Karapetkov N., Karaivanova E., Georgieva R., Surdjiiska S.
Lactina Ltd., Bulgaria

The aim of the study was to demonstrate the efficacy and tolerance of a probiotic preparation based on viable cells of the strains Lactobacillus acidophilus NBIMCC 8242, Lactobacillus bulgaricus NBICCM 8244, Lactobacillus helveticus NBIMCC 8269, Lactobacillus lactis NBIMCC 8250, Streptococcus thermophilus NBIMCC 8253 and Enterococcus faecium NBIMCC 8270 by targeting sensitive parameters in comparison to a negative control group and by evaluating the short-term toxicity of the strains. This broad range of bacteria was selected hopping to achieve an extensive beneficial effect in the target animals.

The study included the offspring of twelve rabbit’s mothers (Californian rabbit breed), which were aligned by age and weight. The experimental design consisted of four groups: one control without supplementation of the probiotic feed additive and three experimental units (300, 500 and 700 g probiotic mixture/t feed). The weaning of the rabbits took place on the 35-th day, when their gender was determined and they were sorted in cages for fattening. The duration of the experiment was 77 days. The tolerance study included three groups: a control group and tolerance groups with the ten-fold of the hundred-level of the optimal recommended dose.
During the trial, the following indicators were controlled:
- Survival rate of the rabbits - daily by groups;
- Bodyweight on first day, seventh day, 35-th day, at weaning, on 56-th day and on 77-th day;
- Feed consumption per unit of growth;
- Pathoanatomical examination of the carcasses and the internal organs.

The addition of six lactic acid bacteria strains to the feed of the animals led to a significantly higher bodyweight when applied at 700 g/t in the pelleted feed from birth to the weaning on 35-th day compared with the control group by 8,5% (P <0,05). The bodyweight of the rabbits at 56 days of age was also positively influenced. The difference of 7.3% compared to the control group was statistically significant (P <0,05). The feed consumption per 1 kg live weight gain in all experimental groups was lower than the control group by 12% to 14% (P <0.01).
The tenfold and hundredfold increase of the recommended optimal dose of the feed additive did not adversely affect the taste of the feed, the appetite of rabbits and the daily feed consumption. The pathological examination conducted with the slaughtered rabbits showed no changes and negative effects. The use of the probiotic mixture is therefore presumed safe for the target species. During the test period there were no dropped out rabbits neither in the control group, nor in the other experimental groups.

The experiment showed that supplementation of the feed with the mixture of six lactic acid bacteria strains to the fodder of the animals has a potential to increase the live weight of the rabbits, to improve the feed conversion and decrease morbidity. All these effects are probably due to the modulation of the intestinal microbiota of the animals. Further studies are required to clarify the exact mechanism of action.

Keywords: Probiotic feed additive, Probiotics, Rabbits, LAB, Feed conversion, Live weight gain

Karapetkov N., Karaivanova E., Georgieva R., Surdjiiska S. (2016). Efficacy and tolerance of six lactic acid bacteria strains in trials with rabbits.  Conference Proceedings of IPC2016. Paper presented at the International Scientific Conference on Probiotics and Prebiotics, Budapest (p. 101.). IPC2016

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