Foetal development in quail during the final stages of incubation

Fertile eggs of the bobwhite and Japanese quail were opened and examined during the last 4 days before hatching and the foetal position and stage of development recorded at known times after the beginning of incubation. A comparison is made between these stages in the quail and similar stages in the domestic fowl.     

Effects of increasing photoperiod length on performance and health of broiler chickens

1. Broiler performance and health were compared from 0 to 42 d for lighting programmes consisting of near-continuous light 23L:1D (23L), a lighting programme where photoperiod gradually increased from 6 to 23 h between days 4 and 35 (INC) or an increasing-lighting programme with 1 h of light mid-way through the scotophase (INC + 1). 2. The increasing lighting programmes reduced growth rate and increased gain:food ratio from 0 to 21 d; INC + 1 growth rate was intermediate to the 23 L and INC treatments. From 0 to 42 d there were no differences in growth rate or gain:food ratio among lighting treatments. Males grew faster, ate more food and converted food more efficiently than females. 3. The increasing-lighting programmes (INC and INC + 1) resulted in less skeletal disease than the 23L control. The incidence of sudden death syndrome (SDS) and mortality other than SDS were numerically lower for the increasing lighting treatments. More males died as a result of SDS and were affected by skeletal defects than females. 4. In terms of health, increasing lighting programmes were superior to near-continuous light for broiler chickens.     

The effect of incubation temperature on pre- and post-hatching development in chickens

Chicks hatched from eggs incubated at two temperatures (36.8 °C, 37.8 °C) but similar humidities (30 mmHg during the first 18 d and 40 mmHg thereafter) were reared for 12 weeks in groups of six at 22 °C and in a relative humidity of 45 to 55%.

The lower incubation temperature resulted in a longer incubation period. Female embryos utilised the energy of the egg better than males.

A possible difference in the relationship between the post‐hatching development of males and females and pre‐hatching environmental conditions was indicated by a higher viability at 14 d and a higher body weight after 12 weeks of cocks incubated at 36.8 °C. There were significant effects of sex on food conversion efficiency. Results suggest that pre‐hatching temperatures may influence post‐hatching energy utilisation.     

Hepatic lipolysis in broiler chickens with different fat deposition during embryonic development

The aim of this study was to explore the hepatic lipolysis in broiler chickens with different fat deposition during embryonic development. The mRNA expression of CPT-1 (carmitine palmtoyltransferase-1), PPARα (peroxisome proliferator-activated receptor alpha) and LPL (lipoprotein lipase) genes were determined using Real time RT-PCR. The start of incubation was called day 1 (E1) and after hatching called day 1 (H1). On incubation days 9 (E9), 14 (E14) and 19 (E19) as well as at hatching (H1), samples of liver were collected. Blood samples were obtained during days 14 (E14) and 19 (E19) of embryonic development and at hatching. This study showed that serum TG (triglycerol) decreased and TC (total cholesterol) and NEFA (non-estered fatty acid) increased during embryonic development. The expression of CPT-1, PPARα and LPL genes exhibited different developmental changes. For example, little LPL gene was expressed at hatching and PPARα gene expression peaked before hatching. However, CPT-1 gene exhibited no significance during the embryonic development. Our results showed that expression of these genes in Arbor Acres (AA) broilers was significantly higher than that in San Huang (SH) broilers. Therefore, this study suggested that hepatic lipolysis in broiler chickens exhibited developmental changes during embryogenesis and breed difference which may be one of the factors in the fat deposition difference between fat line and lean line broilers during embryonic development.     

Histochemical and histological evaluations of the effects of high incubation temperature on embryonic development of thymus and bursa of Fabricius in broiler chickens

1.?The effects of experimentally induced heat-stress on the embryonic development of bursa of Fabricius and thymus of the chicken were investigated by means of histological and enzyme histochemical methods.

2.?In the experiments, 250 fertile eggs of the Ross 308 broiler strain were divided into two groups. The control eggs were maintained under optimal conditions (37?8°C and 65 ± 2% relative humidity, RH) during the whole incubation period. Heat stressed eggs were maintained under normal conditions (37?8°C and 65 ± 2% RH) until the 10th d of incubation and then exposed continuously (24 h per d) to high temperature (38?8°C and 65 ± 2% RH). Blood and tissue samples were taken from 10 animals of each group at d 13, 15, 18 and 21 of incubation and at d 2, 4 and 7 post-hatch. Tissue samples were processed for enzyme histochemical methods in addition to routine histological techniques.

3.?The results revealed that egg temperatures were higher than incubator air temperature. Long-term heat-stress (40?1–40?6°C egg temperature) retarded development of thymus and bursa of Fabricius. Peripheral blood ACP-ase and ANAE-positive lymphocyte levels of heat-stressed animals were lower than in the controls.

