Dietary Addition with Fermented Sorghum Distiller's Dried Grains with Soluble Improved Carcass Traits and Meat Quality in Growing-Finishing Pigs

Abstract

The fermented sorghum distiller's dried grains with soluble (FS-DDGS) contain numerous nutrients, yet its nutritional effects on growing-finishing pigs remain unclear. The present study was conducted to evaluate the effects of dietary FS-DDGS addition on growth performance, carcass traits, and meat quality in growing-finishing pigs. A total of 48 healthy male crossbred (Large White × Landrace × Duroc) barrows with initial body weight (BW) of 39.95 ± 2.15 kg were allocated to one of four dietary treatments (12 pigs per treatment). The dietary treatments were as follows: basal diet without (FS-DDGS0 group) or with 50 g/kg (FS-DDGS50 group), 100 g/kg (FS-DDGS100 group), or 150 g/kg (FS-DDGS150) FS-DDGS, respectively. Results showed that dietary FS-DDGS addition increased (linear, P < 0.05) the pH_24h value, and contents of ash, crude protein, and Pro in Longissimus dorsi muscle, and Ala, Arg, Asp, Glu, Ile, Leu, Lys, Ser, and Tyr in Biceps femoris (BF) muscle. Meanwhile, dietary FS-DDGS addition decreased (linear, P < 0.05) the drip loss, b* value, and L* value. In addition, an effect (quadratic, P < 0.05) on total bone percentage and Gly and Pro contents in BF muscle were observed. Collectively, these findings suggested that dietary FS-DDGS addition could improve carcass traits and meat quality; nevertheless, more research is warranted to determine the underlying mechanism associated with the alterations.

Introduction

China is the country with the largest population with increasing consumption of animal products, such as meat, eggs, and milk. Thus, there is a huge feed demand in the livestock and poultry industry. However, there is a shortage of feed resources in China. Consequently, it is urgent to develop effective technologies to fully use the available feed resources and to explore any potential feed resources. One of such material is the by-product from liquor production. China produces more than 12 million tons of liquor and over 30 million tons of the by-product of solid-state alcohol distillation annually. This by-product is a promising option because it contains relatively high levels of nutrients, such as protein, fiber, phosphorous, and minerals. Thus, there could be a guaranteed supply of feed resources for the animal industry (Choi et al. 2009).

The distiller's dried grains with soluble (DDGS) is a by-product from liquor production. Unlike maize, the DDGS are mainly composed of low fermentable insoluble non-starch polysaccharides, such as arabinoxylans, cellulose, and lignin (Gutierrez et al. 2014). Considering the anti-nutritional properties, these nutrients cannot be easily used by animals. However, Agyekum et al. (2013) indicated that the DDGS could replace a certain amount of regular feed ingredients and reduce feed cost. In addition, the beneficial effects of in vitro fermentation of feed ingredients have been well documented. For example, Song et al. (2010) indicated that in vitro fermentation effectively increased the nutrient bioavailability for animals. Shi et al. (2017) found that serial fermentation with Bacillus subtilis and Enterococcus faecium improved the nutritional availability of corn-soybean meal by degrading anti-nutritional factors. In this regard, a proper in vitro process, such as solid state fermentation, is required before the DDGS can be used as a feed resource (Yang et al. 2012).

Mao-tai liquor is one of the main products from sorghum fermentation. Approximately 150,000 tons of sorghum DDGS can be produced annually by the production of Mao-tai liquor. Such DDGS contains numerous nutrients, such as cellulose, amino acids, and organic acids. A previous study indicated that dietary addition with 5% fermented potato pulp improved weight gain and feed conversion without any detrimental effects on carcass traits in growing-finishing pigs (Li et al. 2011). However, little is known the beneficial effects of fermented sorghum DDGS (FS-DDGS) from Mao-tai liquor production on the growth performance and carcass traits of pigs. Therefore, the present study was conducted to determine the effects of dietary addition with the FS-DDGS on growth performance, carcass traits, and meat quality in crossbred growing-finishing pigs.

