GENETIC VARIATION OF CHICKEN TECHNOLOGICAL MEAT QUALITY

E. L. Bihan-Duval^1,*, C. Berri¹, J. Nadaf¹, M. Debut², V. Brunel², C. Beaumont¹, and M. J. Duclos¹

¹ Poultry Research Center, INRA, 37380 Nouzilly, France

² ITAVI, Poultry Research Center, BP 1, 37380 Nouzilly, France

* Corresponding author e-mail : lebihan@tours.inra.fr

ABSTRACT

In poultry as in other animal species, several attributes of the meat such as colour, water-holding capacity or texture have become of major importance, since meat is nowadays offered to customers as parts or further-processed products rather than as whole carcasses. In the same time, a very high variability of the technological quality of poultry meat has been put in evidence, as indicated by recent results on chicken meat pH measured under commercial conditions. Recent results obtained on experimental divergent lines point out that selection for growth or abdominal fatness may lead to significant changes in meat quality attributes such as colour, pH or water-holding capacity. These experimental lines are valuable tools for genomic research aimed at identifying genes or markers useful for selection on meat quality. Meat quality can also be improved by a more classical approach of selection as indicated by the strong heritabilities obtained in a heavy commercial line for different breast meat indicators. The estimated genetic correlations suggested that ultimate pH could be a relevant selection criterion, because of its strong relationship with the colour, the water-holding capacity and the texture of the meat.

KEY WORDS: Chicken, Genetic parameters, Meat Quality, Meat pH

INTRODUCTION

In poultry as in other animal species, several technological parameters of meat have become of major importance, since meat is nowadays often offered to customers as parts or further-processed products rather than as whole carcasses. This highlights the importance of meat characteristics such as color, water-holding capacity and texture, which strongly influence yields during processing and sensorial quality of the raw and cooked meat. As described by Berri (2000), many factors including rearing and slaughtering conditions as well as bird characteristics may influence meat properties. The variation of ultimate pH within slaughter hatch was estimated recently by a French study on chicken meat processed in a commercial plant. It appeared very high since extreme values ranging from 5.4 to 6.5 could be detected within a same slaughter hatch (Brunel et al., 2006). As already reported in the literature, such extreme pH values can lead to meat defects: high final pH produces dark, firm and dry (DFD) meat with a poor storage quality due to faster rate of off-odor production and accelerated microbiological growth (Allen et al., 1998). On the contrary, low final pH produces meat with an improved shelf-life but a pale aspect and reduced water-holding capacity (Barbut, 1996, 1997). This highlights the need for homogenizing the quality of poultry meat, both by improving the rearing and slaughtering conditions, but also by adapting selection processes to the current cutting and processing practices. In this paper we will report recent results on the genetic variation of chicken meat quality, obtained either by comparing extreme divergent experimental lines or by estimating genetic parameters of meat traits within a commercial heavy line.

MEAT QUALITY VARIATION IN EXPERIMENTAL CHICKEN LINES DIVERGENTLY SELECTED FOR GROWTH OR BODY COMPOSITION

Even if they may present performances rather far from current commercial birds, experimental lines of chickens constitute quite interesting tools for identifying changes in bird characteristics that may have been induced by selection for growth or for body composition, applied in most commercial breeding programs. High Growth (HG) and Low Growth (LG) chicken lines from the Poultry Research Center (Nouzilly, FRANCE) have been divergently selected for growth rate at juvenile and adult ages (Ricard, 1975). Body weight, body composition and several breast meat parameters were recently characterized on a total of 53 HG and 56 LG male birds, bred under regular conditions and slaughtered at 9 weeks in the experimental facility of the Poultry Research center. Meat pH at 15 min post-slaughter (pH15), ultimate pH (pHu), meat colour (defined as the lightness L*, the redness a* and the yellowness b*) at 24 h post-slaughter, and drip loss after 2 days of storage were measured as described by Le Bihan-Duval et al. (1999) and Berri et al. (2005). As shown in Table 1, body weight at 9 weeks was 2.8 fold higher in HG than in LG line. A large correlated response was observed for abdominal fatness which was extremely low in LG line and higher in HG line (11.8 fold difference). Interestingly, these results indicated that HG chickens exhibited a less coloured breast meat with lower redness and yellowness, and higher lightness than LG birds. Post-mortem pH values also differed between the two lines, HG birds exhibiting lower pH15 and pHu values. The lower ultimate pH of HG bird was likely to contribute to the paler aspect of the meat since a negative phenotypic correlation of -0.54 was observed between pHu and lightness.

Table 1. Body weight, body composition and breast meat parameters (mean ± standard deviation) in the high growth (HG) and low growth (LG) lines, as well as in the high fat (HF) and low fat (LF) lines compared at 9 wks of age

NS = non significant; NA = non available