Silvafeed® polyphenols: the right tool to control lipid oxidation in meat.
Rabbit meat stands out for its excellent nutritional properties, with lower fat and cholesterol content compared with other types of meat. However, the high proportion of polyunsaturated fatty acids renders rabbit meat more prone to oxidation, a major issue for meat quality and shelf life. Moreover, high ambient temperature is an important stress factor for rabbits, which may accelerate post-mortem changes of the muscle (e.g. higher ultimate pH, lightness and drip loss) and impair gut integrity.
The use of synthetic antioxidants for controlling rabbit product stability has raised concerns because of undesirable effects for consumers. Therefore, the meat industry is now considering alternatives such as diet supplements enriched in natural antioxidants. Silvafeed® ATX is a blend of polyphenols selected for their strong antioxidant properties.
The effects of Silvafeed® polyphenols on carcass traits, meat quality, welfare and live performances of rabbits were assessed under normal and high ambient temperatures.
Silvafeed ATX effects under high temperature:
New Zealand 45 day-old male rabbits were randomly assigned into three groups (n=40 single housed animals per group) for a feeding trial lasting 21 days. A basal diet was given ad libitum to rabbits maintained at 20 °C (control group at normal temperature) or at 33 °C (control group at high temperature). In the third group, the same basal diet was supplemented with Silvafeed® ATX and fed to rabbits kept at 33 °C.
Heat stress affected the oxidative stability of rabbit muscle, as shown with the TBARS values after 30 min of forced oxidation (Figure 2). The inclusion of Silvafeed® ATX allowed to reduce significantly lipid oxidation of muscle from rabbits maintained at 33 °C.
Figure 2. TBARS values of Longissimus lumborum muscle from rabbits non-supplemented (control) or supplemented with Silvafeed® ATX and reared at 20 or 33 °C.
After putting down the rabbits, in terms of meat quality, heat stress significantly affected pH 24h post-mortem (-0.7), cooking loss (+3.21%) and lightness (L*, +2.12) (P < 0.05). The values in Silvafeed® group were intermediate for these parameters (P > 0.05), therefore the undesirable effects were partly mitigated by Silvafeed® ATX.
Adding Silvafeed® ATX to the dietary treatment greatly improved animal performances compared with control rabbits kept at 33 °C (+13.6% daily gain; -16.6 % conversion rate; +4.6 % final bodyweight; P < 0.05). Moreover, the growth performances of rabbits in Silvafeed® group (33 °C) were not statistically different compared with control rabbits kept at 20 °C. Feed intake was not significantly different between the three groups. Overall, it showed that Silvafeed® ATX could alleviate adverse effects of high temperature on growth performances, more likely by the scavenging of reactive oxygen species and the prevention of damage on intestinal membrane.
Silvafeed® ATX effects under normal ambient temperature
Bianca Italiana 32 day-old male rabbits were randomly divided into two groups (n=24 single housed animals per group) for a feeding trial of 49 days. A commercial diet was offered ad libitum and was either not supplemented (control group) or supplemented with Silvafeed® ATX.
The inclusion of Silvafeed® ATX in the diet of rabbits showed a strongly positive antioxidant effect according to the iron-induced thiobarbituric-acid reactive substances (TBARS) method. In fact, Silvafeed® ATX reduced significantly the production of malondialdehyde (MDA) in the muscle, an indicator of lipid oxidation, in comparison with the control.
Figure 1. Average TBARS values of Longissimus thoracis et lumborum muscle from rabbits.
Under such conditions, Silvafeed® ATX did not influence the live performances of rabbits (feed intake, weight gain, conversion rate) compared with the control, nor the carcass characteristics (carcass and organ weights, dry matter, crude fat and protein contents), meat quality and the fatty acid composition of muscle (contents for saturated, monounsaturated and n-3, n-6 polyunsaturated fatty acids).
To summarise, the inclusion of Silvafeed® ATX in the diet of rabbits is an effective tool to reduce lipid peroxidation of the meat regardless of the rearing conditions. This is possible due to the scavenging of radicals and the activation of endogenous antioxidant system triggered by the polyphenols based product, characterised by its natural antioxidant properties. Moreover, Silvafeed® ATX shows great effectiveness to alleviate the detrimental effects of heat stress on the live performances and meat quality of rabbits.