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1.
In determining the effect of prior feeding of antimicrobials on subsequent antimicrobial therapy in induced colibacillosis of piglets with Escherichia coli serotype O62 (Dey et al., 1977), study groups in one trial developed spontaneous colibacillosis due to a different Escherichia coli serotype O147. This paper reports the results and conclusion drawn from this outbreak.
Both groups, irrespective of antimicrobial feeding, developed disease, and the attack rates for the groups were not significantly different. Neither mortality nor the clinical course of illness in animals without therapy changed significantly as a function of antimicrobial feeding. The antimicrobial feeding had no effect on the therapeutic efficacies of chloramphenicol or chlortetracycline utilized for treating the disease. Chloramphenicol therapy was more effective in terminating the disease. 相似文献
2.
The purpose of the present study was to compare the ability of enrofloxacin, oxytetracycline, and sulfadimethoxine to reduce morbidity and mortality caused by Escherichia coli (colibacillosis) in broiler chickens. The chickens were raised in 80 pens (20 birds per pen) with 20 pens representing each treatment group under simulated commercial conditions that produced a colibacillosis challenge scenario. Each group of 20 randomized pens (replicates) was given one of four water treatments. Chickens that received enrofloxacin had significantly less mortality (P < 0.01), lower average gross pathology (colibacillosis) scores (P < 0.01), and better feed-conversion ratios (P < 0.05) than did chickens that received either oxytetracycline or no medication. Chickens that received enrofloxacin had significantly less mortality and lower pathology scores than those that received sulfadimethoxine and numerically lower feed conversion than the sulfadimethoxine group. Results from the present study show that enrofloxacin is superior to oxytetracycline and sulfadimethoxine for the control of morbidity and mortality caused by E. coli in broiler chickens. Our findings will help veterinarians choose and prescribe the most efficacious antimicrobial when treating colibacillosis. 相似文献
3.
Chang‐Hoon Kwon Seung‐ Jae Han Sung‐Jae Kim Byung‐Chul Park Insurk Jang Jeong‐Hee Han 《Animal Science Journal》2014,85(8):805-813
This study was aimed to evaluate the effect of dietary supplementation of lipid‐encapsulated (coated) zinc oxide ZnO on post‐weaning diarrhea (colibacillosis) in weaned piglets challenged with enterotoxigenic Escherichia coli (ETEC). Thirty‐two 35‐day‐old weaned piglets were orally challenged with 3 × 1010 colony forming units of ETEC K88 while eight piglets received no challenge (control). Each eight challenged piglets received a diet containing 100 ppm ZnO (low ZnO), 2500 ppm ZnO (high ZnO) or 100 ppm of lipid (10%)‐coated ZnO (coated ZnO) for 7 days; control pigs received the low ZnO diet. Daily gain, goblet cell density in the villi of the duodenum, jejunum and ileum, and villus height in the jejunum and ileum, which decreased due to the challenge, were equally greater in the coated ZnO and high ZnO groups versus low ZnO group. Fecal consistency score, serum interleukin‐8 concentration, subjective score of fecal E. coli shedding, and digesta pH in the stomach, jejunum and ileum, which increased due to the challenge, were equally low in the coated ZnO and high ZnO groups versus low ZnO. Results suggest that a low level of coated ZnO might well substitute for a pharmacological level of native ZnO in dietary supplementation to alleviate colibacillosis of weaned piglets. 相似文献
4.
文章旨在研究酵母培养物在动物生产上的实际使用效果,试验选取断奶仔猪300头(21日龄断奶),随机分成3组,每组5个重复,每个重复20头仔猪,单栏饲养。分别饲喂基础日粮、基础日粮+1%的酵母培养物、基础日粮+100 mg/kg的金霉素,试验期为42 d。结果表明,在饲料中调价酵母培养物断奶仔猪的末重、平均日增重得到显著提高(P<0.05),而断奶仔猪的料重比和腹泻率得到显著降低(P<0.05),但酵母培养物对这些指标的改善效果都比不上金霉素(P<0.05)。而与添加金霉素和基础日粮相比,酵母培养物可以显著提高仔猪血清中T-AOC和GSH-Px(P<0.05),MDA含量显著降低(P<0.05)。此外,与基础日粮和添加金霉素相比,在饲料中添加酵母培养物还能显著提高血清免疫球蛋白A(IgA)的水平(P<0.05),但对IgG和IgM无显著影响(P>0.05)。综上所述,在断奶仔猪日粮中添加酵母培养物可以改善仔猪生产性能,提高免疫功能和机体抗氧化能力,但效果不及金霉素,说明目前单独利用酵母培养物还没办法完全替代抗生素。 相似文献
5.
