Several alternatives to replace antibiotics as animal growth promoters are currently being explored. These include biotherapeutic agents (probiotics, prebiotics and symbiotic), classified as products of natural origin, beneficial for health, with active biological properties and preventive and therapeutic capacity (Blanch et al. 2015, Corzo et al. 2015 and Pandey et al. 2015).
Different research projects were carried out for the development of probiotic products at the University of Matanzas, which improve animal productive performance and health (Milián 2009 and Rondón 2009). PROBIOLACTIL® is one of them, which is a biopreparation made with Lactobacillus salivarius C65 strain. Its effect was evaluated in poultry and pigs with excellent results in improving productive indicators and health of these animals (Rondón et al. 2012, Rondón et al. 2013 and Rondón et al. 2018). However, the potential of this biopreparation in lactating calves, which are at a critical moment after separation from their mother, has not yet been evaluated. Frequently, these animals have diarrhea that can lead to live weight decrease and even death.
During weaning in rearing animals, calves are susceptible to enteric disorders caused by changes in diet and imbalances of the digestive microbiota, which, together with deficiency diseases and disorders in immunity, favor the appearance of health issues, with the consequent effect on productive indicators and delay in the incorporation of animals to development units (Rondón et al. 2019).
In recent years, Lactobacillus salivarius has been used as a probiotic for its high growth capacity and production of lactic acid and short-chain fatty acids (SCFA) (Sayan et al. 2018 and Seo et al. 2019). Instead, it is unknown whether this bacterium grows in the feed provided to calves during artificial rearing, or if it develops any fermentative activity in this supplement.
To carry out this research, the objective was to evaluate in vitro metabolic activity of Lactobacillus salivarius and its probiotic effect on productive and health indicators in lactating calves.
Materials and Methods
Biological material and culture media. Lactobacillus salivarius C-65 strain was used, isolated by Rondón et al. (2008) from cecum mucosa of broilers. It was obtained from the strain collection of the Centro de Estudios Biotecnológicos (CEBIO) of the University of Matanzas. Agar and MRS broth (CONDO, Spain) were among the culture media used (De Mann et al. 1960).
For metabolic activity characterization of Lactobacillus salivarius C-65, the tests described below were performed.
Cellulose hydrolysis. Lactobacillus salivarius C-65 was cultured on dishes with MRS agar, to which glucose was replaced by 1% carboxymethyl cellulose. They were incubated for 48h at 37ºC. Hydrolysis halos were developed with a 1% Congo red solution, exposed for 15 min. Subsequently, excess dye was removed and washed with a 2 mol. L-1 NaCl solution (Lu et al. 2006).
Determination of carbohydrate fermentation capacity and production of specific enzymes. A strain culture was prepared in MRS broth (Condo, Spain) and incubated at 37 °C for 24 h. Cultures were centrifuged and washed in saline solution (0.9% NaCl), and from this moment on, the methodology described for API 50 CH, API 50 CHL and API -ZYM galleries was followed (BioMerieux, S.A., France).
Determination of in vitro growth capacity and fermentative activity of Lactobacillus salivarius C-65 in RALTEC ® Milk 17-1 milk replacer for calves. An experiment with a completely randomized design and three repetitions was performed. Growth kinetics of L. salivarius C-65 was developed in the milk replacer for 10 h at 37 ºC. For this, the milk replacer was diluted at a rate of 100 g.L-1 of drinking water at 55ºC, distributed into 18 Erlenmeyers, of 250 mL with 100 mL of effective volume. These were sterilized at 121 °C for 15 min. Subsequently, they were inoculated at 10% with bacterial culture, grown in MRS broth at 37ºC for 18 h. To determine the growth every two hours, the method of serial dilutions in peptone water of (1%) and plating with MRS agar (Harrigan and McCance 1968) were used. The pH was also determined using a digital pH meter (Sartorius Meter PP-25), as well as total reducing sugars (TRS), using the 3.5 dinitrosalicylic acid method (Miller 1959).