4.?These results give some morphological evidence for immunosuppression induced by high temperature exposure during the embryonic development. Temperature distribution and air circulation in incubator should be questioned in the case of lower broiler flock immunity.     

Hormone-mediated maternal stress affects embryonic development during incubation without adverse effect on chick weight and body composition

1. The objective of this study was to evaluate the effect of maternal stress (MS) induced by supplementing the hen’s diet with 2 mg/hen/d dietary corticosterone (CORT) on embryonic development, biochemical blood parameters and hatching performance of broiler chicks.

2. A total of 200 Ross broiler breeder hens at 42 weeks of age were randomly divided into two groups: MS or control. Hens in the MS were fed 2 mg/hen/d CORT for 14 d. Eggs (648 and 635 eggs for MS and control, respectively) were collected from d 3 to 14 of dietary CORT supplementation and incubated. Weights of embryo, chicks and organs and body composition were determined during incubation and at hatch. Biochemical blood parameters were measured at internal pipping stage and day of hatch. Hatching performance and embryonic mortalities were recorded.

3. Hens fed a diet supplemented with CORT had lighter body weight and produced less eggs at the end of the 14-d treatment period. Although MS embryos were heavier than control from 12 to 18 d of incubation, chick weight was similar at the day of hatch. Lower relative weights for yolk sac and bursa were observed at 12 d of incubation for MS chicks compared to control. Chicks from both groups had similar body content in spite of higher fat content of MS embryos on d 18 of incubation.

4. MS had no effect on the duration of incubation or hatching performance but increased mortality at the pipping stage.

5. The results suggest that hormone-mediated MS might affect embryonic development during incubation without adverse effect on chick weight and body composition.     

Effects of high CO2 level during early incubation and late incubation in ovo dexamethasone injection on perinatal embryonic parameters and post-hatch growth of broilers

1. A total of 1200 Cobb broiler breeder eggs were incubated under either standard conditions (C group) or high CO(2) levels (CO(2) group) during the first 10 d of incubation. The CO(2) level of the CO(2) incubator was attained gradually by a natural build-up of CO(2) due to air-tight closure of the incubator. From d 10 of incubation onwards, all eggs were incubated under standard incubation conditions. At d 18 of incubation, the eggs of both incubation groups (CO(2) and C group) were either injected with water-soluble dexamethasone (DEXA group) or with saline (0.9% NaCl; saline group) or were not injected (control). 2. Body weights, plasma hormonal concentrations (T(3), T(4) and corticosteroid) and glucose concentrations were measured regularly during the perinatal (at IP, internal pipping) and post-hatch period (at 1, 2, 4 and 6 weeks post-hatch). Additionally, hatchability and pattern of embryonic mortality were determined after hatch. 3. The results showed that high CO(2) levels during the first 10 d of incubation or dexamethasone injection at d 18 of incubation decreased embryo mortality, mainly because of a reduction in embryo malpositioning. However, a combination of a CO(2) incubation and a dexamethasone injection led to an increase in embryo mortality and therefore a decrease in hatchability. 4. Although dexamethasone injection at embryonic d 18 decreased body weight in the second week of the rearing period and CO(2) incubation increased body weight during the first 2 weeks of the rearing period, no consistent effect of both the incubation and injection treatments on body weight at slaughter age was observed.     

Effects of increasing photoperiod length and anticoccidials on performance and health of roaster chickens.

Male broiler chickens were raised to 63 days of age under different lighting and anticoccidial treatments. A constant-light program was compared with two interrupted and increasing-light programs in which the photoperiod length was 6 hours between 7 and 14 days of age and then increased gradually to continual light by 49 days of age in the first program and more gradually to 18 hours by 49 days of age in the second program. By 63 days of age, the increasing-light programs significantly increased body-weight gain and decreased feed/grain ratio, but not significantly. The increasing-light programs reduced the incidence of skeletal disease from 7.56% to 2.88% in the first program and to 3.53% in the second program, reduced the incidence of acute death syndrome from 5.94% to 3.37% in the first program and to 4.65% in the second program, and reduced total mortality from 18.81% to 11.71% in the first program and to 11.38% in the second program. The lighting programs had no effect on the incidence of ascites and right heart failure, the ratio of right ventricular weight to total ventricular weight, the incidence of clinical and subclinical tibial dyschondroplasia, and the number of cartilaginous and osseous nodules in the lungs. The anticoccidials compared were monensin and amprolium/ethopabate, from 0 to 35 days of age. These treatments had no significant direct effects on any of the parameters measured.     