T Tsukahara K Ushida 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2001,63(12):1351-1354
A chemical characteristic of the feces of diarrheal piglets permits differentiation among piglets receiving antibiotic treatment and those with colibacillosis or dyspepsia. A high concentration of lactic or succinic acid was observed in the diarrheic feces of piglets receiving antibiotic treatments and those with dyspepsia; however, no lactic or succinic acids were detected in piglets with colibacillosis. There was, however, little difference in the total concentration of organic acids among the three types of diarrheal illnesses. A quantitative analysis of lactic and succinic acids in diarrheic feces might provide a means for rapidly differentiating between colibacillosis and non-pathogenic diarrheas in piglets. 相似文献
6.
利用Meta分析方法对已发表的中草药在断奶仔猪阶段应用试验研究进行评价,为断奶仔猪保健治疗提供参考。通过计算机检索CNKI、Wanfang Data、Science Direct、Web of Science、VIP数据库,全面收集中草药在断奶仔猪阶段添加的对照试验。采用Cochrane协作网推荐的Review Manager 5.3软件对各效应指标进行Meta分析。共纳入27篇文献,1 870头仔猪,试验组935头,对照组935头,试验组均采用中药治疗,对照组采用金霉素、硫酸黏杆菌素、硫酸黏杆菌素+杆菌肽锌等抗生素治疗。结果显示：中药组对日增重的影响优于整体抗生素组[SMD=1.22,95% CI（0.69~1.75）,P<0.01],但与金霉素组统计学无差异（P>0.05）;中药组日采食量优于整体抗生素组[SMD=0.77,95% CI（0.34~1.20）,P<0.01],但与金霉素组作用相当（P=0.05）;中药组和抗生素组的料重比差异不显著[SMD=-0.35,95% CI（-0.78~0.09）,P=0.12>0.05],但显著优于硫酸黏杆菌素和金霉素亚组（P<0.01）;中药组的腹泻率极显著低于抗生素组{SMD=-1.77,95% CI[-2.52~（-1.01）],P<0.01},但与硫酸黏杆菌素+杆菌肽锌组相比,效果相当（P>0.05）。仔猪断奶阶段添加中草药,在日增重、日采食量、腹泻率指标上优于抗生素组,即中药在断奶仔猪阶段研究具有重要潜力。 相似文献
7.
The efficacy of a novel, live delivery vaccine was examined for protection against post-weaning diarrhea in pigs. An expression/secretion plasmid harboring genes encoding enterotoxigenic Escherichia coli K88ab, K88ac, FedA and FedF fimbriae was constructed and harbored in an attenuated Salmonella, which was used as the vaccine candidate. Groups A (n=3) and B (n=3) sows were orally immunized with the candidate vaccine and PBS as a control, respectively, at 8 and 11 weeks of pregnancy. All group piglets were challenged with two challenge strains at 5-week-old. All immunized sows had significantly increased IgG and IgA levels in both serum and colostrum to individual adhesins compared to the control (p ≤ 0.05). Immune response in Group A piglets were significantly increased (p ≤ 0.05). Furthermore, no clinical signs were observed in Group A piglets after the challenge and no challenge strains were detected in rectal swabs, while diarrhea was observed in 47.8% control piglets and challenge strains were isolated from all the diarrheic piglets. These results show that immune response of sucking piglets can maintain at higher levels through the milk of the immunized sows and vaccination of sows with the candidate may protect colibacillosis in weaned piglets. 相似文献
8.
