Effects of YGF251 on the growth performance, nutrient digestibility, meat quality, and fecal gas emission of finishing pigs

ABSTRACT

This study examined the effects of young growth factor (YGF251) on the growth performance, nutrient digestibility, meat quality, and fecal gas emission of finishing pigs. A total of 80 119-day-old crossbred finishing pigs [(Yorkshire × Landrace) × Duroc], with an average initial body weight (BW) of 65.53 ± 3.89 kg, were used in a 61-day experiment with a completely randomized block design. The pigs were fed with either a basal control diet (CON) or a basal diet supplemented with 0.04% YGF251 (YGF). There were 10 replicate pens per treatment, with four pigs (two barrows and two gilts) per pen. In this study, pigs consuming the YGF251-supplemented diet had a higher average daily gain (ADG) and growth rate, as well as a lower feed conversion ratio (FCR), than the pigs consuming the CON diet. Moreover, with regard to meat quality, increased water-holding capacity (WHC) and decreased drip loss on day 7 were observed in pigs consuming the YGF diet. However, nutrient digestibility and fecal gas emission did not differ between the CON and YGF diet groups. In conclusion, the YGF251 diet group showed superior growth performance, WHC, and drip loss.

KEYWORDS:

• YGF251
• finishing pig
• growth performance
• meat quality
• herbal extract

Introduction

The subtherapeutic use of antibiotic growth promoters in livestock diets can enhance growth performance and production (Petrujkić et al. 2018). However, due to bacterial resistance and antibiotic residues in animal products, many countries (e.g. European Union countries and South Korea) have banned the use of antibiotic growth promoters in animal diets (Levy 2014). Recently, considerable attention has been given to natural herbal extracts due to their safety and environmentally friendly characteristics. Several studies have reported positive effects of herbal extracts on growth performance, nutrient digestibility, fecal microbial community, and meat quality (Hossain et al. 2018; Lei et al. 2018).

Young growth factor (YGF251) is extracted from herbs including Phlomis umbrosa Turcz, Cynanchum wilfordii Hemsley, Zingiber officinale Rosc, and Platycodi Radix. Choi et al. (2002) reported positive effects of this plant extract on the physical growth of humans. Dietary supplementation with YGF251 has been reported to have a positive effect on the growth performance of growing pigs (Devi et al. 2015), as well on the dry matter and energy content of sow colostrum (Upadhaya et al. 2016). Moreover, increased body weight (BW), energy retention, and femur length were observed in broiler chicken following supplementation of the diet with YGF251 (Begum et al. 2014).

Based on the above, YGF251 probably positively affects the performance of animals. The information on the effects of YGF251 on finishing pigs is currently limited. The objective of this experiment was to test the hypothesis that supplementing the diet of finishing pigs with YGF251 would have beneficial effects on growth performance and production characteristics (nutrient digestibility, meat quality, and fecal gas emission).

Material and methods

The protocols employed in this experiment were approved by the Animal Protocol Review Committee of Dankook University, South Korea.

Source of herbal extract

The plant extract used in the present study was a commercial product obtained from Doosan Feed Inc. (Bucheon, South Korea) that consisted of Phlomis umbrosa Turcz (25%), Cynanchum wilfordii Hemsley (30%), Zingiber officinale Rosc (15%) and Platycodi Radix (30%) extracts (5.20% YGF251). YGF251 was selected from among various natural herbal extracts due to its in vivo efficacy and safety, and its ability to induce insulin-like growth factor 1 (IGF-1). The active ingredients of YGF251 were extracted in hot water (60–95°C); extraction at temperature below 60°C is less effective, while temperatures higher than 95°C reduce the levels of active ingredients. The crude extract was then cooled and the precipitate was removed through centrifugation. The resulting extract was separated on the basis of molecular weight to obtain a relatively low-molecular-weight compound with the desired active ingredients (Kim et al. 2002).

Animals and housing

Eighty 119-day-old crossbred finishing pigs [(Yorkshire × Landrace) × Duroc] with an average initial body weight of 65.53 ± 3.89 kg were used in a complete randomized block experiment. The pigs were housed into a thermostatically controlled ambient environmental temperature (25°C) with the slatted plastic floor, and equipped with one side self-feeder and nipple drinker.

