Introduction
The amount of feed accounts up to 70% of entire production costs, and the agricultural and industrial byproducts are evaluated as feed ingredients to reduce the costs (Ewan, 2001). Corn-Soybean meal (SBM) based diets are commonly used as energy and protein sources in swine diets at South Korea. The consumption of agriculture residues and its byproduct in the past as substitutes to soybean meal in feeds was not effective due to high fiber content in those feeds which lead to poor digestibility in animals (Sayehban et al., 2016). The oligosaccharides in soybean meal have two α-galactosides (i.e., stachy-ose and raffinose) which was not metabolized in monogastric animals because of the absence of α-1,6-galactosidase enzyme activity in the intestinal mucosa (Gitzlemann and Auricchio, 1965). A soybean has oligosaccharides which increases the intestinal feed passage rate and lowers the fiber digestion. So, consideration is paid on enzyme application in livestock nutrition. Exogenous enzyme supplementation in Corn-SBM diet targets non-starch polysaccharides (NSP) and protein that consequently improves the digestion, weight gain in monogastric animals (Kim et al., 2006; Fang et al., 2007). It also absorbs energy and protein, reducing the feed costs (Jo et al., 2012). Further, improvement in growth performance and feed efficiency are due to increasing dietary energy from the added enzyme. Whitney et al. (2006) and Ying et al. (2011) stated that growth performance was improved by the enzyme-based liquid supplementation in pigs. Balasubramanian et al. (2020) showed that enzyme blend supplementation could increase body weight (BW) and average daily gain (ADG) in grower-finisher pigs. Therefore, our present study was to investigate the influence of enzyme mixture supplementation on growth performance and fecal score of growing pigs.
Materials and method
Source of feed additive and animal ethics
In this study, a commercial product (Alcopro®, Simco Nutrition Group™, Irvine, California, CA, USA) containing about 10,000 kcal·kg-1 metabolizable energy (ME), high energy source ingredients (corn distillers condensed soluble and ethyl alcohol) and a natural digestive enzyme mixture (glucoamylase from Aspergillus niger, alpha-amylase from Bacillus stearothermophilos, lipase, maltase, cellulose, protease) were used. The energy supplementation quantity used as diet was based on the guidance level given by the manufacturer. The product supplemented to the animal was not oxidized or rancid and was a stable liquid in storage. The experiment protocol was reviewed and approved by the Animal Care and Use Committee of Dankook University (DK-1-2006), Cheonan, Republic of Korea, for animal experimentation.
Animals and facilities
A total of 72 crossbred growing pigs (Landrace × Yorkshire × Duroc) with an initial average weight of 20.23 ± 1.46 kg (Mean ± SE) were used in 19-days experimental trial. Growing pigs were divided into pens according to their initial body weight, 4 pigs per pen. Eighteen pens were randomly assigned to 2 treatments, where each pen was counted as one replication and each treatment had 9 replications. Pigs were fed a basal diet (control) and the basal diet supplemented with 0.5% enzyme mixture. The corn-soybean meal diet was formulated as per recommendation of NRC (2012) (Table 1). Pigs were caged in a thermostatically controlled ambient environmental temperature (25℃) with the slatted plastic floor and equipped with one side self-feeder and nipple drinker. Each pig was individually identified by using tags and the feed and water were provided by ad libitum throughout the experimental period.