Madec F Bridoux N Bounaix S Cariolet R Duval-Iflah Y Hampson DJ Jestin A 《Veterinary microbiology》2000,72(3-4):295-310
The aim of this study was to develop a reliable model system of porcine post-weaning colibacillosis, and in doing so to assess the primary relationship of enterotoxigenic Escherichia coli to post-weaning diarrhoea and digestive disorders as encountered in the field. Six sequential experiments were carried out using 168 SPF piglets weaned into an optimal controlled environment at 28 days of age. The piglets were allocated to 23 treatment groups, 17 of which were inoculated either orally or intragastrically with enterotoxigenic strains of E. coli (LT+, STI+, STII+) possessing adhesive factors including K88 (F4). The piglets were challenged either once (Day 4 post-weaning) or on several days post-weaning, with the challenge load for each inoculation varying from 10(8) to 10(12) CFU.Overall 14.5% of inoculated pigs developed severe illness and died: these had lesions in their digestive tracts typical of colibacillosis. Diarrhoea occurred on at least 1 day in 50% of inoculated pigs, but was transient (1.7 days on average), appeared very soon after challenge (sometimes within half a day), and was accompanied by signs of depression and low weight gain. Generally a prompt recovery then occurred. In the second 2 weeks post-inoculation daily weight gain reached the same level in most inoculated groups of pigs as in the uninoculated controls. Only a small number of pigs developed a chronic enteritis lasting several days, as is typically observed in field cases. Diarrhoea was more common in the piglets that were tested adhesive positive to the K88 fimbriae receptor, but the disorders were no more severe in these animals. The response of all pigs depended primarily on the inoculum used, and especially on the challenge load. Although enterotoxigenic E. coli are clearly important in the aetiology of post-weaning diarrhoea, other factors are also required for the production of the chronic post-weaning digestive disorders and ill-thrift that are commonly encountered in commercial piggeries. 相似文献
9.
丁酸钠对断奶仔猪生长性能及免疫功能的影响 总被引：3，自引：0，他引：3
本试验旨在研究丁酸钠对断奶仔猪生长性能及免疫功能的影响。试验选用162头28日龄(8.25±0.18)kg断奶去势仔猪,随机分为6组,每组3个重复,每个重复9头猪。对照组饲喂基础饲粮,试验组分别在基础饲粮中添加0.01%抗生素(Ⅰ组)、0.10%丁酸钠(Ⅱ组)、0.10%丁酸钠+0.01%抗生素(Ⅲ组)、0.30%氧化锌+0.01%抗生素(Ⅳ组)和0.10%丁酸钠+0.30%氧化锌+0.01%抗生素(Ⅴ组)。试验期21 d。结果表明:1)Ⅲ、Ⅳ、Ⅴ组末重、平均日采食量和平均日增重显著高于对照组(P<0.05)。2)除Ⅰ组外,其他4个试验组的脾脏指数、胰脏指数、淋巴结指数均显著高于对照组(P<0.05);与对照组相比,各试验组免疫球蛋白G含量均显著升高(P<0.05),各试验组肠道黏膜免疫球蛋白A阳性(IgA+)细胞含量均有所上升,其中Ⅲ组上升最显著。3)Ⅲ、Ⅴ组的二胺氧化酶活性分别比对照组降低了46.22%和44.83%(P<0.05);Ⅲ、Ⅳ、Ⅴ组的皮质醇含量分别比对照组降低了43.13%、43.14%、47.01%(P<0.05)。结果提示,饲粮中添加丁酸钠能促进断奶仔猪生长和免疫器官发育,提高血清免疫球蛋白含量,刺激机体肠道黏膜分泌免疫球蛋白A阳性细胞,提高其免疫功能。此外,丁酸钠与抗生素一起使用对促进生长性能和降低腹泻率作用效果更明显。 相似文献
10.
为了评价金石翁芍散对仔猪大肠杆菌病的临床疗效,设立金石翁芍散高、中、低3个剂量组及药物对照组,通过混饲给药方式治疗仔猪大肠杆菌病,进行临床治疗效果比较。结果表明,金石翁芍散对仔猪大肠杆菌病有较好的治疗效果,高剂量组治愈率为91.6%,总有效率为94.4%;中剂量治愈率为88.9%,总有效率为94.4%;低剂量组治愈率为72.2%,总有效率为77.8%。高剂量组、中剂量组在降低死亡率、提高治愈率等方面均优于恩诺沙星可溶性粉（治愈率为72.2%,总有效率为77.8%）。低剂量组的治疗效果低于高、中剂量组;中、高剂量组死亡率、治愈率和总有效率均无显著性差异。 相似文献
11.
