Effect of an in-vivo and/or in-meat application of a liquorice (Glycyrrhiza glabra L.) extract on fattening rabbits live performance, carcass traits and meat quality

Abstract

The present study tested the effect of a liquorice root extract (L) administration in the diet of growing rabbits and/or in their minced meat. A total of fifty-six rabbit does and their kits (3 weeks of age) were divided into 4 groups receiving a commercial diet (C) or the C diet supplemented with increasing levels of L: 2 g/kg (L2), 4 g/kg (L4), 6 g/kg (L6). At weaning (5 weeks of age), sixty rabbits/group were randomly selected, caged by 3, and fed ad libitum with the experimental diets until slaughter (12 weeks of age). At 6 weeks of age, 6 rabbits/diet were selected for gastrointestinal tract pH and caecal microbial count analyses. Live performance and health status were recorded weekly and daily, respectively. Carcass traits were measured after slaughter and hind leg (HL) and Longissimus lumborum (LL) meat were dissected for pHu and L*a*b* colour measurements. Minced meat from HL belonging to C and L6 dietary treatments was each split in two parts to incorporate liquorice extract at 0.25% (w/w), obtaining four groups of meat burgers: CC; CL; L6C and L6L. The pH, L*a*b* colour and microbial count (TVC, Coliforms, and Pseudomonas) were measured at days 0, 3 and 6 of refrigerated storage. A sensory analysis was conducted on LL meat of C and L6 dietary treatments, and tested attributes were odour, taste, flavour, texture and off-flavours. Liquorice dietary inclusion did not show a clear effect on live performance, resulting comparable among groups, with exception of the lowest growth rate for L2 rabbits (P < 0.001) that impaired their slaughter yield. Total aerobic bacteria of the caecal content increased with L inclusion level (P < 0.05). Rabbits of the L6 group exhibited the highest carcass weight with higher proportion of the mid part of the carcass (P < 0.01), but to the detriment of the hind part (P < 0.05), compared to the C group rabbits. Liquorice dietary inclusion level significantly increased dissectible fat proportion on the chilled carcass, due to the increase of perirenal fat depot (P < 0.05). Sensory analysis on the loin meat did not reveal differences in the considered attributes due to the dietary treatment. The L6C and L6L burgers exhibited the lowest microbial growth (particularly Pseudomonas) during refrigerated storage. In conclusion, live performance traits of rabbits seem not to benefit from the dietary supplementation of liquorice extract. However, the dietary inclusion was more effective than the incorporation into meat as antimicrobial on meat burgers. The combination of dietary and in-meat supplementation of liquorice extract exhibited the most effective antimicrobial effect.