eggs that were collected for 2 consecutive d every 8 wk starting at 28 wk of age were used to measure egg traits. In Experiment 4, egg traits were determined once at 52 week of age. Birds at the highest population density had the lowest percentage hen-day egg production and had one of the poorest feed efficiencies. Egg production was negatively correlated (P < or = .01, Experiments 1, 2, 3; P < or = .05, Experiment 4) with population density. Feed required to produce a dozen eggs was positively correlated (P < or = .01, Experiments 1, 2; P < or = .05, Experiment 3) with population density in three out of the four experiments. The addition or removal of a cage mate to or from a multiple-bird cage in Experiment 4 did not (P > .05) affect egg production or feed efficiency. Final BW, mortality, and egg weight were not (P > .05) affected by population density. Only in one out of the four experiments was feed consumption (Experiment 1), eggshell thickness (Experiment 2), or albumen height (Experiment 3 lowered (P < or = .05) by having more than one bird per cage. This study showed that increasing population density decreased laying performance of the birds.

Animals↗
PubMed2000

Avian pneumovirus infections of turkeys and chickens.

Avian pneumoviruses (APVs) cause major disease and welfare problems in many areas of the world. In turkeys the respiratory disease and the effect on egg laying performance are clearly defined. However, in chickens, the role of APV as a primary pathogen is less clear, although it is widely believed to be one of the factors involved in Swollen Head Syndrome. The mechanisms of virus transmission over large distances are not understood, but wild birds have been implicated. APV has recently been reported in the USA for the first time and the virus isolated was a different type or possibly a different serotype from the APVs found elsewhere. Good biosecurity is crucial for controlling infection and highly effective vaccines are available for prophylaxis. Although different subtypes and possibly different serotypes exist, there is good cross protection between them. Diagnosis is usually based on serology using ELISAs, but the available kits give variable results, interpretation is difficult and improved diagnostic tests are required.

Animal Welfare↗
PubMed2004

Effects of dietary conjugated linoleic acid and fish oil supplementation on performance and egg quality in laying hens.

1. Laying hen performance, yolk fat fatty acid concentrations and firmness of eggs were evaluated with respect to the inclusion in the diet of conjugated linoleic acid (CLA) and fish oil. 2. Nine diets were arranged factorially, with three levels of supplementation of CLA (1, 3 and 5 g/kg) and fish oil (0, 14 and 20 g/kg). 3. Type of diet did not affect egg production traits. 4. CLA addition increased yolk weight and yolk fat concentrations of CLA, saturated and total long-chain n-3 fatty acids, but decreased those of monounsaturated and total long-chain n-6 fatty acids. 5. Fish oil addition increased long-chain n-3 fatty acids yolk fat concentrations but decreased those of CLA, saturated and long-chain n-6 fatty acids. 6. Effects of CLA addition on yolk fat concentrations of C22:4 n-6 and C20:5 n-3 were greater when no fish oil was added to the diet. 7. CLA supplementation increased linearly yolk moisture and firmness and altered albumen and yolk pH.

Animal Feed↗
PubMed2005

Effects of dietary conjugated linoleic acid and high-oleic sunflower oil on performance and egg quality in laying hens.

(1) Laying hen performance, yolk fatty acid (FA) concentrations, sensory quality and firmness of eggs were evaluated with respect to the inclusion in the diet of conjugated linoleic acid (CLA) and high-oleic acid sunflower oil (HOSO). (2) Nine diets were arranged factorially, with three concentrations of CIA (0, 1 and 2 g/kg) and HOSO (10, 20 and 30 g/kg). (3) Type of diet did not affect egg production traits. (4) Dietary addition of CLA decreased yolk lipid content and yolk lipid concentrations of monounsaturated FA, C(20:4 n-6) and C(22:6 n-3), but increased those of CLA and saturated FA. (5) Dietary addition of HOSO increased monounsaturated FA concentrations in the yolk lipid but decreased those of CLA and saturated FA. (6) CLA supplementation increased yolk moisture and firmness and impaired the sensory quality of eggs. (7) An interaction between CLA and HOSO addition was found as effects of CLA addition on yolk lipid CLA concentrations and egg quality traits were smaller when the amount of HOSO in the diet increased. (8) Regression equations have been calculated in order to predict yolk CLA and C(18:1), concentration from dietary composition, and yolk firmness from yolk FA composition.

