Effects of Clostridium butyricum and corn bran supplementation on growth performance, nutrient digestibility, faecal volatile fatty acids and microbiota in weaned pigs

ABSTRACT

This study was conducted to evaluate effects of Clostridium butyricum and corn bran supplementation on growth performance, nutrient digestibility, faecal volatile fatty acids, and microbiota in weaned pigs. Hundred and forty-four weaned pigs (7.01 ± 0.62 kg BW) were randomly assigned to 1 of 4 treatments, including the basal diet and 5% corn bran diet with or without Clostridium butyricum supplementation. The results showed the supplementation of 0.1% Clostridium butyricum in diets increased average daily gain (p < 0.05) and tended to increase gain to feed ratio (G/F; p = 0.07) in weaned pigs during 15–28 d. Dietary Clostridium butyricum supplementation improved (p < 0.05) the apparent total tract digestibility (ATTD) of organic matter (OM) and the SOD and T-AOC levels in serum in weaned pigs. The inclusion of 5% corn bran in diets had no significant effect on growth performance in weaned pigs. Moreover, dietary Clostridium butyricum supplementation decreased (p < 0.05) faecal Escherichia coli count, and increased faecal Lactobacillus and Bifidobacterium counts in weaned pigs. In conclusion, inclusion of 0.1% Clostridium butyricum in diets could benefit the growth performance and gut health of weaned pigs. Meanwhile, 5% corn bran supplementation in diets had no negative effect on weaned pigs.

KEYWORDS:

• Clostridium butyricum
• corn bran
• growth performance
• gut health
• weaned pigs

Introduction

Probiotics are defined as live microorganisms that seem to promote gut health and regulate intestinal homeostasis (Hu et al. 2017). They are commonly used as feed additives in livestock, and can serve as alternatives to antibiotics to improve growth performance and enhance gut health and immunity function (Meng et al. 2010; Hu et al. 2017). Members of Lactobacillus and Bacillus are typical strains that commonly used as probiotics, which were shown to increase the growth rate and feed efficiency and benefit the gut health in weaned and growing-finishing pigs (Meng et al. 2010). Clostridium butyricum is an anaerobic Gram-positive Bacillus that lives in the intestine of health animals and can produce butyric acid. Clostridium butyricum was reported to have antioxidant capacity, and could accelerate the growth of Lactobacillus and Bacillus species and suppress the growth of E. coli in animal gut (Zhang et al. 2016).

Dietary fibre is generally considered as a proportion with low energy values, and can decrease the digestibility of almost all the nutrients and energy (NRC 2012). However, recent studies have shown that dietary fibre supplementation with appropriate amount could reduce the incidence of post-weaning diarrhoea (Meng et al. 2010). The fermentation of dietary fibre can produce short chain fatty acids (Jha and Leterme 2012), which could support the growth of beneficial bacteria and suppress the growth of harmful bacteria in animal gut (Pieper et al. 2008). The corn by-product, corn bran, as a common insoluble dietary fibre (IDF) source, has been widely used in animal feed because of its low price. Previous studies also demonstrated that IDF had beneficial effects on growth performance and gut health of young pigs (Molist et al. 2009; Molist et al. 2010).

Although several previous studies have focused on the individual effect of Clostridium butyricum or corn bran addition in diets on pigs, the comprehensive effect of Clostridium butyricum and corn bran supplementation at the same time has not been reported. Therefore, this study was conducted to evaluate the effects of dietary Clostridium butyricum supplementation, dietary corn bran supplementation, and their interaction effect on growth performance, nutrient digestibility, serum characteristics, and faecal volatile fatty acids (VFA) and microbiota in weaned pigs.

Materials and methods

All procedures used in this experiment were approved by the China Agricultural University Institutional Animal Care and Use Committee (Beijing, China).

