Introduction
Yeast as the beneficial fungi genera has been widely used in animal husbandry production. And yeast is one of the most commonly supplemented in the dietary for improving nutritional strategies (Jiang et al., 2015). Live yeast dietary supplementation in weaning piglets enhanced intestinal morphology and growth performance (Bontempo et al., 2006). Saccharomyces cerevisiae is the predominant species used in food, beverage (distilled spirits and beer), and fuel ethanol production processes, where selected strains convert glucose and sucrose to ethanol (Reed and Nagodawithana, 1991). Saccharomyces cerevisiae is a non-pathogenic yeast. Yeast based products consist of products of fermentation, residual yeast cells, yeast cell wall fragments, and the culture used during fermentation (Shen et al., 2011). The report on Sauerwein et al. (2007) suggested that yeast cell wall supplemented in the diet of weaning piglets and fattened pigs diet, improved acquired immunity and growth performance. Yeast cultures supplemented in pigs, enhance gut immune response and nutrient digestibility (Shen et al., 2009). The pigs’ gastrointestinal microbiota is primarily composed of not only Gram-positive bacteria, such as aerotolerant Streptococcus, microaerobe or obligate anaerobe Lactobacillus, Bifidobacterium, obligate anaerobe Peptostreptococcus, Clostridium, but also obligate anaerobe Gram-negative bacteria such as Fusobacterium, Bacteroides, Selenomonas, Butyrivibrio, Prevotella and Salmonella, facultative anaerobe Escherichia (Gaskins, 2000). It has been reported that about 11% of mortality rate in post weaning piglets were due to the incidence of diarrhea (Owusu-Asiedu et al., 2003). The application of Saccharomyces cerevisiae fermented product for weaned pigs during Salmonella infection, had a positive effect on improved growth performance (Price et al., 2010).
In view of Saccharomyces cerevisiae advantages in swine, the aim at the present study was to investigate the effect of brewer’s yeast (Saccharomyces cerevisiae) supplementation on growth performance, nutrient digestibility and fecal score of growing pigs.
Materials and methods
Preparation of brewer’s yeast hydrolysate (Saccharomyces cerevisiae)
The brewer’s yeast used in the experiment was provided by Plantinum Brewery company (Seoul, Korea). The hydrolysated brewer’s yeast production contains 4,240 kcal·kg-1 digestible energy (DE), 53.2% crude protein (CP), 1.8% crude fat (ether extract), 5.2% ash. The main compounds of brewer’s yeast hydrolysate are presented in Table 1.
Animals, experiment design, diets and facilities
In total 60 pigs (Duroc × [Landrace × Yorkshire]) with an average 25.50 ± 1.63 kg were selected and randomly allotted to two treatment groups with 6 replications of 5 pig per replicate pen for each treatment. The experiment treatments were as follows: 1) control basal diet (CON); 2) 1.00% brewer’s yeast, basal diet with 1.00% brewer’s yeast. The diets were based on the nutrient requirements recommended by NRC (2012) (Table 2). They were fed treatment diet for 6 weeks. Pigs were housed in environmentally controlled rooms at 23 ± 1℃, each pen provided a self-feeder and nipple drinker.
Sampling and measurement
The individual body weight (BW) of pigs and feed consumption from each pen were determined at the start, week 4 and week 6 of the experiment to calculate the average daily gain (ADG), average daily feed intake (ADFI), and gain : feed ratio (G/F). Chromium oxide (Cr2O3) was added to the diet at 0.2% of the diet as an indigestible marker for 7 days prior to fecal collection on weeks 6 to calculate dry matter (DM), nitrogen (N) and energy. Fecal score based on the standard of 5 grade score system: 1-standing for hard, dry pellets in a small, hard mass, 2-hard formed stool that remains firm and soft, 3-soft formed and moist stool that retains its shape, 4-soft unformed stool that assumes the shape of the container, 5-watery liquid stool that can be poured (Hu et al., 2012). The fecal score was determined as the average value of five pigs of each pen.