The objective of this experiment was to determine whether decreasing dietary protein content and increasing weaning age could improve piglet health and decrease the occurrence and severity of post-weaning colibacillosis (PWC) in the absence of in-feed antimicrobial growth promoters (AGPs). The experiment consisted of a 2 × 2 × 2 factorial combination of weaning age (4 vs 6 weeks), dietary protein content (H vs L; 230 vs 130 g CP/kg) and experimental enterotoxigenic Escherichia coli (ETEC) challenge (+ vs −). On day 3 post-weaning half of the piglets were challenged per os with 109 cfu ETEC. A sample of piglets was euthanased on days 0 and 6 to assess digesta pH and lactobacilli to coliform (L:C) ratio. ETEC excretion persisted longer in the 4-week-weaned piglets than those weaned at 6 weeks (P = 0.003), and the numbers of ETEC shed tended to be higher on the H than L diet, especially in the 4-week-weaned piglets (P = 0.093). Decreasing protein level led to significantly firmer faeces, decreased pH and increased L:C ratio of proximal colon digesta. These results suggest that in the absence of AGPs, increasing weaning age and decreasing dietary protein level, especially in earlier weaned piglets, may help to minimize the effects of PWC. 相似文献
12.
试验旨在研究发酵床饲养模式下饲粮中添加抗菌肽对仔猪生长性能、胰腺和小肠内容物消化酶及小肠黏膜二糖酶和垫料蛋白酶、脲酶、铵态氮的影响。选用108头35日龄、体重13kg左右的健康苏钟猪随机分为3组,每组3重复,每重复12头,分别饲喂基础饲粮（对照组）、基础饲粮＋40mg/kg杆菌肽锌＋20mg/kg硫酸黏杆菌素（抗生素组）和基础饲粮＋300mg/kg抗菌肽（抗菌肽组）的试验日粮,试验期49d10结果表明：（1）各组间仔猪生长性能差异不显著（P〉0.05）。（2）与对照组相比,饲粮中添加抗菌肽能够显著提高仔猪胰腺、十二指肠和空肠内容物淀粉酶及空肠内容物胰蛋白酶活性（P〈0.05）;并显著提高仔猪十二指肠黏膜麦芽糖酶和空肠黏膜蔗糖酶、乳糖酶及回肠黏膜蔗糖酶活性（P〈0.05）;抗菌肽组十二指肠黏膜麦芽糖酶活性比抗生素组提高（P〈0.05）。（3）各组间发酵床垫料蛋白酶和脲酶活性及铵态氮含量差异不显著（P〉0.05）。综上所述,本试验条件下,饲粮添加300mg/kg的抗菌肽能够在一定程度上提高仔猪生长性能;提高胰腺、小肠内容物及小肠黏膜消化酶活性;同时不影响垫料蛋白酶、脲酶活性和垫料铵态氮含量。 相似文献
13.
添加枯草芽孢杆菌制剂对仔猪生产性能的影响 总被引：5，自引：1，他引：4
试验选择16窝8日龄杜长大三元杂交哺乳仔猪,按分娩日期、产仔数相近的原则随机分成4组,每组4窝。对照组(Ⅰ组)饲喂基础日粮添加0.01%金霉素,试验组(Ⅱ、Ⅲ、Ⅳ组)饲喂基础日粮中添加0.01%、0.05%和0.10%的枯草芽孢杆菌,研究枯草芽孢杆菌对仔猪生产性能的影响。结果表明,饲喂枯草芽孢杆菌的试验猪与金霉素对照组相比,仔猪平均日增重明显提高、腹泻发生率得到降低,枯草芽孢杆菌各组均高于金霉素对照组;枯草芽孢杆菌以0.10%添加为最好,但各组间均差异不显著(P0.05)。因此,枯草芽孢杆菌对提高仔猪生产性能有良好的效果,枯草芽孢杆菌完全能够替代饲料中的金霉素。 相似文献
14.
Two trials were made to assess the efficacy of including calcium fosfomycin in the drinking water or in the feed for four days to control the adverse effects of experimentally induced colibacillosis in broiler chickens. Trial 1 had five groups of 15 chicks each: one group of negative controls; an untreated infected control group and three groups treated with 50, 100 or 200 ppm of calcium fosfomycin in drinking water. Trial 2 had the same groups but the antibiotic was incorporated into the feed. The chickens were infected via their air sacs with 1.7 x 108–3.6 x 108 CFU/chick of Escherichia coli O78:K80. The morbidity and mortality, a score for the gross lesions, the relative weight of the liver and spleen, performance and re-isolation of the challenge bacteria were recorded. Calcium fosfomycin in the drinking water controlled the colibacillosis, particularly in the group treated with 200 ppm. However, no effect of the antibiotic was seen when calcium fosfomycin was incorporated into the feed, the mortality, score of lesions and re-isolation of E. coli from the organs in the three treated groups being similar to those for the infected unmedicated group. The amount of antibiotic ingested in trial 1 was three times more than in trial 2. These results suggest that calcium fosfomycin is best used in the drinking water for the treatment of colibacillosis. 相似文献
15.
