Pharmacokinetics of doxycycline in laying hens after intravenous and oral administration

1. The pharmacokinetics of doxycycline in laying hens was investigated after a single intravenous (IV) or an oral (PO) dose at 20 mg/kg body weight.

2. The concentrations of doxycycline in plasma samples were determined by high-performance liquid chromatography with an ultraviolet detector, and pharmacokinetic parameters were calculated using a compartmental model method.

3. The disposition of doxycycline after one single IV injection was best described by a two-compartment open model and the main pharmacokinetic parameters were as follows: volume of distribution (V_d) was 865.15 ± 127.64 ml/kg, distribution rate constant (α) was (2.28 ± 0.38) 1/h, elimination rate constant (β) was 0.08 ± 0.02 1/h and total body clearance (Cl) was104.11 ± 18.32 ml/h/kg, while after PO administration, the concentration versus time curve was best described by a one-compartment open model and absorption rate constant (K_a), peak concentration (C_max), time to reach C_max (t_max) and absolute bioavailability (F) were 2.55 ± 1.40 1/h, 5.88 ± 0.70 μg/ml, 1.73 ± 0.75 h and 52.33%, respectively.

4. The profile of doxycycline exhibited favourable pharmacokinetic characteristics in laying hens, such as quick absorption and slow distribution and elimination, though oral bioavailability was relatively low. A multiple-dosing regimen (a dose of 20 mg/kg/d for 3 consecutive days) of doxycycline was recommended to treat infections in laying hens. But a further study should be conducted to determine the withdrawal time of doxycycline in eggs.

     

Studies on reducing the crude protein content of feeds fed to chicks and young hens (laying stock)]

2 rearing trials were carried out on a total of 8550 hybrid chicks (White Leghorn) to investigate in which way food mixtures containing reduced levels of crude protein (supplemented or unsupplemented with amino acids) might influence the growth of chicks and young hens. Decreases from 21.5% to 16.5% in the crude protein content of chicken feed and from 15% to 13% in feeds feed to young hens (greater than 8 weeks of life) did not reduce the live weight of birds at the end of the rearing period to any appreciable extent. No clearly defined differences were found to exist between the different types of feed tested concerning the amount of food and energy consumed per unit of weight gain and the mortality rate among the birds; it was shown, however, that the demand for crude protein per unit of weight gain was clearly reduced in birds reared at the lower crude protein level. For young hens receiving the diet poorer in protein the date when the birds began laying was slightly delayed. Otherwise, no statistically significant differences were found to exist between the young birds fed varying levels of crude protein, concerning the age at 50% laying performance and other parameters that are characteristic of the entire laying period (laying performance, weight of individual eggs, food consumption, mortality, fertilization of hatching eggs, hatchability of eggs). It appears that the feeding of a reduced protein diet to chicks and young hens (laying stock) did not have any detrimental effect on the growth and later laying performance of the birds. Apart from the fact that the demand for protein feeds is considerably reduced during the rearing period the costs of feeding per bird can also be cut down.     

Study of enrofloxacin and flumequine residues depletion in eggs of laying hens after oral administration

Two groups of laying hens (each n=12) were administered 10 mg/kg enrofloxacin (ENRO) (group A) or 26.6 mg/kg flumequine (FLU) (group B) by gastric catheter daily for five consecutive days. A third group (n=6) was untreated controls. Eggs were collected from day one of treatment and up to 30 days after withdrawal of the drug. Egg white and yolk from each egg were separated, and ENRO, its metabolite ciprofloxacin (CIP) and FLU residues were analysed by a high-performance liquid chromatography method with fluorescence detection. The sum of ENRO and CIP was detectable in egg white on the first day of treatment in high-level concentrations (2007.7 μg/kg) and remained steady during administration. In egg yolk, residues were detectable at day one in lower concentrations (324.4 μg/kg), increasing to the end of treatment. After treatment, these residues decreased and were detectable up to day 8 in egg white, and day 10 in yolk. FLU residues during drug administration in white were detectable in high concentrations from day one to five (6788.4-6525.9 μg/kg), and in yolk, concentrations were lower during administration (629.6-853.9 μg/kg). After drug withdrawal, FLU residues remained longer in egg white (30 days) than in yolk (26 days). For both drugs, differences of concentrations between matrices were significant.     