Materials And Methods

Preparation and nutrient levels of FS-DDGS

The FS-DDGS was obtained from Road Biological Technology (Gulin) Co., Ltd., Sichuan, China. A two-stage brewing process using yeast with high activity in solid culture was adopted for the preparation of FS-DDGS with Mao-tai flavor distillate as the main medium. The first stage optimized conditions to promote the proliferation of yeast, and the second stage involved exposing the material to high temperatures and the hydrolysis of yeast cell walls (autolysis) to an anaerobic environment. The FS-DDGS were dried at 65°C to calculate the dry matter content.

Chemical analyses were performed according to the Association of Official Analytical Chemists’ methods (AOAC, 2016). The ash level was determined in accordance with standards provided by AOAC-942.05. The crude protein (CP) level (N × 6.25) was measured using the Kjeldahl method following AOAC-968.06. The crude fat level was measured using the Soxhlet extraction method (2055 Soxtec Main Unit, Sweden) and gross energy level was measured by automatic isoperibolic oxygen bomb calorimeter (Parr Instrument Co., Moline, IL, USA). The method for measuring neutral detergent fiber and acid detergent fiber levels is based on the AOAC-2002.04 and AOAC-973.18, respectively. Determination of calcium and phosphorus level follows the AOAC-984.27. The specific nutrient levels are shown in Table 1.

Table 1

Nutrient levels of fermented sorghum distiller's dried grains with soluble (FS-DDGS) (g/kg)
Items	Nutrition level
Gross energy (MJ/kg)	18.29
Dry matter	929.70
Ash	92.80
Crude protein	239.60
Crude fat	53.90
Acid detergent fiber	380.60
Neutral detergent fiber	472.80
Calcium	5.30
Phosphorus	5.50

Animal and experimental design

A total of 48 healthy male crossbred (Large White × Landrace × Duroc) barrows with initial body weight (BW) of 39.95 ± 2.15 kg were employed in the present study. The pigs were allocated randomly to one of four dietary treatments (12 pigs per treatment) according to the BW. The dietary treatments were as follows: the basal diet without (FS-DDGS0 group) or with 50 g/kg (FS-DDGS50 group), 100 g/kg (FS-DDGS100 group), or 150 g/kg (FS-DDGS150 group) FS-DDGS. Pigs in each group were housed in specially designed pens (3.5 m × 5.0 m) in a room with an average temperature of 28°C, and each cage was equipped with a feed intake recorder (Beijing Hamoer Automation Equipment Co., Ltd., Beijing, China). The cages allowed one pig at a time to freely consume feed, and water was freely available. The pigs were labeled with an individual electronic ear marker. During the first week of adaptation, all pigs were fed a corn and soybean meal-based diet (Table 2), formulated by following the National Research Council-recommended (NRC 2012) requirements of nutrients for growing-finishing pigs. Then, they consumed their assigned daily allowance in a 90-day trial. Feed and water were available ad libitum. The initial and final BW and daily feed intake for each pig were recorded for the determination of the average daily gain (ADG), average daily feed intake (ADFI), and F:G (Hu et al. 2017).

Table 2

Composition and nutrient levels of the basal diets (g/kg)
Ingredient	Growing phase (45 to 75 kg)	Finishing phase (75 to 110 kg)
Corn	596.10	597.80
Barley	80.00	80.00
Soybean oil	15.00	10.00
Soybean meal	250.00	255.00
CaHPO₄	1.00	—
Calcium carbonate	10.80	10.80
Salt	4.30	4.30
Lys	1.80	1.30
Met	0.30	—
Thr	0.70	0.80
Premix¹	40.00	40.00
Nutrient levels²
Digestible energy (MJ/kg)	13.78	13.65
Crude protein	164.00	165.00
Crude fat	43.00	38.00
L-Lys hydrochloride	10.80	10.50
DL-Met hydrochloride	3.00	2.80
L-Thr hydrochloride	7.10	7.30
Met + Cys	0.55	0.42
Calcium	7.40	6.60
Total P	5.20	4.50
¹ Provided for 1 kg of complete diet: Cu as copper sulfate, 10 mg; Fe as iron sulfate, 100 mg; Se as sodium selenite, 0.30 mg; Zn as zinc sulfate, 100 mg; Mn as manganese oxide, 10 mg; vitamin D₃, 386 IU; vitamin A as retinyl acetate, 3 086 IU; vitamin E as D-α-tocopherol, 15.4 IU; vitamin K as menadione sodium bisulfate, 2.3 mg; vitamin B₂, 3.9 mg; calcium pantothenate, 15.4 mg; niacin, 23 mg; and vitamin B₁₂, 15.4 mg.
² Nutrient levels were calculated from NRC (2012) values.