Jin Hur Suck Oh Song Jae Sam Lim In Kie Chung John Hwa Lee 《Veterinary immunology and immunopathology》2011,139(2-4):250-256
We have previously developed a novel attenuated Salmonella Typhimurium (S. Typhimurium) ΔcpxR Δlon vaccine. This study was carried out to examine whether this vaccine could effectively protect growing piglets against Salmonella infection. Attenuated S. Typhimurium secreting the B subunit of Escherichia coli heat-labile enterotoxin was also used as a mucosal adjuvant. Pregnant sows in groups A and B were primed and boosted with the vaccine and mucosal adjuvant, whereas sows in groups C, D and E received PBS. Piglets in groups A and C were intramuscularly primed with formalin-inactivated vaccine and orally boosted with live vaccine, while piglets in groups B, D and E received PBS. Piglets in groups A, B, C, and D were challenged with a wild type virulent S. Typhimurium at the 11th weeks of age. Colostrum sIgA and IgG titers in vaccinated groups A and B sows were approximately 50 and 40 times higher than those of non-vaccinated groups C, D and E sows (P < 0.001). Serum IgG titers of group A piglets were also significantly higher than those of groups D and E piglets during the study (P < 0.001). Furthermore, no clinical signs were observed in group A piglets during the entire experimental period after the challenge, while diarrhea was observed in many of the piglets in groups B, C, and D. No Salmonella was isolated from fecal samples of the groups A and C piglets on day 14 after challenge, whereas the challenge strain was isolated from several piglets in groups B and D. These results indicate that vaccination of the piglets with the vaccine and mucosal adjuvant in addition to vaccination of their sows induced effective protection against Salmonella infections in the growing piglets. 相似文献
16.
Takamitsu Tsukahara Takeshi Tsuruta Nobuo Nakanishi Chie Hikita Masami Mochizuki Keizo Nakayama 《Animal Science Journal》2013,84(4):316-321
Porcine edema disease (ED) is caused by Shiga toxin 2e‐producing Escherichia coli (STEC). Post‐weaned piglets often suffer from ED as a result of intestinal infection with STEC, which causes impaired growth performance and high mortality. Antimicrobial therapy is a curative treatment for piglets infected with STEC, but the emergence of antimicrobial‐resistant STEC has become a serious problem for Japanese pig farmers. Therefore, an alternative strategy other than antimicrobial therapy is needed for the prevention or treatment of ED. In this study, we evaluated the effect of oral administration of Bacillus subtilis DB9011 (DB9011) to prevent the experimental infection of STEC in weaning piglets. Eight 21‐day‐old piglets were divided into two groups: STEC challenge with the basal diet, and STEC challenge with DB9011 supplemented diet. The challenge was carried out when the animals were 25, 26 and 27 days old using STEC contained in capsules resistant against gastric digestion. All pigs were euthanized at 36 days of age. DB9011 improved the symptoms of ED and decreased the number of STEC in the ileal digesta and feces. Accordingly, oral administration of DB9011 in weaned piglets prevents ED through the suppression of the growth of STEC in the ileum. 相似文献
17.
P Wallgren T Segall A Pedersen M?rner A Gunnarsson 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1999,46(4):261-269
The present study was aimed at scrutinizing the efficacy of oral antimicrobial treatments at experimental challenge using a strain of Actinobacillus pleuropneumoniae serotype 2 known to cause severe disease. SPF pigs aged 10 weeks were infected intranasally and the antimicrobial treatments were initiated 5 h prior to that exposure. Several antimicrobial drugs, as well as the length of the treatment period, were elucidated. The outcome of the challenge was monitored by registration of clinical symptoms, weight gains and the development of serum antibodies to A. pleuropneumoniae. At necropsy, the magnitude of pathological lesions in the respiratory tract and the rate of reisolation of the infective strain were recorded. Animals that became diseased displayed a decreased growth rate caused, to a large extent, by a reduced feed intake. The performance with respect to daily weight gain and feed conversion corresponded well with the clinical signs developed and serologic reactions, as well as with the findings made at necropsy. The results obtained among pigs treated with enrofloxacin, but also with florfenicol or chlortetracycline, were superior to those of pigs treated with penicillin, tiamulin or tilmicosin. A positive effect was obtained using a strategic in-feed medication against infection with A. pleuropneumoniae. Provided that the drug used is effective against the target microbe, initiating treatment prior to infection appeared to be more important than the length of the treatment. It should, however, be remembered that A. pleuropneumoniae was reisolated from all but one medicated group following an experimental challenge given after initiating the medication. Consequently medical treatment as described did not eradicate the microbe. 相似文献
18.
