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.     

Increased sensitivity to triiodothyronine (T3) of broiler lines with a high susceptibility for ascites

1. In the studies reported here, broiler lines divergently selected for susceptibility to ascites under low temperature conditions were tested for their sensitivity to 3,3’,5‐triiodothyronine (T3) with respect to growth rate, rate of mortality, plasma concentrations of T3, right ventricular hypertrophy (RVH) and incidence of ascites.

2. Mean body weight of the ascites‐susceptible line (BC‐line) was higher than that of the ascites‐resistant line (A‐line). Adding 0.5 mg T₃/kg of the diet depressed growth rate to the same extent in both lines. The effect of T3 on growth was more pronounced for males than for females.

3. T3‐supplementation increased the relative weight of the heart and the incidence of RVH to the same extent in both lines. More of the T3‐treated BC‐line chickens had fluid accumulation in the abdominal cavity than the T3‐treated A‐line chickens.

4. Dietary T3‐treatment depressed the plasma concentration of growth hormone (GH) profoundly and insulin‐like growth factor (IGF‐I) slightly but to the same extent in both lines. The coefficient of variation of GH concentrations indicate that T3 treatment mainly decreased GH‐pulsatility in young growing broilers.

5. Higher doses of dietary T3 (1 and 2 mg/kg) increased mortality in a dose‐dependent manner. With 2 mg T₃/kg, mortality in the BC‐line was almost double that in the A‐line.

6. These studies indicate that the development of ascites could be linked with thyroid function. Moreover, dietary T3 supplementation could be used to help identify ascites‐inducing factors or genetic lines with differential sensitivity for ascites.     

Influence of thermal stimulation during the late phase of incubation on hatching results and post-hatch broiler performance under commercial conditions

1. Two experiments, which differed in breeder age, strain and season, were conducted to study the influence of low-intensity, short-duration thermal stimuli during the late phase of incubation on hatchability and performance. The first experiment conducted in April–June used eggs from Cobb × Ross broiler breeders at 35–41 weeks of age and the second experiment performed in February–April used eggs from Hubbard × Cobb broiler breeders at 49–53 weeks of age.

2. Eggs in the test group had the same physical environment as eggs in the control group except that incubation temperature was increased by 1?C for 2 h/d above the control group from 18 to 20 d of incubation (DI).

3. The results demonstrated that thermal stimulation of 1?C for 2 h/d above control incubation temperature during 18–21DI did not have any adverse effects on hatch and post-hatch performance of broilers.

4. In both experiments, treatment did not significantly alter the secondary sex ratio in hatched chickens, but hatch residue showed that the proportion of unhatched male embryos was significantly lower in the test groups than in the control groups.

5. In the first experiment, thermal stimulation improved feed conversion by 1.82% compared with the control.

     

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.     

Brooding temperatures for chicks acclimated to heat during incubation: effects on post-hatch intestinal development and body weight under heat stress

1.?The objective was to evaluate the effects of brooding temperature on intestinal development, oxidative organ damage, and performance of chicks acclimated to high temperature during incubation. The effects of acclimation and brooding temperatures on slaughter weights of broilers under heat stress were also investigated.

2.?Eggs were incubated at either 37?8°C (INC_Cont) or heat-acclimated at 39?5°C for 6 h daily from d 10 to d 18 of incubation (INC_H). Brooding temperatures at floor level were set at 32, 33?5 and 35°C (Bt₃₂, Bt_33?5, Bt₃₅, respectively) for the first 5 d. The temperature was reduced gradually to 30°C from d 6 to d 10. From 21 to 42 d, broilers from INC_Cont Bt₃₂ and INC_H Bt₃₂ and Bt₃₅ were divided into two groups; half from each group was exposed to daily cyclic higher ambient temperatures, while the other half was reared at control temperature.

3.?INC_H chicks had lower jejunum, but greater liver and residual yolk sac weights than INC_Cont chicks on the day of hatching. Although INC_H chicks from Bt_33?5 and Bt₃₅ had lighter body weights than Bt₃₂ on d 5, no significant differences were observed in the body weight of broilers among treatments at 10 and 21 d.

4.?Similar jejunum protein, alkaline phosphatase, maltase, glutathione, and malondialdehyde contents of chicks from INC_Cont and INC_H suggested that heat acclimation during incubation has no effect on jejunum enzyme activity or oxidative status of chicks.

5.?Taking into account INC_H Bt₃₅ chicks having lower T₃ levels on d 5, lower heterophil/lymphocyte (H/L) ratios and similar weights at 42 d under heat stress compared with control broilers, the results suggested that although higher brooding temperatures had no effect on body weights of INC_H chicks during the brooding period, those broilers may able to cope better with heat stress.     