Sampling measurements
BW was measured at initial, 4th day, 14th day, and 19th day. To calculate the ADG, average daily feed intake (ADFI) and feed conversion ratio (FCR), the feed consumption was recorded on a pen basis. To calculate apparent total tract digestibility (ATTD) of dry matter (DM), nitrogen (N), and energy, 0.20% chromium oxide was added to the diet as an indigestible marker for 7 days prior to fecal collection at day 19. Fecal samples were collected randomly from at least 2 pigs (1 barrow and 1 gilt) per pen then pooled with representative sample and stored in a freezer at -20℃. All feed and fecal samples were freeze-dried and finely ground to pass through a 1 mm screen. DM and N amounts were determined using methods established by the Association of Official Analytical Chemists (AOAC, 2000). UV absorption spectrophotometry (UV-1201, Shimadzu, Kyoto, Japan) was used to determine chromium in the diets. The energy was determined by using a Parr 6100 oxygen bomb calorimeter (Parr Instrument Co., Moline, Illinois, USA). The apparent total tract digestibility was calculated using the following formula: digestibility (%) = [1− {(Nf × Cd)/ (Nd × Cf)}] × 100, where Nf = nutrient concentration in faeces (% DM), Nd = nutrient concentration in diet (% DM), Cd = chromium concentration in diet (% DM), and Cf = chromium concentration in faeces (% DM). The fecal score was measured and recorded at 4th day, 14th day and 19th day and it was determined by the following 1 = 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. Fecal Scores and signs of stool consistency were recorded on a pen basis of an individual pig.
Statistical analysis
All data were statistically analyzed by t test using SAS program (SAS Inst. Inc., Cary, NC, USA). Results were considered significant at p < 0.05 level and p < 0.10 was considered as a trend.
Results and Discussions
The present research was aimed to evaluate the effect of an enzyme mixture supplementation on growing pig’s growth performance, nutrient digestibility and fecal score. According to the studies of Balasubramanian et al. (2020) enzyme blend supplementation had positive influence on BW, ADG and gain : feed (G : F) in grower-finisher pigs. The xylanase, amylase and protease enzyme had improved the digestion and ADG in monogastric animals (Fang et al., 2007; Moehn et al., 2007; Nortey et al., 2007; Li et al., 2010). Enzyme mixture supplementation on growing pig’s growth performance was shown in Table 2. The enzyme mixture supplementation had tendency to increase ADG during day 14, day 19 and overall period with 0.5% enzyme mixture supplementation to the basal diet (p < 0.10) and no significant effects on ADFI. This result is suited for low energy composition of the diet and Kerr et al. (2003) reports it was concluded that the diet has a change in energy content which is lower than 124 kcal which is not suitable for the feed intake. There was no influence on BW during overall experiment with the addition of enzyme mixture supplementation. However, earlier studies indicated contrary results, that dietary enzyme mixture liquid feed additive had no effect on growth performance in nursery pigs (Ying et al., 2012). These inconsistent results in the study were due to amount of dosage given to the experimental animal, their health status, breed and differences in dietary compositions. Xylanases have been a preferred choice for enhancing nutrient digestibility due to their advantages such as enabling access to trapped nutrients to digestive enzymes and their action of cell wall degradation (Woyengo et al., 2008). Previously, Balasubramanian et al. (2020) and Li et al. (2010) reported that enzyme blend supplementation had positive effect on nutrient digestibility of DM and energy. But the present study revealed that dietary inclusion of enzyme mixture supplementation in growing pigs had no significant effect (p > 0.05) on nutrient digestibility of DM, N, energy (Table 3). The reason for the absence in nutrient digestibility is due to the better development of digestive system as pigs become older (Hoque and Kim, 2021).
Lan et al. (2017) reported that fecal score was decreased in weaning pigs when xylanase supplementation was added in diet. In contrary, the present study (during 4th day, 14th day, and 19th day) showed no significant difference (p > 0.05) on fecal score associated with the inclusion of enzyme mixture supplementation (Table 4). In addition, the present study did not test the fecal microbiota. An excess of coliform bacteria which is present in the gastrointestinal system causes diarrhea, that leads to a decline in the growth performance in domesticated animals. If the microbiota balance in the gut can be optimized it may enhance the utilization of nutrients and reduced fecal score. Hence, more studies are needed with different levels of enzyme mixture supplementation to know the exact cause for the absence of a substantial change in fecal score and growth performance.
Conclusion
The present study will be the base of our future research. The supplementation of enzyme mixture had beneficial effects on ADG of growth performance but failed to show the significant effect of growth performance (BW), nutrient digestibility and fecal score. On other hand further research with different standards of enzyme mixture is required to understand the influences of enzyme mixture in growing pigs.
