Influence of preslaughter fasting on live weight loss, carcass yield and meat quality in rabbits

The study was carried out on forty-eight growing rabbits (77 days-old; 2.5 kg live weight), reared and slaughtered under commercial conditions. At the farm, the rabbits were divided into three groups (n=16/group) and feed was removed at 0, 6 or 12 h before crating. Subsequently the rabbits were transported for 1.5 h and laired at abattoir for 1.5 h prior to slaughter so that the following 3 groups were obtained: short fasting (SF; total fasting: 3 h), medium fasting (MF; total fasting: 9h); long fasting (LF; total fasting: 15 h). The results showed that rabbits fasted for short time had higher live weight both at crating and at slaughter (P<0.05) in respect with MF and LF. This result was determined by the lower live weight loss observed between feed removal and crating (0.00 vs. 2.38 and 2.82%; P<0.01) which produced a lower total live weight loss (from feed removal to slaughter) (2.25 vs. 4.55 and 5.15%; P<0.01). The incidence of full gastrointestinal tract exhibited a decrease (P<0.01) going from SF (21.2%) to MF (19.8%) and LF (18.6%), determining a lower (P<0.05) carcass yield in SF compared to MF and LF. Moreover, in comparison with MF and SF, the long fasting produced a lower percentage (4.45 vs. 4.83 and 4.95%; P<0.01) and a higher pH (6.00 vs. 5.94 and 5.96; P<0.01) of the liver, indicating a higher depletion of energetic substrates. Concerning the meat quality traits, the duration of fasting did not significantly modify the rate of muscle acidification and depletion of energy stores as evidenced by both pH and R-value at 45 min post mortem. However, the rabbits fasted for short time exhibited a lower pH at 24 h post mortem (5.58 vs. 5.69 and 5.70; P<0.01), a lighter colour (L*, 55.0 vs. 52.2 and 52.9; P<0.01) and a superior cooking loss (29.6 vs. 28.1 and 27.5%; P<0.01) in respect to those submitted to medium and long fasting. The LF-NMR analysis of the T2 distribution revealed that the differences in relative amounts of water populations were not significant. Overall, the results obtained in this study confirm that preslaughter fasting allow to pursue the empty of the gut with the aim to reduce carcass faecal contamination during slaughtering. Moreover, it was established that a long preslaughter fasting can lead to an increase in muscle ultimate pH, higher water holding capacity and darker colour of the meat. However, the differences observed in meat quality traits are not so large to determine a deterioration of product quality so that it can be concluded that the application of a correct fasting protocol by the rabbit production chain can allow to pursue the emptying of the gut, improve carcass yield and maintain satisfactory meat quality.