Effect Of Cyadox On Growth Performance And Its Endocrinal Profile In Swine

It is well established that the antimicrobials enhance growth rate and efficiency ofanimal. Whereas the precise mechanisms of growth promoting effects were, and are stillunknown. It is widely accepted that antimicrobials altered gastrointestinal microfloralpopulation and decreased the thickness of the small intestinal barrier. Growth is process,which is determined by genotype, environment, nutrition and the endocrine system. Andthe endocrine system plays an important role in regulation of the growth process in meatanimals and in the partitioning of nutrients between muscle and adipose tissues.Furthermore, some metabolic hormones such as growth hormone (GH), insulin, epidermalgrowth factor (EGF), insulin-like growth factor-I (IGF-I) and gastrointestinal hormonesare related to protein biosynthesis and improve development of intestine and growth.Quinoxalines have been used extensively in food animals since 1970s. Olaquindox andcarbadox are the members, but they have been banned or strictly limited to use in foodanimals in some countries for their genetic or potential toxicities. Cyadox is a newmember of quinoxalines. Numerous studies show that cyadox increased average dailygain and food efficiency in swine and chicken with much lower toxicity. Pigs are cyadoxstarget animals, but the study of its is still lack. Therefore, we took advantage of cyadox asgrowth promoter to evaluate the effect of antimicrobial on the growth of weaned piglets,metabolic hormones, growth factors, gastrointestinal hormones and small intestinalmorphology. The results clarified the various rules of growth and hormones, andsuggested the mechanism of cyadox inducing the growth promoting. If it is identified,alternatives to antimicrobials may be sought.1. Effect of cyadox supplementation on growth performance and endocrinalprofile in swine. Two experiments were conducted with Landrace×Largewhite crossedpigs. In Exp. 1, 60 crossbred pigs (35±7d, BW=10.95±0.22kg) were randomly allotted to one of five treatments. Pigs were fed one of five diets including a control diet or thecontrol diet supplemented with olaquindox at 50 mg/kg or cyadox at either 25,50 or 100mg/kg for 112d. Growth performance data and serum were collected once two weeks.Serum epidermal growth factor (EGF), insulin, thyroid hormones (triiodothyronine andthyroxine), cortisol (COR), hormones (testosterone and estradiol) and aldosterone (ALD)concentrations were determined using radioimmunoassay (RIA). And serum biochemicalparameters were determined. In Exp.2, 75 crossbred pigs were weaned at 35d of age(BW=12.09±0.89kg) and allotted to one of three treatments (five pigs per pen with fivepens per treatment). All pigs were fed one of three diets including a control diet or thecontrol diet supplemented with olaquindox at 100 mg/kg or with cyadox at 100 mg/kg for28d. Growth performance data and blood were collected (five pigs in each treatment)every week. Serum insulin-like growth factor-I (IGF-I), growth hormone (GH),somatostatin (SS), gastrin (Gas), parathyroid hormone (PTH), calcitonin (CT) weremeasured. And serum biochemical parameters were determined.Result indicated that average daily gain (ADG) and gain: feed increased linearly andquadratically with increasing cyadox levels. The treatment containing cyadox at 50 mg/kgand 100mg/kg improved ADG by 39% and 13.2% and feed: gain by 20% and 11.4%during the entire experiment. ADG during the 16 week-study and 4 week-study increasedby 19.2% and 16.1% respectively. Similarly, gain: feed increased by 12.4% and 20.1%.However, there was no difference in feed intake for pigs fed cyadox or olaquindox orcontrol diets. It suggested that the feasible doses of cyadox in pigs should be 50 to 100mg/kg.Pigs fed cyadox diets had great EGF, insulin, T₃, T₄ and low COR and ALD levels.EGF (4-8wk), insulin (4-6wk), thyroid hormones (6wk) concentrations increasedquadratrically (P＜0.05) and the cortisol concentrations (6wk) decreased linearly (P＜0.01)with increasing supplementation of cyadox. Pigs fed 50 mg/kg cyadox diets had greater(P＜0.05) EGF concentrations than pigs fed other diets throughout the experiment. Anincrease (22%) in serum insulin concentrations in cyadox group was also observed(P＜0.05) in 4～6wk. From 2wk to 8wk, the T₄ concentrations of cyadox group increasedby 50% (P＜0.05). Moreover, feeding cyadox to pigs elevated their serum T₃concentrations (P＜0.05) in 4wk and 8wk. The COR concentrations of cyadox group weredecreased (P＜0.05) in 4wk. Similarly, pigs fed cyadox diets had great GH, IGF-I, Gasconcentrations and low SS and CT levels. IGF-I level in cyadox group was elevated in3wk (P＜0.05) and tended to be enhanced in 1wk (P＜0.1). GH concentrations in cyadox group tended to increase (P＜0.1) in 1wk and 2wk. The concentrations of Gas in cyadoxgroup increased by 24% and 34% (P＜0.1) compared to those in control group. And the SSconcentrations in cyadox group decreased by 20% and 30% (P＜0.1) compared to those incontrol group.In our study, pigs fed with cyadox diets had higher metabolic enzyme (GOT, GTP,AKP) activities than pigs fed olaquindox or control diets. Furthermore, it suggested thatcyadox growth promotion might be due to promoting protein and lipid metablisms.It indicated that cyadox as growth promoter may improve pig performance by twomechanisms. First, cyadox improves the anabolic effect and stimulates protein synthesisin skeletal muscle by increasing the concentrations of insulin, IGF-I and GH anddecreasing COR and SS concentrations. Second, cyadox enhanced the levels of EGF,which accelerated intestine development and maintained its integrity combining withinsulin and IGF-I, thereby, the amount of absorbable nutrients was increased.2. Effect of cyadox supplementation on gastrointestinal hormones in weanedpigs. 75 crossbred pigs were weaned at 35d of age (BW=12.09±0.89kg) and allotted toone of three treatments (five pigs per pen with five pens per treatment). All pigs were fedone of three diets including a control diet or the control diet supplemented witholaquindox at 100 mg/kg or with cyadox at 100 mg/kg for 28d. Pigs were killed (five pigsin each treatment) every week . Gastric pylorus and small intestine were collected formeasurement of gastrointestinal hormones with immunohistochemistry and villus heightand crypt depth at three sites (duodenum, jejunum and ileum).The results showed that cyadox caused to increase Gas, and reduce secretin (Sec),cholecystokinin (CCK), substance P (SP), vasoactive intestinal peptide (VIP) and5-hydroxytryptamine (5-HT) levels. And feeding cyadox diet to pigs induced taller meanvillious height (P＜0.05), but did not alter crypt depth. It suggested that cyadox improvedintestinal mucosa structure, function and the use of nutrient for growth, reduce immunereaction by regulating gastrointestinal hormones secrete.3. Effect of cyadox on growth performance and hormones in weaned pigs orallyinoculated with enterotoxigenic Escherichia coli. 150 pigs were weaned at 35d of age(BW=12.12±1.00kg) and allotted to one of six treatment group (five pigs per pen withfive pens per treatment) in a 2×3 factorial design that included a dietary treament (acontrol diet or the control diet supplemented with olaquindox at 100 mg/kg or withcyadox at 100 mg/kg) and an Enterotoxigenic Escherichia coli (ETEC) challenge(challenged or not challenged). On d 7, the challenged groups were orally administered with ETEC. Growth performance, serum metabolic hormones and intestinal morphologywere measured weekly throughout the four-week experiment.The results showed that ETEC inoculation reduced ADG after the challenge whilesupplemental cyadox tended to improve ADG (P＜0.05) during the entire experiment.However, there was no difference in feed intake for pigs fed cyadox or olaquindox orcontrol diets. At the same time, pigs fed with cyadox had greater GH, IGF-â… concentrations (P＜0.05) and taller villous height (P＜0.05) after ETEC challenge, whereascrypt depth was greater (P＜0.05). It suggested that cyadox might aid in the recovery oftraumatized gastric and intestinal tissues, which improve nutrients digestibility andabsorbability. Furthermore, cyadox improve anabolic effect by increasing theconcentrations of GH and IGF-â… .In conclusion, these results demonstrated that cyadox improved the anabolic effectand stimulated protein synthesis in skeletal muscle by increasing the concentrations ofinsulin, IGF-â… and GH. And cyadox enhanced the levels of EGF that accelerated intestinedevelopment and maintained its structure and function integrity combining with insulin,IGF-â… , and gastrointestinal hormones, thereby, the amount of absorbable nutrients wasincreased. All these might lead to improve growth performance. We systemicallyinveatigated the growth promoting of cyadox, and effect of cyadox on endocrinalhormones. The effect of cyadox on growth performance and its endocrinal profile in pigswere elucidated. It demonstrated that cyadox causes alternations of concentrations ofperipheral metabolic hormones and growth factors that lead to improve pig performance.The result provided the technical project for tha study of alternatives to antimicrobials.The research was firstly conducted on the relationship between gastrointestinal hormonesand growth of pigs. It gave a explanation for cyadox increasing absorption of nutrients.