Animal Feed↗
PubMed1984

Effects of the naked-neck gene on traits associated with egg laying in a dwarf stock at two temperatures.

Naked-neck (NaNa and Nana+) and normal hens, all dwarf (dw), were compared for laying performance in two groups at 15 to 20 or 30 degrees C. Naked-neck hens, especially homozygotes, weighed less only at the cooler temperature. Body fatness was not different. Normal, but not naked-neck birds, showed a depression in food intake and egg output at 30 degrees C. In the hot environment mean egg weight and egg mass output were highest for naked-neck homozygotes. At the cooler temperature mean egg weight was also higher for this genotype, at fixed body weight. The decline in egg mass with time seemed greater for fully-feathered layers at high temperature. At moderate temperature residual food intake was slightly increased by the naked-neck gene, but owing to the reduced body weight, food utilisation was not poorer for the NaNa or Nana+ genotypes. At higher temperature Nana+ and especially NaNa hens utilised food more efficiently. An increase in wattle size and a slight decrease in body temperature were associated with the Na allele.

Animals↗
PubMed1989

Selection experiment for increased egg production under 23 H and 24 H light-dark cycles in the domestic fowl.

A selection experiment was conducted for increased rate of lay under 23-h (23 HS line) and 24-h (24 HS line) light-dark cycles over 5 generations. In generation 5, rate of lay was higher in the 23 HS line than in the 24 HS line, and the proportion of hens with mean intra-sequence intervals of less than 24 h in the 23 HS line increased to 88% in the generation 5 from 15% in the base generation. The realised heritability for rate of lay was 0.25 plus/minus 0.04 in the 23 HS line and 0.15 plus/minus 0.05 in the 24 HS line. Egg weight and shell weight decreased in both lines, and the decrease in the proportion of shell was larger in the 23 HS line than in the 24 line. It is suggested that a regimen of 23 h light and dark may be an effective environment for selection to improve the laying performance of a population approaching a plateau for egg production.

Animals↗
PubMed1994

EDS 76 HI antibodies in a flock of free-range layers.

An investigation of poor laying performance in a flock of free-range hens revealed high levels of serum antibodies to EDS 76 in the flock initially examined and in another, older flock on the same farm. These flocks had contact with ducks on a farm dam and were supplied with untreated drinking water from the dam. Serological evidence indicated that another flock supplying the same egg packing station had been infected with EDS 76 virus. Little serological evidence of EDS infection was detected from five other flocks supplying the packing station, parent breeders or the ducks resident on the dam. Therefore, the source of the EDS 76 virus remains conjectural.

Journal Article↗
PubMed2005

Effect of Ligustrum lucidum and Schisandra chinensis on the egg production, antioxidant status and immunity of laying hens during heat stress.

The experiment was conducted to evaluate the effect of two plants belonging to Chinese herbal medicines, Ligustrum lucidum (LL) and Schisandra chinensis (SC), on the laying performance, antioxidant status and immunity of hens during heat stress. The results showed that diets supplement with 1% of either LL or SC had beneficial effects on egg production and FCR of hens during heat stress (p < 0.05), compared with the control group. Either LL or SC significantly reduced malondialdehyde (MDA) concentration of heart, liver, sera and egg yolk. In addition, glutathione reductase (GR) activity of tissues and sera of the birds was significantly elevated by supplementation LL or SC. Furthermore, LL or SC supplementation significantly elevated lymphoblastogenese of the birds and the antibody values against Newcastle disease virus (NDV). The results suggest that diets supplement with 1% of either LL or SC may enhance egg production, immune function, and antioxidant status of hens during heat stress.

Animals↗
PubMed1979

[Utilization of 15N-labelled urea by laying hens. 1. Survey of the literature, 15N-excretion in feces and urine].