Animals and diets

A total of 144 pigs [Duroc × (Landrace × Large White)] weaned at 28 d of age were assigned into 4 dietary treatments according to their sex and weight in a completely randomized design. Each dietary treatment was fed to six replicate pens with six pigs (three barrows and three gilts) per pen. The four treatment diets included the corn-soybean meal basal diet with 0% or 0.1% Clostridium butyricum supplementation and the 5% corn bran diet with 0% or 0.1% Clostridium butyricum supplementation. Chromic oxide (Cr₂O₃) was used as an indicator marker in all diets. The experiment lasted for 28 d. The corn bran used in the experiment was purchased from Wellhope Agri-tech Co. (Beijing, China). Clostridium butyricum (China General Microbiological Culture Collection Center, Strain No. 1.336) was kindly provided by Ministry of Agricultural Feed Industry Centre (Beijing, China) and added in the diet with 1 × 10⁸ CFU/g in spore state. The analysed nutrient composition of the corn bran is presented in Table 1. In the corn bran diet, the amount of corn and soybean meal were adjusted, and soybean oil and crystalline lysine (Lys), methionine (Met), threonine (Thr), and tryptophan (Trp) were added to keep the digestible energy, crude protein (CP), and standardized ileal digestible (SID) Lys/Met/Thr/Trp concentrations the same as those in the basal diet. All diets were formulated to meet or exceed the nutrient requirements for pigs in NRC (2012), and no antibiotics were added in all diets. The ingredients and analysed chemical compositions of the experimental diets are shown in Table 2.

Table 1. Analysed chemical composition of corn bran used in the experiment (g/kg, as-fed basis).

Items	Corn bran
Gross energy (MJ/kg)	17.3
Dry matter	921
Crude protein	138
Acid hydrolysed ether extract	39
Ash	25
Total dietary fibre	541
Soluble dietary fibre	60
Insoluble dietary fibre	481
Water-binding capacity (g/g)	42
Rhamnose	12
Arabinose	88
Xylose	147
Mannose	12
Galactose	8
Glucose	117
Uronic acids	16
Total non-starch polysaccharides	398

Table 2. Ingredients and analysed chemical compositions of the experimental diets (g/kg, as-fed basis).

Items	Diets
	Control	Corn bran
Corn	556.0	508.9
Soybean meal	122.0	115.0
Corn bran	–	50.0
Whey powder	100.0	100.0
Fish meal	30.0	30.0
Plasma protein powder	20.0	20.0
Soy protein concentrate	40.0	40.0
Extruded full-fat soybean	50.0	50.0
Surcose	20.0	20.0
Soybean oil	21.0	24.0
Dicalcium phosphate	12.0	12.0
Limestone	7.5	7.5
NaCl	2.0	2.0
L-Lysine-HCl	4.5	4.7
DL-Methionine	2.0	2.2
L-Threonine	1.5	1.8
L-Tryptophan	1.0	1.2
L-Valine	2.0	2.2
Chromic oxide	2.5	2.5
Zinc oxide	1.0	1.0
Premix^a	5.0	5.0
Calculated nutrient levels (g/kg)
Digestible energy (MJ/kg)	14.8	14.8
SID^b Lys	13.5	13.5
SID Met	5.00	5.00
SID Thr	8.00	8.00
SID Trp	3.00	3.00
Analysed nutrient levels (g/kg)
Gross energy (MJ/kg)	16.76	16.92
Dry matter	891	894
Organic matter	829	831
Crude protein	191	191
Acid hydrolysed ether extract	61.7	62.9
Total dietary fibre	173	208
Carbohydrate	587	579
Water-binding capacity	2.70	2.80
Calcium	8.00	8.00
Phosphorus	6.50	6.50

^aVitamin and mineral premix provided the following per kg of complete diet: vitamin A, 12,000 IU; vitamin D₃, 3000 IU; vitamin E, 30 IU; vitamin K₃, 2.5 mg; vitamin B₁₂, 20 μg; riboflavin, 4.0 mg; pantothenic acid, 12.5 mg; niacin, 40 mg; choline chloride, 400 mg; folacin, 0.7 mg; thiamine 2.5 mg; pyridoxine 3.0 mg; biotin, 70 μg; Mn, 30 mg (MnO); Fe, 100 mg (FeSO₄·H₂O); Zn, 80 mg (ZnO); Cu, 90 mg (CuSO₄·5H₂O); I, 0.25 mg (KI); Se, 0.15 mg (Na₂SeO₃).