Experimental design and diets

The present experiment lasted for 61 days. Pigs were fed either a basal diet (CON; Table 1) or a basal diet supplemented with 0.04% YGF251 diet (YGF). Each treatment had 10 replicate pens, with 4 pigs (two barrows and two gilts) per pen. The basal diet was formulated to meet the nutrient requirements recommended by the National Research Council (NRC 2012). The feed and water were provided ad libitum throughout all periods of the experiment.

Table 1. Composition of the experimental finishing pig diets (as-feed basis).

Items
Ingredients (%)
Yellow corn	53.39
Wheat	15.00
Soybean meal (Crude Protein 44%)	14.30
Soybean meal (Crude Protein 45.4%)	6.64
Limestone	0.84
Salt	0.30
Dicalcium phosphate	1.30
Methionine (50%)	0.06
L-Lysine H2So4 (51%)	0.45
L-Threonine (98.5%)	0.15
Vitamin premix^a	0.05
Mineral premix^b	0.12
Animal fat	4.25
Choline (50%)	0.15
Molasses	3.00
Total	100.00
Calculated composition, %
Dry matter	87.35
Moisture	12.65
Crude protein	15.55
Crude fat	6.69
Calcium	0.72
Total phosphorus	0.54
Available phosphorus	0.28
Lysine	0.90
Methionine	0.26
Digestive energy (kcal kg^−1)	3560

^aProvided per kilogram of complete diet: 4,000 IU vitamin A; 800 IU vitamin D₃; 171 IU vitamin E; 2 mg vitaminK₃; 4 mg riboflavin; 20 mg niacin; 4 mg thiamine; 11 mg d-pantothenic acid; 166 mg choline; 0.08 mg biotin; 16 μg vitamin B₁₂.

^bProvided per kilogram of complete diet: 15 mg Cu (as CuSO₄·5H₂O); 80 mg Fe (as FeSO₄·7H₂O); 56 mg Zn (as ZnSO₄); 73 mg Mn (MnO₂); 0.3 mg I (as KI); 0.5 mg Co (as CoSO₄·5H₂O); 0.4 mg Se (as Na₂SeO₃·5H₂O).

Sampling and measurements

On the 59th day of the experiment, the fresh feces were collected via the rectal massage method from randomly selected two pigs in each pen for analyzing ammonia (NH₃), hydrogen sulfide (H₂S), and total mercaptan (R-SH) concentrations. Samples from the same pen were mixed and stored together. For the analysis of gas emission, sub-samples of feces were stored in the 2.6-L sealed plastic box in duplicates. After being sealed in the boxes, samples were fermented 24 h at room temperature (25℃). Before measurement, the sample was manually shaken 30s for homogenization. A gas-sampling pump (model GV-100S; Gastec Corp., Japan; Gastec detector tube No.3La for ammonia; No.4LK for hydrogen sulfide; No.70L for total mercaptans) was utilized for NH₃, H₂S, and R-SH detection. Air samples were taken 100 ml at the head space above the surface of excreta through the small hole, the sampling height was about 2.0 cm. Two samples from each pen were measured and then the average was calculated.

The individual body weight (BW) and pen-based feed consumption were recorded at the beginning and end of this experiment to calculate the average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR) accordingly. The growth rate was calculated as the ratio of body weight at the end of the period to body weight at the beginning of the period. During the 55th day of the experiment, 0.20% chromium oxide (Cr₂O₃) was added into dietary feed as an indigestible marker to determine the apparent total tract digestibility (ATTD) of dry matter (DM), nitrogen (N), and gross energy (GE). The typical feed samples were collected. On the 60th day of the experiment, fresh feces samples were collected from randomly selected 2 pigs per pen via rectal massage. All feed and fecal samples were stored at –20℃ until analysis. Before chemical analysis, samples were oven-dried at 60℃ for 72 h and then grind as powdery, which can through 1-mm sieve. The method of AOAC (2007) was used to analyze the DM (method 930.15) and N (method 984.13) of feed and fecal samples. The combustion heat was measured by a bomb calorimeter (Parr 6100; Parr Instrument Co., Moline, IL, USA) to determine the GE. The chromium level was analyzed via UV absorption spectrophotometry (UV-1201, Shimadzu, Kyoto, Japan). The ATTD was calculated using the following formula:$\begin{array}{rl}& \mathrm{ATTD}(\text{\%})=[1-\{(\mathrm{Nf}\times \mathrm{Cd})/(\mathrm{Nd}\times \mathrm{Cf})\}]\times 100,\\ & \mathrm{Nf}=\mathrm{nutrient}\mathrm{concentration}\mathrm{in}\mathrm{feces}(\text{\%}\mathrm{DM}),\\ & \mathrm{Nd}=\mathrm{nutrient}\mathrm{concentration}\mathrm{in}\mathrm{diet}(\text{\%}\mathrm{DM}),\\ & \mathrm{Cd}=\mathrm{chromium}\mathrm{concentration}\mathrm{in}\mathrm{diet}(\text{\%}\mathrm{DM}),\\ & \mathrm{Cf}=\mathrm{chromium}\mathrm{concentration}\mathrm{in}\mathrm{feces}(\text{\%}\mathrm{DM}).\end{array}$At the beginning and end of this study, 10 pigs were randomly selected from each treatment (one pig/pen) to determine the back-fat thickness (BFT). The real-time ultrasound instrument (Piglog 105, SFK Technology, Herlev, Denmark) was used to measure 6-cm off the mid-line of the body at the 10th rib.

