Optimization of embryonic thermal programming confirms increased liver fattening in mule ducks and changes in lipid metabolism.

Introduction: The embryonic thermal programming (TM) in birds has been shown to impact several physiological parameters such as resistance to thermal stress, muscle growth or immunity. In mule ducks, it has recently been shown that TM can induce metabolic programming resulting in increased liver weight and fat storage after overfeeding. However, a decrease in hatchability and foie gras quality was also observed, suggesting that this technique needs to be optimized. Here, we tested a new thermal manipulation condition determined with the objective of avoiding negative impacts while maintaining or improving liver properties. Methods: The eggs of the control group were incubated at 37.6°C during the whole incubation period while those of the experimental group (TM group) were incubated at 39.3°C 16 h/24 h from the 11th day of incubation to the 21st. After hatching, all the animals were fed and raised under the same conditions until the age of 12 weeks. At this stage, one part of the animals was overfed and then slaughtered 2 h (to measure rapid changes in metabolism) or 10 h after the last meal (to obtain the best technological yields), while the other part was ration-fed and slaughtered 2 h after the last meal, at the same age. Results: An 8% increase in foie gras production was measured in the TM group compared to the control group without altering the quality of the final product (nor hatchability), confirming the successful optimization of the metabolic programming. Interestingly, these results allowed us not to reject the previously suggested hypothesis of a potential delay in metabolic processes involved in liver fattening in programmed animals, in particular by measuring a trend reversal regarding the amount of total hepatic lipids in both groups at 2 h and then 10 h after the last meal. Discussion: This study therefore validates the optimization of metabolic programming by embryonic thermal manipulation for duck liver fattening. The understanding of the mechanisms of embryonic thermal programming in birds remains today very incomplete and the search for epigenetic marks (main hypothesis of the concept of programming) at the origin of the observed phenotypes could be the next step of this work.

Short communication: Effects of in-ovo injection of endocrine disruptors and methyltransferase inhibitor on quail growth and egg-laying performances.

Early experiences, including prenatal environment, are known to influence a wide variety of mechanisms involved in the phenotype elaboration. We investigated the effect of the addition of endocrine disruptors or of a methyltransferase inhibitor during the embryonic development of quails from different genetic backgrounds (four different quail lines) on their growth and egg-laying performances. Fifty-four pairs of parents per line were used and fertilised eggs from each pair were randomly divided into five groups: a control group without any injection, an injected control group treated by injection into the egg of sesame oil, and three groups treated by injection of Genistein, Bisphenol A or 5-Aza-2'-deoxycytidine. All quails were individually weighed at 8, 21, 36 and 78 days. The age at first egg laid and the number of eggs laid were recorded. These analyses revealed a significant impact of the treatment on growth but no influence on the egg-laying traits. All three molecules significantly affected at least one of the analysed growth traits. In conclusion, we showed that the injection of endocrine disruptors or DNA methyltransferase inhibitor into the egg had significant effects on quail development; these effects were specific to each treatment, but no interaction between line and treatment was observed.

Identification of different critical embryonic periods to modify egg incubation temperature in mule ducks.

Egg incubation of mule ducks, mainly used for fatty liver production, is one of the critical phases in this sector. Based on hatching rate, the best incubation parameters have already been well described for poultry, but the literature on ducks is lacking. In this study, we tested different incubation conditions by varying two important factors, temperature and relative humidity, in mule ducks. These variations were applied at different periods during embryogenesis in order to measure the impact of environmental disturbances on different zootechnical performances. The temperature was increased by 1.5 °C (16 h/24) and the relative humidity was set up to 65%, during 10 days. Six 10-day developmental windows were tested, from embryonic day 9 to embryonic day 14. Our results are in line with previous reports showing that increasing incubation temperature, even when relative humidity is adjusted, can have a negative impact on duck embryonic mortality up to 24.5% for the condition E10-E20 (P < 10-5). However, the hatchability can be maintained at the level of the control groups when these modifications are applied on the latest windows (from the 11th embryonic day). Sex ratio, hatching BW, and internal temperature are also sensitive to these incubation changes, and their modification could have a major impact on later zootechnical performance. These results should contribute to the development or embryonic temperature programming approaches, especially for the fatty liver production industry.

Short cold exposures during incubation and postnatal cold temperature affect performance, breast meat quality, and welfare parameters in broiler chickens.

