Feeding Chlortetracycline Research Articles

Case-control study to identify management practices associated with morbidity or mortality due to bovine anaplasmosis in Mississippi cow-calf herds

Bovine anaplasmosis (BA) is a costly disease affecting the U.S. beef cattle industry. Chlortetracycline (CTC) in feed or mineral supplements is often used to control clinical signs of BA. The objective of this study was to determine if manage­ment practices, such as feeding CTC, are associated with ill­ness or death from BA in Mississippi cow-calf herds. Case and control herds were solicited from veterinary practices across Mississippi. Cases were herds with clinical BA diagnosed by a veterinarian within the previous calendar year. Controls were herds under the care of the same practice with no clini­cal BA diagnosed in the previous year. Blinded interviewers conducted telephone surveys of case and control herd owners. Management and biosecurity factors were tested for associa­tion with herd status using a logistic regression generalized linear mixed model with veterinary practice as a random vari­able. Twenty-two case and 25 control herds from 6 veterinary practices across Mississippi were interviewed, representing 22 counties. The average herd size was 132 for case herds, and 136 for control herds. Twenty case herds and 13 control herds fed CTC medicated mineral or feed. Providing CTC was associated with case herd status (OR = 9.2, 95% C.I. = 1.7-50.7). The association observed between case herds and feeding CTC might be because: 1) herds that had experienced previous BA morbidity and mor­tality subsequently began feeding CTC, or 2) some individual cattle consume enough CTC to achieve clearance of the per­sistent carrier state, thereby increasing risk of reinfection and clinical BA.

265 Evaluating the route of antibiotic administration and its effect on nursery pig growth performance

Abstract A total of 2,592 pigs (L337×1050, PIC, Hendersonville, TN; initially 5.58 kg BW) were used in a 28-d study to evaluate the route of antibiotic administration (in-feed vs in-water) on pig performance. Pigs were weaned at 21 d of age and placed in a commercial research facility with 27 pigs per pen. After a 7-d pre-trial period, pens of pigs were assigned to weight blocks in a randomized complete block design. There were 12 replications per treatment with pen as experimental unit for in-feed medication treatments and a pairs of pens as the experimental unit for water medication treatments. Treatments included a control (no medication), chlortetracycline (CTC) provided via feed or water to achieve 22 mg/kg BW, tiamulin in feed (5 to10 mg/kg BW) or water (23 mg/kg BW), or a combination of CTC and tiamulin in feed. Experimental treatments were provided for 14-d followed by a 14-d period without medication. Data were analyzed using R Studio (Version 3.5.2). From d 0 to 14, there was an antibiotic×route of administration interaction for ADG and G:F. For ADG, pigs fed diets containing CTC had increased (P< 0.05) ADG compared with those fed tiamulin in feed, with pigs provided CTC or tiamulin in the water intermediate. For G:F, pigs provided tiamulin in feed had decreased G:F compared to pigs fed CTC in feed or CTC or tiamulin supplied in water. Pigs fed CTC in the diet had increased ADFI compared to the control with pigs provided antibiotics in the water or tiamulin in feed intermediate (P< 0.05). Pigs provided the combination of CTC and tiamulin in feed were not different than those provided CTC in feed. There was no evidence of difference among treatments in subsequent performance. In summary, providing CTC in feed with or without tiamulin improved nursery pig growth performance.

Evaluating the Route of Antibiotic Administration and its Effect on Nursery Pig Growth Performance