^bSID = standardized ileal digestibility.

Pigs were housed in pens with half cement floor and half woven mesh floor. All pigs had free access to feed and water throughout the experiment. The temperature of the pig barn was controlled between 23°C and 28°C, and the relative humidity was controlled between 60% and 70%.

Sample collection

All pigs were individually weighed at d 14 and d 28 of the experiment, and feed intake was recorded at the same time on the pen basis. Faeces were scored consistently on a pen basis using the WALTHAM faecal scoring system (Moxham 2001) every day by visual inspection on at least three randomly chosen fresh droppings per pen (grade 1 = hard, dry and crumbly; grade 5 = watery diarrhoea). The incidence of diarrhoea was also calculated on a pen basis as the proportion of days in which pigs showed clinical signs of diarrhoea with respect to the total number of days on trial (Moxham 2001).

At the end of the experiment, approximately 300 g of faeces were collected by rectal massage from each pen during the last 3 d and the faecal samples were stored at −20°C. The 3-d collected faeces was pooled by pen and then oven-dried at 65°C for 72 h. All samples were ground to pass through a 1.0 mm screen (40 mesh) before analysis. Moreover, six fresh faecal samples (one pig per pen) per treatment group were collected into plastic tubes by rectal palpation on the last day, and then kept at −80°C for VFA concentration analysis and bacterial count. After faecal collection, pigs were fasted for 12 h and then blood samples (8 ml) were collected via jugular vena puncture into vacutainer tubes (Becton Dickinson Vacutainer Systems, Franklin Lakes, NJ, USA), and immediately centrifuged at 3000×g for 15 min at 4°C to recover serum, which was immediately stored at −20°C for further analysis.

Chemical analysis and calculation

Corn bran, treatment diets, and faecal samples were analysed in terms of crude protein (CP; AOAC 2007; method 976.05), dry matter (DM; AOAC 2007; method 930.15), acid hydrolysed ether extract (AEE; AOAC 2007; method 996.01), ash (AOAC 2007; method 942.15), calcium and phosphorous (AOAC 2007; method 935.13), and total dietary fibre (TDF; AOAC 2007; method 985.29). Gross energy (GE) was determined by an automatic adiabatic oxygen bomb calorimeter (Parr 1281, Automatic Energy Analyzer; Moline, IL, USA). In addition, IDF (AOAC 2007; method 991.43) of corn bran was also measured and soluble dietary fibre (SDF) was calculated as difference between total and IDF. The concentration of carbohydrate in diets and faecal sample was calculated according to the following equation:$\mathrm{Carbohydrates}=100-[\mathrm{CP}+\mathrm{AEE}+\mathrm{ash}+(100\text{–}\mathrm{DM})]$

Water holding capacity was measured in corn bran and diets according to the procedure of Robertson et al. (2000) and its value was expressed as the amount of water retained by the pellet (g/g). The acid insoluble ash (AIA) in diets and faeces was measured as described by De et al. (2009). The monosaccharide component of corn bran was measured on the basis of alditol acetates by gas–liquid chromatograph (Aglilent GC 6890) with a column of 30 m × 0.25 mm × 0.25 mm (Agilent DB-225) at speed of 20 ml/min as described by Yu et al. (2016). The column temperature was 220°C and the injector and detector temperature were 250°C. The apparent total tract digestibility (ATTD) of CP, DM, GE, TDF, OM, and carbohydrate were determined using the indicator method as follows:$\mathrm{ATTD}=1-(\mathrm{DC}\times \mathrm{FN})/(\mathrm{FC}\times \mathrm{DN})$

where DC is the content of Cr₂O₃ in the diets, FN is the content of the target nutrient in the faeces, FC is the content of Cr₂O₃ in the faeces, and DN is the content of the target nutrient in the diets (Medel et al. 1999).

