Influence of heat stress on broiler meat quality

Weather changes and thermal distribution throughout the year make it difficult to differentiate seasons since, even in winter, hot days occur in some regions of Brazil. (Silva and Vieira, 2010). In tropical countries, high temperatures contribute to aggravate other stress factors, since heat stress prior to slaughter affects animal welfare and exerts a negative impact on meat quality traits. In accordance with Brossi et al. (2009) in his studies about meat quality-associated stress factors, affect all poultry production sectors. The productive sectors must comply with the requirements imposed by the processing industry and, these, in turn, must comply with the demands of and acceptance by the consumers. Taking into account the presence of abnormalities affecting meat quality due to heat stress during the grow out phase, the purpose of this study was to evaluate the effect of acute heat stress on some quality traits of broiler meat.

The experiment was carried out in the experimental climate chambers, College of Agrarian and Veterinary Science, SFRAV, UNESP, Jaboticabal Campus, SP, Brazil. Four hundred (400) Cobb broilers were used. These animals were placed in a climate chamber at the temperature of 32ºC. At 21 days de age, the birds were subjected to heat stress (HS) for various periods i.e., 0 (start), 24, 48 and 72 hours. Meat quality analyses were performed on the pectoralis major muscle in the Animal-Origin Product Technology Laboratory (TPOA), SFRAV, UNESP. Water retention capacity analyses (WRC) were performed in triplicate, using 1.0 g samples. Samples were placed immediately between to filter paper sheets, then between two acrylic plates. A weight of 10 Kg was then applied on top, for 5 minutes. After this time the samples were weighed again and the mean WRC was calculated (Hamm, 1960). Meat consistency was analyzed by shear force resistance (SFR) inn the cooked samples, placing the cutting blade perpendicular to muscle fiber orientation, using a Warner-Bratzler blade coupled to a Stable Mycro Systems TA-XT2i texture meter, and the results were expressed as the maximum shear force in kg of force (kgf) (Wheeler et al., 1996). In order to determine cooking weight loss (CWL) the samples were wrapped in plastic bags, then cooked in a water bat at 85°C until an internal temperature of 75°C was reached (30 minutes). After releasing the exudated water, the samples were set aside for them to cool down to ambient temperature. Samples were then weighed and compared against their start weight (Cason et al., 1997). The experimental design was completely at random. Results were subjected to analysis of variance, and the means were compared using Tukey's test at a 5% significance level, using the AgroEstat (System for the Statistical analysis of Agronomic Assays) version 1.0 (Barbosa and Maldonado, 2010).

WRC, SFR and CWL results are shown in Tables 1, 2 and 3, respectively. Table 1 shows no statistical difference in the WRC between the HS animals and the controls.

Table 1. Water retention capacity (WRC)

Regarding HS periods, the animals subjected to a 48-h HS had WRC values significantly (67.27%) lower than those in the 0 h period (73.72%). In agreement with Brossi et al. (2009), due to the intrinsic properties of no water retention as a regular meat, this type of meat can suffer irreparable disorders during further processing. Woelfel (2002) stated that the meat with these characteristics has poor yields during processing, due to the difficulty of retaining its own water and marinating brine.

 

Table 2. Shear force resistance (SFR) results

Table 3. Cooking weight loss (CWL) results

Results in Tables 2 and 3 show no significant difference in both SFR or CWL. These results differ from those reported by Souza et al. (2010), whose chickens grown under automated and semi-automated systems during the hottest season of the year showed significantly higher SFR means, when compared to flocks grown during cooler seasons.

With the results reported herein, it can be concluded that the heat stress periods experienced by the broilers during the grow out phase can impact end meat quality.

Barbosa JC & Maldonado JRW. 2010. AgroEstat - Sistema para Análises Estatísticas de Ensaios Agronômicos, Versão 1.0.

Brossi C, Contreras-Castillo CJ, Amazonas EA, Menten JFM. 2009. Estresse térmico durante o pré-abate em frangos de corte. Ciência Rural 39(4)

Cason JA, Lyon CE, Papa CM. 1997. Effect of muscle opposition during rigor on development of broiler breast meat tenderness. Poultry Science 76:785-787.

Hamm R. 1960. Biochemistry of meat hydratation. Advances in Food Research 10(2):335-443.

Silva IJO & Vieira FMC. 2010. Ambiência animal e as perdas produtivas no manejo pré-abate: o caso da avicultura de corte brasileira. Archivos de Zootecnia 59(R):113-131.

Souza VLF, Buranelo GS, Gasparino E, Cardozo RM, Barbosa MJ. 2010. Efeito da automatização nas diferentes estações do ano sobre os parâmetros de desempenho, rendimento e qualidade da carne de frangos de corte. Acta Scientiarum. Animal Sciences 32(2):175-181.

Wheeler TL, Cundiff LV, Koch RM. 1996. Characterization of biological types of cattle (Cycle IV): carcass traits and longissimus palatability. Journal of Animal Science 74(5):1023-1035.

Woelfel RL. 2002. The characterization and incidence of pale, soft, and exudative broiler meat in a commercial processing plant. Poultry Science 81:579-584.