This experiment was conducted to determine the influence of the route of antibiotic administration (in-feed vs. in-water) on nursery pig growth performance. A total of 2,592 pigs (L337 × 1050, PIC Hendersonville, TN; initially 14.5 lb) were used in a 28-d trial. Pigs were weaned at 21 d of age and placed in a commercial research facility with 27 pigs per pen. After a 7-d pre-trial period, pens of pigs were assigned to weight blocks in a randomized complete block design. There were 12 replications per treat­ment with pen as experimental unit for in-feed medication treatments and a pair of pens as the experimental unit for water medication treatments. The six treatments included a control (no medication), chlortetracycline (CTC) provided via feed or water to achieve 9.98 mg/lb body weight (BW), tiamulin in feed (2.27 mg/lb BW) or water (10.43 mg/lb BW), or a combination of CTC and tiamulin in feed. Experimental treat­ments were provided for 14-d followed by a 14-d period without medication. For statis­tical analysis, the interaction of antibiotic type × route of administration was tested in a 2 × 2 factorial with main effect of antibiotic type (CTC or tiamulin) and route of administration (in-feed or in-water). Pairwise comparisons were also made between the control and all individual treatments. From d 0 to 14 (P < 0.05), d 14 to 28 (P < 0.10), and d 0 to 28 (P < 0.05) there was an antibiotic × route of administration interac­tion observed for average daily gain (ADG). The interactions were a result of pigs fed diets containing CTC having improved (P < 0.05) ADG compared to CTC in-water, whereas pigs provided tiamulin in-water exhibited improved ADG compared with tiamulin in feed. There was an antibiotic × route of administration interaction observed for feed-to-gain ratio (F/G) from d 0 to 14 and 0 to 28. Pigs provided tiamulin in the feed had the poorest F/G, whereas F/G was not different among the other treatments. Providing CTC in the feed or water or tiamulin in the water improved (P < 0.05) ADG compared to pigs fed the control diet. Providing either CTC or tiamulin in the feed increased (P < 0.05) average daily feed intake (ADFI) as compared with providing the antibiotics in water. Pigs fed antibiotics in the feed had increased (P < 0.05) ADFI compared to the control with those provided antibiotics in the water being margin­ally greater (P < 0.10) in ADFI than the control. For ADG (d 0 to 28), pigs provided CTC in feed, tiamulin in the water, or the combination of CTC and tiamulin in the feed during the treatment period had increased ADG (P < 0.05) compared to pigs fed the control diet. For ADFI, there was no evidence of an interaction or main effects; however, when compared to the control, pigs provided CTC in-feed, tiamulin in-water, or the combination in the feed all had increased ADFI. In summary, providing CTC in feed with or without tiamulin or tiamulin in the water improved nursery pig growth performance.

Saccharomyces cerevisiae var. boulardii CNCM I-1079 and Lactobacillus acidophilus BT1386 influence innate immune response and serum levels of acute-phase proteins during weaning in Holstein calves

The aims of this study were to investigate the effect of Saccharomyces cerevisiae var. boulardii CNCM I-1079 (SCB) or Lactobacillus acidophilus BT1386 (LA) on (1) innate immune response, (2) markers of acute-phase reaction, and (3) immune gene expression of rumen and ileum tissues of Holstein calves. Forty eight calves (∼5 d old) were randomly allocated to four treatments as follows: (1) control (CTRL) fed milk replacer followed by starter feed, (2) CTRL supplemented with SCB in milk and feed, (3) CTRL supplemented with LA in milk and feed, and (4) CTRL supplemented with antibiotics (ATB; chlortetracycline and neomycin in milk, and chlortetracycline in feed). Tumor necrosis factor α (TNF-α) decreased (P &lt; 0.05) on day 66 (post-weaning) for the ATB-treated calves. There were no treatment effects on production of interferon γ (IFN-γ) and interleukin 6 (IL-6) proteins and on expression of TLR4, TLR6, TLR9, TLR10, CLDN3, MUC1, and MUC20 genes. Calves fed SCB or LA had a greater (P &lt; 0.05) oxidative burst at weaning (day 53) compared with CTRL. Oxidative burst was also greater (P &lt; 0.05) after weaning (day 59 and day 87) for SCB-fed calves. Calves fed SCB and ATB had higher (P &lt; 0.05) phagocytosis activity during weaning (day 47) compared with CTRL. The concentration of serum amyloid A2 (SAA2) increased (P &lt; 0.05) in SCB- and LA-fed calves (day 53), whereas the concentration of C-reactive protein (CRP) increased (P &lt; 0.05) in SCB-fed calves during weaning as compared with CTRL. Our results suggest that SCB could improve innate immune response (oxidative burst and phagocytosis) and markers of acute-phase reaction (CRP and SAA2), especially during critical periods like weaning.

