Gas exchange and hatchability of chicken eggs incubated at simulated high altitude
Chicken eggs laid at sea level were incubated at sea level (control conditions), at a simulated altitude of 5.5 km without any further measures (natural conditions), and at a simulated altitude of 5.7 km at optimal incubator gas composition (optimal conditions). Under optimal conditions the incubator relative humidity was 70% throughout incubation, the gas mixture supplied to the incubator contained 45% O2-55% N2, and the ventilation rate was reduced to 6% of control in order to maintain the normal air-space gas tensions and to compensate for the increased eggshell conductance at altitude. The embryos that developed under control conditions showed a normal CO2 production with 94% hatchability of fertile eggs. Under natural conditions at altitude all embryos died within a few days. Optimal conditions resulted in an almost normal gas exchange and in an improvement of hatchability from 0 to 81% of fertile eggs.
Available from: ajol.info
- "The partial pressure of oxygen (O 2 ) becomes lower with increasing altitude (Visschedijk, 1985) and a decrease in barometric pressure and O 2 partial pressure at high altitude causes a lack of O 2 (hypoxia), carbon dioxide (CO 2 ) (hypocapnia) and water (dehydration) in chickens (Visschedijk, 1991). Growth increases the need for O 2 consumption (Beker et al., 2003), and rapidly growing broiler chickens need O 2 for their high metabolic requirements (Julian et al., 1989). "
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ABSTRACT: The objective of this study was to investigate the effect of oxygen supplementation on broiler eggs in a hatchery at high altitude on the growth performance and ascites syndrome of broilers reared at low altitude. The treatment groups were low altitude with no oxygen supplemented in the hatchery (LA-NOX); high altitude with oxygen supplementation in the hatchery (HA-OX); and high altitude with no oxygen supplemented in the hatchery (HA-NOX) group. Growth performance, heart weight, the concentrations of the hormones, T3, T4, T3/T4, and and plasma concentrations of haematocrit, haemoglobin, glucose and parameters of ascites syndrome during the growing period were investigated. A total of 243 one-day-old broilers were used for this study. During the growing period, excluding days 7, 28 and 35, oxygen supplementation at high altitude did not affect the live weight of broilers compared with the HA-OX and HA-NOX groups. The cumulative feed consumption was determined to be lower in the LA-NOX group and the same in the HA-OX and HA-NOX groups on the 42nd day. Between 21 and 42 days old, the LA-NOX group had a better feed conversion ratio (FCR) than the HA-OX and HA-NOX groups. Chick weight (CW), yolk sac weight (YSW) and chick heart weight (CHW) were higher in the LA-NOX group than in the HA-OX and HA-NOX groups. At 42 days old, there were no differences between the groups in heart weight, right ventricle weight (RV), left ventricle and septum (LV+Sept.), total ventricle (TV) weight and the RV : TV ratio. The plasma T3 level was lower in the LA-NOX group than in the HA-OX and HA-NOX groups and T4 levels were higher in the HA-OX than in the others at 42 days old. The hypoxic conditions that occurred during the embryonic stage . which altered endogenous functions of prenatal chicks and affected several blood parameters, and oxygen supplementation at high altitude . improved chick quality. However, it did not improve subsequent FCR and feed consumption performance of chickens when they were reared at low altitude.
Available from: PubMed Central
- "Specific processes that take place during embryonic lung development and structures in animals that live at high altitudes are the basis for highly efficient pulmonary ventilation, which leads to altitude adaptation , . For plain chickens at low altitudes, inadequate oxygen exchange results in hypoxia syndrome and is lethal –. Therefore, determining the particular altitude adaptation characteristics of high-altitude chickens is important. "
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ABSTRACT: The lungs undergo changes that are adaptive for high elevation in certain animal species. In chickens, animals bred at high elevations (e.g., Tibet chickens) are better able to hatch and survive under high-altitude conditions. In addition, lowland chicken breeds undergo physiological effects and suffer greater mortality when they are exposed to hypoxic conditions during embryonic development. Although these physiological effects have been noted, the mechanisms that are responsible for hypoxia-induced changes in lung development and function are not known. Here we have examined the role of a particular microRNA (miRNA) in the regulation of lung development under hypoxic conditions. When chicks were incubated in low oxygen (hypoxia), miR-15a was significantly increased in embryonic lung tissue. The expression level of miR-15a in hypoxic Tibet chicken embryos increased and remained relatively high at embryonic day (E)16-20, whereas in normal chickens, expression increased and peaked at E19-20, at which time the cross-current gas exchange system (CCGS) is developing. Bcl-2 was a translationally repressed target of miR-15a in these chickens. miR-16, a cluster and family member of miR-15a, was detected but did not participate in the posttranscriptional regulation of bcl-2. Around E19, the hypoxia-induced decrease in Bcl-2 protein resulted in apoptosis in the mesenchyme around the migrating tubes, which led to an expansion and migration of the tubes that would become the air capillary network and the CCGS. Thus, interfering with miR-15a expression in lung tissue may be a novel therapeutic strategy for hypoxia insults and altitude adaptation.
Available from: Aureliano Hernandez
- "There are three currently recognised HIF isoforms: HIF-1a, HIF-2a and HIF-3a (Wang & Semenza 1995; Tian et al. 1997; Hara et al. 2001), but only HIF-2a is expressed in the extraembryonic tissues (Ota et al. 2007). Tengerdy et al. (1970) and Visschedijk (1985) found that chick embryos exposed to hypoxic conditions reduced their hatchability, which suggests that decreasing the availability of oxygen (O 2 ) impairs embryonic survival (Mortola 2009), and in non-fatal cases, hypoxia delays embryonic growth, especially in the early ( B10 days) and late stages (16 days) of incubation (Taylor et al. 1971). "
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ABSTRACT: Vascular density of the yolk sac membrane (YSM), protein and mRNA expression of hypoxia-inducible factor 2alpha (HIF-2α), vascular endothelial growth factor (VEGF-A) and its type 2 receptor (FLK-1) in the YSM were compared in subjects incubated at two different altitudes: 355 and 1378 metres above sea level (masl) in Colombia. On days 3 or 4 of incubation, higher vascular density of YSMs (pα mRNA (ppppppα, VEGF-A and its receptor FLK-1 in the endoderm, mesoderm and ectoderm in the YSM on days 3 and 4, and it is demonstrated that endothelial cells in the YSM on day 3 of incubation express HIF-2α, which had not been previously reported.
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