Nesting and floor laying by domestic hens in a commercial flock

1. The nesting behaviour of broiler breeders was studied in a commercial flock of nearly 4000 birds kept on deep litter by tagging a sample of 200 hens. Use of nest boxes by tagged birds was recorded on 52 d over 34 weeks.

2. Forty hens were never observed in nest boxes and 33 others were recorded only in ground‐level boxes. These 73 birds were recorded significantly less often in nest boxes and more often apparently laying on the floor than others. Fewer of them perched during observations and they started doing so later than birds which used raised nest boxes.

3. These results suggested that there were consistent floor layers, which had difficulty reaching raised nest boxes, as found previously in experimental conditions. Many or all floor layers may, however, have used ground‐level boxes sometimes.

4. Hens were inconsistent in their use of particular nest boxes, and some even nested in two distinct areas.

5. Most individuals were, however, consistent in their reaction to one or more features of the nest boxes, including height, aspect and area. Individual choices for these features varied, so no boxes were used particularly heavily, with the exception of those at ground level.     

日粮中添加富硒酵母生产富硒鸡蛋的研究

采用短期饲喂试验研究了富硒酵母硒在鸡蛋中的沉积。将600羽46周龄产蛋率约为80％的罗曼蛋鸡随机分为4个组，A组为对照组喂基础日粮(添加了0．3mg／kg无机硒，来源于亚硒酸钠)，B、C、D组为试验组，在基础日粮中分别加0．2、0．4、0．6mg/kg有机硒(来源于富硒酵母)。结果显示，日粮中加富硒酵母可显著提高鸡蛋中硒含量，但对蛋鸡生产性能无显著影响，硒主要存在于蛋黄中；A、B、C、D组蛋中硒平均含量分别为6．84、10．02、18．24、27．18μg/只；而且蛋黄中硒含量增高使蛋黄的维生素E水平也增高，富硒鸡蛋在贮藏中哈氏单位下降缓慢，可延长鸡蛋的贮藏期。     

Abnormal characteristics of eggs laid by hens fed with high levels of cottonseed meal

In China, consumers sometimes get special eggs, which are characterized by the pasty, firm, and elastic texture of yolk from hard-boiled eggs and are usually called “rubber eggs” by Chinese customers. Consumers do not like the texture of rubber eggs and often associate the odd texture of the yolk to food safety risks. The objective of this study was to assess the physical and chemical characteristics of these eggs. A total of 200 46-week-old Hy-Line Brown laying hens were divided into 2 groups and were fed for 2 weeks. One group was fed on a corn-soybean meal based diet (BD) and served as control whereas the second group’s diet contained 6% cottonseed meal (CSM), which was in replacement of the SBW. The yolks of hard-cooked eggs of the CSM group had harder and more elastic yolks than those of the control group (P < 0.05). Also, the levels of stearic and myristic acids in the yolk of the CSM group also were increased (P < 0.01), while the myristoleic, pentadecanoic, arachidic, cis-11-eicosenoic and cis-11, 14-eicosadienoic acids and crude protein, fat, phospholipids, chloride, calcium, and iron were decreased (P < 0.05). In conclusion, hens fed a diet that was incorporated with 6% cottonseed meal laid eggs that had unique physical and chemical characteristics and lower nutritional values. These results might help to guide limited incorporation of CSM in laying hen diet, and provide some evidences on the mechanism of the observed physical and chemical changes.     

Selection for high and low percentages of chicken eggs with blood spots 1

Eggs were examined for presence of blood spots in a base generation of White Leghorns part of which were fed on an adequate diet and part on a diet inadequate in vitamin A that increased blood spot incidence. From theory and data, the selection differential was larger for low incidence selection for pullets on the inadequate diet than pullets on the adequate diet. Statistical and genetical models were given for estimating variances of this all‐or‐none trait with h ² = 0.16 and 0.60 for the lines on the adequate and inadequate diets respectively.

Predicted selection gains for individual selection of females alone were: adequate diet, low ‐0.91%, high 2.36%; inadequate diet, low ‐10.71%, high 14.58%. After eight generations of selection for high and low incidence on each of the diets there was a difference of 23.5% between high and low lines selected on the adequate diet and 37.7% on the inadequate diet. Evidence was inconclusive that selection for low incidence on the inadequate diet produced birds with a lower incidence on the adequate diet than birds selected on that diet.

Specific gravity showed a negative correlated selection response in both lines on the adequate diet but no correlated response was evident in the lines on the inadequate diet. There was a negative correlated response for Haugh units and a positive correlated response for blood spot size in all lines. Egg weight did not show a correlated selection response.     

Lead contamination of chicken eggs and tissues from a small farm flock.

