The effect of feed withdrawal on broiler blood glucose and nonesterified fatty acid levels, postmortem liver pH values, and carcass yield.

Feed withdrawal should start 5 h before broilers are captured and transported to the processing plant. This practice results in a total feed withdrawal period of about 8 h before slaughter. To check observance of this period at the plant reliably, blood samples were collected at slaughter from broilers. These samples were analyzed for glucose and nonesterified fatty acid (NEFA). Glucose levels decreased, whereas the amount of NEFA increased as a consequence of deprivation. It was found that the decrease in glucose was smaller than could be expected from data in the literature, whereas the level tended to rise again after longer deprivation periods. The increase of the NEFA was lower in males than in females, and the glucose: NEFA ratio also showed a difference between the sexes. Therefore, it was concluded that these blood metabolites were not suitable for use as an indicator of the duration of feed withdrawal. The estimation of liver pH seemed to be a more reliable indicator of the length of feed withdrawal. Longer periods of feed withdrawal resulted in higher ultimate liver pH values, which were 6.10 to 6.20 in full-fed broilers, increasing to 6.60 in livers from broilers deprived during longer withdrawal periods. Further research, however, is needed because broilers in the present study were exposed to minimal amounts of stress. Other carcass characteristics such as slaughter, evisceration, and oven-ready yields matched results previously described in the literature.