Comparing the Genetic Diversity and Antimicrobial Resistance Profiles of Campylobacter jejuni Recovered from Cattle and Humans.

Campylobacter jejuni, a leading cause of gastroenteritis in humans, is a foodborne pathogen that can reside in chickens, pigs, and cattle. Because resistance to fluoroquinolones and macrolides, which are commonly used to treat human infections, has emerged in C. jejuni, it is imperative to continously monitor resistance patterns and examine the genetic variation in strains from human infections and animal reservoirs. Our previous study of C. jejuni from human campylobacteriosis cases showed a significantly higher rate of tetracycline resistance compared to national trends, and identified multilocus sequence type (ST)-982 and a history of cattle contact to be associated with tetracycline resistance. To further investigate these associations, we conducted a cross-sectional study to determine the frequency of antimicrobial resistance and examine the genetic diversity of C. jejuni recovered from 214 cattle at three Michigan herds. Overall, the prevalence of C. jejuni was 69.2% (range: 58.6–83.8%) for the three farms, and 83.7% (n = 113) of isolates were resistant to one or more antimicrobials. Resistance to only tetracycline predominated among the cattle isolates (n = 89; 65.9%) with most resistant strains belonging to ST-459 (96.5%) or ST-982 (86.4%). Among the 22 STs identified, STs 459 and 982 were more prevalent in one feedlot, which reported the use of chlortetracycline in feed upon arrival of a new herd. PCR-based fingerprinting demonstrated that the ST-982 isolates from cattle and humans had identical banding patterns, suggesting the possibility of interspecies transmission. Resistance to macrolides (1.5%) and ciprofloxacin (16.3%) was also observed; 14 of the 22 ciprofloxacin resistant isolates represented ST-1244. Together, these findings demonstrate a high prevalence of antimicrobial resistant C. jejuni in cattle and identify associations with specific genotypes. Continuous monitoring and identification of risk factors for resistance emergence are imperative to develop novel methods aimed at decreasing pathogen persistence in food animal reservoirs and the frequency of resistant infections in humans.

Effects of timing of chlortetracycline in combination with decoquinate on growth performance, health, and carcass characteristics of feeder steers

Steer calves (n=1690) were used in a 220-day study to evaluate the effects of chlortetracycline (CTC) plus decoquinate (DEQ) on health and performance of feedlot cattle. Treatments were (1) control (CON); (2) CTC+decoquinate early (CTC+DEQ Early), and (3) CTC+decoquinate delayed (CTC+DEQ Delayed). Ten mg of CTC/lb (22 mg/kg) body weight (BW) was fed daily for 5 consecutive days beginning either on day 0 (Early) or day 6 (Delayed); decoquinate was fed at 22.7 mg/100 lb (45.4 kg) BW for 28 days. There were 6 pens per treatment, and 85 to 105 steers per pen. Steers in the CTC+DEQ groups had higher (P&lt;0.01 to 0.05) dry matter intake and average daily gain than CON steers, but feed efficiency did not differ among treatments. Respiratory morbidity and re-treatment rates were lower (17 vs 23%, and 11 vs 22%, respectively, P&lt;0.01) for steers in the CTC+DEQ groups than for those in the CON group. Timing of the initial CTC treatment had minimal effect on health and performance; however, feeding CTC for at least 10 days during the receiving period reduced morbidity and improved overall performance.

A survey of chlortetracycline concentration in feed and its residue in chicken egg in commercial layer farms.

The worldwide increase in the use of antibiotics as an integral part of poultry and livestock production industry has recently received increasing attention as a contributory factor in the international emergence of antibiotic-resistant bacteria in human beings. To gauge the presence of the aforementioned scenario in the Indian context, a preliminary survey was conducted to assess the use of chlortetracycline (CTC) in 12 commercial layer farms and to quantify and confirm its residue in the egg. Samples of feed and eggs were collected at day 0 (prior to CTC addition), 3rd, 5th and 7th day during treatment and on the 9th and 14th day (2nd and 7th day after withdrawal of CTC) from each of the 12 commercial poultry farms studied. Concentration of CTC in feed was significantly (P less than 0.01) high on the 3rd, 5th and 7th day. On the 9th day and 14th day CTC concentration in feed was significantly (P less than 0.01) lower compared to the earlier 3 days studied. A highly significant difference (P less than 0.01) of the antibiotic residue in egg was observed in all the 5 days with high residual levels of CTC in egg. CTC in feed and its residue in egg were detected even on the 9th and 14th day respectively.