Twenty mixed-breed adult laying hens from a small farm flock in Iowa were clinically normal but had been exposed to chips of lead-based paint in their environment. These chickens were brought to the Iowa State University Veterinary Diagnostic Laboratory, Ames, Iowa, where the concentration of lead in blood, eggs (yolk, albumen, and shell), and tissues (liver, kidney, muscle, and ovary) from 5 selected chickens was determined over a period of 9 days. Blood lead levels ranged from less than 50 to 760 ppb. Lead contamination of the yolks varied from less than 20 to 400 ppb, and shells were found to contain up to 450 ppb lead. Albumen contained no detectable amount. Lead content of the egg yolks strongly correlated with blood lead levels. Deposition of lead in the shells did not correlate well with blood lead levels. Mean tissue lead accumulation was highest in kidneys (1,360 ppb), with livers ranking second (500 ppb) and ovarian tissue third (320 ppb). Muscle contained the lowest level of lead (280 ppb). Lead contamination of egg yolks and edible chicken tissues represents a potential public health hazard, especially to children repeatedly consuming eggs from contaminated family-owned flocks.     

Space use at night and social relationship between roosting partners in a large flock of laying hens

1. Laying hens in two aviary flocks of 1250 females and 12 males were investigated to determine if hens used the same roosting site more often than expected by chance and whether hens that roost next to each other for two consecutive nights (close groups) had fewer agonistic interactions than hens roosting far away from each other (distant groups) when put into a new environment in groups of 4 birds.

2. Hens showed a significant preference for using the same roosting site on consecutive nights. There was no difference between close groups and distant groups in agonistic interactions. However, in close but not distant groups, a low or high level of interaction on day 1 predicted a low or high level on day 2 that might reflect established relationships in the close groups.

3. It was concluded that hens prefer the same roosting site in the short term but further research is needed to investigate whether hens roosting next to each other recognise roosting partners or not.     

Residues of dimetridazole in eggs after treatment of laying hens

Laying hens were dosed orally with dimetridazole (DMZ) (50 and 250 mg/kg) for 3 days or intramuscularly (50 mg/kg), also for 3 days, and the residues were determined by liquid chromatography in albumen and yolk. The sensitivity of the whole procedure was 2 ng/g. The drug was excreted preferentially into the yolk (about 57% of the total) and the elimination period lasted for 4–6 days after treatment.Abbreviations AUC area under the plasma concentration-time curve - depletion time the time needed for the DMZ concentration to fall below 0.01 g/g - elimination rate constant - Cl clearance - DMZ demetridazole     

Depletion of colistin in eggs following medication of laying hens

The depletion of colistin in eggs was determined separately for the albumen, the yolk and the whole egg after oral and intramuscular administrations of colistin sulphate. Residues were assayed by an agar plate diffusion method with Bordetella bronchoseptica ATCC 4617 as test organism. Colistin residues were not detected after drug administration by the oral route, but could be detected in the yolk until eight days after intramuscular injection. The total amount excreted represented 0.9% of the dose applied.     

Residues of gentamicin in eggs following medication of laying hens

1. Gentamicin was injected subcutaneously and intramuscularly into 5 groups of 10 laying hens and its concentration was determined in albumen, yolk and whole egg. 2. Groups 1 and 3 were intramuscularly injected with doses of 10 and 25 mg/kg while groups 2, 4 and 5 were subcutaneously injected with doses of 10, 25 and 50 mg/kg, respectively. 3. The final gentamicin concentration in albumen was measured on d 3 for groups 1 and 2; on d 4 for groups 3 and 4, and on d 5 for group 5. Concentrations in yolk and whole egg were measured on d 7, 10 and 12. 4. Gentamicin recovery was as follows: 2% in groups 1 and 2, 2.5% in groups 3 and 4, and 3% in group 5. 5. Most of the residue (approximately 90%) was recovered from the yolk.     

Distribution of 15N-chlorocholine chloride in eggs of laying hens

The distribution of Chlorocholine chloride (CCC) in the eggs of laying hens was studied using 15N-CCC. Twelve layers (37 weeks old) were divided into four groups and used in this study consisting of three feeding phases. In phase one (7 days), all the hens received a CCC-free diet [165 g CP/kg dry matter (DM); 11.58 MJ ME/kg DM]. In phase two (11 days), four levels of 15N-CCC: 0, 5, 50 and 250 ppm were added to the respective diets, while in phase three (7 days), CCC-free feed was again offered. Egg samples were taken and the 15N content of egg yolk and albumin were determined. At the end of phase two, there was a significant (p < 0.05) increase in 15N content in egg yolk from hens fed the 50 and 250 ppm CCC diets and in albumin from hens fed the 250 ppm CCC diet. The estimated 15N-CCC residue was 1.71, 6.64, 28.80 ppm in egg yolk and 1.58, 1.08 and 4.50 ppm in albumin from hens fed 5, 50 and 250 ppm CCC, respectively. The CCC residue, from quantitative analysis ranged from 0.21 to 0.93 and 0.93 to 2.43 ppm in yolk of hens fed 50 and 250 ppm CCC, respectively, whereas a range of 0.40-1.46 ppm, was found in the albumin of hens fed 250 ppm. The difference in measured CCC in yolk and albumin and that estimated from 15N-CCC could have been due to breakdown products of 15N-CCC. Seven days after withdrawal of 15N-CCC, the estimated 15N-CCC residue in egg yolk decreased to 0.43, 2.45 and 15.59 ppm, on 5, 50 and 250 ppm CCC dietary treatments, respectively, and to 2.46 ppm in albumin from hens fed 250 ppm CCC. The higher increase in 15N content could have been due to a higher incorporation of 15N-CCC into yolk than albumin during the process of rapid yolk deposition. This experiment showed that consumed CCC is distributed both into yolk and albumin in a dose dependent manner and that CCC is metabolized in laying hens. However, the level of CCC in the diet which could lead to accumulation of detectable CCC levels in eggs as observed in this study, is much higher than the established maximum residual limits in grains.     