Three colostomated leghorn hybrids with an average laying performance of 75% received a ration with 17.7% crude protein and an energy content of 519 energetic feed units for hens per kg mixed feed over a period of 8 days. In the first six days of the experiment the 1%-supplement of urea to the ration was labelled. Its atom-% 15N excess (15N') amounted to 96.06%. During the last two days the urea supplement was not labelled. The total N, trichloracetic acid (TCA)-soluble N and the ammonia N were determined in the feces samples collected daily. In the urine samples collected daily the total N, urea N and ammonia N per hen were determined as well. In all samples the atom-% 15N excess (15N') was measured. The percentage of 14N in feces of the 14N dose was, on an average of the three hens, 21.3% and the analogous quota of 15N' 4.6%. The quota of ammonia 14N of the total 14N in feces had an average of 2.5%, the corresponding 15N' quota was 10.1%. The atom-% 15N' of the urea N in urine was considerably above that of the total urine N and had a maximum of more than 50%. The quota of urine 14N of the 14N taken in had an average of 44.4%, and the corresponding 15N' quota was 56.9%. On an average of the three hens, 61.6% of the 15N' were excreted in feces and urine during the 8-day test period.

Ammonia↗
PubMedDate not supplied

[Dynamics of amino acid and protein metabolism of laying hens after the administration of 15N-labeled wheat protein. 4. 15N-incorporation into the amino acids of egg fractions].

12 colostomized laying hybrids with an 81% laying performance received 36 g wheat containing a 15N excess (15N') of 14.37 atom-% in a customary ration over 4 days. The wheat lysine contained 13.58 atom-% 15N', the histidine 14.38 and the arginine 13.63 atom-% 15N'. In the 4-day period of 15N' application 540 mg 15N', 18.1 mg lysine 15N', 21.5 mg histidine 15N' and 47.9 mg arginine 15N' were consumed per hen. Subsequently the animals received the same ration with unlabelled wheat. 12 h, 36 h, 60 h and 108 h after the last 15N' application 3 animals each were butchered. The atom-% 15N' of the lysine was below that of the two other basic and of the non-basic amino acids. The labelling of the amino acids of the white of egg decreased rapidly 2 days after the 15N' application. The atom-% of the 15N' of the yolk of egg, however, increased after the discontinuation and remained the same for 4 days after the last 15N' application. The 14N and 15N' amounts measured in the complete experiment period are distributed over the 3 basic and the 12 non-basic (excluding thioamino acids) amino acids in the white of egg for 14N as 25.0%: 57.6% and for 15N' as 18.2%: 57.5%. In the yolk of egg 28.5% 14N for the basic and 56.8% for the non-basic amino acids could be calculated; the corresponding values for 15N' were 17.8% and 55.5%.

Amino Acids↗
PubMed1999

Vitamin E hypervitaminosis in laying hens.

The aim of this investigation was to contribute to the problem of overdosing vitamin E. A total of 80 laying hens, divided into 5 groups, were fed diets supplemented with 0, 100, 1000, 10,000 and 20,000 mg/kg vitamin E over a period of 20 weeks within two brooding tests. Laying performance and hatching parameters were registered. All vitamin E doses did not significantly influence health and performances of hens. Vitamin E content of eggs increased from 1 to 4, 21, 46 and 51 mg per egg with vitamin E supplementation. High doses decreased oxidative stability of abdominal fat, vitamin A concentration of liver and egg yolk colour. In both tests vitamin E supplements of 10,000 and 20,000 mg/kg feed resulted in a decrease of living hatched chicken, which demonstrated an adverse effect. Further studies seem to be necessary to explain the effect.

Animal Feed↗
PubMed1996

Diel rhythms of oviposition and fecundity of Anopheles aquasalis (Diptera:Culicidae) under laboratory conditions.

