Chinese herb feed additives improved the growth performance, meat quality, and nutrient digestibility parameters of pigs

Abstract Background Since the use of antibiotics in animal feed has become a critical concern worldwide due to severe threats to human health and environment, we are in need of finding alternatives to antibiotics in pig breeding, maintaining the health of pigs, and getting high‐quality pork. As traditional Chinese herbs (TCH) are rich natural resources in China and show great benefits to human health we propose to transfer this abundant resource into animal production industry as additives. Methods Three groups of Chinese herbs (groups A, B, and C) were used as feed additives in the diet for pigs. In total 32 pigs were arranged in four groups (groups A, B, C, and control group, NC), fed in the same facility, eight pigs (one group) in each colony, free drinking, for 120 days. The feed:gain ratio (F/G), meat quality, total protein, and amino acid concentration of muscle were checked in the experiments. Results After 120 days of feeding, the feed:gain ratio (F/G) of pigs in groups A, B, and C was decreased 17.56%, 9.31%, and 13.86% compared with NC treatment, respectively. The diets supplemented with Chinese herbs improved meat quality, increased loin eye area (especially group A and C showed significant difference, P < .001), the total protein (increased ratio vs NC was A = 4.54%, B = 0.38% and C = 3.53%), amino acid concentration of muscle, increased the villus height:crypt depth ratio, and induced positive effects on serum biochemical parameters and immune function (serum TC and TG concentrations were significantly lower than those in the NC group, P < .05.). Conclusions The use of Chinese herbal feed additives can reduce the cost of pig breeding and produce high‐quality pock. The combination of these effects would contribute to better absorption ability of the intestinal tract and yield a better growth performance.


| INTRODUC TI ON
Antibiotics have long been of great benefit for people, both in the medical treatment of human disease and in animal food, where they improve the growth performance and feed utilization during animal production. 1 Antibiotics as in-feed supplements affect all stages of pork production, including the gestation, nursing, growing, and terminal stage, although the effects show stage-dependent differences. 1 However, the use of antibiotics in animal feed has become a critical concern worldwide due to the severe threats to human health and the environment. [1][2][3] Therefore, many researchers have investigated alternative feed additives or supplements, such as probiotics, enzymes, minerals, organic acids, and herbs. 3 Phytogenic comprise a wide variety of herbs, spices, and their derived products, especially essential oils. 4,5 The available evidence indicates that phytogenic compounds may specifically enhance the activities of digestive enzymes and nutrient absorption. 4 In addition, some phytogenic compounds seem to promote intestinal mucus production. 4 Traditional Chinese herbs (TCH) have been used for more than 3000 years. 6 As TCH are rich natural resources in China and show great benefits to human health we propose to transfer this abundant resource into animal production industry as additives.
Recently, Chinese herbs are garnering growing interest as feed additives in animal production, but data on the effects of Chinese herbs on swine production are scarce. 7 In thi study, three groups of Chinese herbs were used as feed additives in the diet of swine.
The herbs were put in the feed for 120 days, and growth performance, meat quality, serum biochemical parameters, intestinal villus morphology, and gut microbiota were investigated. The results confirm the feasibility of Chinese herbs as feed additives in the production of pigs.

| Experimental design, animals, housing, and diets
The animal protocol for this experiment was approved by the Animal Care Committee of Fujian Academy of Agricultural Sciences, China.
Animals were maintained and processed in accordance with the Fujian Academy of Agricultural Sciences Guide for the Care and Use of Laboratory Animals.
Antibiotic-free basal diet was purchased from Hualong Group, Fujian province, China (Table 1). A total of 32 swine with an average initial body weight (BW) of 38 kg were used in a 120-day experiment. The swine were housed in an environmentally controlled, slatted-floor facility in adjacent pens (1.2-1.5 m 2 ) and were allowed ad libitum access to feed and water through a self-feeder and nipple drinker throughout the experimental period. Swine were randomly allocated into four groups (eight pigs per group, including four males and four females). Piglets in the control group were fed a basal diet that was formulated based on a corn powder and soybean meal diet that met the National Research Council (2012) swine requirements and China swine standards. Dietary treatments included negative control (NC, antibiotic-free basal diet), group A (NC + Chinese herb feed additive group A), group B (NC + Chinese herb feed additive group B), and group C (NC + Chinese herb feed additive group C).
Each group of Chinese herb feed additives was smashed, mixed, and directly added into the basal diet.