Production of Salmonella enteritidis-contaminated eggs by experimentally infected hens

Laying hens of three different ages were experimentally infected with a strain of Salmonella enteritidis by either oral inoculation or contact transmission. Total egg production was depressed in exposed hens of all three age groups. Persistent intestinal shedding was observed in a small number of hens. Eggs with contents contaminated by S. enteritidis were produced by exposed hens at a high frequency, but only during a fairly short period of time that extended through approximately 1 week postinoculation for older hens and through 2 weeks for younger hens. S. enteritidis was recovered from whole yolks and albumen of these eggs at similar frequencies, but not from the content of yolks. Eggs with contaminated shells were also produced, but at a lower frequency. Contaminated eggs were produced by orally inoculated and contact-exposed hens at similar frequencies. S. enteritidis was not isolated from the contents of eggs laid by hens infected with other S. enteritidis strains.     

Plasma concentrations of luteinising hormone and body weights during somatic maturation in intact and castrated Australorp cockerels from a line of hens selected for increased ovulation rate

1. Plasma concentrations of luteinising hormone (LH), comb size and body weight were measured between 46 and 208 d of age in intact and castrated cockerels from lines of selected and control Australorp domestic chickens. The selected line had been selected for increased rate of lay by reducing oviposition intervals within sequences. The cockerels were reared and maintained on 15.25 h light/d. 2. Concentrations of plasma LH in the intact control cockerels were low in the 'immature' phase (less than 100 d old) and increased during the 'mature' phase (older than 175 d) with a peak occurring when the testes are beginning to grow at the onset of the 'mature' phase. In comparison with the control line of cockerels, the selected line had significantly higher plasma LH concentrations at the onset of the 'mature' phase. Selection had no effect on the mean concentration of plasma LH in either the immature phase or a few weeks after the onset of the mature phase. 3. There was no effect of selection in sibling females for higher rates of lay on changes in comb size or body weight during sexual maturation in the intact cockerels. 4. Castration at 45-46 d of age resulted in increased plasma LH concentrations and no comb growth. Plasma LH concentration increased progressively between 40-208 d. There was no difference between the two lines of cockerels in plasma LH concentration or rate of body growth after castration. 5. It is concluded that selection of females for a change in the rate of egg production has resulted in increased plasma LH concentrations in sibling males around the onset of sexual maturation. Selection appears to have caused this effect by altering an unidentified component of the inhibitory feedback mechanism which controls the tonic secretion of LH.     

Residues of drugs in eggs after medication of laying hens for eight days.

Drug residues in blood plasma, egg-white and -yolk have been measured for 3 weeks after 8 days of continuous treatment with sulphanilamide, sulphadimidine, sulphaquinoxaline and pyrimethamine. The results are discussed with reference to physiological data concerning eggwhite and -yolk formation. From this, it is concluded that a withdrawal period of at least 10 days after the disappearance of drug in blood plasma is necessary to avoid residues of drugs in eggs from treated hens.     

Residues of aminoglycoside antibiotics in eggs after medication of laying hens

1. The transfer of aminoglycoside antibiotics into eggs was determined separately from albumen, yolk or whole egg after oral administration of dihydrostreptomycin (DHS), neomycin and spectinomycin and after an intramuscular injection of DHS. Residues were assayed by an agar plate diffusion method in cylinders with a specific test organism for each antibiotic. 2. Only DHS, administered by the intramuscular route, led to detectable residues in eggs. The total amount of DHS excreted via the eggs represented 1% of the dose administered. 3. Residues in the whole egg were detected for 8 d.     

Residues of macrolide antibiotics in eggs following medication of laying hens

1. The elimination kinetics of four macrolide antibiotics (tylosin, erythromycin, spiramycin and josamycin) in eggs were determined separately for albumen and yolk after oral administration through either drinking water or diet or after intramuscular injection. 2. Residues were assayed by a plate diffusion technique in cylinders with Micrococcus luteus as the test-organism. 3. Drug excretion was usually over a longer time in the yolk. Spiramycin was the most highly excreted in the egg whereas seven to eight times less tylosin and erythromycin was transferred. The conditions for the use of macrolide antibiotics in laying hens are discussed.