Data analysis
All data obtained in the current study were analyzed in accordance with a completely randomized block design using the GLM procedure of SAS (SAS Institute, 1996). Duncan's multiple range test was used to compare the means of the treatments. Variability in the data is expressed as the standard error (SE) and a probability level of p<0.05 was considered statistically significant.
Results
Growth performance
Dietary supplementation with brewer’s yeast led to a significant improvement (p<0.05) in BW at weeks 4 and 6, and higher ADG and G/F during week 4 and overall compared with CON, however, ADFI remained unaffected (Table 3).
Nutrient digestibility
The effect of brewer’s yeast supplementation on the apparent total tract digestibility (ATTD) of DM, N and energy is shown in Table 4. Compared with CON, brewer’s yeast supplementation increased the ATTD of DM (p<0.05), also no effected on N and energy digestibility.
Table 4. Effect of brewer’s yeast on nutrient digestibility in growing pigs.
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CON, the control; Brewer’s yeast, 1.00% Brewer’s yeast; SEM, standard error of means. |
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Fecal score
The fecal score in pigs was not affected with brewer’s yeast supplementation compared with those fed control diet (Table 5).
Discussion
Studies involving yeast products have reported increased growth performance of nursery pigs (Shen et al., 2009), improved ADG in weaned piglets (Liu et al., 2018). This shows that Saccharomyces cerevisiae supplementation in pig diet has positive effect of growth performance (Shen et al., 2009). In the present study also, the ADG and G/F was improved on pigs receiving brewer’s yeast supplemented diet. So, these results showed that brewer’s yeast supplementd in the diet not only promoted the growth of weaning pigs, but also promoted the growth of growing pigs. Yeast derivatives typically contain a complex of manna oligosaccharides (MOS), polysaccharides and β-glucans (Hasan et al., 2018). These polysaccharides not only interact directly with immune cells (Ruiz-Herrera, 2016), and also had positive effects on feed intake (Hiss and Sauerwein, 2003; Sauerwein et al., 2007). Although there was no significant difference on ADFI, but the performance tends to increase during the experiment. The variable response to yeast could be due to dose of yeast, types of yeast strain used for preparing the extract, procedure for animal physiological status and farm conditions.
The ATTD not only reflects the utilization of nutrients, but also reflects the growth performance of growing pigs. Shen et al. (2009) demonstrated that the supplementation of yeast in weaning pigs’ diet, improved digestibility of DM. Digestibility measurements were made at the fecal level, and therefore, through absorption and bacterial assimilation of nutrients in the small and large intestine calculations include disappearance of nutrients. Van Heugten et al. (2003) reported that yeast supplementation had a positive effect on pig digestibility. But from this data, the total tract digestibility no significant effect, and the result was similar with Pinloche et al. (2012). Liu et al. (2018) and Li et al. (2019) reported that supplementation with yeast cultures on weaning pigs, the total tract digestibility also has no significant difference. It may the microbiota have relatively stable due to the age of pigs in our experiment. So a suitable dose of yeast may require to initiate a shift in the microbiota.
Collier et al. (2011) reported oral administration of Saccharomyces cerevisiae reduced mortality for infected E. coli in weaned piglets. Polysaccharides were the major components of yeast and yeast cell wall products (Kogan and Kocher, 2007). Polysaccharides not only interacted directly with immune cells, but also were able to bind bacteria to prevent attachment and colonization of pathogens in the gastrointestinal tract (Broadway et al., 2015; Ruiz-Herrera, 2016). So, yeast had positive effects on improved intestinal microbiota and preventd diarrhea. Although there was no significant difference in fecal score compared with the control group in this experiment, but there was a tendency to improve fecal matter in our experiment, which may relate to the relative stability of intestinal microorganisms in the experimental animal group.