| Sampling and measurements
Piglets were weighed at the beginning and end of this dietary experiment to obtain information about average daily gain (ADG). Feed added to the feeder and any wasted feed were weighed to calculate average daily feed intake (ADFI). The feed:gain ratio (F/G) was further calculated based on the ADG and ADFI data.
Pigs were stunned using electronarcosis and killed at the end of the experiment. Meat quality and amino acid levels in meat were measured. The duodenum, jejunum, ileum, and intestines were sampled and examined for morphology as well as intestinal microflora.

| Statistical analysis
For each set of assays, at least three independent experiments were carried out. The results are expressed as the means ± standard deviations (SD). Statistical significance was calculated using the t test, followed by comparing the additive-treated groups with the NC group. Statistical analysis was carried out using GraphPad Prism software version 5 (GraphPad Software). The results were statistically significant at P < .05.

| Growth performance
The effects of Chinese herb feed additives on the growth performance of pigs are shown in in Table 2. Pigs in the Chinese herb feed additive groups showed greater ADG and lower F/G compared with NC treatment. The F/G of pigs in groups A, B, and C was decreased 17.56%, 9.31%, and 13.86% compared with NC treatment. The ADG of pigs in group A was higher than that in groups B and C, while the F/G of pigs in group A was lower than groups B and C. There was no difference in ADFI between herb-treated groups and the control group. These results indicate that three Chinese herb feed additive mixtures can enhance the growth performance of swine.

| Meat quality and amino acid levels
The qualitative characteristics of the meat quality are shown in Table 3. The loin eye area tended to be increased in pigs fed with the Chinese herb feed additives. Specifically, the loin eye area was significantly increased in groups A and C compared with the control group. In contrast, the drip loss rate tended to be decreased in the Chinese herb feed additive diet groups, and the drip loss rate of groups A and C was significantly decreased compared with the control group. The pH1, pH24, and cooked meat percentage did not differ significantly between the groups (Table 3). Total protein, total amino acids, total lipids, crude ash, calcium, and phosphorus in the meat of pigs treated with Chinese herb feed additives tended to be increased over the control group. The total protein of pigs in groups A, B, and C was increased by 4.54%, 0.38%, and 3.53%, respectively.
The total amino acids of pigs in groups A, B, and C were increased by 5.67%, 1.44%, and 3.94%, respectively. The total lipid of pigs in groups A, B and C was increased by 14.19%, 12.84%, and 17.57%, respectively. The crude ash of pigs in groups A, B, and C was increased by 1.38%, 8.00%, and 9.80%, respectively. The calcium of pigs in groups B and C was increased by 3.70% and 1.01%, respectively, while it was decreased in group A by 4.04%. The phosphorus of pigs in groups B and C was increased by 1.47% and 4.12%, respectively, while it was significantly decreased in group A by 7.47% (P < .001).
These results indicate that dietary feed supplemented with Chinese herbs can improve the meat quality of swine.
The amino acid concentration in muscle is shown in Table 4. The concentration of total amino acids showed a significant increase in the Chinese herb feed additive treatment groups compared with the control group, with 5.67%, 1.44%, and 3.94% increases, respectively.
The concentration of essential amino acids increased 6.75%, 1.38%, and 4.99% in the treatment groups compared with the control group, respectively. The concentration of isoleucine showed a significant increase in the treatment groups compared with the control group. Group A was the best among the three investigated Chinese herb feed additives in improving meat quality.

| Serum biochemical parameters
The results of serum biochemical parameters are given in Table 5.