Dysgalactia associated with Mycoplasma suis infection in a sow herd

A sudden onset of extreme dysgalactia in gilts and sows in a 1,000-head farrow-to-wean herd was observed in December 2009. Signs of dysgalactia were identified in sows beginning 1 day after parturition and lasted 4 to 6 days. This resulted in a mean piglet preweaning mortality rate of 18% because of starvation. Sows were neither off feed nor febrile. Udders were not inflamed or congested. Feed sample analysis did not find ergotamine, mycotoxin contamination, or ration formulation errors. Management practices were acceptable. Piglets attempted to stimulate milk production but none was elicited. Oxytocin (20 U) caused milk ejection but the effect was short-lived. Blood samples from sows with affected litters were positive for Mycoplasma suis (formerly Eperythrozoon suis) by PCR assay, and blood samples from sows with unaffected litters were negative. Chlortetracycline fed to the entire sow herd at 22 mg/kg/d (10 mg/lb/d) for 2 weeks resulted in a near complete absence of dysgalactia in sows farrowing within 5 weeks after the start of treatment. Dysgalactia did occur in sows that received chlortetracycline > 5 weeks prior to farrowing. Currently, gestating sows and gilts receive chlortetracycline in feed at a dosage of 22 mg/kg/d for 2 weeks beginning 3 weeks prior to farrowing. M suis is spread primarily by blood contact from animal to animal, and diagnosis of infection with this organism can be easily missed by means of standard diagnostic protocols unless PCR assays or specific stains are used. Therefore, its current prevalence and impact are likely to be greatly underestimated.

Effects of concurrent metaphylaxis with chlortetracycline and tulathromycin on the health and performance of high-risk beef calves

A total of 463 steers and bull calves (average body weight 447 lb or 203 kg) were used to determine the effect of feeding chlortetracycline (CTC) to calves metaphylactically treated with tulathromycin at arrival processing in a research feedlot. Experimental treatments consisted of three growing diets top-dressed with either no pellets (CON) or pellets containing CTC (4 g/lb or 8.89 g/kg) administered at a rate of 10 mg/lb (22 mg/kg) body weight (BW) for two five-day intervals with a one-day break in between (CTC) or pellets containing no CTC fed in the same amount per unit of BW (1.12 lb or 2.46 kg/hd) and for the same time period as the CTC treatment (PP). Calves were enrolled in the study for 41 days. No difference in performance, morbidity or mortality was found among the three treatments.

Antimicrobial susceptibility of enteric bacteria recovered from feedlot cattle administered chlortetracycline in feed

Antimicrobial susceptibility of enteric bacteria recovered from feedlot cattle administered chlortetracycline in feed

Antimicrobial susceptibility of enteric bacteria recovered from feedlot cattle administered chlortetracycline in feed

To evaluate administration of chlortetracycline in feed of cattle as a method to select for tetracycline resistance among enteric bacteria in feedlot settings. 20 steers. Steers were randomly assigned to an exposed cohort (n = 10) or an unexposed cohort (control cohort; 10). Chlortetracycline (22 mg/kg) in cottonseed meal was administered to the exposed cohort on days 0 through 4, 6 through 10, and 12 through 16. The control cohort was administered only cottonseed meal. Fecal samples were collected from 16 steers on days -7, 0, 2, 6, 8, 12, 14, 19, 22, 26, and 33, and Escherichia coli and Enterococcus spp were isolated. Minimum inhibitory concentration (MIC) of selected antimicrobials was estimated. Overall, 56.0% and 31.4% of E coli and Enterococcus isolates, respectively, were resistant to tetracycline. Exposure to chlortetracycline was associated with a significant temporary increase in log(2) MIC for both genera but returned to preexposure values by day 33. Averaged across time, the proportion of tetracycline-resistant E coli and Enterococcus isolates was significantly greater in exposed than in unexposed steers. Although all ceftiofur-resistant E coli isolates were coresistant to tetracycline, exposure to chlortetracycline led to a significant decrease in the proportion of E coli resistant to ceftiofur during exposure. Exposure to chlortetracycline was associated with a temporary increase in the likelihood of recovering resistant bacteria. Exposure to chlortetracycline decreased the likelihood of recovering ceftiofur-resistant E coli isolates, even though isolates were coresistant to tetracycline. These findings warrant further investigation.