Sample collection and carcass trait determination

At the end of the trial, all pigs were fasted overnight for 12 h and then electrically stunned (250 V for 5–6 s) followed by exsanguination in a commercial slaughterhouse. The carcass yield and back-fat thickness between the 6th and 7th ribs were determined as previously described (Hu et al. 2017). The skeletal muscle, fat, and bone of the left-side carcass weight were isolated and weighed for the determination of carcass composition (Tan et al. 2009). Subsequently, the Longissimus dorsi (LD) muscle (subcutaneous fat removed), subcutaneous fat between the 6th and 7th ribs, and Biceps femoris (BF) muscle were collected from the right side of the carcass and stored at -80°C for further analysis.

Analysis of meat quality and chemical composition

The drip loss, pH value, and muscle color of the LD muscle were measured as previously described (Hu et al. 2017). Briefly, the LD muscle was cut from the anterior section between the 7th and 8th ribs on the right side of the carcass. A piece of LD muscle was used to calculate the drip loss, which was based on the weight loss of the LD muscle at 4°C after 24 h. The LD muscle was also used to determine the pH at 45 min (pH_45min) and at 24 h (pH_24h) postmortem, using a hand-held pH meter (Russell CD700, Russell pH Limited, Fife, UK). Moreover, the LD muscle was used to evaluate the meat color (including L*, a*, and b* values) using a Konica Minolta chroma meter (CR410, Konica Minolta Sensing, Inc., Tokyo, Japan). The CP and intramuscular fat (IMF) contents of the LD and BF muscles were measured following the AOAC (2016). The amino acid content in the LD and BF muscles was measured as previously described (Liu et al. 2015).

Statistical analysis

Data were statistically analyzed by the GLM procedure of SAS (version 9.2; SAS Inst. Inc. Cary, NC). For the parameters, the individual pig was the experimental unit. Results are expressed as means ± standard error of the mean (SEM). P < 0.05 indicated statistical significance, whereas 0.05 ≤ P < 0.10 was considered a trend.

Results

The effects of dietary FS-DDGS addition on growth performance of growing-finishing pigs

As presented in Table 3, there were no differences (P > 0.05) in the final BW, ADFI, ADG, and F:G of pigs during 1–50 days, 51–90 days, and 1–90 days of the trials among the four groups.

Table 3

Effects of dietary addition with fermented sorghum distiller's dried grains with soluble (FS-DDGS) on growth performance of growing-finishing pigs (n = 12)
Items	Treatments¹				SEM	P-values
Items	FS-DDGS0	FS-DDGS50	FS-DDGS100	FS-DDGS150	SEM	Linear	Quadratic
Initial BW (kg)	41.97	40.93	38.50	37.83	2.729	0.09	0.23
Final BW (kg)	108.57	112.03	106.00	106.23	4.142	0.22	0.38
Average daily feed intake (kg/day)
1–50 days	2.04	1.91	1.94	1.92	0.121	0.39	0.57
51–90 days	2.01	2.10	2.15	2.07	0.137	0.63	0.61
1–90 days	2.02	2.02	2.07	2.00	0.115	0.98	0.92
Average daily gain (kg/day)
1–50 days	0.77	0.81	0.78	0.80	0.036	0.55	0.77
51–90 days	0.69	0.77	0.71	0.71	0.029	0.83	0.21
1–90 days	0.74	0.79	0.75	0.76	0.025	0.73	0.44
F:G
1–50 days	2.66	2.37	2.54	2.41	0.178	0.29	0.47
51–90 days	2.91	2.73	3.04	2.91	0.169	0.54	0.81
1–90 days	2.75	2.56	2.76	2.63	0.137	0.75	0.91
¹ FS-DDGS0, 0 g/kg FS-DDGS group; FS-DDGS50, 50 g/kg FS-DDGS group; FS-DDGS100, 100 g/kg FS-DDGS group; FS-DDGS150, 150 g/kg FS-DDGS group. BW, body weight.