| Intestinal villi morphology
Dietary supplementation with Chinese herb feed additive increased the villus height:crypt depth ratio in the ileum, jejunum, and duodenum compared to the NC (Table 6 and Figure 1). Dietary Chinese herb feed additive supplementation tended to reduce crypt depth in the duodenum and jejunum. There was no effect on villus height in the intestinal segments of any treatment group. These results indicate that Chinese herb feed additive can improve the nutrient digestion and absorption capacity of the small intestine.

| D ISCUSS I ON
Phytogenic feed additives, referring to essential oils, spices, herbs or plant extracts, combine bioactive ingredients and flavoring substances, which have recently been gaining considerable interest due to their ability to improve performance by sustaining a healthy gut environment. 5  can improve the growth performance, feed efficiency, and nutrient digestibility in pigs. [8][9][10][11] However, the effects of herb combinations on pig production were unknown. Thus, this study was designed to

| Growth performance and nutrient digestibility
The results of this study demonstrate that three groups of Chinese herb feed additives enhanced the growth performance of pigs. The F/G of pigs in groups A, B, and C was decreased by 17.56%, 9.31%, and 13.86% compared with NC treatment. Furthermore, the results also demonstrated that the diets supplemented with Chinese herbs improved meat quality and the amino acid concentration of muscle, as the total protein, total amino acids, total lipid, and crude ash of pigs in group A, B, and C were increased.
Intestinal crypts are invaginations of the epithelium around the villi that are lined by epithelial cells that secrete enzymes. The base of each crypt is constantly dividing to maintain the structure of the villus. 12,13 Therefore, an increase in crypt depth produces more developed villi. 12 This experiment showed that dietary supplementation with Chinese herb feed additive increased villus height:crypt depth in the ileum, jejunum, and duodenum compared to the NC (Figure 1), indicating that Chinese herbs can improve nutrient digestibility.
The results of this study indicate that the three groups of Chinese herb feed additives can improve the weight gain and meat quality of pigs, as well as the nutrient digestion and absorption capacity of the small intestine.

| Serum biochemical parameters
The three groups of Chinese herb feed additives induced positive effects on serum biochemical parameters. The serum concentrations of TP, ALB, and BUN are commonly regarded as indicators of protein synthesis and metabolism, which are related to the growth performance in piglets, and BUN is the product of protein degradation in vivo. 8,14 In this study, serum TP and ALB levels were increased in the groups treated with Chinese herb feed additives compared with the control group, and serum BUN levels were decreased. Moreover, ALP is an important enzyme that contributes to the absorption of Ca and P and protein synthesis, and the serum GLU level is used as an indicator of energy supply ability. 8 GTP is a transferase that catalyzes the transfer of gamma-glutamyl functional groups from molecules such as glutathione to an acceptor that may be an amino acid, a peptide, or water. 16 This transferase is found in many tissues and has been used as a diagnostic marker in liver. 17  AMS is an enzyme that catalyzes the hydrolysis of starch into sugars. Higher blood serum amylase may reflect acute inflammation of the pancreas. 21 In this study, serum AMS was lower than in the control group, indicating the Chinese herbs improved pancreas health. CREA is a product of creatine phosphate in muscle, and serum CREA is an important indicator of renal health. 22 In this study, serum CREA was increased in the treated groups compared with the control group. Additionally, A/G was increased in the treated groups compared with the control group, while GLO was decreased.
Together, the results in this study suggested that diets supplemented with Chinese herb feed additives could induce positive effects on serum biochemical parameters and immune function in swine.

| CON CLUS ION
In conclusion, the diets supplemented with Chinese herbs improved meat quality, increased the amino acid concentration of muscle,

CO N FLI C T O F I NTE R E S T
None. F I G U R E 1 Immunohistochemistry of the ileum, jejunum, and duodenum of swine. The intestinal tissues were dehydrated to make paraffin slides, which were stained with hematoxylineosin (HE). Under an optical microscope (100×), images of the ileum, jejunum, and duodenum were captured. Scale bar: 500 µm

E TH I C S A PPROVA L
The animal protocol for this experiment was approved by the Animal Care Committee of Fujian Academy of Agricultural Sciences, China.
Animals were maintained and processed in accordance with Fujian Academy of Agricultural Sciences Guide for the Care and Use of Laboratory Animals.