The milk replacer contains whey powder, lard, lactose-free whey powder, soy protein concentrate (genetically modified), lactalbumin powder, wheat gluten, and pregelatinized wheat starch. Table 1 describes the analytical components of this milk replacer.
Components | % |
---|---|
Crude protein | 21 |
Crude fiber | 0.7 |
Crude fats and oils | 17.30 |
Crude ash | 7.00 |
Calcium | 0.65 |
Sodium | 0.40 |
Phosphorous | 0.55 |
For evaluating the probiotic effect PROBIOLACTIL® on the productive and health indicators in lactating calves, an experiment was developed in which the following aspects were considered:
Preparation of the biopreparation. The probiotic additive was prepared according to the methodology described by Rondón (2009) for PROBIOLACTIL®.
Experimental design. The experiment was carried out for eight weeks in Recría 306, belonging to the Empresa Pecuaria Genética de Matanzas. A completely randomized design was used and 45 male Mambí de Cuba calves were used, from seven weeks (50 d) of age. Three treatments were organized with 15 animals each: Group I-Control; Group II, 10 mL of PROBIOLACTIL® per kg of food and Group III, 20 mL of PROBIOLACTIL® per kg of food. Productive and health indicators, such as live weight and weight gain, daily mean gain (DMG) and diarrhea incidence, were weekly evaluated.
Management and feeding conditions. Before calves were transferred to a rearing experimental unit, dedicated to weaning animals, it underwent a sanitary fitting out according to IMV (1998). A basal diet was supplied, prepared from the complete lactation concentrate/RALTEC Milk 17 or milk replacer (diluted in drinking water at 50-55 ºC for the intake of calves, in proportion of 100 g of food per liter of water, at a temperature between 38 and 40 ºC) and complementary lactation concentrate (Raltec 2019).
Statistical analysis. The data were evaluated by applying a simple analysis of variance model, with prior verification of normal distribution of data and of variance homogeneity. In case of differences, Duncan (1955) comparison test was applied. All tests were performed using INFOSTAT statistical program, 2012 version (Di Rienzo et al. 2012). To statistically analyze the results of diarrhea incidence, the ComparPro program, version 1, was used (Font et al. 2007).
Results and Discussion
In vitro characterization of the metabolic activity of Lactobacillus salivarius C-65 was performed. Table 2 shows the results of carbohydrates fermentation by this bacterium. Of the evaluated substrates, the strain used 14 of them. This result indicates that the microorganism under study has enzymatic batteries, in charge of catalyzing the fermentation of different carbohydrates.
Carbohydrates |
|
Carbohydrates |
|
---|---|---|---|
Control | - | Arbutin | - |
Glycerol | - | Esculin | - |
Erythritol | - | Salicin | - |
D-Arabinose | - | Cellobiose | - |
L-Arabinose | - | Maltose | + |
Ribose | - | Lactose | + |
D-Xylose | - | Melibiose | + |
L-Xylose | - | Sucrose | + |
Adonitol | - | Trehalose | + |
α-Methyl-D-xyloside | - | Inulin | + |
Galactose | + | Melezitose | - |
D-Glucose | + | D-Raffinose | + |
D-Fructose | + | Starch | - |
D-Mannose | + | Glycogen | - |
L-Sorbose | - | Xylitol | - |
Rhamnose | - | α-Gentiobiose | - |
Dulcitol | - | D-Turanose | - |
Inositol | - | D-Lyxose | - |
Mannitol | + | D-Tagatose | - |
Sorbitol | + | D-Fucose | - |
α-Methyl-D-Mannoside | - | L-Fucose | - |
α-Methyl-D-Glucoside | - | D-Arabitol | - |
N-Acetyl-Glucosamine | + | L-Arabitol | - |
Amygdaline | - |
+ positive; - negative
Lactobacilli are demanding in terms of amino acids, peptides, nucleotides, vitamins, minerals, fatty acids and carbohydrates. They are classified as homolactic and hetero-lactic based on the fermentation route they use. Under conditions of glucose excess and limited use of oxygen, homolactic ones transform one mole of glucose through the Embden-Meyerhof-Parnas glycolytic pathway, to form two moles of pyruvate. Intracellular redox balance is maintained by NADH oxidation, with the concomitant reduction of pyruvate in lactic acid. This process generates two moles of ATP for each consumed mole of glucose (Jurado-Gámez et al. 2013).