Pharmacokinetics of tapentadol in laying hens and its residues in eggs after multiple oral dose administration

1. The aim of the study was to evaluate the pharmacokinetics (PKs) of tapentadol (TAP), a novel opioid analgesic, in laying hens after intravenous (IV) and oral (PO) administration and to quantify the concentrations of TAP residues in eggs.

2. Twenty healthy laying hens were divided into three groups: A (n = 6), B (n = 6) and C (n = 8). The study was conducted in two phases. Groups A and B received TAP by IV and PO routes at the dose of 1 and 5 mg/kg, respectively.

3. No visible adverse effects were observed after administration of the drug. TAP plasma concentrations were detectable up to 4 h following administration. Following IV administration, TAP plasma concentrations were only higher than the minimal effective concentration (148 ng/ml) reported for humans for 1 h. After single PO administration, plasma concentrations of TAP would not conform to software algorithms and the PK parameters were not calculated. TAP concentration following multiple PO doses at 5 mg/kg for 5 d was found to be higher and more persistent (12 h vs. 7 h) in yolk compared with albumen.

4. This is the first PK study on the novel atypical opioid TAP in laying hens. Further studies are required to investigate the analgesic efficacy and actual effective plasma concentration of TAP in this species.     

Elimination of oxolinic acid in eggs after oral treatment of laying hens

1. Oxolinic acid is often used in poultry as a therapeutic agent. The aim of this study was to determine both its elimination into eggs, following oral dosing through the drinking water (12 mg/kg/d) or diet (13 mg/kg/d) for 5 d and its plasma concentrations. 2. Samples (albumen, yolk, plasma) were analysed by high performance liquid chromatography (HPLC) with fluorimetric detection. The limits of quantification were 10 ng/g in plasma and 5 ng/g in albumen and yolk. Residues were much higher in albumen than in plasma, whereas they were lower in yolk. 3. 95% of the overall oxolinic acid detected in eggs was concentrated in the albumen. 4. Detectable residues persisted for 9 d and 7 d, respectively, in albumen and yolk after the treatment was discontinued.     

Lead concentrations in the blood and eggs of backyard laying hens

AIMS: To investigate the prevalence of lead exposure in hens and eggs from backyard poultry in a sample of Auckland households, the relationship between concentrations of lead in the blood of the hens and in the shells and yolks of eggs from the same household, and to examine associations with measures of hen health, environment and husbandry factors.

METHODS: Thirty households participated in the study from August to November 2016, each providing one adult hen for sampling, an egg from the household if available, and completing a questionnaire on hen husbandry. Concentrations of lead in blood were determined using a portable lead analyser. Eggs were analysed for concentrations of lead in the yolk and shell using inductively coupled plasma mass spectrometry after biological digestion with a mixture of nitric and hydrochloric acid.

RESULTS: Twenty three of 30 hens (77%) showed evidence of lead exposure, with median concentrations of lead in blood of 0.77 (min?<0.16, max 8.02) μmol/L. All eggs showed evidence of lead exposure, with concentrations of lead in the yolk ranging from 0.003–1.07?mg/kg, and concentrations of lead in the eggshell ranging from <0.1–0.82?mg/kg. A positive correlation existed between concentrations of lead in the blood of a hen and concentrations of lead in egg yolk from the same hen (R²=0.97), and both the yolk (R²=0.58) and shell (R²=0.30) of an egg from her flock. No association was found between concentrations of lead in blood and hen health indices measured in this study. Concentrations of lead in blood were higher in hens from properties with homes built before 1941 than between 1941–1960 (p=0.03), and in hens from properties with weatherboard homes than brick homes (p=0.049).

CONCLUSIONS AND CLINICAL RELEVANCE: There was a high prevalence of lead exposure in this sample of Auckland backyard chickens, with the majority of hens being sub-clinically affected. Associations were found between concentrations of lead in the blood of the hens, and properties with homes built before 1941 and clad in weatherboard. Concentrations of lead in over half the egg yolks sampled were at levels sufficient to warrant human health concern. The assessment of concentrations of lead in backyard poultry and eggs intended for human consumption is recommended to protect human and bird health.     