At the end of the experiment, all pigs were slaughtered at a local commercial slaughterhouse. Piece of the right loin sample was removed between the 10th and 11^th ribs after chilling at 2°C for 24 h, ten pigs were randomly selected from each treatment (one pig/pen). According to the description of National Pork Producers Council Standards (NPPC 2000), the sensory evaluation of colour, marbling, and firmness score were conducted at ambient temperature (25°C). After the subjective tests, Model CR-410 Chroma metre (Konica Minolta Sensing, Inc., Osaka, Japan) was used immediately to measure the lightness (L*), redness (a*) and yellowness (b*) values at three locations on the surface of each sample. At the same time, a pH metre (Pittsburgh, PA, USA) was used to measure and record the pH value at two different positions. Thereafter, a 0.30 g meat sample was pressed at 3,000 psi for 3 min on a 125-mm-diameter piece of filter paper. The areas of the pressed sample and the expressed moisture were delineated and then determined using a digitizing area-line sensor (MT-10S; M.T. Precision Co. Ltd., Tokyo, Japan) to calculate the water-holding capacity (WHC). Simultaneously, the longissimus muscle area (LMA) was measured by tracing the longissimus muscle surface at the 10th rib, which also used the above-mentioned digitizing area-line sensor. Thereafter, 5 g of meat sample was heat-treated in plastic bags separately in a water bath (100°C) for 5 min to measure cooking loss. Samples were cooled at room temperature (25℃). Cooking loss was calculated as (sample weight before cooking − sample weight after cooking)/ sample weight before cooking × 100. The plastic bag method was used to calculate the drip loss, approximately 2 g of meat sample was used to measure the drip loss at the 1^st, 3^rd, 5^th, and 7^th days after chilling 24 h at 2°C.

Statistical analysis

All data were statistically analyzed using the GLM procedure of SAS (SAS Inst. Inc., Cary, NC, USA), with the replicate pen being defined as the experimental unit. Differences among all treatments were statistical using Tukey’s multiple range test. The data were presented as means and pooled standard error of the mean. Differences among the treatment means were determined with P ≤ 0.05 indicating the significance and P < 0.10 indicating trends.

Results

As shown in Table 2, a higher growth rate (P < 0.05), higher average daily gain (ADG) (P < 0.05), and lower feed conversion ratio (FCR) (P < 0.05) were observed in pigs fed a diet supplemented with YGF251 than pigs fed the CON diet. There was also a tendency for the final BW to increase (P = 0.06) in pigs consuming the YGF diet compared to those consuming the CON diet. However, the average daily feed intake (ADFI) and backfat thickness (BFT) were not different between the YGF and CON diet groups. The apparent total tract digestibility (ATTD) of dry matter (DM), nitrogen (N), and the gross energy (GE), were also similar between the YGF251 and CON diet groups (Table 2).

Table 2. Effects of YGF251 on the growth performance and nutrient digestibility in finishing pigs¹.