The concentrations of superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) in serum were determined by commercial kits (Jiancheng Biochemical Reagent Co., Nanjing, China) according to the manufacturer’s instructions. The concentrations of albumin (ALB), globulin (GLB), total protein (TP), total cholesterol (TC), glutamic-pyruvic transaminase (ALT), glutamic oxalacetic transaminase (AST), creatinine (CREA), alkaline phosphatase (ALP), serum urea nitrogen (UREA), glucose (GLU), and total triglyceride (TG) in serum were measured by corresponding commercial kits (BioSino Bio-technology and Science Inc., Beijing, China) using an automatic biochemical analyzer (Hitachi 7160, Hitachi High-Technologies Corporation, Japan).

The VFA concentrations in faeces were determined using a modified method of Yu et al. (2016). A 1.0 g sample was diluted with 2.0 ml of 0.10% HCl solution and put on ice for 30 min and then centrifuged at 12,000×g at 0°C for 15 min. Exactly 1.0 ml of the supernatant was passed through a 0.22 m Nylon Membrane Filter (Millipore, Bedford, OH) and then 5.0 ml of the solution was injected into a gas chromatographic system (Agilent HP 6890 Series, Santa Clara, CA).

To measure the faecal bacterial count, 10 g of samples were blended under CO₂ in 90 ml of anaerobic dilution solution. Quadruplicate plates were then inoculated with 0.1 ml samples and incubated at 37°C anaerobically. Three dilutions were plated for each medium. Bacteria were enumerated on MRS agar (Oxoid; Lactobacillus), reinforced clostridial agar plus supplements (Munoa and Pares; Bifidobacterium), and Mac-Conkey’s no. 2 (Oxoid; E. coli). Single colonies were removed from selective media plates and grown in peptone yeast glucose (PYG) broth (Holdeman et al. 1977). Subsequently, the bacteria were characterized to genus level on the basis of colonial appearance, gram reaction, spore production, cell morphology, and fermentation end-product formation (Bryant 1972).

Statistical analysis

Data generated in the present experiment were analysed using the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC) with two-way ANOVA. The pen was treated as the experimental unit. The statistical model included the main effects of dietary corn bran inclusion, and dietary Clostridium butyricum supplementation, and their interaction effect. Significant differences were declared at p < 0.05, whereas 0.05 < p < 0.10 were considered as a tendency toward significant difference.

Results

Effects of dietary Clostridium butyricum and corn bran supplementation on growth performance, diarrhoea rate, and nutrient digestibility of weaned pigs

There was no interaction effect (p > 0.10) between dietary Clostridium butyricum and corn bran supplementation on growth performance and incidence rates of diarrhoea in weaned pigs (Table 3). Dietary Clostridium butyricum supplementation at 0.1% increased (p < 0.05) average daily gain (ADG) and tended to increase (p = 0.07) G/F of weaned pigs during 15–28 d. During 1–28 d, dietary Clostridium butyricum supplementation at 0.1% also tended to increase (p = 0.08) G/F of weaned pigs. However, 0.1% Clostridium butyricum addition in diets had no effect (p > 0.05) on the incidence rate of diarrhoea in weaned pigs. Furthermore, 5% corn bran supplementation in diets did not affect (p > 0.10) growth performance and diarrhoea frequency of weaned pigs.

Table 3. Effect of dietary Clostridium butyricum (CB) and corn bran supplementation on growth performance and diarrhoea rate in weaned pigs^a.