Protective effect of ubiquinone (coenzyme Q9) on ascites in broiler chickens

1. The effect of ubiquinone (C0Q9) on ascites in broiler chickens was investigated.

2. The commercial broilers were divided into 2 groups of 100 birds each; CoQ9‐treated group and non‐treated group.

3. The chickens were grown in a positive‐pressured house with double high efficiency particulate air filtered intakes and exhaust, and thus were strictly isolated from infectious agents.

4. The chickens (15 to 21 d old) were exposed to cold stress in order to induce ascites.

5. The number of birds with ascites in the C0Q3‐treated group was significantly lower than in the non‐treated group.

6. Survival and production rates were better in the CoQ^‐treated group than in the non‐treated group.     

Erythropoiesis regulation during the development of ascites syndrome in broiler chickens: a possible role of corticosterone

The ascites syndrome in broiler chickens is attributed to metabolic burdening, which results from intensive genetic selection for rapid growth coupled with exposure to extreme environmental conditions, such as low ambient temperature. These conditions impose on the broilers difficulties in fulfilling tissue demands for oxygen, and the birds exhibit a decrease in blood oxygen saturation and high hematocrit values. It is unknown whether the increase in hematocrit results from alteration in erythropoiesis or from fluid exudation out of the blood system to the abdominal cavity. The present study was conducted to examine the association between abnormal stress response and erythropoiesis process in ascitic broilers. Ascitic chickens revealed a uniquely continuous stress response: expressing an increase (P < or = 0.05) in plasma corticosterone concentration 2 to 3 wk before death. At 5 wk of age, ascitic broilers exhibited an increase (P < 0.05) in hematocrit, blood cell count, and packed cells and blood volumes, with no significant change in plasma volume. These results confirm an accelerated erythropoiesis process in ascitic birds. Increased blood cell production in ascitic birds was matched by an increase (P < 0.05) in the proportion of immature red blood cells (23%) in comparison with broilers that remained healthy (7%), and by decreased (P < 0.05) hemoglobin content relative to red blood cells. We conclude that continually increased corticosterone concentrations, as an inducer of erythropoiesis proliferation and differentiation arrest, in ascitic chickens, resulted in increased production of red blood cells (partially immature) with decreased hemoglobin content; this decrease in hemoglobin might have contributed to enhanced development of hypoxemia and to aggravation of the syndrome.     

Performance and physiological variables in broiler chicken lines differing in susceptibility to the ascites syndrome: 2. Effect of ambient temperature on partial efficiencies of protein and fat retention and plasma hormone concentrations.

1. Male broilers of 5 genetic stocks (A, B, C, D and E), selected in different ways for fast growth and low food conversion rate (FCR) and differing in sensitivity to ascites, were subjected to 2 different ambient temperature (Ta) step-down programmes: normal (HT) and low (LT) Ta. 2. Ascites incidence was followed daily. Growth and food intake were measured weekly. Heat production (Hp), oxygen consumption (Oxc) and energy- metabolism parameters were calculated according to the comparative slaughter method. At week 4 blood samples were taken for the analysis of plasma T4, T3, growth hormone (GH) and insulin-like growth factor-I (IGF-1) concentrations. 3. Within-line changes of GH and IGF-1 point to the relative independence of both hormone concentrations. 4. Partial protein efficiency was higher in lines with lower GH, especially at LT. 5. The increase in plasma T3 concentration at LT was accompanied by a decrease in relative fat deposition from the increased energy expenditure. 6. The combination of fast growth and low FCR, linked to a low plasma T4 concentration at LT is indicative of a thyroid insufficiency which is related to an increased occurrence of ascites in these lines.     

Performance and physiological variables in broiler chicken lines differing in susceptibility to the ascites syndrome: 1. Changes in blood gases as a function of ambient temperature.

1. Male broilers of 5 genetic stocks (A, B, C, D, E) selected in different ways for fast growth and low food conversion ratio (FCR) and differing in ascites sensitivity were subjected to 2 different ambient temperature step down regimens: high temperature (HT: 33 to 20 degrees C over 33 d) and low temperature (LT: 30 to 15 degrees C over 17 d). 2. Ascites incidence was recorded daily. Food intake and body weight gain were measured weekly and FCR was calculated. Heat production (Hp) was calculated using the comparative slaughter method. At 28 d venous samples were taken for blood gas analysis and haematocrit and relative heart, lung and liver weights were recorded. 3. Populations A and C showed the highest growth rates combined with a low FCR and a higher ascites incidence. A low FCR in these stocks was attributable to low values for Hp. These stocks also had low PO2 and high pCO2 in venous blood at low ambient temperature compared with other stocks. Stock B, which exhibited the slowest growth rate and the highest FCR, was not susceptible to ascites and showed higher Hp and PO2 and pCO2 at low ambient temperature. Populations D and E were intermediate for almost all variables. Heart and lung weights were both increased at LT, while liver weight did not differ between temperature regimes. 4. Our results show that a high haematocrit is not necessarily linked with an increased susceptibility to ascites.     

