Effect of available dietary carbohydrate on glycolytic potential and meat quality of swine muscles

The aim of this study was to determine whether glycolytic potential (GP) in pork muscle could be modified by the availability of carbohydrates in the diets and, if so, to what extent meat color and drip loss were affected. Biopsy samples of longissimus muscle (LM) from 48 Swiss Large White pigs (25 gilts, 23 barrows) weighing 70 kg were collected, and the GP was determined to vary from I I I to 187 mumol g(-1) wet weight. At 90-kg body weight, pigs were moved into individual pens and assigned (blocked by GP and sex) to be fed 2.8 kg of a diet either high (H) or low (L) in available carbohydrate up to 104 kg. Pigs were fasted overnight (15 h) before slaughter. Glycogen, glucose, glucose-6-phosphate and lactic acid content were determined in samples of LM (predominantly glycolytic muscle) collected 30 min and 24 h post-mortem and in samples of the dark part of the semitendinosus (ST, oxidative part of the muscle) 24 h post-mortem. After slaughter, the decline in pH and temperature was recorded in the LM from 30 min to 24 h after bleeding. Regardless of the diet, content of glycolytic intermediates and lactic acid were higher in the LM compared to the ST. Diet did not alter the GP, and did not affect color or drip loss of the LM. However, in gilts fed the H diet muscle pH was lower by 0.2 units from 30 min until 6 h post-mortem than in gilts fed the L diet. These effects were not observed in barrows. ST of gilts fed the H diet had higher levels of glycolytic intermediates and lactic acid and, therefore, higher GP compared to gilts on the L diet, but no dietary effects occurred in barrows. Increased GP resulted in paler color and higher drip loss, whereas ultimate pH was not affected. The GP was positively correlated with L* (0.52), a* (0.49), b* (0.59) and drip loss (0.77) of the ST, whereas poor correlations were observed in the LM. In conclusion, dietary treatment only affected paleness and drip loss of the ST muscle and the effects were more pronounced in gilts than barrows. Increased GP resulted in paler meat with higher drip loss.