Items	Corn bran		CB		SEM	p-value
	Basal	Corn bran	0%	0.1%		Corn bran	CB	Interaction
1–14 d
ADFI (g/d)	476	474	476	475	25	0.96	0.95	0.96
ADG (g)	300	313	303	320	18	0.63	0.29	0.62
G/F (%)	0.62	0.66	0.63	0.68	0.06	0.23	0.16	0.22
Diarrhoea rate (%)	4.05	2.98	3.81	3.22	0.52	0.14	0.59	0.43
Faeces score	2.59	2.70	2.72	2.58	0.06	0.70	0.89	0.94
15–28 d
ADFI (g/d)	680	662	673	669	18	0.57	0.90	0.90
ADG (g)	432	420	419	443	7	0.25	0.03	0.26
G/F (%)	0.63	0.63	0.62	0.66	0.05	0.95	0.07	0.46
Diarrhoea rate (%)	1.51	1.67	1.85	1.33	0.70	0.69	0.32	0.57
Faeces score	2.24	2.33	2.30	2.26	0.04	0.89	0.91	0.91
1–28 d
ADFI (g/d)	560	561	567	554	21	0.86	0.85	0.72
ADG (g)	361	361	358	370	14	0.99	0.42	0.32
G/F (%)	0.65	0.65	0.63	0.67	0.04	0.69	0.08	0.11
Diarrhoea rate (%)	2.78	2.37	2.85	2.30	1.28	0.50	0.42	0.36
Faeces score	2.37	2.49	2.45	2.49	0.05	0.80	0.88	0.98

^aData represent least square means based on six replicates per treatment. ADFI, average daily feed intake; ADG, average daily gain; G/F, gain/feed ratio.

There was no interaction effect (p > 0.10) between dietary Clostridium butyricum and corn bran supplementation on the ATTD of nutrients in weaned pigs (Table 4). Corn bran supplementation at 5% in diets decreased (p < 0.05) the ATTD of DM, OM, CP, and CHO when fed to weaned pigs. On the contrary, Clostridium butyricum supplementation at 0.1% in diets improved (p < 0.05) the ATTD of OM in weaned pigs.

Table 4. Effect of dietary Clostridium butyricum (CB) and corn bran supplementation on ATTD of nutrients in weaned pigs^a.

ATTD (%)	Corn bran		CB		SEM	p-value
	Basal	Corn bran	0%	0.1%		Corn bran	CB	Interaction
GE	82.1	80.4	81.2	81.4	0.8	0.16	0.68	0.87
DM	82.8	81.2	81.8	82.2	0.7	0.04	0.60	0.88
OM	84.7	83.1	83.3	85.3	0.7	0.02	0.03	0.91
CP	80.2	77.9	79.2	78.9	2.3	0.05	0.98	0.90
AEE	73.4	73.2	71.9	73.7	1.2	0.98	0.22	0.85
TDF	61.2	62.3	61.4	62.4	1.7	0.92	0.38	0.89
CHO	88.1	85.7	87.1	86.6	1.0	0.03	0.61	0.96

^aData represent least square means based on six replicates per treatment. GE, gross energy; DM, dry matter; OM, organic matter; CP, crude protein; AEE, acid hydrolysed ether extract; TDF, total dietary fibre; CHO, carbohydrate.

Effects of dietary Clostridium butyricum and corn bran supplementation on serum characteristics in weaned pigs

There was no interaction effect (p > 0.10) between dietary Clostridium butyricum and corn bran supplementation on serum characteristics in weaned pigs (Table 5). Corn bran supplementation at 5% in diets did not affect (p > 0.10) all serum characteristics tested in weaned pigs. Clostridium butyricum supplementation at 0.1% in diets increased (p < 0.05) the concentrations of SOD and T-AOC in serum of weaned pigs. There is a tendency (p = 0.06) that 0.1% dietary Clostridium butyricum addition decreased the concentration of UREA in serum of weaned pigs.

Table 5. Effect of dietary Clostridium butyricum (CB) and corn bran supplementation on serum characteristics in weaned pigs^a.