Embryonic development in the ostrich (Struthio camelus) during the first 7 days of artificial incubation

1. Early development of ostrich embryos was investigated in relation to time of egg collection and genotype.

2. A total of 321 ostrich eggs were collected during the 2008 and 2009 breeding seasons and the development of the embryo for up to the first 168 h of incubation was described and analysed. A sample of the incubated eggs was weighed and opened daily to investigate developmental changes.

3. In fresh eggs, the blastoderm contained a round, translucent dark area pellucida (AP) in the centre, with a surrounding thin white ring, likely to be the beginning of the area opaca (AO). Fresh eggs were considered infertile if the blastoderm was absent and instead numerous white droplets were present surrounded by vacuoles.

4. The average blastoderm area of a fresh fertile egg was 15.8 mm², increasing to 143.3 mm² after 2 d of incubation. By 72 h of incubation the area vasculosa (AV) was discernible in the posterior half of the blastoderm.

5. At 48 h of incubation the blastoderm area in eggs from the South African Black genotype (SAB) × Zimbabwean Blue genotype (ZB) crosses (104.5 ± 18.6 mm²) was lower than the pure SAB (141.0 ± 10.5 mm²), ZB (161.7 ± 13.5 mm²) and ZB × SAB crosses (166.1 ± 14.2 mm²).

6. Embryo length was 5.01 mm after 72 h of incubation and 14.5 mm after 168 h of incubation. At 168 h of incubation AV lengths for both ZB × SAB (53.2 mm) and SAB × ZB crosses (54.1 mm) were longer than in embryos from the pure breeds.

7. Results from this study can be put to practical use when determining whether eggs are infertile or fertile and also in investigating the age of early embryonic mortalities.     

Effects of two wheat cultivars on physico-chemical properties of wheat flours and digesta from two broiler chicken lines (D+ and D-) differing in digestion capacity

1. The current experiment is the second part of a study about the effects of wheat quality on digestibility of pelleted diets for broiler chickens. In the first part, it was shown that a hard cultivar resulted in a negative effect on starch digestibility in two divergent lines of chickens (D+ and D-) selected for digestion capacity. The aim of this second part was to investigate the reasons for this negative effect of a hard cultivar (Baltimor) compared to a soft one (Scipion) in D+ and D- lines. 2. Proventriculus pepsin activity and pancreas proteolytic and amylolytic activities were estimated in 4 pools of birds: 'D+ line (Baltimor fed)', 'D+ line (Scipion fed)', 'D- line (Baltimor fed)' and 'D- line (Scipion fed)'. Results suggested the greatest amount of pepsin units per g BW for D+ birds and the lowest amount of pancreas proteolytic units per g BW for D+ birds fed Scipion wheat. Pancreas showed very similar alpha-amylase activities among treatments. 3. In vitro hydrolyses of wheat gluten proteins with proventriculus extracts from pools of D+ and D- birds did not show any differences between hard and soft cultivars, whatever the origin of pools. 4. Pepsin hydrolysis of fine (300 to 425 microm) and coarse (1180 to 1600 microm) fractions from wheat flours (Baltimor or Scipion) showed that the 30 min proteolysis rate was highest for the fine fraction in both cultivars. No difference was observed with extended hydrolysis time. 5. In vitro digestion simulation of whole wheat flours confirmed the results previously obtained in vivo, with a negative effect of hard cultivar on starch digestion rate and no effect on protein digestion. 6. Laser particle size analyses showed that ileum digesta from birds fed with hard wheat cultivar showed the highest proportion of coarse particles. 7. Microscopic analyses of D+ ileum digesta revealed that the concentration of undigested starch granules in the subaleurone area of wheat bran particles was the highest with hard cultivar. 8. The results suggested that physical entrapment of starch granules in coarse particles was a major explanation for decreased starch digestibility values in chickens fed hard wheat diets.     

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.     