The effects of dietary FS-DDGS addition on carcass traits of growing-finishing pigs

As presented in Table 4, no linear or quadratic effect (P > 0.05) of dietary FS-DDGS addition was detected on carcass yield, fat percentage, and average backfat thickness. However, a quadratic effect (P < 0.05) for lean percentage and bone percentage were observed, and the highest value of lean percentage and lowest value of bone percentage were gained in the FS-DDGS50 group.

Table 4

Effects of dietary addition with fermented sorghum distiller's dried grains with soluble (FS-DDGS) on carcass traits of growing-finishing pigs (n = 12)
Items	Treatments¹				SEM	P-values
Items	FS-DDGS0	FS-DDGS50	FS-DDGS100	FS-DDGS150	SEM	Linear	Quadratic
Carcass weight (kg)	74.11	76.70	73.98	72.17	3.225	0.62	0.56
Carcass yield² (kg/100 kg)	68.26	68.46	69.79	67.94	0.286	0.28	0.61
Lean percentage³ (kg/100 kg)	65.72^ab	67.35^a	66.29^ab	65.29^b	0.722	0.34	0.03
Fat percentage³ (kg/100 kg)	10.66	10.28	10.53	10.62	0.672	0.95	0.88
Bone percentage³ (kg/100 kg)	18.33^a	16.89^b	17.36^b	18.41^a	0.280	0.57	< 0.01
Backfat thickness⁴ (cm)	2.15	2.07	2.11	2.14	0.083	0.98	0.63
¹ FS-DDGS0, 0 g/kg FS-DDGS group; FS-DDGS50, 50 g/kg FS-DDGS group; FS-DDGS100, 100 g/kg FS-DDGS group; FS-DDGS150, 150 g/kg FS-DDGS group.
² Carcass yield = carcass weight / live body weight.
³ Expressed as tissue weight / left side carcass weight.
⁴ Between the 7th and 8th ribs from the anterior section of the right side carcass.

The effects of dietary FS-DDGS addition on meat quality of growing-finishing pigs

As presented in Table 5, no effect of dietary FS-DDGS addition was detected on the a* value and pH_45min value. The drip loss, b* value, and L* value were decreased (linear, P < 0.05), while the pH_24h value was increased (linear, P < 0.05) in LD muscle of pigs fed the increasing level of dietary FS-DDGS.

Table 5

Effects of dietary addition with fermented sorghum distiller's dried grains with soluble (FS-DDGS) on meat quality in growing-finishing pigs (n = 12)
Items	Treatments¹				SEM	P-values
Items	FS-DDGS0	FS-DDGS0	FS-DDGS0	FS-DDGS0	SEM	Linear	Quadratic
Drip loss (g/100 g)	9.07^a	6.96^b	5.35^bc	4.11^c	0.679	< 0.01	< 0.01
Color measurement
a*	13.12^b	13.69^a	13.60^ab	13.40^ab	0.210	0.29	0.03
b*	4.89^a	4.51^ab	4.27^b	4.11^b	0.220	< 0.01	< 0.01
L*	56.05^a	52.61^b	52.90^b	52.73^b	1.063	< 0.01	< 0.01
pH_45min	5.47	5.52	5.62	5.66	0.098	0.03	0.11
pH_24h	5.37^b	5.38^b	5.43^ab	5.47^a	0.031	< 0.01	< 0.01
¹ FS-DDGS0, 0 g/kg FS-DDGS group; FS-DDGS50, 50 g/kg FS-DDGS group; FS-DDGS100, 100 g/kg FS-DDGS group; FS-DDGS150, 150 g/kg FS-DDGS group.
a: redness; b: yellowness; L*: lightness.