Study of some Impact Of Enterococcus faecium As Probiotic On Chick 1- Body Weight And Pathological Changes In Air Sacs And Intestine

To investigate the impact of Enteococcus faecium as probiotic in layer chicks,this bacteria was given in feed at a dose rate of 1.5 gm per kg feed, each kg offeed contained 5×1011 cfu along the period of the study (57 days). 150 one dayold males were divided into five groups, 30 males each. The 1st group was giventhe probiotic only in the feed, the 2nd group was given the probiotic and exposedto high temperature and bad ventilation as a stress, and the third group wasgiven the probiotic with chlortetracycline in feed while the fourth group wasgiven the probiotic and then infected with E. coli on 21 day of age and the fifthgroup was given feed with out probiotic as the control group. The resultsshowed that there was increase in body weight especially in the last weeks of theexperiment. Turbidity of the air sacs was mild in the four group compared withcontrol. Intestinal villi became elongated due to using of probiotic and there wasless sloughing compared with control, and those groups showed resistancetoward E. coli infection.

Effects of tilmicosin phosphate, administered prior to transport or at time of arrival, and feeding of chlortetracycline, after arrival in a feedlot, on Mannheimia haemolytica in nasal secretions of transported steers.

To determine effects of time of administration of tilmicosin and feeding of chlortetracycline on colonization of the nasopharynx of transported cattle by Mannheimia haemolytica (MH). 454 steers (body weight, 200 kg). 3 studies included 4 truckloads of steers assembled and processed in the southeastern United States. For each truckload of steers, a third received tilmicosin before transportation (PRIOR), then all were transported to a feedlot in New Mexico (23 hours). At arrival (day 0), another third received tilmicosin (ARR). The remaining third did not receive tilmicosin (control steers [CTR]). Steers in studies 1 and 2 were housed in a feedlot, and steers in study 3 were housed on wheat pasture. One half of the steers from each group in studies 2 and 3 were fed chlortetracycline on days 5 to 9. Steer with signs of respiratory tract disease were treated. Nasal swab specimens were examined for MH to determine colonization. PRIOR and ARR steers had a lower incidence of respiratory tract disease and MH colonization than CTR steers, but PRIOR and ARR steers did not differ. Feeding chlortetracycline did not have an effect. Tilmicosin can inhibit MH from colonizing the nasopharynx of cattle. Because tilmicosin inhibits the growth of MH in the respiratory tract, medication with tilmicosin prior to transport should reduce the incidence of acute respiratory tract disease during the first week at the feedlot when calves are most susceptible to infectious organisms.

Effects of preshipping vs. arrival medication with tilmicosin phosphate and feeding chlortetracycline on health and performance of newly received beef cattle.

