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

Abstract

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.

Keywords: broiler; incubation; meat quality; welfare; white striping.

Figure 1

Experimental design. Number of birds per treatment is reported in the Materials and Methods section.

Figure 2

Effects of sex, incubation condition and postnatal rearing condition on the occurrence of white striping on the breast meat observed 24 h after slaughter at day 40. Control incubation I₀ corresponds to egg incubation at 37.6°C, 56% RH. Cold incubation I₁ corresponds to egg exposure for 30 min at 15°C at days 18 and 19 of incubation, eggs being incubated under the same conditions than for I₀ the remaining time. Chickens were reared in floor pens either under control temperature T₀ from 32°C at day 0 to 21°C at day 21 or under cold temperature T₁ from 29°C at day 0 to 21°C at day 21. From day 22 to day 40, the ambient temperature in T₀ and T₁ was maintained at 21°C. Different letters (a, b, c) correspond to significant differences (P < 0.05) between groups.

Figure 3

Effects of sex, incubation condition, and postnatal rearing condition on parameters related to welfare troubles observed on carcasses after slaughter at day 40. (A) Occurrence of hock burns. (B) Occurrence of pododermatitis. Control incubation I₀ corresponds to egg incubation at 37.6°C, 56% RH. Cold incubation I₁ corresponds to egg exposure for 30 min at 15°C at days 18 and 19 of incubation, eggs being incubated under the same conditions than for I₀ the remaining time. Chickens were reared in floor pens either under control temperature T₀ from 32°C at day 0 to 21°C at day 21 or under cold temperature T₁ from 29°C at day 0 to 21°C at day 21. From day 22 to day 40, the ambient temperature in T₀ and T₁ was maintained at 21°C. Different letters (a, b, c) correspond to significant differences (P < 0.05) between groups.