Temperatuursmanipulaties tijdens de laatste fase van incubatie en hun effecten op het metabolisme en de performantie van het kippenembryo en het vleeskuiken
Year: 2011
Type: dissertation
Abstract: Incubation temperature is one of the most important single physical factors determining or influencing chick embryo development, hatching process and hatchability as well as post hatch performance. Manipulation of incubation temperature is known to have an influence on embryonic development, hatching process and hatching success. In addition, incubation temperature manipulations during critical periods in embryogenesis (epigenetic temperature adaptation) is a tool used to induce alterations in the thermoregulatory system and therefore improve post hatch performance such as improved heat or cold tolerance. Due to genetic selection, the body weight gain of broiler chickens has improved vastly, resulting in a decreased production cycle time by 60% within 40 years. However, the development of the thoracic organs lags behind, leading to an insufficient pulmonary and cardiac output. This discrepancy causes significant difficulties for broilers to cope with and adapt to extreme and stressful environmental conditions, such as high and low environmental temperatures. To induce an epigenetic response during incubation, four critical parameters have to be considered: (1) the timing of thermal manipulations during incubation, (2) the duration, (3) the amplitude and (4) the dynamics of the temperature manipulation. The timing of thermal manipulations in this thesis, from embryonic day (ED) 16 until ED 18, has been chosen based on three arguments. First, although endothermic reactions during the prenatal development are inefficient, they have an ultimate influence on the efficiency of the thermoregulatory system. Therefore, they may support adaptivity to postnatal environmental conditions and play a role in epigenetic temperature adaptation processes. Second, near the end of incubation, embryonic reactions, especially blood flow in the chorio-allantoic membrane (CAM), to changed environmental conditions change from being uncoordinated and nonadaptive reactions (aspecific reactions) to coordinated adaptive reactions (specific reactions). Hence, it is hypothesized that these characteristic reaction patterns at the end of incubation could be a physiological tool that helps characterize a critical period in the development of the thermoregulatory system. Third, the end phase in the ontogeny of the hypothalamus-pituitary-thyroid axis and hypothalamus-pituitary-adrenal axis is situated in this same period near the end of incubation. These hormonal axes are important in the intermediary metabolism, the thermoregulatory response and stress response. Also, they play a major role in the hatching process. During this critical period during embryogenesis, the incubation temperature was manipulated with 2 or 3°C higher or lower than standard incubation temperature (37.6°C) and this continuously (24/ED) or intermittently (4h/ED). The aim of this thesis can be summarized as an investigation of different incubation temperature manipulations and their achievement in improving tolerance to high and low environmental temperatures without impairing the genetic potential ofthe chick embryo during incubation and the chicken post hatch.The effect of incubation temperature manipulation on embryonic growth, intermediary metabolism, heat production and hatching process was different according to the amplitude and duration of manipulation. Indeed, continuous and intermittent 2°C higher or lower than standard incubation temperature manipulation resulted in a slight shift in embryonic growth and hatching process. However, the differences between temperature treatments were minor.In contrast, temperature manipulation with a 3°C deviation from standard incubation temperature caused major shifts in embryonic growth, intermediary metabolism and hatching process according to the direction of the temperature deviation and duration of the manipulation. A continuous increase with 3°C from ED 16 until ED 18.5, resulted in a reduced embryonic growth, chick weight at hatch, hatchability and a pronounced delay in hatching process. An overall decrease in embryonic metabolism and more specifically an inhibition of the carbohydrate and lipid metabolism corroborated these negative findings. An intermittent 3°C high temperature treatment for 4h on ED 16, ED 17 and ED 18 temporarily increased embryonic metabolism during the 4h treatment period. Due to an efficient use of the anaerobic metabolism, the necessary energy for a normal development could be provided resulting in a non-influenced embryonic growth, chick weight at hatch, hatchability and caused only a slight delay in hatching process.Low temperature treatment with 3°C either continuously or intermittently resulted in less severe repercussions than the 3°C high temperature treatment. Changes in metabolism were also