Early heat acclimation during incubation improves Japanese quail performance under summer conditions

Effects of exposing quail eggs to high temperature on the heat tolerance ability and productivity of birds were investigated. Four groups of 600 fertile eggs were randomly selected; the first group was incubated under 37.5 °C and the hatched chicks were reared under a gradual decrease in temperature from 35 to 24 °C (Control). The second group was exposed to 39.1 °C for 2 h/day during 4–14 days of embryogenesis and the hatched chicks were reared under a gradual decrease in temperature from 35 to 24 °C. The third group was incubated under 37.5 °C and the hatched chicks were exposed to 39?±?1 °C for 2 h/day during 4–14 days of age. The fourth group was exposed to 39?±?1 °C for 2 h during 4–14 days of embryogenesis and the hatched chicks were exposed to 39?±?1 °C for 2 h/day during 4–14 days of age. The temperature applied changed (P?<?0.01) embryo weight and incubation period. Birds exposed to high temperature during brooding had superior growth performance, dressed carcass, body temperature and health traits. Birds subjected to 39?±?1 °C during brooding exhibited decreased feed consumption and body weight gain. Finally, this work suggests that thermal acclimation during embryogenesis might offer a practical method for easing heat stress.

     

孵化时间对家禽行为的影响（续完）——胚胎发育后期孵化环境的影响

上期回顾：上期概述了胚胎发育时期环境因素对家禽行为的影响,其中详细介绍了孵化期间的声音信号对出雏的同步化和出雏后行为的影响。3光照、大脑发育和孵化后行为的关系对早熟型鸟类而言,在胚胎形成过程中光照刺激对大脑的正常发育非常重要。尤其鸟类大脑半球的特化（脑不对称）取决于出雏时胚胎的光照刺激。出雏前的最后几天,光照对大脑不对称的影响与胚胎在蛋中的体位相关;左眼被身体覆盖,无法接受到光照;     

交感神经对小鼠妊娠早期血清中性激素的影响

本文运用交感神经阻断剂6-OHDA(100 mg/kg体重)腹腔注射昆明系小鼠,研究交感神经对妊娠早期外周血清性激素水平的影响.结果显示:交感神经损毁后,妊娠早期外周血清中雌二醇浓度着床前(E3)升高明显,着床期下降;血清中孕酮浓度着床前升高,着床后降低.结论:交感神经通过调控妊娠早期外周血性激素的生理水平,从而维持妊娠的发生,促进妊娠早期胚胎发育.     

Interaction between ascites susceptibility and CO during the second half of incubation of two broiler lines. Effect on embryonic development and hatching process

1.?Because CO₂ during the second half of incubation is known to influence air cell and blood gases, and embryo development, it is postulated that post-hatch development and ascites sensitivity could also be influenced.

2.?An ascites susceptible (A) and an ascites resistant (E) broiler line were incubated under standard incubation or high CO₂ conditions (up to 4%) from embryonic day (ED) 10 onwards. The embryonic development and the hatching process of these two lines were compared when incubated under standard or high CO₂ conditions from over the second half of incubation.

3.?The A line, selected for high post-hatch growth rate, exhibited a higher relative embryo weight from ED10 until ED16, which was supported by a higher air cell pCO₂, lower air cell pO₂, higher corticosterone and thyroid hormones and earlier hatching time.

4.?Incubation under high CO₂ increased air cell pCO₂, retarded yolk consumption, and decreased glycogen concentration in the liver at hatch. Hatchability decreased in both lines when incubated under high CO₂, due to an increased late mortality of embryos that died before IP.

5.?These results suggest that the development and metabolism of CO₂-incubated embryos differ from control incubated embryos.     

Non-ventilation during early incubation in combination with dexamethasone administration during late incubation: 1. Effects on physiological hormone levels, incubation duration and hatching events

This study investigated the effect of non-ventilation of the incubator during the first 10 days of incubation and its combination with dexamethasone administration at day 16 or 18 of incubation on hatching parameters and embryo and post-hatch chick juvenile physiology. A total of 2400 hatching eggs produced by Cobb broiler breeders were used for the study. Blood samples were collected at day 18 of incubation, at internal pipping stage (IP), at the end of hatch (day-old chick) and at 7-day-post-hatch for T(3), T(4) and corticosterone levels determination. From 448 to 506 h of incubation, the eggs were checked individually in the hatcher every 2h for pipping and hatching. The results indicate that non-ventilation during the first 10-day shortened incubation duration up to IP, external pipping (EP) and hatch, had no effect on hatchability and led to higher T(3) levels at IP but lower corticosterone levels at 7-day-post-hatch. The injection of dexamethasone at days 16 and 18 of incubation affected hatching and blood parameters in both the ventilated and non-ventilated embryos differentially and the effect was dependent on the age of the embryo. Dexamethasone increased T(3) levels and T(3)/T(4) ratios but the effect was greater with early non-ventilation of eggs. Dexamethasone decreased hatchability but the effect was greater when injected at day 16 and especially in ventilated embryos. The effects of incubation protocols and dexamethasone treatments during incubation were still apparent in the hatched chicks until 7 days of age. The changes in T(3), T(4) and corticosterone levels observed in response to the early incubation conditions and late dexamethasone treatments in this study suggest that incubator ventilation or non-ventilation may influence the hypothalamic-pituitary-adrenal axis (HPA) regulation of stress levels (in terms of plasma corticosterone levels) and thyroid function in the embryo with impact on incubation duration, hatching events and early post-hatch life of the chick. Our results also suggest that some stages of development are more sensitive to dexamethasone administration as effects can be influenced by early incubation protocols.     