The oviposition patterns of Anopheles aquasalis Curry collected from a grass swamp in Gloudon, Caroni Swamp, Trinidad, were studied in the laboratory by recording the egg-laying performance of 30 individuals and a group of 150 females at 2-h intervals. Oviposition was nocturnal, with a peak between 2400 and 0400 hours when 72% of the eggs were laid. Wild-caught females engorged on human blood matured 89.8 +/- 21.3 follicles (range, 50-118). These findings provide vector control workers with the opportunity to maximize the effect of adulticides on An. aquasalis populations by restricting their operations to the time of peak flight activity.

Animals↗
PubMed2004

Oral administration of pravastatin reduces egg cholesterol but not plasma cholesterol in laying hens.

The effect of different 3-hydroxy-3-methyl-glutaryl coenzyme A reductase (HMGR)-inhibitors (statins) on plasma and egg cholesterol in laying hens was investigated. Forty-four ISA brown layers were fed lovastatin, simvastatin, or pravastatin at 0.03 or 0.06% for 4 wk. Cholesterol levels in plasma, liver, and egg yolk as well as hen laying performance were studied. Egg weight was significantly lowered with all statin treatments, although egg production was relatively unaffected. Total plasma cholesterol was significantly reduced by 0.06% lovastatin, 0.03% simvastatin, and 0.06% simvastatin, in agreement with previous reports, whereas pravastatin had no effect. In contrast, liver cholesterol concentrations showed a significant decrease in response to 0.03 and 0.06% pravastatin, implying selective regulation of liver cholesterol synthesis. Furthermore, oral administration with 0.06% pravastatin reduced egg cholesterol levels by almost 20% compared with the control diet. This suggests that pravastatin, unlike other classes of statin, may be a good candidate for commercial production of low cholesterol eggs with limited impact on hen physiology and egg production.

Administration, Oral↗
PubMed2004

Parallel multigrid preconditioner for the cardiac bidomain model.

The bidomain equations are widely used for the simulation of electrical activity in cardiac tissue but are computationally expensive, limiting the size of the problem which can be modeled. The purpose of this study is to determine more efficient ways to solve the elliptic portion of the bidomain equations, the most computationally expensive part of the computation. Specifically, we assessed the performance of a parallel multigrid (MG) preconditioner for a conjugate gradient solver. We employed an operator splitting technique, dividing the computation in a parabolic equation, an elliptical equation, and a nonlinear system of ordinary differential equations at each time step. The elliptic equation was solved by the preconditioned conjugate gradient method, and the traditional block incomplete LU parallel preconditioner (ILU) was compared to MG. Execution time was minimized for each preconditioner by adjusting the fill-in factor for ILU, and by choosing the optimal number of levels for MG. The parallel implementation was based on the PETSc library and we report results for up to 16 nodes on a distributed cluster, for two and three dimensional simulations. A direct solver was also available to compare results for single processor runs. MG was found to solve the system in one third of the time required by ILU but required about 40% more memory. Thus, MG offered an attractive tradeoff between memory usage and speed, since its performance lay between those of the classic iterative methods (slow and low memory consumption) and direct methods (fast and high memory consumption). Results suggest the MG preconditioner is well suited for quickly and accurately solving the bidomain equations.

Algorithms↗
PubMed1985

Follicular growth and atresia in the ovaries of hens (Gallus domesticus) with diminished egg production rates.

Diets containing 3.5, 1.0 and 0.1% calcium were fed from the age of 42 weeks to individually caged laying hens. Ovaries were examined at 46-49 and 70 weeks of age for changes in the follicular population corresponding to the lowered egg production rates of birds given calcium-deficient diets (1.0% and 0.1%) and older birds given a normal diet (3.5%). Growth rates of follicles from 3.5 mm diameter to ovulation were not changed by the level of dietary calcium in 46-49-week-old birds. The number of atretic small follicles (less than or equal to 8 mm diam.) increased in old and calcium-deprived birds, resulting in lower numbers of viable follicles in the intermediate stages of growth (3-8 mm diam.). There was also an increase in the number of small follicles (1-2 mm diam.) starting to grow in 70-week-old birds which may have partly compensated for the increased loss by atresia. Birds of all ages on all diets were able to produce large follicles up to ovulable size. The main feature of poor laying birds was a reduction in the ovulation rate due to the loss of large follicles (greater than 8 mm diam.) by atresia, an event seen rarely in the birds with good laying performance. As atresia is the normal fate of most of the small follicles, the mechanisms controlling atresia in the small follicles and the large follicles appear to be independent.

