The strong negative genetic correlation between glycogen
content of breast muscle (estimated through the glycolytic
potential) and ultimate pH represents a major result in
the present study. The genetic control of glycolytic potential
and its genetic relationships with meat quality have
been more widely studied in pigs than in poultry. Genetic
studies in pigs have focused on either post-mortem glycolytic
potential (PMGP), as for the present study, or on in
vivo glycolytic potential (IVGP) obtained from muscle
biopsy on live animals (which is not yet available for the
chicken). In pigs, fairly negative genetic correlations
(ranging from -0.74 to -0.99) have been reported between
PMGP and pHu measured on the same muscle or on different
muscles with close metabolic characteristics [13].
Corresponding correlations were slightly lower when
IVGP was considered [13]. Heritability values for IVGP
were around 0.25 in a population of pigs without the RNallele
[13], while an average value of 0.21 was reported for
pHu [1]. These genetic results together demonstrated that
GP and pHu have close genetic control, and that in poultry,
as in pigs, both traits can be modified by selection. In
agreement with a previous genetic study in an experimental
broiler line [10], the present study indicated that the
rate and the extent of decrease in pH post-mortem are
under the control of different genes. A similar conclusion
was drawn from a selection experiment in pigs, in which
a very low genetic correlation was found between IVGP
and pH measured 30 min post-mortem [14]. In the
chicken, the rate of decrease in pH was shown to be influenced
by behavior at slaughter and hastened by struggle
activity of the birds on the shackle line, especially wing
flapping [15]. However, little is known to date about the
influence of genetics on such behavioral traits and the
implications for meat quality.