The effects of dietary FS-DDGS addition on muscle nutrient composition of growing-finishing pigs

As presented in Table 6, the contents of ash and crude protein were increased (linear, P < 0.05) in the LD muscle of pigs fed the increasing level of dietary FS-DDGS. Meanwhile, the dietary FS-DDGS levels had no linear or quadratic effects (P > 0.05) on the contents of ash, crude protein, and IMF in the BF muscle.

Table 6

Effects of dietary addition with fermented sorghum distiller's dried grains with soluble (FS-DDGS) on nutrient contents of muscle in growing-finishing pigs (g/100 g muscle, as-fresh basis; n = 12)
Items	Treatments¹				SEM	P-values
Items	FS-DDGS0	FS-DDGS0	FS-DDGS0	FS-DDGS0	SEM	Linear	Quadratic
Longissimus dorsi muscle
Ash	1.37^b	1.32^b	1.35^b	1.53^a	0.045	< 0.01	< 0.01
Crude protein	21.90	22.08	22.39	22.53	0.289	0.02	0.06
Intramuscular fat	1.52	1.68	1.82	1.89	0.248	0.11	0.27
Biceps femoris muscle
Ash	1.32	1.26	1.33	1.33	0.044	0.41	0.46
Crude protein	20.57	20.61	20.82	21.03	0.309	0.10	0.25
Intramuscular fat	1.84	1.84	1.98	2.11	0.218	0.16	0.35
¹ FS-DDGS0, 0 g/kg FS-DDGS group; FS-DDGS50, 50 g/kg FS-DDGS group; FS-DDGS100, 100 g/kg FS-DDGS group; FS-DDGS150, 150 g/kg FS-DDGS group.

As presented in Tables 7 and 8, the Pro content in the LD muscle was increased (linear, P < 0.05) as the increasing level of dietary FS-DDGS. In addition, the Cys content in the LD muscle was showed a tendency for a quadratic effect (P = 0.087), and the highest value was observed in the FS-DDGS50 group. However, the Gly content in the LD muscle was showed a tendency for a decrease (linear, P = 0.056) as the increasing level of dietary FS-DDGS up to 15%. The increasing dietary FS-DDGS levels had linear (P < 0.05) effects on the contents of Ala, Arg, Asp, Glu, Ile, Leu, Lys, Ser, and Tyr in the BF muscle, and there was highest contents of Gly and Pro in the FS-DDGS150 group (quadratic, P < 0.05).

Table 7

Effects of dietary addition with fermented sorghum distiller's dried grains with soluble (FS-DDGS) on amino acid contents of *Longissimus dorsi* muscle in growing-finishing pigs (g/100 g fresh muscle; n = 12)
Items	Treatments¹					SEM	P-values
Items	FS-DDGS0	FS-DDGS0	FS-DDGS0		FS-DDGS0	SEM	Linear	Quadratic
Ala	1.22	1.19	1.20	1.22		0.024	0.92	0.40
Arg	1.33	1.31	1.33	1.32		0.024	0.87	0.98
Asp²	1.98	1.96	2.00	1.97		0.037	0.85	0.93
Cys	0.08^b	0.12^a	0.08^b	0.08^b		0.011	0.38	0.09
Glu³	2.94	2.90	2.87	2.94		0.050	0.85	0.30
Gly	0.90	0.86	0.87	0.86		0.019	0.06	0.09
His	0.93	0.92	0.95	0.93		0.021	0.78	0.93
Ile	1.01	1.00	1.00	1.00		0.025	0.74	0.94
Leu	1.69	1.67	1.71	1.69		0.034	0.67	0.91
Lys	1.92	1.87	1.90	1.91		0.035	0.96	0.46
Met	0.56	0.55	0.57	0.58		0.016	0.11	0.22
Phe	0.94	0.95	0.92	0.98		0.024	0.22	0.16
Pro	0.76^b	0.78^b	0.80^ab	0.84^a		0.015	< 0.01	< 0.01
Ser	0.78	0.76	0.77	0.77		0.014	0.71	0.49
Thr	1.02	0.99	1.00	1.00		0.026	0.54	0.69
Tyr	0.78	0.74	0.77	0.77		0.017	0.91	0.25
Val	1.04	1.05	1.06	1.02		0.019	0.59	0.17
¹ FS-DDGS0, 0 g/kg FS-DDGS group; FS-DDGS50, 50 g/kg FS-DDGS group; FS-DDGS100, 100 g/kg FS-DDGS group; FS-DDGS150, 150 g/kg FS-DDGS group.
² Including aspartate and asparagine.
³ Including glutamate and glutamine.