Items	Corn bran		CB		SEM	p-value
	Basal	Corn bran	0%	0.1%		Corn bran	CB	Interaction
GLU (mmol/L)	5.90	5.70	5.80	5.80	0.23	0.39	0.89	0.27
UREA (mmol/L)	3.10	2.80	3.50	2.50	0.43	0.87	0.06	0.71
CREA (umol/L)	78.1	81.7	82.5	77.3	3.6	0.33	0.17	0.47
TP (g/L)	56.2	59.2	57.9	57.5	2.1	0.13	0.84	0.88
Alb (umol/L)	23.0	24.7	23.6	24.1	0.9	0.27	0.72	0.38
Glo (umol/L)	33.1	34.5	34.3	33.4	2.4	0.57	0.72	0.69
TG (mmol/L)	0.70	0.80	0.70	0.80	0.09	0.31	0.39	0.43
TC (mmol/L)	2.50	2.50	2.50	2.50	0.23	0.72	0.84	0.71
SOD (U/ml)	111	123	111	128	5	0.28	0.03	0.56
T-AOC (U/ml)	4.50	4.80	4.00	5.20	0.72	0.36	0.01	0.81
ALT (U/L)	53.8	48.6	53.9	48.5	7.3	0.44	0.33	0.13
AST (U/L)	61.0	69.9	64.8	66.1	6.4	0.56	0.53	0.70
ALP (U/L)	60.6	63.2	63.5	60.3	5.0	0.71	0.65	0.20

^aData represent least square means based on six replicates per treatment. GLU, glucose; urea, serum urea nitrogen; CREA, creatinine; TP, total protein; Alb, albumin; Glo, globulin; TG, total triglyceride; TC, total cholesterol; SOD, superoxide dismutase; T-AOC, total antioxidant capacity; ALT, glutamic-pyruvic transaminase; AST, glutamic oxalacetic transaminase; ALP, alkaline phosphatase.

Effects of dietary Clostridium butyricum and corn bran supplementation on faecal VFAs and microbiota in weaned pigs

There was no interaction effect (p > 0.10) between dietary Clostridium butyricum and corn bran supplementation on the concentration of VFA in faecal samples of weaned pigs (Table 6). Both 5% corn bran and 0.1% Clostridium butyricum addition in diets increased (p < 0.05) the concentrations of butyrate in faeces of weaned pigs. Meanwhile, pigs fed the diet containing 0.1% Clostridium butyricum tended to have greater concentrations of total VFA and propionate (p = 0.07 and p = 0.06, respectively).

Table 6. Effect of dietary Clostridium butyricum (CB) and corn bran supplementation on faecal VFA (mg/g) in weaned pigs^a.

Items	Corn bran		CB		SEM	p-value
	Basal	Corn bran	0%	0.1%		Corn bran	CB	Interaction
Total VFA	7.28	8.17	8.38	9.12	0.29	0.08	0.07	0.43
Acetate	3.19	3.44	3.65	3.57	0.12	0.79	0.51	0.37
Propionate	2.07	2.14	2.33	2.98	0.07	0.87	0.06	0.71
Butyrate	1.21	1.74	1.44	2.11	0.06	0.03	0.01	0.78
Valerate	0.45	0.47	0.55	0.47	0.04	0.69	0.66	0.69

^aData represent least square means based on six replicates per treatment.

There was no interaction effect (p > 0.10) between dietary Clostridium butyricum and corn bran supplementation on faecal microflora in weaned pigs (Table 7). The 5% corn bran supplementation in diets had no effects (p > 0.10) on microflora counts in faeces of weaned pigs. Dietary Clostridium butyricum supplementation at 0.1% increased (p < 0.05) the counts of Lactobacillus and Bifidobacterium and decreased (p < 0.05) the count of E.coli in faeces of weaned pigs.

Table 7. Effect of dietary Clostridium butyricum (CB) and corn bran supplementation on faecal microbiota (log cfu/g wet faeces) in weaned pigs^a.

Items	Corn bran		CB		SEM	p-value
	Control	Corn bran	0%	0.1%		Corn bran	CB	Interaction
Total bacterial	13.63	13.77	13.56	13.83	0.92	0.44	0.12	0.66
Lactobacillus	7.58	7.75	7.33	8.00	0.25	0.61	0.01	0.53
Bifidobacterium	4.79	5.14	4.70	5.26	0.09	0.09	0.01	0.37
Escherichia coli	3.57	3.71	3.95	3.33	0.12	0.38	0.02	0.41

^aData represent least square means baseans based on six replicates per treatment.