Our objective was to determine the effects of preshipping (PRE) vs. arrival (ARR) medication with tilmicosin phosphate (MIC; Exp. 1 and 2) and feeding chlortetracycline (CTC; 22 mg/kg of BW from d 5 to 9; Exp. 2) on health and performance of beef calves received in the feedlot. Ninety-six steers (Exp. 1; pay weight 236 kg) and 240 (Exp. 2; average pay weight 188 kg) steer and bull calves were used. For Exp. 1, treatments included no MIC (CON), PRE, and ARR. For Exp. 2, treatments were arranged in a 3x2 factorial. Treatments included CON, PRE, and ARR, either with CTC or without CTC. For Exp. 2, serum concentrations of immunoglobulin (Ig)G and alpha-1-acid glycoprotein (AGP) were determined on samples collected on d 0, 5, 10, and 28 and d 0, 5, and 10, respectively. No MIC x CTC interactions were observed. No differences were noted among MIC or CTC treatments in any of the experiments for ADG, daily DMI, or gain:feed ratio for the overall receiving periods. For Exp. 1, percentage of steers treated for bovine respiratory disease (BRD) was decreased (P<.05) for MIC-treated animals vs CON (71.9, 45.2, and 46.9 for CON, PRE, and ARR, respectively), and the week that calves were treated for BRD differed (P<.10) among treatments. For Exp. 2, the number of calves treated for BRD was decreased (P<.01) for MIC-treated steers vs CON and decreased (P<.05) for ARR vs. PRE (40.0, 18.7, and 7.5% for CON, PRE, and ARR, respectively). Averaged across days, serum IgG was decreased (P<.05) for MIC-treated steers vs. CON, with no differences noted among treatments for AGP. Results suggest that preshipping medication programs are no more effective than arrival medication programs using tilmicosin phosphate.

Tetracyclines and their metabolites in egg white and yolk

4-Epimers of tetracycline (TC) and chlortetracycline (CTC) were formed in vivo in laying hens and excreted in substantial amounts besides the residues of the administered parent compounds via the egg. The recent observation of isochlortetracycline (i-CTC) and its 4-epimer as being the principal metabolites in eggs after feeding CTC could be confirmed. The ratio of 4-epimer to parent compound of TC, CTC and i-CTC was lower in egg white and higher in yolk and did not change during medication with TC or CTC. Further, yet unidentified, in vivo formed metabolites were observed.

Effects of oral chlortetracycline and dietary protein level on plasma concentrations of growth hormone and thyroid hormones in beef steers before and after challenge with a combination of thyrotropin-releasing hormone and growth hormone-releasing hormone.

The objective of this study was to determine the effect of a subtherapeutic level of chlortetracycline (CTC) fed to growing beef steers under conditions of limited and adequate dietary protein on plasma concentrations of GH, thyroid-stimulating hormone (TSH), and thyroid hormones before and after an injection of thyrotropin-releasing hormone (TRH) + GHRH. Young beef steers (n = 32; average BW = 285 kg) were assigned to a 2x2 factorial arrangement of treatments of either a 10 or 13% crude protein diet (70% concentrate, 15% wheat straw, and 15% cottonseed hulls) and either a corn meal carrier or carrier + 350 mg of CTC daily top dressed on the diet. Steers were fed ad libitum amounts of diet for 56 d, and a jugular catheter was then placed in each steer in four groups (two steers from each treatment combination per group) during four consecutive days (one group per day). Each steer was injected via the jugular catheter with 1.0 microg/kg BW TRH + .1 microg/kg BW GHRH in 10 mL of saline at 0800. Blood samples were collected at -30, -15, 0, 5, 10, 15, 20, 30, 45, 60, 120, 240, and 360 min after releasing hormone injection. Plasma samples were analyzed for GH, TSH, thyroxine (T4), and triiodothyronine (T3). After 84 d on trial, the steers were slaughtered and the pituitary and samples of liver were collected and analyzed for 5'-deiodinase activity. Feeding CTC attenuated the GH response to releasing hormone challenge by 26% for both area under the response curve (P<.03) and peak response (P<.10). Likewise, CTC attenuated the TSH response to releasing hormone challenge for area under the response curve by 16% (P<.10) and peak response by 33% (P<.02), and attenuated the T4 response for area under the curve by 12% (P<.08) and peak response by 14% (P<.04). Type II deiodinase activity in the pituitary was 36% less (P<.02) in CTC-fed steers than in steers not fed CTC. The results of this study are interpreted to suggest that feeding subtherapeutic levels of CTC to young growing beef cattle attenuates the release of GH and TSH in response to pituitary releasing hormones, suggesting a mechanism by which CTC may influence tissue deposition in cattle.