	CON	YGF	SEM	P-value
Body weight, kg
Initial	65.51	65.53	0.05	0.76
Final	105.01	106.59	0.51	0.06
Growth rate, %	1.60^b	1.63^a	0.01	0.04
Growth performance
ADG, g	718.18^b	746.59^a	8.58	0.04
ADFI, g	2292.41	2317.96	29.57	0.56
FCR	3.19^a	3.11^b	0.02	0.03
Apparent total tract digestibility, %
DM	72.79	73.39	0.72	0.57
GE	72.76	74.18	0.63	0.15
N	72.35	72.50	0.71	0.88
Back-fat thickness, mm
Initial	12.05	12.25	0.18	0.46
Final	17.05	17.50	0.29	0.30

Abbreviation: ADG, average daily gain; ADFI, average daily feed intake; FCR, feed conversion ratio; DM, dry matter; GE, gross energy; N, nitrogen.

¹Dietary treatments were: CON, Basal diet; YGF, Basal diet + 0.04% YGF251.

^a,bDifferent superscripts within a row indicate a significant difference (p < 0.05).

The effects of dietary supplementation of YGF251 on meat quality are shown in Table 3. Increased water-holding capacity (WHC) (P = 0.05) and decreased drip loss on day 7 (P < 0.05) were observed in pigs consuming the YGF diet compared to those consuming the CON diet. However, there were no statistical differences in sensory characteristics (colour, marbling, and firmness), meat colour parameters (lightness, redness, and yellowness), pH, drip loss on days 1, 3, and 5, or longissimus muscle area (LMA) between the CON and YGF groups.

Table 3. Effects of YGF251 on the meat quality in finishing pigs¹.

	CON	YGF	SEM	P-value
Sensory evaluation
Colour	3.38	3.34	0.04	0.64
Marbling	3.00	3.09	0.06	0.32
Firmness	2.91	2.88	0.19	0.92
Meat colour
Lightness, L*	47.81	47.26	1.50	0.81
Redness, a*	13.99	14.07	0.21	0.80
Yellowness, b*	3.92	3.77	0.06	0.18
pH	5.55	5.46	0.05	0.30
Cooking loss, %	32.51	31.70	1.26	0.68
Drip loss, %
Day 1	6.27	6.41	0.81	0.91
Day 3	12.78	12.64	0.12	0.46
Day 5	18.37	17.68	0.87	0.62
Day 7	23.64^a	21.73^b	0.24	0.01
WHC, %	44.29^b	47.80^a	0.77	0.05
LMA, cm^2	60.52	61.16	0.82	0.62

Abbreviation: WHC, water-holding capacity; LMA, longissimus muscle area.

¹Dietary treatments were: CON, Basal diet; YGF, Basal diet + 0.04% YGF251.

^a,bDifferent superscripts within a row indicate a significant difference (p < 0.05).

The fecal gas emission from pigs (Table 4), including NH₃, H₂S, and R-SH were not different between the YGF251 and CON diet groups.

Table 4. Effects of YGF251 on the fecal gas emission in finishing pigs¹.

	CON	YGF	SEM	P-value
NH3, ppm	6.00	6.25	1.03	0.88
H2S, ppm	7.53	7.25	0.34	0.61
R-SH, ppm	5.38	5.00	0.33	0.47

Abbreviation: NH₃, ammonia; H₂S, hydrogen sulfide; R-SH, total mercaptans.

¹Dietary treatments were: CON, Basal diet; YGF, Basal diet + 0.04% YGF251.

Discussion

The results of this study showed that ADG, FCR, and growth rate, but not ADFI, were improved in the YGF versus CON diet groups of finishing pigs. A previous study showed that plant extract can exert positive effects on the growth and health of pigs (Windisch et al. 2008). Devi et al. (2015) observed that, in growing pigs fed a diet supplemented with YGF251 (0.05 or 0.10%), ADG increased while ADFI and FCR were not affected. However, Lei et al. (2019) noted that ADG, ADFI, and FCR were not improved in growing pigs fed a diet supplemented with 0.05% YGF251. Devi et al. (2015) suggested that the improvement in ADG of pigs fed a diet supplemented with YGF251 (0.05 or 0.10%) was due to the amelioration of plasma IGF-1 concentration. Begum et al. (2014) noted that IGF-1 levels in broiler chicken were improved by 0.10% YGF251, which also increased the BW. The concentration of circulating IGF-1 was found to be positively correlated with growth (Li et al. 2019). Lee et al. (2002; 2005) observed that IGF-1 levels were positively correlated with the ADG of pigs. Liu et al. (2020) noted that serum IGF-1 was positively associated with the growth rate and feeding efficiency of pigs, but not with the BFT (Cameron et al. 2003; Devi et al. 2015). In the present study, BFT did not differ between the YGF251 and CON diet groups, while the ADG, FCR, and growth rate were superior in pigs consuming the YGF diet. These findings are consistent with the results of the above-mentioned studies. Therefore, a diet supplemented with 0.04% YGF251 may increase the IGF-1 concentration in finishing pigs. Although the IGF-1 concentration was not measured in the present study, based on the above studies we speculated that the improvement in ADG, final BW, and growth rate, as well as the reduction in FCR, may have been due to the increase in IGF-1 concentration. For validation, further experiments should be conducted comparing the serum IGF-1 concentration in pigs fed a YGF251-supplemented diet versus a basal diet.