产蛋鸡群发病后的科学管理

产蛋鸡群的科学管理是最大发挥蛋鸡生产性能、提高效益的根本保证，也是提高鸡群防御机能、防治鸡病的关键措施。目前，产蛋鸡群发病后由于管理不当造成病愈后产蛋难以达到高峰或恢复以前水平的现象在大多数蛋鸡场普遍存在，严重影响了蛋鸡生产性能的发挥。因此，必须加强和重视产蛋鸡群发病后的科学管理。现将产蛋鸡群发病后的科学管理作一概述，以供养鸡同行参考。     

Decreasing half-life of dieldrin in egg yolk following a single oral administration of aldrin to laying hens

Laying hens were treated orally with a single dose of aldrin (AD) 1 mg/kg body weight. Concentrations (microgram/g) of AD or its epoxide (= dieldrin, DD) in the yolk of eggs laid for 21 days after AD treatment were determined by normal-phase high-performance liquid chromatography. The limits of determination were 0.02 microgram/g for AD and 0.03 microgram/g for DD, respectively. After AD treatment, although the low levels of AD (mean 0.02-0.03 microgram/g) were observed only during a three-day period (from 4th to 6th days), DD (mean 0.15 microgram/g) was found already on the 2nd day, indicating that the epoxidation of AD to DD in the hen's body is rapid. The highest level of DD (mean 0.40 microgram/g) was detected on the 6th day, and then DD levels decreased slowly and were detected up to the 21st day. In this decreasing phase, the half-life of DD in the yolk was estimated to be 25.6 days with a 95% confidence interval from 22.7 to 29.4 days.     

Effects of dietary copper on production and egg cholesterol content in laying hens

1. This experiment was carried out to determine the effects of diets supplemented with different amounts of copper on egg production, food intake, food conversion ratio, egg weight, damaged egg ratio, specific gravity, mortality and cholesterol concentration in yolk. The experiment lasted 90 d and 400 Hisex-Brown hens, aged 27 weeks at the start of the study, were used. 2. There were no statistically significant effects of supplementary copper on egg production, food intake or food conversion efficiency. 3. There were no statistically significant differences between the groups in terms of damaged eggs, egg weight, specific gravity and live weight. 4. At the end of the experiment, the lowest yolk cholesterol concentrations were obtained in the 150 kg/kg copper group and the greatest concentrations were in the control group. 5. Consequently, the use of supplementary copper to provide 150 kg/kg in poultry diets was concluded to decrease yolk cholesterol concentrations without any effect on production performance.     

碱式氯化锌对绿壳蛋鸡产蛋性能和蛋黄中锌沉积量的影响

本试验旨在研究碱式氯化锌对蛋鸡生产性能、蛋品质及蛋黄中锌沉积量的影响。选取240羽东乡黑羽绿壳蛋鸡随机分成4组,每组6个重复,每个重复10羽。A组为对照组,饲喂基础日粮,B、C、D组为试验组,分别在基础日粮中添加80、120 mg/kg和160 mg/kg碱式氯化锌。预试期7 d、正式期28 d。结果表明,与对照组相比,从第二周开始,各试验组产蛋率不同程度提高,各试验组料蛋比有所下降;试验各组间蛋壳厚度、蛋形指数、蛋黄色泽和哈氏单位差异均不显著;B组和D组蛋黄中锌含量显著高于对照组(P<0.05),分别较对照组提高17.39%和27.74%,C组蛋黄中锌含量极显著高于对照组(P<0.01),较对照组提高32.29%。由此可见,日粮中添加碱式氯化锌能改善蛋鸡生产性能,提高鸡蛋中锌的沉积量,综合考虑,120 mg/kg为适宜添加量。     

The in vivo estimation of body fat content in laying hens

1. A comparison was made between the determined water space of 16 laying hens weighing between 1.1 and 3.5 kg and that predicted from tritiated water space, with the object of estimating body fat content.

2. The predicted water space over‐estimated the determined water space by 15%, but body fat content in living hens with fat levels representing 8.6 and 39% of carcass weight could be predicted with a coefficient of variation of 14%.     