observed for the low temperature treatment as a lowering of the carbohydrate metabolism was found for the continuous low temperature treatment and a lowering of both the carbohydrate and lipid metabolism was found for the intermittent low temperature treatment. However, these changes did not appear to have grave repercussions as no differences in embryonic growth, chick weight at hatch and hatchability were observed. Only a pronounced delay in hatching process was observed for the low temperature treatment. In addition, the investigation of the link between chick embryonic metabolism and the AMPK (AMP-activated protein kinase) pathway revealed possible new topics for future research. The injection of AMPK activators/inhibitors in broiler eggs during incubation and evaluation of the effects on chick embryo heat production and intermediary metabolism would bring further insight into the role of the AMPK pathway in the chick embryo metabolism.In a last part of the thesis, long lasting effects on overall performance, heat and cold tolerance and ascites susceptibility were investigated. As with embryonic development and metabolism, the effects of incubation temperature manipulation on post hatch performance were different according to the amplitude and duration of the manipulation. Intermittent manipulation, whatever the amplitude, did not result in long lasting effects. In contrast, continuous manipulations did. Indeed, reduced post hatch body weights were observed for the continuous 2 and 3°C high temperature treatment and for the continuous 3°C low temperature treatment. However, programming effects of incubation temperature manipulation, both to induce better heat and cold tolerance and to reduce ascites susceptibility could not be observed. <w:latentstyles deflockedstate="false" defunhidewhenused="true" <w:lsdexception locked="false" priority="0" semihidden="false" <w:lsdexception locked="false" priority="9" semihidden="false" <w:lsdexception locked="false" priority="10" semihidden="false" <w:lsdexception locked="false" priority="11" semihidden="false" <w:lsdexception locked="false" priority="22" semihidden="false" <w:lsdexception locked="false" priority="20" semihidden="false" <w:lsdexception locked="false" priority="59" semihidden="false" <w:lsdexception locked="false" priority="1" semihidden="false" <w:lsdexception locked="false" priority="60" semihidden="false" <w:lsdexception locked="false" priority="61" semihidden="false" <w:lsdexception locked="false" priority="62" semihidden="false" <w:lsdexception locked="false" priority="63" semihidden="false" <w:lsdexception locked="false" priority="64" semihidden="false" <w:lsdexception locked="false" priority="65" semihidden="false" <w:lsdexception locked="false" priority="66" semihidden="false" <w:lsdexception locked="false" priority="67" semihidden="false" <w:lsdexception locked="false" priority="68" semihidden="false" <w:lsdexception locked="false" priority="69" semihidden="false" <w:lsdexception locked="false" priority="70" semihidden="false" <w:lsdexception locked="false" priority="71" semihidden="false" <w:lsdexception locked="false" priority="72" semihidden="false" <w:lsdexception locked="false" priority="73" semihidden="false" <w:lsdexception locked="false" priority="60" semihidden="false" <w:lsdexception locked="false" priority="61" semihidden="false" <w:lsdexception locked="false" priority="62" semihidden="false" <w:lsdexception locked="false" priority="63" semihidden="false" <w:lsdexception locked="false" priority="64" semihidden="false" <w:lsdexception locked="false" priority="65" semihidden="false" <w:lsdexception locked="false" priority="34" semihidden="false" <w:lsdexception locked="false" priority="29" semihidden="false" <w:lsdexception locked="false" priority="30" semihidden="false" <w:lsdexception locked="false" priority="66" semihidden="false" <w:lsdexception locked="false" priority="67" semihidden="false" <w:lsdexception locked="false" priority="68" semihidden="false" <w:lsdexception locked="false" priority="69" semihidden="false" <w:lsdexception locked="false" priority="70" semihidden="false" <w:lsdexception locked="false" priority="71" semihidden="false" <w:lsdexception locked="false" priority="72" semihidden="false" <w:lsdexception locked="false" priority="73" semihidden="false" <w:lsdexception locked="false" priority="60" semihidden="false" <w:lsdexception locked="false" priority="61" semihidden="false" <w:lsdexception locked="false" priority="62" semihidden="false" <w:lsdexception locked="false" priority="63" semihidden="false" <w:lsdexception locked="false" priority="64" semihidden="false" <w:lsdexception locked="false" priority="65" semihidden="false" <w:lsdexception locked="false" priority="66" semihidden="false" <w:lsdexception locked="false" priority="67" semihidden="false"
Source: Lirias
Author: Willemsen, Hilke
Language: English
Subfield: Animal Science and Zoology
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W7071538782