Cold stimulations during egg incubation were reported to limit the occurrence of ascites in broilers subjected to cold temperature after 14 d of age. However, data are lacking on the impacts of such strategy in case of cold temperature conditions at start. This study aimed to evaluate the effects of incubation and posthatch cold challenge on performance, breast muscle integrity, and meat processing quality in broiler chickens. Ross 308 eggs were incubated under control temperature (I0, 37.6°C) or subjected to 15°C during 30 min on day 18 and 19 of incubation (I1). Chicks from each group were reared in floor pens either at standard rearing temperature (T0), from 32°C at 0 d to 21°C at 21 d of age, or exposed to colder rearing temperature (T1), from 29°C at 0 to 21°C at 21 d of age. All birds were then kept at 21°C until slaughter (day 40), when body weights (BW), feed conversion ratio (FCR), breast muscle yield, meat processing quality, and the occurrences of meat defects, hock burns, and pododermatitis were recorded. No significant impact of incubation conditions on hatchability was observed. At day 40, BW was more under T1 than under T0 conditions, with T0 females (but not males) presenting more BW after I1 than after I0 conditions. In the whole period, T1 chickens presented lower FCR than T0 chickens and higher breast meat yields at day 40. The occurrence of white striping was more in I1T1 males than in all other groups, except for the I0T1 males. Hock burns were more frequent in I1T1 males than in all females and I0T0 males, whereas the occurrence of pododermatitis was lower in T0 males than in other groups. Despite some positive effects of I1 incubation on growth after starting under low ambient temperature, this study reveals the limits of such strategy concerning chicken health and welfare, demonstrating that early thermal environment is a major component of the quality and sustainability of chicken meat production.

Effect of low incubation temperature and low ambient temperature until 21 days of age on performance and body temperature in fast-growing chickens.

Thermal manipulation during embryogenesis was previously reported to decrease the occurrence of ascites and to potentially improve cold tolerance of broilers. The objective of our study was to explore the effects of the interaction of cold incubation temperatures and cool ambient temperatures until 21 d of age on performance and body temperature. Ross 308 eggs were incubated either under control conditions I0 (37.6°C) or with cyclic cold stimulations I1 (6 h/d at 36.6°C from d 10 to 18 of incubation) or with 2 cold stimulations I2 (30 min at 15°C) at d 18 and 19 of incubation. These treatments were followed by individual rearing and postnatal exposure to either standard rearing temperature T0 (from 33°C at hatching to 21°C at d 21) or continuously lower temperature T2 (from 28°C at hatching to 21°C at d 21) or exposure to cyclically lower temperature T1 (with circadian temperature oscillations). Treatments I1 and I2 did not significantly alter hatchability compared to control incubation (with 94.8, 95.1, and 92.3%, respectively), or hatching BW and overall chick quality. Hatching body temperature (Tb) was 0.5 and 0.3°C higher in I1 than in I0 and I2 groups, respectively (P = 0.007). A doubled occurrence of health problems was observed with T2 condition, regardless of incubation or sex. At d 3, BW was 2% lower with treatment I1 than with I0 and I2 and was 3% higher in T1 and T2 groups than in T0, but these effects disappeared with age. Group T2 presented a 5% higher feed intake than the control group T0 between 3 and 21 d of age (P = 0.025). Feed conversion ratio (FCR) was affected by experimental conditions (P < 0.001), with low FCR values obtained with I2 incubation in control or cyclically cold postnatal conditions. Maximal FCR values were observed in the continuously cold postnatal conditions, in males submitted to control incubation and in females submitted to I1 incubation, revealing sex-dependent effects of the treatments on performance.

A simple PCR method for sexing Japanese quail Coturnix japonica at hatching.

1. The quail is a potentially important avian model for molecular studies; a major drawback is the inability to sex visually before 3 weeks of age. Molecular sexing is therefore an absolute requirement when animals are sampled before that age. 2. A low-cost method using common laboratory equipment based on Allele-Specific Multiplex-Polymerase Chain Reaction was developed to undertake reliable molecular identification of the sex of Coturnix japonica directly at hatching. 3. This simple method works with down feathers collected from behind the neck of the newly hatched quail and includes internal controls during the PCR to limit risks of error. Males and females can be discriminated on the basis of the presence of one or two amplicons, respectively.

Cyclic variations in incubation conditions induce adaptive responses to later heat exposure in chickens: a review.

Selection programs have enabled broiler chickens to gain muscle mass without similar enlargement of the cardiovascular and respiratory systems that are essential for thermoregulatory efficiency. Meat-type chickens cope with high ambient temperature by reducing feed intake and growth during chronic and moderate heat exposure. In case of acute heat exposure, a dramatic increase in morbidity and mortality can occur. In order to alleviate heat stress in the long term, research has recently focused on early thermal manipulation. Aimed at stimulation of long-term thermotolerance, the thermal manipulation of embryos is a method based on fine tuning of incubation conditions, taking into account the level and duration of increases in temperature and relative humidity during a critical period of embryogenesis. The consequences of thermal manipulation on the performance and meat quality of broiler chickens have been explored to ensure the potential application of this strategy. The physiological basis of the method is the induction of epigenetic and metabolic mechanisms that control body temperature in the long term. Early thermal manipulation can enhance poultry resistance to environmental changes without much effect on growth performance. This review presents the main strategies of early heat exposure and the physiological concepts on which these methods were based. The cellular mechanisms potentially underlying the adaptive response are discussed as well as the potential interest of thermal manipulation of embryos for poultry production.