Discussion

Effects of 0.1% Clostridium butyricum supplementation in weaned pig diets

Clostridium butyricum is an anaerobic Gram-positive Bacillus that has been shown to improve growth performance and utilization efficiency of nutrients in animals (Dowarah et al. 2017). In the current study, we also showed that Clostridium butyricum improved growth performance of weaned pigs. The improved growth performance observed by dietary Clostridium butyricum supplementation might be associated with the increased nutrient digestibility in diets. However, some previous studies did not observed improvement in pig performance with the supplementation of Bacillu-based probiotic in diets (Jørgensen et al. 2016). These differences may be resulted from the different diet compositions, probiotic strains, growth phase of animal, and the interaction with environment.

Total antioxidant capacity is considered to be the integrated action of all the antioxidants present in serum, thus providing an insight into a delicate balance in animal between oxidants and antioxidants (Ghiselli et al. 2000). SOD is the main antioxidant enzyme in the body, which contributes to the antioxidant activity of animals. It can protect cells from free radicals which cause the oxidation of bio-molecules and lead to cell injury and death (Fridovich 1995). In the present study, the SOD and T-AOC levels in serum increased with the inclusion of Clostridium butyricum in diets fed to weaned pigs. This result agreed with Zong et al. (2019) who reported that supplementation with Clostridium butyricum increased the serum concentrations of SOD and decreased the level of MDA in weaned pigs. Moreover, the beneficial effect of Clostridium butyricum on antioxidant status of tissues was also observed in mice (Sun et al. 2016). Serum urea nitrogen is the product of protein degradation in vivo, and decreased UREA indicated that more proteins were synthesized with amino acids (Kohn et al. 2005). In the current study, there was a trend that dietary Clostridium butyricum addition could decrease the concentration of UREA when fed to weaned pigs. This result was consistent with Meng et al. (2010) who reported that the UREA level in the probiotic treatment group tend to decrease in serum compared with the treatment group with no probiotic addition in growing-finishing pigs.

The major end-products of Clostridium butyricum is butyric acid, which increased the concentration of VFA in the gut when fed to weaned pigs (Jha and Leterme 2012). Similarly, the concentrations of total VFA, propionate, and butyrate increased when pigs fed the diets with Clostridium butyricum supplementation in the current study. The increased VFA may be attributed to that Clostridium butyricum can stimulate the metabolism of specific bacteria to produce VFA.

Faecal microbial status is widely used as an indicator to assess the intestinal microbial colonization. Lactobacillus and Bifidobacteria are considered beneficial bacteria due to their positive effects on gut microbiota balance, intestinal epithelium integrity, maturation of gut, and neuroendocrine system function (Leser et al. 2002). Escherichia coli is considered detrimental for the host, because they could adhere to the gut mucosa and release specific enterotoxins in gastrointestinal tract to induce the imbalances of gut ecosystem, then resulting in the post-weaning diarrhoea in weaned pigs (Kim et al. 2012). Kong et al. (2011) reported that Clostridium butyricum improved the growth of Lactobacillus and Bifidobacteria, and modulated the balance of gastrointestinal microflora. Diets supplemented with Bacillus-based probiotics were reported to increase the faecal count of Lactobacillus bacteria and Bifidobacteria (Dowarah et al. 2017). In our study, we also found that dietary Clostridium butyricum supplementation increased the counts of Lactobacillus and Bifidobacteria, and decreased the count of E.coli.

Effects of 5% corn bran supplementation in weaned pig diets

In our study, 5% corn bran supplementation in diets, which contains more IDF than SDF, did not affect the ADFI of pigs, which agreed with the previous studies focusing on high-insoluble fibre ingredients (Yu et al. 2016; Shang et al. 2020). Similarly, Chen et al. (2019) also reported that dietary cellulose (IDF) supplementation at 1% did not have any significant alternation in ADFI of weaned pigs. On the other hand, a previous study reported that the inclusion of sugar beet pulp in diets, which contains more SDF than IDF, decreased ADFI by increasing digesta viscosity and prolonging satiety time (Hopwood et al. 2004). These different results can be attributed to the different composition and physico-chemical properties of the fibre ingredients.