猪大肠杆菌病的诊断与综合防治 总被引：1，自引：0，他引：1
猪大肠杆菌病是从出生至断乳期仔猪的常见病,是引起仔猪死亡的主要原因之一。主要对近年来猪大肠杆菌病防治的研究进展作一概述,并以临床实际病例的诊断和治疗为例,介绍了诊断和防治猪大肠杆菌病的有效措施,以期为临床有效防治该病提供参考。 相似文献
19.
Abstract The development of disease following oral challenge with Yersinia pseudotuberculosis (serotype 11) was compared in four groups of five birds treated with a parenteral dose of 10 mg iron dextran (Imferon), 10 mg of iron dextran plus 10 mg of the chelating agent desferrioxamine (Desferal), 10 mg of desferrioxamine or 10 mg of dextran 2 days before the experiment. Four groups of two birds received the above treatment regimens but no bacterial challenge. In iron dextran treated birds, oral challenge resulted in faecal shedding for the 10 day duration of the experiment, whereas in those birds which received dextran or desferrioxamine alone, the duration of faecal shedding was significantly less. Serological titres to the lipopolysaccharide antigen of the challenge bacteria were also lower in the groups not pretreated with iron dextran. The birds pretreated with iron dextran had diarrhoea and were clinically unwell 2 days following the initial oral challenge. Birds not given iron dextran showed no clinical signs of disease. Histological examination of five selected areas in the liver, spleen and intestine of each bird indicated that birds in the groups treated with iron dextran prior to bacterial challenge had significantly more intestinal lesions than birds in the groups not treated with iron. In contrast, there were significantly more lesions in the spleens of birds not pretreated with iron dextran. There was no evidence of stainable iron in the livers of birds challenged with Y pseudotuberculosis 10 days after an injection of 10 mg of iron dextran. This is in contrast to birds given iron dextran and no bacteria. It was concluded that pretreatment of birds with iron dextran resulted in more severe clinical disease, prolonged faecal shedding with associated intestinal lesions and higher serological titres to bacterial antigen. The number of lesions in the spleen and liver was not necessarily correlated with the severity of clinical disease, and in all infected birds the hepatic iron levels were significantly lower than in the non-infected control birds 10 days after oral challenge. It seems probable that the chicken has a high requirement for iron during infection with Y pseudotuberculosis and mobilises stored and exogenously supplied iron for tissue repair and immunological function. 相似文献
20.
The study objective was to determine the effect of chlortetracycline in an ad libitum trace-mineralized salt mix given to heifers before and(or) during bull exposure on the proportion pregnant and the time to conception in a fixed breeding period. Heifers (n = 768), 13 to 15 mo of age, were individually identified, immunized (Leptospira, Campylobacter fetus), examined (body condition score, vaginal lesion score, BW), and randomly allocated within 2 x 2 factorial blocks of treatments where trace mineral salt with and without chlortetracycline medication was provided in similar but nonadjacent pastures either before and(or) during bull exposure. The chlortetracycline feeding period was about 30 d for each. In the 2 d immediately before bull exposure, heifers were examined (body condition score, vaginal lesion score, reproductive tract evaluation) and reallocated to treatment pastures. Pregnancy was determined by per rectal palpation at 45 d following bull removal. Mineral intake was below that expected for heifer groups and, as a result, chlortetracycline intake was estimated at less than one-third of that targeted. Many heifers were not cycling reproductively at the onset of bull exposure (n = 456, 60.3%, based on a reproductive tract score < 3). Despite these limitations, heifers receiving chlortetracycline treatment before breeding had a pregnancy percentage of 65% (chlortetracycline before and during breeding 67% and chlortetracycline before breeding 61.8%) compared to those receiving no treatment before breeding (53%, P < 0.03; no chlortetracycline before or during breeding 60.4% and chlortetracycline during breeding 47.4%). Heifers receiving chlortetracycline treatment before breeding were 57% more likely to become pregnant than those not treated before breeding. Change in vaginal lesion score was associated with the proportion pregnant, but neither body condition score nor average daily gain were. 相似文献