L. salivarius C-65 was found to be a bacterium capable of using carbohydrates within the diet of animals, so once they are provided with food, they must participate in sugar degradation to produce, fundamentally, lactic acid. Hence, they are considered as homofermentative. This characteristic supports its selection as a probiotic because homofermentative cultures provide food with better organoleptic characteristics for human and animal consumption (Brizuela 2003).
Lactic acid bacteria are studied due to their ability to grow in difficult environments and generate antagonisms with other microorganisms. From these sugars, organic acids will be produced, such as lactic acid, which is one of the substances that inhibit the growth of pathogenic microorganisms (Jurado-Gámez et al. 2015). These results can be related to what happens at GIT level, because it is known that, in this ecosystem, microorganisms produce short-chain fatty acids (SCFA), product of the fermentation of many of these carbohydrates. These compounds are the main final products of bacterial fermentation, regulate the development and cell differentiation of the GIT, and have trophic or nutritional effects on the intestinal epithelium, which contributes to the recovery of inflammatory effects and to reduction of risks of bacterial translocation during alteration of the intestinal barrier (Kolb 1976).
For the above, if these bacteria are applied to diet, they would contribute to the contribution of SCFA as an energy source for animals, because these acids are produced in the GIT, metabolized in the mucosa and efficiently transported, so considerable amounts can reach the blood for later use. The contribution of SCFAs is considered to be 25-30% for energy requirements of pig maintenance, 50% for rabbits and 17% for poultry (Savón 2002). Therefore, if there is an increase of SCFA in the intestine, there will be greater bioavailability of these substances as energy sources (Rondón and Laurencio 2008).
It was also confirmed that Lactobacillus salivarius C-65 ferments lactose. It is known that this disaccharide cannot be assimilated in its natural form, so its hydrolysis is necessary to assimilate monomers it generates (glucose and galactose). The ability to produce β-galactosidase, responsible for hydrolysis in the small intestine, decreases as the individual grows. By the time the animal reaches it maturity, it is possible that it may have partially or totally lost hydrolysis activity in its intestine. This will cause that, when it consumes lactose, either in milk or its derivatives, it presents flatulence, abdominal pain, with or without diarrhea, which is called lactose intolerance (Sánchez et al. 2015).
Another important result is inulin fermentation. Some authors, such as Ayala et al. (2018), report that this substance stimulates the development of lactic acid bacteria. Rondón et al. (2019) developed a symbiotic biopreparation with Lactobacillus salivarius and henequen pulp (Agave fourcroydes Lem.), rich in inulin, and demonstrated that the application of this bioproduct in calves increased live weight and decreased the incidence of diarrhea in these animals.
Table 3 shows the production of specific enzymes by the strain. Out of 19 substrates present in the API-ZYM Tests, nine were used by L. salivarius. It was demonstrated that this bacterium has a strong catabolic action due to the production of peptidases (leucine, valine, and cystine aminopeptidase), phosphatases, phosphohydrolases, and galactosidases. Rada (1997) carried out an enzymatic study of several species of Lactobacillus and Bifidobacterium, including three Lactobacillus salivarius species, isolated from feces and caeca of poultry, and obtained similar results.
