Effect of level and source of vitamin E addition of a diet enriched with sunflower and linseed oils on growth and slaughter traits of rabbits

As part of a trial to improve the fatty acid profile, vitamin E content and shelf-life of rabbit meat, this work studied the effects of level and source of vitamin E dietary addition on growth and carcass traits in NZW rabbits. A 10.6 MJ/kg digestible energy diet without added oil and with 60 mg/kg synthetic vitamin E (dl-α-tocopheryl-acetate) served as a control (C). Five other diets were 4% oil-enriched, i.e. with 2% sunflower and 2% linseed oils and so having slightly higher digestible energy contents (11.4 MJ/kg) than the C feed. In three oil-rich diets, only synthetic (S) vitamin E was used at 60, 150 or 300 mg/kg concentration (diet 60-S, 150-S or 300-S, respectively). In two oil-rich diets, 60 mg/kg synthetic plus 90 mg/kg or 240 mg/kg natural (N) vitamin E (a fatty acid distillate, i.e. d-α-tocopherol) were used to reach the 150 mg/kg (diet 150-SN) or 300 mg/kg (diet 300-SN) level of added vitamin E contents. In each group, 11 litters of 7 to 9 kits were studied in the pre-weaning period from 21 to 35 days and post-weaning to harvest at 84 days (n = 46–50). Litter and doe performance were poorer in the 300-SN rabbits than with lower levels of vitamin E. Compared to the C rabbits, the 35–84-day mortality was significantly higher only in the 60-S rabbits. The 84-day final weight of the 300-S and 300-SN rabbits was higher than the controls (2745 and 2733 vs 2594 g, P = 0.049). The 35–84-day feed conversion of the C rabbits was poorer than any other rabbits (3.3 vs 3.0–3.1, P = 0.001). Carcass traits were assessed with sub-samples of 15 rabbits per group and were differently affected by both the level and origin of added vitamin E. Chilled and reference carcass weights (P = 0.001) and dressing out percentages (P = 0.001) were higher in the 60-S and 150-S than in the C, 300-S and 150-SN rabbits. Considering all traits studied, the 150 mg/kg synthetic vitamin E dietary addition was best for maximising production. However, the effects on meat quality and shelf-life should also be considered to give correct practical advices. Our results confirm the importance of both the level and source of vitamin E when it is used as a dietary additive in oil-enriched diets.