Ostrich (Struthio camelus) embryonic development from 7 to 42 days of incubation

1. Hatching success of ostrich eggs is poor (50–60% of fertile eggs). The current study was designed to identify the timing of key stages in the development of the ostrich embryo.

2. Growth of both embryo and wing length during 42 d of incubation was comparable and approximately linear, with a more or less weekly doubling in size up to 35 d of incubation.

3. The embryo eye size increased more rapidly than beak length and reached a maximum of ~16.2 mm by 28 d of incubation, whereas beak length increased continuously until hatching at 42 d.

4. Linear regression equations were derived from morphometric measurements of embryos between 7 and 42 d.

5. Information stemming from these results can be used to estimate the age of dead-in-shell embryos in an attempt to identify timing of incubation problems that potentially result in low hatchability of fertile eggs.     

卵母细胞质移植对兔原核胚体外发育的影响

卵母细胞胞质中存在着大量的母源性信息，正常受精卵的发育启动和早期卵裂主要由这些母源性信息所控制。为了评估卵胞质含量对早期胚胎发育的影响，以假显微注射兔原核胚为对照，采用显微注射技术将兔原核期胚胎去除或增加一定量的细胞质：试验一，增加5％和20％的细胞质；试验二，移入5％小鼠MⅡ期卵母细胞胞质。胚胎经显微操作后进行R1／R2序贯培养。结果显示，（1）增量5％组胚胎的2细胞胚（72．00％）、8细胞胚（60．00％）、桑椹胚（58．00％）和囊胚（54．00％）的发育率均显著（P〈0．05）高于增量20％组胚胎（分别为47．62％、35．71％、33．33％和30．95％），但与对照组之间无显著差异（P〉0．05）；囊胚细胞数在2个增量组和对照组3者之间也无显著差异（P〉0．05）。（2）将5％小鼠MⅡ期卵胞质移入兔原核胚后，各阶段胚胎发育率和囊胚细胞数与增量5％组、对照组相比均无显著差异；早期胚胎经PCR检测，在2细胞胚（5／5）、8细胞胚（5／5）和桑椹胚（5／5）均全部检测到了供体小鼠mtDNA的D—loop区3’端片段，而在囊胚却仅有1枚（1／5）能够检测到。结果表明，增加少量细胞质不会对兔原核胚的体外发育造成显著影响，但胚胎发育率随着细胞质体积的增加有下降趋势，而异种卵胞质对兔原核胚的发育没有明显影响，在囊胚期虽仍能检测到异种卵胞质中mtDNA的存在，但异种mtDNA会随胚胎发育而逐渐减少。     

光照周期和饲喂水平对蛋鸡生殖器官发育的影响

本试验旨在研究限饲和光照周期对蛋鸡卵巢和输卵管发育及形态学的影响。试验采用3×2双因子设计,即3个光照周期（8L：16D、12L：12D和16L：8D）和2个饲喂水平（自由采食和限饲鸡自由采食量的80%）。选用体质健康的10周龄海兰灰蛋鸡240只,分成6组,每组4个重复,每个重复10只鸡。结果表明,光照周期显著影响20 w输卵管重（P〈0.05）,长光照周期（16L：8D）组和中长光照周期（12L：12D）组的20 w输卵管重显著高于短光照周期（8L：16D）组,对卵巢卵泡直径及单位面积内卵巢卵泡个数影响不显著（P〉0.05）;饲喂水平对20 w体重、卵巢重、输卵管重及卵巢卵泡直径和单位面积内卵巢卵泡个数影响均不显著（P〉0.05）;光照周期和饲喂水平互作对20 w卵巢卵泡直径影响显著（P〉0.05）,其中,β和VI组卵巢卵泡直径显著高于V组（P〈0.05）,其他各组间差异不显著（P〉0.05）。饲喂水平、光照周期影响输卵管发育,Ⅱ、Ⅳ、VI自由采食组发育程度优于Ⅰ、Ⅲ、V限饲组,并且16L：8D光照组输卵管的发育状况最好。