Substrata | Enzyme | |
---|---|---|
Control | Control | - |
2-naphthyl phosphate | Alkaline phosphatase | 2 |
2- naphthyl butyrate | Esterase (C1) | - |
2- naphthyl caprylate | Esterase lipase | - |
2- naphthyl myristate | Lipase (C14) | 2 |
L-leucyl-2-naphthylamide | Leucine arylamidase | 5 |
L-valyl-2- naphthylamide | Valine arylamidase | 4 |
L-cystyl-2- naphthylamide | Cystine arylamidase | 4 |
N-benzoyl-DL-arginine-2- naphthylamide | Trypsin | - |
N-glutaryl-phenylalanin-2- naphthylamide | α -chymotrypsin | - |
2-naphthyl-phosphate | Acid phosphatase | 4 |
Naphthol-AS-BI-phosphate | Naphthol-A-S-BI phosphohydrolase | 5 |
6-Br-2-naphthyl-aD-galactopyranoside | α -galactosidase | 4 |
2-naphthyl-bD-galactopyranoside |
|
5 |
Naphthol-AS-BI-bD-glucuronic |
|
- |
2-naphthyl-aD-glucopyranoside | α -glucosidase | - |
6-BR-2-naphthyl-bD-glucopyranoside |
|
- |
1-naphthyl-N-acetyl-bD-glucosaminide | N-acetyl- |
- |
6-BR-2-naphthyl-aD-mannopyranoside | α -mannosidase | - |
Numeric values are ranges of color intensity in the test, from 0 (-) (negative reaction) up to 5 (maximum activity)
It is stated that ingestion of lactic acid bacteria, which produce and release hydrolytic enzymes, may help the digestion of farm animals (Seifert and Gessler 1996). The evaluated strain produces β-galactosidase, which is an enzyme that contributes to lactose digestion in the GIT, especially in newborn mammals that consume mother’s milk (Marteaum et al. 1997). In addition, it was found that this bacterium does not produce β-glucuronidase and β-glucosidase, enzymes that generate the release of toxic or carcinogenic substances, out of harmless complexes in GIT (De Ross and Katan 2000).
Figure 1 shows the result of cellulose decomposition test by Lactobacillus salivarius C65. The image shows the hydrolysis halo around the colony grown in MRS agar with carboxymethyl cellulose as carbon source.
There are only few studies on cellulolytic activity of Lactobacillus spp. in the consulted literature. Herdian et al. (2018) reported that some LABs, such as Pediococcus acidilactici MK 20, isolated from the colon region of an Indonesian duck named Mentok, selected for the highest cellulolytic activity. Other authors, such as Frediansyah and Kurniadi (2017), observed the cellulases produced by Lactobacillus plantarum, using cassava (Manihot esculenta) meal as a substrate.
The manifestation of this characteristic has great significance because it indicates that this bacterium is capable of producing enzymes that intervene in cellulose decomposition, which is present in the cell walls of plants. It is known that animals do not produce these substances, so they require cellulolytic microorganisms from the tract to obtain these foods. Cellulose is the most abundant renewable carbon source on Earth. However, the structure of this polymer constitutes a physical and chemical barrier to access carbon, which limits its use. In nature, a small percentage of microorganisms can degrade it through the expression of cellulases (Gutiérrez et al. 2015). From these results, it would be possible to use this microorganism as an additive in silages, to improve grass conservation process.
Figure 2 shows in vitro growth of Lactobacillus salivarius C-65 in the RALTEC Milk 17-1 milk replacer for calves. It can be seen that, at 10 h, the two doses of this bacterium grew above 15 LN CFU.mL-1. It was verified that, at that time, there were differences between both treatments, when a higher count was found with the 20 mL inoculum.
These results agree with the previously demonstrated metabolic activity, since the milk replacer is enriched with different sugars and proteins that can be decomposed by these microorganisms. Hence, these bacteria could multiply in this food and, subsequently, colonize the digestive tract.
Figure 3 shows the effect of the two doses of PROBIOLACTIL® on TRS concentration and pH. The fermentative activity of this bacterium was verified, when observing the production of organic acids and intake of sugars within the milk replacer. Short chain fatty acids (SCFA) are known to decrease intestinal pH and inhibit the growth of some pathogens. They also promote the growth of intestinal cells and cell differentiation, which contributes to improving digestion and absorption of nutrients (Papadopoulos et al. 2017).
