Addition of protease in pig diets is a way to improve protein utilization. The main mechanism of dietary protease is to increase the hydrolysis of proteins in the small intestine , resulting in liberating amino acids and peptides for utilization and absorption by pigs . Previous studies showed that dietary protease in pig diets decreased the nitrogen (N) pollution by enhancing N digestibility of pigs and reducing N excretion of pigs [3–5]. In addition, enzyme cocktails including protease and other nutrient enzymes are commonly used in the swine industry to improve growth performance and nutrient utilization for pigs [6–14].
Probiotics are live microorganisms which have beneficial effects on the gut health of the host . Moreover, probiotics for farm animals have positive effects on growth, gastrointestinal ecosystem, efficiency of feed utilization, immune system, or gastrointestinal tract diseases . Probiotics may act directly on the host to enhance anti-pathogen defense line and to secrete certain probiotics agents that can adversely affect the survival of deleterious bacteria . Most microorganisms used as probiotics are common intestinal microbes such as Bacillus, Lactobacillus, or Bifidobacterium species . Previous studies reported that probiotics have beneficial effects on growth performance, nutrient digestibility, and etc. for pigs [19–22].
Recently, the swine industry has been trying to make some dietary mixtures using enzymes and/or probiotics to have their beneficial effects all together. There are some studies to verify the effects of dietary mixtures of enzymes and probiotics [2,10,23,24], but the experimental evidence for their positive or negative effects in pig diets is limited. Therefore, the objective of this study was to investigate effects of dietary mixture of protease and probiotics on growth performance, blood constituents, and carcass characteristics of growing-finishing pigs.
Materials and Methods
The experimental protocol for this research was reviewed and approved by the Institutional Animal Care and Use committee at the National Institute of Animal Science. This experiment was conducted at the facility of National Institute of Animal Science Farm.
A total of 48 pigs (Landrace × Yorkshire × Duroc; 35.3 ± 0.69 kg of average initial body weight (BW); all barrows) were randomly assigned to 2 dietary treatments (6 pigs/pen; 4 replicates/treatment) in a completely randomized design. The treatments were a diet based on corn and soybean meal (CON) and CON supplemented with 0.01% of dietary mixture of protease and probiotics (MULTI). The MULTI used in this study was a commercial product (Syncra® SWI 201, Dupont feed enzyme and probiotics system, United Kingdom). The basal diet was formulated to meet or exceed the nutrient requirements of NRC (2012) for growing-finishing pigs (Table 1). The pigs were fed respective dietary treatments with a 2-phase feeding program for 12 weeks. Pigs were housed in conventional facilities with an all-slatted concrete floor (3.2 × 3.6 m2) and allowed ad libitum access to diets and water during the overall experimental period.
1) The vitamin-mineral premix provided the following quantities of vitamins and minerals per kilogram of diets: vitamin A, 10,000 IU; vitamin D3, 2,000 IU; vitamin E, 250 IU; vitamin K3, 0.5 mg; vitamin B1, 0.49 mg as mononitrate; thiamin, 0.49 mg as thiamin mononitrate; riboflavin, 1.50 mg; pyridoxine, 1 mg as pyridoxine hydrochloride; vitamin B12, 0.01 mg; niacin, 10 mg as nicotinic acid; pantothenic acid, 5 mg as calcium pantothenate; folic acid, 1 mg; biotin as d-biotin, 0.1 mg; choline, 125 mg as choline chloride; Mn, 60 mg as manganese sulfate; Zn, 75 mg as zinc sulfate; Fe, 20 mg as ferrous sulfate; Cu, 3 mg as cupric sulfate; I, 1.25 mg as calcium iodate; Co, 0.5 mg as cobaltous carbonate; and Mg, 10 mg as magnesium oxide.
The pig BW and average daily feed intake (ADFI) were weighed and recorded at the starting day and end of each phase. The gain to feed ratio (G:F) was calculated using average daily gain (ADG) and ADFI. Blood samples were collected from the jugular vein of 2 pigs per replicate using 8 mL EDTA tubes. The blood samples were analyzed to measure number of white blood cells and proportions of their differentiation using a multi-parameter automated hematology analyzer calibrated for porcine blood (Hemavet 950FS, Drew Scientific, UK).
After completion of the finishing period, pigs fed experimental diets until slaughtered. Approximately four hours before transport, feed was withdrawn. The live BW of finishing pigs used in the experiments was recorded before slaughter. To reduce stress, the pigs were showered with water, and water was freely available for drinking during lairage. The pigs were rested for about eight hours. Pigs were slaughtered according to industry accepted procedures (Korea Institute for Animal Products Quality Evaluation). The final live BW of pigs was recorded, and then they were slaughtered through electrical stunning and scalding-singeing. The hot carcass weight (HCW) was recorded, and dressing percentage was calculated by comparing final live BW and HCW. After splitting, the back fat depth at the 11th and 12th thoracic vertebra and between the last thoracic vertebra and the 1st lumbar vertebra was measured.
Data were analyzed with the PROC GLM procedure of SAS (SAS Inst. Inc., Cary, NC, USA) in the completely randomized design. The experimental unit was the pen. The statistical model for growth performance, blood constituents, and carcass characteristics included dietary treatments as the fixed effect and initial BW as the covariate. Results are presented as a mean ± SEM. Statistical significance and tendency were considered at p < 0.05 and 0.05 ≤ p < 0.10, respectively.
Results and Discussion
The MULTI did not affect growth performance of growing-finishing pigs during the overall experimental period (Table 2). Most previous studies showed that pigs fed diets with dietary protease or probiotics had higher growth rate of pigs than those fed diets without dietary protease or probiotics [2,7,9,25–28]. However, some research reported that addition of dietary protease or probiotics in pig diets did not affect growth rate of pigs [29,30]. The reason for the no beneficial effect of dietary MULTI on growth rate may be related to the basal diet with sufficient nutrients because some studies showed positive effect of enzyme supplementation in low-nutrient or low-CP content diets [12,25]. In addition, low concentration of the protein enzyme and/or probiotics may contribute to no beneficial effect on growth rate of pigs because some studies showed a dietary mixture of protease and probiotics with higher concentrations.
Addition of MULTI in the pig diet did not modulate blood constituent of pigs (Table 3). These results were similar to the results reported by Chen et al. , Tactacan et al. , and Yan et al. . In addition, the blood constituent of all pigs in this experiment showed a normal range of values maybe because of normal condititinos without any diseases. Generally, blood indicators for immunity of pigs do not change well in normal pig, feed, and environment conditions . Moreover, there were no differences on carcass characteristics among dietary treatment (Table 4). These results were similar to the results of previous studies reported by O’Shea et al. , Zamora et al. , and Burnham et al. . However, some research reported that addition of dietary protease or probiotics in pig diets influenced carcass characteristics of pigs [7,33,35,36].
|Live weight (kg)||117.60||117.16||1.71||0.857|
|Hot carcass weight (kg)||85.29||84.87||1.34||0.827|
|Dressing percentage (%)||72.52||72.43||0.32||0.845|
|Backfat thickness (mm)||27.50||26.07||1.44||0.489|
Overall, further investigation is needed to verify nutrient digestibility, growth performance, carcass characteristics, or etc. of pigs by increasing the concentrations of protease and probiotics or controlling the nutrient levels of basal diets.