The bovine placenta; a source and target of steroid hormones: observations during the second half of gestation

Apart from estrone-3-sulfate (E1S) the bovine placenta produces progesterone (P4), though the corpus luteum is the major source of P4 responsible for maintaining pregnancy. So far the biological function of placental steroids in cattle is largely unknown. However, since the local availability of free estrone (E1) in the placenta seems to be controlled by sulfatase and sulfotranferase, the hypothesis was developed that placental estrogens and P4 might act as local regulatory factors. To test for such a function placentomes from 150, 220, 240, 270 days (D) pregnant and parturient cows were screened immunohistochemically for progesterone and estrogen receptors (PR, ER). PR were found at all stages in the caruncle in stromal cells and capillary pericytes but only at parturition in arterial walls. Percentage of PR-positive caruncular stromal cells (CSC) increased (P<0.05) from 51.8+/-2.6% at D150 to 58.9+/-1.8% at parturition. ER were detected in CSC, caruncular epithelial (CE) cells and in caruncular capillary pericytes. Mean percentage of ER-positive CSC decreased from 39.0+/-5.9% in pregnant cows to 17.5+/-8.3% at parturition (P<0.05). In CE all cells exhibited positive signals with the exception of those immediately surrounding large primary chorionic villi. Proliferation was assessed immunohistochemically by determining the percentage of Ki67-antigen positive cells. Highest values (P<0.001) were obtained for CE (58.0-68.3%), followed by the trophoblast (23.3-25.4%), CSC (10.6-45.3%) and the stroma of the chorionic villi (2.9-10.5%). A transient depression of proliferation in CSC between D150-270 (P<0.05) paralleled local estrogen tissue concentrations. The results suggest that placental estrogens and P4 are important factors controlling caruncular growth, differentiation and function.     

大气CO2浓度升高对绿色型豌豆蚜生长发育和繁殖的影响

为了研究大气CO₂浓度升高对绿色型豌豆蚜生长发育和繁殖的影响,应用CO₂人工气候箱,CO₂浓度设置中等浓度[(550±27) μL/L]和高浓度[(750±37) μL/L],并以当前浓度[(375±18) μL/L]为对照,观察并记录了饲养在蚕豆上的连续3代绿色型豌豆蚜的生长发育和繁殖指标。结果表明,随着CO₂浓度升高,连续3代绿色型豌豆蚜发育历期均缩短,初产若蚜体重、成蚜体重、体质量差和相对日均体重增长率均呈增加趋势;各世代的繁殖期延长,平均产蚜量和最大产蚜量均增加;各世代的净增殖率(R₀)增大,平均世代周期(T)延长,内禀增长率(r_m)和周限增长率(λ)均减小。因此,绿色型豌豆蚜的种群数量随着CO₂浓度升高而下降,故推测未来大气CO₂浓度的升高可能不利于豌豆蚜的发生。     

Effects of dietary crude protein content and food intake on the production of semen in two lines of broiler breeder males

1. The effects of dietary crude protein (CP) concentration and feeding rate on semen production and quality from 21 to 66 weeks of age were assessed in a factorial experiment with 48 caged broiler breeder males from 2 strains.

2. The probability of obtaining semen and semen volume were lower in one of the two strains but the concentration and yield of spermatozoa were similar.

3. There was no evidence that males which were fed on an increasing quantity of food produced more semen or a greater concentration of spermatozoa than males on a fixed allocation of 120 g/d food.

4. The concentration of spermatozoa was lower in males fed on a diet containing 160 compared with 120 g CP/kg. On termination of the experiment, average testes size was small and testicular function was absent in a large proportion of the males on the high protein diet.     

Limited susceptibility of three different mouse (Mus musculus) lines to Porcine circovirus-2 infection and associated lesions

Porcine circovirus associated disease (PCVAD), a major global problem for pork producers, is characterized microscopically by depletion and histiocytic replacement of follicles in the lymphoid tissues. The objectives of this study were to determine 1) if Porcine circovirus-2 (PCV-2) inoculated mice (Mus musculus) can develop PCV-2 associated lymphoid lesions and serve as a model for PCVAD, and 2) if differences in PCV-2 host susceptibility exist among mice lines. Three groups (n = 48/group) of 4-wk-old male mice were used: BALB/c, C57BL/6, and C3H/HeJ. A 2 × 2 factorial analysis was designed for each group using PCV-2 inoculation and keyhole limpet hemocyanin in incomplete Freund’s adjuvant injections on day 0 and 7 as factors. Necropsies were performed on days 12, 17, 22, 27, 32, and 37. Serum samples collected at each necropsy tested negative for anti-IgG PCV-2 antibodies in all mice at all time points by 2 different PCV-2 enzyme-linked immunosorbent assays (ELISA). The PCV-2 DNA was detected by polymerase chain reaction (PCR) in 93% (100/108) of tissues and 42.6% (46/108) of serum samples from PCV-2-inoculated mice from days 12 to 37. Microscopic lesions consistent with PCV-2 infection were not observed in any mice and PCV-2 DNA and PCV-2 antigen were not detected in tissues by in-situ-hybridization or immunohistochemistry assays, respectively. Based on incidence of PCV-2 DNA in serum samples, the C57BL/6 mouse line was more resistant to PCV-2 infection than the other lines. The results indicate the mouse model likely has limited utility to advance understanding of the pathogenesis of PCV-2 associated lesions, but mice could potentially be important in the epidemiology of PCV-2.