Dairy substitutes are offered up to advanced ages (between 90 and 120 d of age) in intensive artificial calf rearing systems in Cuba, which increases production costs, since part of the liquid feeding of these animals is guaranteed with imported milk replacers (Ybalmea 2015 and Alonso et al. 2016). The growth of microorganisms in these foods should improve their digestibility, by decomposing sugars and producing organic acids. These provide energy to animals, inhibit the growth of pathogenic microorganisms, nourish mucosal cells and solubilize minerals, with their consequent bioavailability and greater nutritional contribution (Nomoto 2005 and Uyeno et al. 2015).
Schneider et al. (2004) carried out the identification of lactic bacteria components of the typical microbiota of calves reared under artificial conditions. These authors demonstrated, by means of 16S DNAr sequence comparison techniques, the presence of Lactobacillus casei, L. salivarius and L. reuteri, indicating that L. salivarius is a native bacterium of this ecosystem.
Figure 4 shows the results of liveweight performance of animals during the seven weeks of the experiment. It can be observed that there were no differences among treatments.
Table 4 shows the differences in WG and DMG at the end of the experiment. The best results were obtained with treatment 2 (20 mL).
Indicators (kg) | Control | T1 (10 mL) | T2 (20 mL) | ±SE | P |
---|---|---|---|---|---|
WG | 8b | 13.71ab | 16a | 2.04 | 0.0351 |
DMG | 0.163b | 0.280ab | 0.326a | 0.041 | 0.0351 |
These results can be associated with the fact that probiotics and prebiotics, once supplied, induce, in the gastrointestinal tract (GIT), several mechanisms by which the balance of intestinal microorganisms is favored, and a better response of digestive processes is provided in the host (Flores 2015, and Uyeno et al. 2015).
According to these results, the importance of including native microorganisms in the diet of these animals to maintain the microbial balance is demonstrated (Yáñez et al. 2015 and Zhang et al. 2018). Probiotics, according to Sánchez et al. (2015), can endure specific conditions in the GIT. They resist for more than four hours to proteolytic enzymes, to low pH values (1.8-3.2) prevailing in the stomach and to bile concentration, pancreatic juices and mucus found in the small intestine, so that the colonizing microorganisms arrive in viable state and in sufficient quantities, once they overcome the acid and bile barriers in the digestive tract.
There is evidence that using probiotic microorganisms, mainly Lactobacillus spp. strains, whether monocultures or mixtures, increases nutrient retention in the diet. Apparent nutrient retention (amount of nutrients consumed minus amount of excreted nutrients) is favored when probiotics are used, mainly due to N, P and Ca retention (Ángel et al. 2005).
These results agree with those obtained by Zhang et al. (2017), who studied the effect of the probiotics Lactobacillus plantarum GF103 and Bacillus subtilis B27 in calves. These authors refer to improvements in nutrient digestibility and productive yields. Similarly, Malik and Bandla (2010) demonstrated that the administration of the probiotic Lactobacillus acidophilus improved daily weight gain and forage digestion efficiency.
Figure 5 shows the performance of diarrhea incidence in animals that consumed PROBIOLACTIL®, with respect to control group. It was found that 100% of animals that reached the rearing had diarrhea. However, from the second week onwards, no dysbiosis was observed in the animals of group III, and, during the third week, they did not appear in group II.
Signorini et al. (2012) and Marín et al. (2016) obtained similar results to those of the current study. These authors defined that the diarrhea index is in correspondence with the proportion of LAB: coliforms. This means that when coliform population is higher than LAB, dysbiosis occurs. Therefore, a systematic supply of Lactobacillus cultures during this stage will increase the population of these bacteria in the GIT, and diarrhea will decrease (Sayan et al. 2018).