Table 8

Effects of dietary addition with fermented sorghum distiller's dried grains with soluble (FS-DDGS) on amino acid contents of *Biceps femoris* muscle in growing-finishing pigs (g/100 g fresh muscle; n = 12)
Items	Treatments¹				SEM	P-values
Items	FS-DDGS0	FS-DDGS0	FS-DDGS0	FS-DDGS0	SEM	Linear	Quadratic
Ala	1.13^bc	1.10^c	1.17^ab	1.20^a	0.022	< 0.01	< 0.01
Arg	1.18^b	1.23^ab	1.27^a	1.27^a	0.027	< 0.01	< 0.01
Asp²	1.79^b	1.77^b	1.88^a	1.86^ab	0.035	< 0.01	0.03
Cys	0.19	0.17	0.17	0.18	0.015	0.53	0.40
Glu³	2.44^b	2.84^a	2.91^a	2.89^a	0.073	< 0.01	< 0.01
Gly	0.88^ab	0.84^b	0.86^ab	0.91^a	0.022	0.15	< 0.01
His	0.75	0.74	0.77	0.72	0.029	0.63	0.52
Ile	0.93^ab	0.90^b	0.95^ab	0.96^a	0.020	0.03	0.05
Leu	1.57^b	1.55^b	1.62^ab	1.65^a	0.027	< 0.01	< 0.01
Lys	1.73^ab	1.71^b	1.80^a	1.79^ab	0.032	0.01	0.05
Met	0.51	0.52	0.54	0.52	0.024	0.73	0.68
Phe	0.91	0.90	0.95	0.91	0.023	0.34	0.36
Pro	0.81	0.77	0.78	0.83	0.024	0.37	0.06
Ser	0.73	0.71	0.75	0.75	0.016	0.04	0.09
Thr	0.92	0.91	0.95	0.94	0.020	0.12	0.29
Tyr	0.66^b	0.68^b	0.72^a	0.72^a	0.014	< 0.01	< 0.01
Val	0.98	0.97	1.00	1.00	0.021	0.11	0.27
¹ FS-DDGS0, 0 g/kg FS-DDGS group; FS-DDGS50, 50 g/kg FS-DDGS group; FS-DDGS100, 100 g/kg FS-DDGS group; FS-DDGS150, 150 g/kg FS-DDGS group.
² Including aspartate and asparagine.
³ Including glutamate and glutamine.

Discussion

The DDGS contain higher levels of protein, fat, and fiber compared with its original grains (Choi et al. 2009). Therefore, replacing a certain amount of feed ingredients with DDGS is economically sound when its nutrients are available to the animals (Alsuwaiegh et al. 2002). It has been well documented that fermented products provide more beneficial microbes, digestive enzymes, and bioactive metabolites to animals and thus beneficially improved the ADG (Jami et al. 2012). However, in the present study, dietary FS-DDGS addition did not affect the ADFI, ADG, and F:G of pigs, suggesting that the addition levels of 50–150 g/kg FS-DDGS does not affect pigs’ growth performance. One possible explanation is that a higher level of dietary FS-DDGS increased the dietary fiber level, and therefore negatively affected the nutrient availability to the animals. Another explanation is that high-fiber diet induced the growth of the visceral organs (Wenk, 2001) and secretion of digestive fluids (Agyekum et al. 2013), and therefore increased energy expenditure for maintenance rather than for catabolic metabolism (Nyachoti et al. 2000). The latter tended to be supported by the increased loin eye area and reduced bone percentage of pigs fed the diets with FS-DDGS. Therefore, our findings suggested that the FS-DDGS could be supplemented to diet of growing-finishing pigs up to 150 g/kg and partially replace grains.