不同锌源对绿壳蛋鸡产蛋性能和蛋黄锌含量的影响

选取180只东乡黑羽绿壳蛋鸡随机分成3组,每组6个重复,每个重复10只。A组为对照组,饲喂基础日粮,B组、C组分别在基础日粮基础上添加120 mg/kg的羟基蛋氨酸锌和碱式氯化锌(按锌含量计)。预试期7 d、正式期28 d。结果表明,与对照组相比,日粮中添加羟基蛋氨酸锌可显著提高蛋鸡产蛋率(P<0.05);碱式氯化锌可极显著提高蛋鸡产蛋率(P<0.01),显著降低料蛋比(P<0.05);试验各组的蛋壳厚度、蛋黄指数、蛋形指数、哈氏单位差异均不显著;两种锌源均可极显著提高蛋黄中锌含量,试验第28天时,分别较对照组提高32.8%和32.3%(P<0.01)。由此可见,日粮中添加羟基蛋氨酸锌和碱式氯化锌均能改善蛋鸡生产性能,提高鸡蛋中锌含量,综合比较,添加碱式氯化锌效果更好。     

Studies on effects of nutritional factors on bone structure and osteoporosis in laying hens

1. A modern hybrid strain of laying hen (Hisex) was fed from point of lay to 68 weeks on a control diet and diets containing oystershell, fluoride, 1,25‐dihydroxycholecalciferol, ascorbic acid, a lower concentration of phosphorus and a combination of a lower concentration of crude protein and higher concentration of vitamin K. Hens from a much older strain (Brown Leghorn J‐line) were fed on the control diet.

2. Plasma variables were measured during lay. End‐of‐lay trabecular and medullary bone volumes in the proximal tarsometatarsus and free thoracic vertebra were measured by histomorphometry.

3. The majority of Hisex hens were considered to be osteoporotic by the end of lay. In contrast, none of the J‐line were osteoporotic.

4. None of the nutritional treatments affected trabecular bone volumes. Medullary bone volumes were increased significantly by feeding oystershell or fluoride.

5. There was no phenotypic correlation between egg production and trabecular bone volume in the Hisex hens.

6. The experiment provided evidence that osteoporosis in laying hens, as assessed by trabecular bone volumes, is not caused by calcium deficiency and could not be prevented by any of the nutritional treatments studied.     

B cell and macrophage response in chicks after oral administration of Salmonella typhimurium strains

Despite the fact that, in a number of countries, vaccination programmes are extensively used to control Salmonella infection in poultry, information on the immune mechanisms, especially the cellular response, is still needed. The aim of the study was to characterise the B cell and macrophage response in caecum (IgA+, IgM+, IgG+ cells, macrophages), bursa of Fabricius (IgM+ cells, macrophages), and spleen (IgM+ cells) of chicks after oral administration of a non-attenuated Salmonella (S.) typhimurium wild-type strain (infection) or an attenuated commercial live S. typhimurium vaccine strain (immunisation) to day-old chicks as compared to non-treated control birds using immunohistochemistry and image analysis. In caecum, higher counts of IgM-secreting cells were detected in infected animals compared with the controls from day 5 until day 12 of age. In contrast, in treated groups, IgA-secreting cells were found in higher numbers only between day 8 and 12 of age. Infected birds showed a higher number of IgA+ cells in spleen and bursa of Fabricius compared to the controls. In the bursa of Fabricius of immunised and infected birds, a depletion of strongly stained IgM+ cells and macrophages was established between day 5 and 9 indicating a possibly special and independent role of this organ during the immunological reaction against Salmonella organisms. The results suggest that IgM- and IgA-secreting cells are of importance in the caecal immune response of chickens against Salmonella strains. Immunised chickens always showed a weaker immune reaction compared to infected animals. Present findings regarding the B cell reaction within avian caeca prove a participation of both humoral and cellular immunity in defence against Salmonella strains. Immunohistochemical examination of the cellular response (B cells and macrophages) in relevant organs of chickens may be an important tool to evaluate the immunogenic characteristics of potential Salmonella live vaccine candidates.     

蛋鸡磷营养状况检测的敏感性指标探讨

本试验在0.1%、0.2%、0.4%3个水平有效磷条件下，测定检测蛋鸡磷营养充足与否的常用指标，结果表明：6周内，0.1%有机磷对生产性能、胫骨总灰重、灰分含量、钙含量及血磷、血钙、血中碱性磷酸酶活性无显著影响（P＞0.05），对骨磷含量有显著（P＜0.05）降低作用。检测机体磷缺乏的常用指标中，骨磷含量最敏感。