Oxidative reactions in meat begin immediately after slaughter. These reactions denature muscle protein and affect meat colour (Haak et al. 2009; Yu et al. 2010), pH (Boruzi and Nour 2019), sensory characteristics (Bidner et al. 2004; Arkfeld 2016), and cooking loss (Aaslyng et al. 2003). However, no statistically significant diet group differences in meat colour (L*, a*, and b*), pH, sensory characteristics (colour, firmness, and marbling), or cooking loss were observed in this study, indicating that oxidation did not occur. Water is a dipolar molecule attracted to charged species, including proteins (Arkfeld 2016). The WHC depends on the proteins and structures that bind and entrap water, specifically myofibrillar proteins. Thus, WHC therefore depends on the protein content of a muscle. Kim (2006) noted that YGF251 promoted protein biosynthesis and skeletal muscle regeneration. Therefore, the increase in WHC and reduction in drip loss on day 7 have been due to the enhanced muscle protein biosynthesis associated with YGF251 supplementation. Increased WHC reduces the weight loss of pork due to drip loss, which reduces the economic losses of retailers. A reduction in drip loss also limits the amount of water present in the packaging bag during sale and storage, which improves the acceptability of the meat to consumers (Ngapo et al. 2007).

In the present study, nutrient digestibility was not significantly different between the CON and YGF diet groups. As reported by Yin et al. (2018), due to the fecal microbial was ameliorated in pigs fed a diet supplemented with herbal extract, thus, the nutrient digestibility and the fecal gas emission were improved. Lei et al. (2019) noted adult pigs were fed a diet supplemented with YGF251. A dose below 0.05% did not affect the intestinal microbial balance, and thus did not impact nutrient digestibility. Gas emissions were related to fluctuations in the intestinal microbial community (Park and Kim 2018). Jiao et al. (2019) noted no effect of a herbal extract on the noxious gas emissions of animals, which was due to the lack of any effect on the fecal microbial community. In this study, fecal gas emission was not affected by YGF251, such that the intestinal microbial balance was probably also unaffected. This may explain why nutrient digestibility was not different between the YGF251 and CON diet groups in this study. However, further experiments on the intestine microbial community are needed to validate these findings.

Devi et al. (2015) noted that fecal NH₃ and R-SH emissions decreased in growing pigs fed with diets containing 0.05%, 0.10%, or 0.15% YGF251. They reported that noxious gas emissions were ameliorated due to the improved nutrient digestibility. Liu et al. (2018) also reported a correlation between nutrient digestibility and fecal gas emission. It is well known that an increase in nutrient digestibility reduces the substrate available for microbial fermentation in the gut, thereby also reducing excreta noxious gas emission (Yan et al. 2011). In the present study, the non-significant difference in fecal gas emission between the 0.04% YGF251 and CON diet groups have been due to a lack of any significant effect of YGF251 on the total tract nutrient digestibility of finishing pigs.

Conclusion

A diet supplemented with 0.04% YGF251 slightly improved the growth performance and meat quality of finishing pigs, but not the nutrient digestibility or fecal gas emission. A better growth performance may shorten the time to market, while higher WHC may increase the value of meat products. However, further experiments on serum IGF-1 concentrations and intestinal microbiota are needed to determine the effects of dietary YGF251 on finishing pigs. In conclusion, the addition of 0.04% YGF251 to the diet of finishing pigs has the potential to improve growth performance and some aspects of meat quality.

Disclosure statement

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