Meat color affects the perception of freshness and is a key driving factor for customer purchase (Brewer et al. 2001). The pH value, color, and water holding capacity of meat indicate meat quality (Ahmed et al. 2016). The pH value of pork in the present study was within 5.3 to 5.7, indicating that it was under the optimal level (Warriss, 1982). In addition, the L* value decreased with the increase in dietary FS-DDGS level, suggesting the improvement in meat quality because the L* value is inversely correlated with the pH value of the muscle (Huff-Lonergan et al. 2002). In our study, dietary FS-DDGS addition decreased b* and L* values while increased a* value, suggesting a component of it might affect meat quality in pigs. In addition, lower drip loss was found in the FS-DDGS groups. Similarly, fermented ginkgo leaves also reduce drip loss value in broilers (Niu et al. 2017). It is well known that most water in the cell is held in myofibrils. The type of muscle fibers and the content of fat are likely to play a significant role in the drip loss (Yang et al. 2019). Since the FS-DDGS addition has no effect on the fat content of the muscles, the reason for the lower drip loss may be the difference in muscle fibers, but this needs further research. In general, dietary FS-DDGS addition ameliorated meat quality by decreasing drip loss and improving meat color and pH value of pork.

In addition, dietary FS-DDGS addition increased the contents of ash and crude protein in LD muscle in the present study. The higher ash content could be attributed to the fermentation process, which increases the availability of ash in the diet supplemented with FS-DDGS by reducing the level of anti-nutritional tannins and flavonoids that inhibit mineral absorption (Ahmed et al. 2016). Amino acids are the building blocks of proteins, and their composition and content represent protein quality. Furthermore, some amino acids play key roles in the aroma and flavor profiles of meat. For example, Arg, Leu, Ile, Val, Phe, Met, and His present a bitter taste; Glu and Asp present a pleasant fresh taste; and Gly, Ala, and Ser present a sweet taste (Lorenzo and Franco, 2012). In the present study, dietary FS-DDGS addition increased the contents of Pro in LD muscle, as well as Ala, Arg, Asp, Glu, Ile, Leu, Lys, Ser and Tyr in BF muscle. Previous study showed that proper industrial fermentation with beneficial microbes on feed ingredients could increase the contents of amino acids and improve the availability of dietary protein, thereby increasing nutrient value of pork (Vong et al. 2016). Taken together, dietary FS-DDGS addition could improve the quality and flavor of pork by improving the muscular contents of flavor amino acids.

Conclusions

In summary, the present study indicated that 50–150 g/kg fermented sorghum distiller's dried grains with soluble (FS-DDGS) did not have any adverse effects on the growth performance of growing-finishing pigs. Importantly, superior meat quality can be achieved by 150 g/kg FS-DDGS addition in pig diet. In addition, future studies should be conducted to confirm and expand upon the beneficial effects of FS-DDGS in animals.

Declarations

Authors’ contributions Huawei Li, Yehui Duan, Fugui Yin, and Fengna Li performed sampling and nutrient measurements, analyzed data, interpreted the results, and drafted the manuscript; Qian Zhu, Chengjun Hu, and Peifeng Xie conducted animal feeding and sampling; Runxi Cheng prepared the FS-DDGS; Xiangfeng Kong and Lingying Wu contributed to experimental concepts and design, provided scientific.

Data availability All data generated or analyzed during this study are included in this published paper.

Funding The present study was jointly supported by the National Natural Science Foundation of China (31772613, China), Special Funds for Construction of Innovative Provinces in Hunan Province (2019RS3022, China), and Collaboration Project of Road Biological (Gulin) Co., Ltd. (Luzhou, China). We thank staffs and postgraduate students from Hunan Provincial Key Laboratory of Animal Nutritional Physiology and Metabolic Process for collecting samples and technicians from CAS Key Laboratory of Agro-ecological Processes in Subtropical Region for providing technical assistance.

Ethical approval The experimental design and procedures in the present study were reviewed and approved by the Animal Care and Use Committee of the Institute of Subtropical Agriculture, Chinese Academy of Sciences (ISA-2017-031, Changsha, China).

Consent to participate Not applicable.

Consent to publication Not applicable.

Conflict of interest The authors declare that there are no competing interests regarding the publication of this paper.

References

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