Study On Rational Use Of Chlortetracycline Premix In Production Of Weaned Pigs

Antibiotics are extensively utilized for livestock with activity against animal diseases,protecting the animal health and growth,and improving the efficiency of production.As one of tetracycline antibiotics,chlortetracycline is widely used in animal husbandry.Since the effects of antibiotics on animal growth promoting,some animal farmers abuse antibiotics in animal production,which results in reduction in efficacy of antibiotics and resistance to antibiotics.Rise in antibiotic resistance seriously threatens the safety of animal products and public health.Therefore,it is very important to study the rational use of antibiotics in animal husbandry.1 Effects of chlortetracycline(CTC)on growth performances and immune indexes of weaned pigsThe aim of this study was to investigate the effects of CTC premix on the performance,immunological indexes of weaned piglets.In the present study,180 35-day-old weaned pigs(PIC pigs)were selected and randomly assigned into 4 groups:Control group,fed the basal diet;T1 group,fed 75 g/t CTC premix and the basal diet;T2 group,fed 75 g/t CTC premix,3 kg/t acidifier and the basal diet;T3 group,fed 75 g/t CTC premix,3 kg/t acidifier,50 g/t Macleaya cordata extract and the basal diet.There were 3 replications(pens)per group and 15 piglets per pen.Blood samples of 24 pigs(6 pigs per group)were collected at 6,72,168,336,600 and 672 h after the first feeding of antibiotics.Plasma was obtained after centrifugation at 40C for 10 min at 3000Xg and stored at-20??The results showed that the effects of CTC on the ADG,and plasma concentration of IgG and IgA of weaned pigs were not significant(P>0.05).The spleen index of the pigs in the diet supplemented with CTC was lower than that of the CTC and acidifier group(P<0.05).There were no significant effects on organ weight and organ index in the other groups(P<0.05).In conclusion,compared with the control group,CTC did not effect the growth performances and immune indexes of weaned pigs after continuously CTC administration for 28 days.CTC did not produce immune suppression in pigs,and acidifier and Macleaya cordata extract did not increased the effects of CTC on the growth perfermances and immune indexes,which indicates that they should not be combined together in the feed of weaned pigs.2 The concentration of CTC in plasma,tissues,chyme samples of weaned pigsThese 24 pigs selected in Trial 1 were sacrificed at 63 d of age,and their tissue samples(heart,liver,spleen,lung,kidney,stomach,duodenum,jejunum,ileum,cecum,colon and rectum)were collected.The concentration of CTC were determined using high performance liquid chromatography(HPLC)in different tissues and chyme of different part of digestive tract of weaned pigs after continuously CTC administration for 28 days.Also,the concentrations of CTC in plasma samples were measured using high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS).The results showed that the CTC concentration in kidney was the greatest among tissues.The CTC concentrations were greater in the T1 and T2 groups than in the control group(P<0.05).The concentration of CTC in the liver of T1 group was greater than that in the other groups(P<0.05).The plasma concentration of CTC in the T1 group was the greatest among four groups.The concentrations of CTC were greater in the T1 group at 600 h than at 6,72,168,226 h(P<0.01).The plasma concentration of CTC in the T3 group reached the peak at 168 h,which was greater than that at 336.600 and 672 h(P<0.05).The concentration of CTC in the stomach chyme was greater in the T1 group than in the control and T2 groups(P<0.05).The concentration of CTC in the ileum chyme were greater in the T1 and T2 groups than in the control group(P<0.05).The concentrations of CTC in the cecum,colon and rectum chyme were greater in the T2 group than in the CT group(P<0.05).The CTC concentration in the colon and rectum chyme was greater in the T3 group than in the CT group(P<0.05).There were no significant effects of acidifier or Macleaya cordata extract administration(P>0.05).3 The metabolism of CTC and its residue in feces and urine of weaned pigletsTwenty healthy 35-day-old weaned pigs were selected and randomly assigned into 4 groups:T1 group,fed CTC premix and basal diet;T2,fed CTC premix,3kg/t acidifier,and basal diet;T3,fed CTC hydrochloride in feed,and basal diet;T4,fed CTC hydrochloride in water and basal diet.There were 5 replications per group.CTC was given by body weight of pigs(10 mg/kg).Blood samples of pigs were collected at 3,6,9,12 and 24 h after administration.All the feces and urine were collected within 24 hours after administration.In the present study,the concentrations of CTC in feces and urine were measured using high performance liquid chromatography(HPLC),and the concentration of CTC in plasma was measured using high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS).The metabolism of CTC within 24 h after administration in weaned pigs had been studied.The results showed that there were no differences of CTC content in the feces and urine between groups(P>0.05).The plasma concentration of CTC was negatively correlated with the time of administration.The plasma concentration of CTC was lower in the T1 and T2 groups than in the T3 and T4 groups at 3 h after administration(P<0.01).The plasma concentration of CTC was the greatest in the T4 group at 6 h(P<0.01)and 9 h(P<0.05)after administration.The differences between other groups were not significant(P>0.05).In short,HPLC can meet the needs of test in feces and urine but not in plasma.HPLC-MS/MS is more accurate than HPLC.Within 24 hours after the CTC administration(10 mg/kg),the amount of CTC in the feces and urine accounted for only 3.97%-7.98%of the total amount of CTC in feed or water for weaned pigs.