Dietary corn bran addition at 5% had no effects on growth performance and diarrhoea frequency of weaned pigs in our study. This result was inconsistent with Molist et al. (2014), who reported that moderating level of IDF might have positive effects on promoting growth performance and alleviating the symptom of diarrhoea in the first two weeks. This positive effect on growth performance was explained that the arabinoxylan in cereal bran improved intestinal barrier function and gut health of pigs (Nielsen et al. 2014). However, Yu et al. (2016) reported that the diet included more than 10% wheat bran did not affect the growth performance of pigs. A plausible explanation of these differences could be the different inclusion levels and sources of dietary fibre.

Structural and functional characteristics of dietary fibre can affect digestion and absorption of nutrients and energy (Yu et al. 2016). In our study, 5% dietary corn bran supplementation decreased the ATTD of GE, DM, OM, CP, and carbohydrate, but did not affect the ATTD of TDF and AEE, compared with the basal diet when fed to weaned pigs. These results were in agreed with many published reports (Molist et al. 2010; Zhang et al. 2013). The negative effect of dietary fibre on nutrient digestibility can be explained that the fibrous ingredients contained more IDF might shorten the retention time of digesta due to its low viscosity and slow ferment capacity (Zhang et al. 2013). In addition, the lower digestibility of CP in corn bran diet may be caused by the increased synthesis of microbial protein in the hindgut of pigs.

Our study also demonstrated that 5% corn bran supplementation in diets can increase the butyrate concentrations in faeces of weaned pigs. A previous study (Molist et al. 2009) has shown a positive relationship between the fermentation of dietary fibre and the butyrate production in the hindgut and the improved gut health of pigs. Molist et al. (2009) reported an increase in the concentration of SCFA in the caecum of pigs fed diets containing 40–80 g/kg wheat bran compared with pigs fed a control diet on 10–15 d post-weaning. However, Zhang et al. (2013) reported that no differences for the concentrations of VFA in the hindgut were observed when fed a diet with 30% maize fibre supplementation compare with the control diet in fattening pigs. It was shown that corn bran contains more IDF and provides substrates which fermented slowly in the distal part of the gastrointestinal tract (Freire et al. 2000). The different results mentioned above may be caused by the different fibre sources, sampling location of gut and growth phase of pig.

In agreement with previous studies (Yu et al. 2016), diets with 5% corn bran supplementation did not affect the populations of Lactobacillus, Escherichia coli, and total bacteria when fed to weaned pigs in our study. However, some other studies showed that the inclusion of fibre increased the Lactobacillus count and decrease the Escherichia coli count in the hindgut digesta due to the synthesis of VFA (Schiavon et al. 2010). Those different results may be caused by the different fibre sources and sampling location of gut. In addition, there was a tendency for the inclusion of corn bran in diets to increase the population of Bifidobacteria in the current research. Numerous studies have also reported that wheat bran stimulated the growth of Bifidobacteria (Nielsen et al. 2014; Yu et al. 2016). These results may be due to the high arabinoxylan and arabinoxylan oligosaccharides levels in cereal bran, which could reach the hindgut and played crucial role in facilitating the growth of Bifidobacteria (Nielsen et al. 2014).

Conclusion

In conclusion, diet supplemented with 0.1% Clostridium butyricum can improve growth performance, antioxidant ability, and gut health of weaned pigs. Furthermore, 5% corn bran supplementation in diets had no negative effect on weaned pigs and may decrease the feed cost in practical production. There was no interaction between corn bran and Clostridium butyricum on growth performance, nutrients digestibility, faecal VFAs, and microbial composition as reflected by the results of this study.

Acknowledgements

This research was financially supported by the National Natural Science Foundation of China (Grant No. 31702121) and the Sichuan Science and Technology Program (Grant No. 2018HH0160).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was financially supported by the National Natural Science Foundation of China [grant number 31702121] and Sichuan Science and Technology Program [grant number 2018HH0160].