INTRODUCTION

Mountain microorganisms (MM), also called beneficial microorganisms, are present in natural ecosystems little affected by anthropic factors, where photosynthetic bacteria, lactic acid bacteria (LAB), yeasts and actinomycetes have been identified (^{Campo et al., 2014};^{Ramírez et al., 2016}) which by growing in an adequate amount of organic matter secrete beneficial substances that inhibit or control the growth of populations of pathogenic microorganisms (^{Cóndor et al., 2007}).

The Lactobacillus, Pediococcus, Leuconostoc, Enterococcus, Lactococcus and Streptococcus genera produce Lactic Acid (LAB) and they are present in the epiphytic microflora of plants (^{Garcés et al., 2004}). On the other hand, the genus Bacillus, from the gastrointestinal content of various animal species or their feces, is the most widely used as probiotics and growth promoters in animal production (^{Sánchez et al., 2015}). Bacillus spp are facultative aerobic bacteria that ferment a wide range of carbohydrates and they are used to inhibit the aerobic spoilage process in silages due to their ability to produce fungicidal substances, however, they are less effective as producers of lactic and acetic acid in comparison with LAB (^{Garcés et al., 2004}; ^{Layton et al., 2011}).

On the other hand, silage is the fermentation process of soluble carbohydrates in forage by means of bacteria that produce lactic acid under anaerobic conditions (^{Garcés et al., 2004}). Through controlled anaerobic fermentation, the composition of the ensiled material is stable for a long time through the acidification of the material used, thus minimizing undesirable secondary fermentations such as alcoholic fermentation, produced by yeasts, which are a toxicity hazard for cattle and butyric fermentation produced by the genus Clostridium (^{Garcés et al., 2004}).

For an optimal and controlled fermentation to exist, the proper ratio between lactic acid bacteria and soluble carbohydrates is necessary. Different additives can be used to induce and optimize the fermentation process, such as molasses, citrus pulp or crushed corn, which provide a source of soluble sugars that the bacteria use to produce lactic acid, thus stabilizing the medium (^{Valencia et al., 2011}). The silage process does not improve the quality of the forage, it only preserves its nutritional value, such as the energetic and protein components through fermentation processes and keeping it stable for a long time (^{Villa and Hurtado, 2016}).

The use of probiotics contributes to the intestinal microbial balance, stimulating the immune system of the animal, producing organic acids, bacteriocins and enzymes that favor the absorption of nutrients, improving the productive parameters (^{Gutiérrez et al., 2014}).

Many studies have been published about probiotics and their different effects, in the case of rabbit production. However, the guarantee of success in rabbits is given by the expected productive results. Rabbits are characterized by their ease of handling, rapid reproduction and obtaining a quality animal protein, which places rabbit farming in a place that favors small and medium-scale production. Rabbit meat represents great advantages, with an adequate balance of fatty acids, protein, vitamins and minerals, low in cholesterol and sodium (^{Para et al., 2015}).

According to data from the National Institute of Statistics, Geography and Informatics (INEGI) the states with the highest production of rabbits are Hidalgo, Puebla, Tlaxcala, States of Mexico and Guanajuato. The development of rabbit farming in Mexico is limited by the lack of official support, coupled with an inadequate management of health and nutrition, in addition to the little promotion of the benefits of rabbit meat, reflected in a low per capita consumption, between 38 and 134 g during 2008 and 2009 (^{Armada, 2016}) (^{Armada 2016}), despite the great advantages from the nutritional point of view (^{Coreno et al., 2017}). The objective of the present work was to evaluate the use of mountain microorganisms in corn silage as probiotics in the fattening of rabbits.

MATERIAL AND METHODS

The present study was carried out at the Salvatierra Headquarters of the University of Guanajuato, located in Salvatierra, Guanajuato, Mexico (20° 12'45.51 "N, 100° 52'30.09" W, at 1,749 m a.s.l) (^{Google Earth, s.f}). The experiment was carried out with hybrid rabbits of the California breed of 30 days of age and similar weight. Each one was housed in individual cages provided with a trough and trough. The experiment lasted four weeks.

RESULTS AND DISCUSSION

The number of total microorganisms present in the liquid phase of MME expressed in CFU/mL are shown in table 1. The results show an increase in the number of microorganisms as time passes, obtaining a total count of 9 X 10⁷ CFU/mL over a 72 hour period.

^{Guo et al. (2017)}, when supplementing with 10⁵, 10⁶ and 10⁷ CFU/g of Bacillus subtilis the diet of rabbits, they observed a better performance in weight with the supplementation of 10⁶ CFU/g. On the other hand, ^{Phuoc and Jamikorn (2017)} supplemented the diet of rabbits with 1X 10⁷ CFU/g of B. subtilis, 1X 10⁷ CFU/g of L. acidophilus or a combination of them at a concentration of 0.5 X 10⁷ CFU/g, suggesting that dietary supplementation with these microorganisms has probiotic benefits in rabbits. In the present work, a total number of 9 x 10⁷ CFU/mL was obtained, a quantity of microorganisms similar to the aforementioned works and that may have a probiotic potential when supplied in drinking water for rabbits.

The results of weight gain and feed conversion are presented in table 2. Statistically, no significant differences are observed between the two treatments with respect to weight gain. However, it can be noted that, in relation to feed conversion, there are significant differences between treatments, with T1 being the treatment with the highest feed conversion 5.65 ± 0.6. ^{Gutiérrez et al. (2014)}, fed pigs with native probiotic microorganisms, reporting that there was no statistically significant difference in weight gain and in relation to feed conversion and that the treatment that had the best conversion profile was to which no probiotic microorganisms were added.

According to ^{Villa and Hurtado (2016)} rabbits fed with silages obtain the highest weight gain, than animals fed with only fresh forages, within the lactic acid bacteria present in the silage and the MM are the genera Lactobacillus, Streptococcus and Bifidobacterium, which produce organic acids, bacteriocins, preservatives, vitamins, sweeteners, flavorings, flavors, antioxidants, among others ^{(Parra, 2010)} that contribute to improving animal production, in relation to parameters of quantity and/or composition of milk, body condition, live weight gain and reproductive development (^{Phipps et al. 2000)}.

In Figures 1 and 2, the variability of the treatments can be observed. In figure 1 it can be seen that the maximum weight gain in T1 was 0.211 kg and the minimum was 0.135 kg, in relation to treatment 2, the maximum weight gain throughout the evaluation time was 0.262 kg and the minimum was 0.167 kg. Figure 2 shows the variability of feed conversion in rabbits treated with and without mountain microorganisms. The maximum feed conversion was 6.22 and the minimum was 4.8 for treatment 1, while for treatment 2 the maximum feed conversion was 4.2 and the minimum was 2.9.

Figure 1 Distribution of average weights in rabbits treated with and without mountain microorganisms 

Figure 2 Distribution of feed conversion averages in rabbits treated with and without mountain microorganisms 

CONCLUSION

The mountain microorganisms obtained from ecosystems little affected in an anthropogenic way are a source of lactic acid producing bacteria, which can improve the nutritional value of the silage and be used as probiotics in drinking water, increasing the performance in the rabbit fattening process, in order to stimulate the development of rabbit breeding techniques in Mexico, and to suggest methods for characterizing lactic acid producing microorganisms.