Increasing the incubation temperature between embryonic day 7 and 10 has no influence on the growth and slaughter characteristics as well as meat quality of broilers

Abstract

Avian embryogenesis can be manipulated by alteration of the temperature during incubation of the brooding egg. Investigations in turkeys showed that a higher temperature during early embryogenesis positively affects the myogenesis accompanied with a higher muscle fibre number (MFN). The aim of this study was to transfer this result to broiler and to investigate if an alteration of the temperature also affects the meat quality after slaughter of the birds. Therefore brooding eggs of the Cobb 500 broiler genetic were either incubated at 37.5°C during the whole incubation period (at normal temperature (NT)), or at 38.5°C during embryonic day (ED) 7 to 10 (at high temperature (HT)). After hatch the chicks were sexed and reared up to an age of 36 days in an experimental stable. Growth and feed conversion properties were determined during this period. After slaughter different meat quality characteristics as well as the muscle microstructure were analysed. The hatch rate and chick weight did not differ between the broiler of the NT and HT group. After 36 days the final body weights and the cumulative feed conversion rates were not different in the NT and HT groups. No differing results were obtained with regard to the slaughter, breast and leg weights of the NT and HT animals. Considering the gender of the animals no differences in the slaughter characteristics could be determined although the carcass and breast weights of the HT cocks were tendentially higher. The muscle fibre areas and MFNs in the breast muscles of the NT and HT cocks did not differ significantly and were in the range of the HT hens. Only the NT hens had significantly larger muscle fibres and less MFN than the other animals. With regard to the meat quality characteristics no clear differences of the pH, electrical conductivity (EC) and colour (L*a*b*) values were found. The L*a*b* values in the investigated breast muscles of all broilers usually increased during ageing. The increase of the incubation temperature had no impact on the hatch, growth, slaughter and meat quality characteristics of the broiler except for the tendentially higher carcass and breast weights of the HT cocks. However, the decrease of the fibre areas in the HT hens is an interesting effect of using a higher incubation temperature, which needs to be considered when implicating further investigations.

Evaluation of DNA methylation and mRNA expression of heat shock proteins in thermal manipulated chicken

“…Though higher incubatory temperature reduces hatchability, the effect mainly depends on the duration and strength of heat exposure, apart from the phase of embryonic growth (Halle and Tzschentke 2011;Narinc et al 2016). Similar to the present findings, other workers too have reported no difference in hatchability (Yahav et al 2004;Werner et al 2010;Loyau et al 2013;Rajkumar et al 2015b) in broiler and turkeys. Alteration in cFos expression in the hypothalamus (Janke and Tzschentke 2010) has been shown to be responsible for the long-lasting sequel of change in incubation temperature which provided the embryos the capacity to adjust to the shortterm rise in temperature without any ill effects on hatching.…”

“…Meanwhile, the higher body weight achieved in the TCHE group implies that embryonic thermal conditioning has had a positive impact on the birds that enabled them to mitigate the heat stress even though they were reared at a temperature of 35°C. In contrast, others had reported that increased incubation temperature did not affect growth traits in broiler chicks (Werner et al 2010;Narinc et al 2016;Morita et al 2016). Recently, Rajkumar et al (2015b) reported higher body weight in thermal manipulated NN chicken but not in PB-2.…”

Altered incubation temperatures between embryonic Days 7 and 13 influence the weights and the mitochondrial respiratory and enzyme activities in breast and leg muscles of broiler embryos

“…In ovo embryogenesis of broiler chickens (Gallus gallus domesticus) can be modified by altering external factors such as the incubation temperature (Leandro et al, 2004;Yahav et al, 2004;Piestun et al, 2009;Werner et al, 2010a;Loyau et al, 2013). For example, adjustments to the incubation temperature during chicken embryonic myogenesis, which is characterized by the formation of primary and secondary myotubes from embryonic Day (ED) 3 to 8 and ED 8 to 14, respectively (Miller and Stockdale, 1986), have an impact on the growth of the embryos.…”

Incubation Temperature and Lighting: Effect on Embryonic Development, Post-Hatch Growth, and Adaptive Response

“…Aside from affecting embryonic development, incubation temperature also affects broiler growth. It is reported that early incubation temperatures changing from 36.5 to 39 °C for a short period (2-3 days) have no effect on slaughter weight and feed conversion ratio however may affect muscle and bone development (Werner et al, 2010;Oksbjerg et al, 2019). Contradictory to these results, Janisch et al (2015) reported that a 1-1.5 °C higher EST than the optimum for 3 days during the first week of embryogenesis positively influenced body weight, but reduced meat quality while low temperature during the first 10 days of incubation reduced body and breast weights (Joseph et al, 2006).…”