Animals↗
PubMed2000

Avian rhinotracheitis.

Turkey rhinotracheitis, now commonly termed avian pneumovirus (APV) infection, is associated with serious welfare and economic problems in susceptible populations of turkeys and probably also of chickens. The infection principally affects the upper respiratory tract, although egg-laying performance may also be affected in breeding turkeys. Secondary infections exacerbate the effects of the primary virus infection. The virus persists for only a short time both in the host and in the environment and is not known to be transmitted via the egg. Highly effective vaccines are available to control APV infections, and hence good biosecurity and careful use of these vaccines should enable infection to be controlled and spread restricted. Diagnosis and surveillance are normally performed serologically using enzyme-linked immunosorbent assays (ELISAs). Several different ELISA kits are available commercially, but these give variable results and are not wholly satisfactory since interpretation of results is difficult.

Animals↗
PubMed1976

Lysine requirement of White Leghorn pullets from 8 to 21 weeks of age.

White Leghorn pullets were fed rations in which the protein supplementary to that provided by the grain portion of the ration was derived from soybean meal, meat and bone meal, anchovy fish meal or cottonseed meal from 8 to 21 weeks of age. Protein levels were varied so that each protein supplement was tested in a feeding program in which pullets received 16% protein diets from 8 to 14 weeks and 14% protein from 14 to 21 weeks and in another feeding program in which 14% protein was fed from 8 to 14 weeks and 12% protein from 14 to 21 weeks. Each of the developing rations contained sufficient nutrient to enable pullets to develop and attain high rate of laying performance. The 14% and 12% protein cottonseed meal diets contained only 0.50% and 0.45% lysine respectively. Thus the lysine requirement of White Leghorn pullets from 8 to 14 weeks and from 14 to 21 weeks is not over 0.50% and 0.45% respectively.

Age Factors↗
PubMed1976

Effects of different cereal grains in diets for laying hens on production parameters and liver fat content.

Two experiments were conducted with White Leghorn laying hens to study the effects of different cereal grains on production criteria and liver fat content. The results of Experiment 1, in which pullets 21 weeks of age were used for a period of 22 weeks indicated that Gaines wheat or triticale (Trailblazer) were equal to corn in supporting egg production, egg weight and body weight, with comparable feed consumption. Henry wheat(a hard red winter class) was slightly, yet significantly (P less than 0.05) inferior to corn for the above criteria. No significant differences were observed among four treatments in wet liver weight and liver fat content. Hens fed the corn diet had significantly (P less than 0.05) lower carcass fat followed by the hens fed triticale in comparison with those fed Gaines or Henyry wheat. Mortality was very low and not related to dietary treatments. Neither dietary fat nor energy content was related to fat content of liver and carcass of the hens. Body weight and liver fat content were not closely related to each other. Wet liver weight was the only significantly (P less than 0.05) related factor to liver fat content. In the second experiment, in which hens 33 weeks of age were used for an experimental period of 20 weeks, opaque-2 corn was slightly superior to normal corn and triticale was comparable to normal corn in supporting egg production and egg weight. Supplementation of the diets containing the two corns and triticale with lysine failed to improve egg production and egg weight. Hens fed the diets containing either normal corn or opaque-2 corn as the only grain in the diet had significantly (P less than 0.05) higher liver fat content in comparison with hens fed the diet containing triticale as the only grain. Mortality, however, was much higher among hens fed triticale-containing diets in comparison with groups fed corn-containing diets in spite of the fact that they had significantly lower liver fat content. Regardless of dietary treatments or grains used, the hens that died were diagnosed to have fatty liver hemorrhagic syndrome. Dietary fat content was postively and significantly (P less than 0.05) related to liver fat content. Dietary energy or body weight was not closely related to liver content. Liver fat content and mortality were negatively related to each other. The higher for content did not adversely affect laying performance.

Animal Feed↗