Feed-conversion ratio of finisher pigs in the USA

Although the feed-conversion ratio is recognized as a prominent indicator of profitability for pork producers, only 212 (50.7%) of 418 producers who were asked the feed-conversion ratio for finisher pigs provided a response during the USA National Animal Health Monitoring System 1995 National Swine Study. Of these, 126 (59.4%) producers furnished a feed-conversion ratio which they characterized as having been calculated from records, while 86 (40.6%) gave a response that they characterized as estimated or guessed. Feed-conversion ratios ranged from 2.18 to 5.91 kg of feed fed for each kg of live-body weight gained during the grower/finisher phase, with a mean of 3.28 and a standard deviation of 0.52. Stepwise regression revealed the following management factors to be associated with improved feed-conversion ratios: ≥3 different rations fed during the grower/finisher phase ( P<0.01); no rations mixed on the farm ( P<0.05); and not giving chlortetracycline in feed or water as a disease preventive or growth promotant ( P<0.01). In addition, operations where ≥3000 pigs entered the grower/finisher-production phase during the six-month period prior to interview had a better mean feed-conversion ratio than operations where <3000 pigs entered the grower/finisher phase ( P<0.01).

Effect of dietary chlortetracycline during breeding and(or) farrowing and lactation on reproductive performance of sows: a cooperative study

A cooperative regional study involving 850 litters was conducted at five experiment stations (Arizona, Florida, Oklahoma, Texas, and Virginia) to assess the effects of feeding 220 mg/kg of chlortetracycline (CTC) from 1 wk before to the initiation of the breeding season to 15 d after the breeding season and(or) from 110 d of gestation through lactation on reproductive performance of sows (2 x 2 factorial). Sows were fed 1.82 kg/d (2.27 kg during December, January, and February) during the breeding period and before farrowing. Feed was consumed on an ad libitum basis during lactation. Feeding CTC during the breeding season increased litter size at birth (10.8 vs 10.3; P < .05) and decreased feed consumption (5.4 vs 5.5 kg/d; P < .05) in the subsequent lactation period. Feeding CTC during lactation reduced lactation weight loss in sows (4.3 vs 6.1 kg; P < .07). Feeding the antibiotic at breeding had no effect on conception rate; however, feeding the antibiotic during lactation improved subsequent conception rate at the first service (80 vs 73%; P < .10) and overall conception rate (89 vs 84%; P < .05). This indicates that some carryover effect of feeding CTC during lactation occurred during the subsequent breeding period. Station x treatment interactions were observed for survival rate to 21 d (P < .05) and to weaning (P < .06). Overall, survival rates were not greatly affected by antibiotic feeding. No treatment interaction was observed for any trait measured, indicating that the effects of CTC during the breeding and lactation periods were independent.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of chlortetracycline supplementation during prebreeding and early gestation on age at puberty, ovulation rate, embryo survival and fetal development in gilts

A total of 166 crossbred gilts weighing approximately 87 ± 1 kg was limit-fed (2.5 kg/d) a corn-soybean meal gestation diet containing either 0 or 220 ppm of chlortetracycline (CTC) from 157 ± 1 d of age until 15 d after breeding. These gilts were slaughtered at 31 ± 1 or 71 d ± 1 d of gestation for evaluation of reproductive performance. Age (190 ± 3 d vs 195 ± 3 d) and body weights (106 ± 2 kg vs 106 ± 2 kg) at puberty were similar for control and CTC-fed gilts, respectively. Although not significant (P > 0.05), ovulation rate was higher in CTC-fed than in control gilts as assessed at both 31 d (14.2 ± 0.7 vs 12.9 ± 0.9, P = 0.31) and 71 d (13.9 ± 0.6 vs 12.4 ± 0.5, P = 0.10) of gestation. There was an increase (P = 0.04) in the number of live embryos for CTC-fed gilts at 31 d (12.1 ± 0.7 vs 9.7 ± 0.7) but not at 71 d (10.0 ± 1.1 vs 9.6 ± 1.0) of gestation. The mean uterine length, placental length, placental weight, fetal length, fetal weight, and allantoic fluid volumes were similar between the control and CTC-fed gilts. Results indicated that feeding CTC during prebreeding and early gestation did not influence the proportion or age of gilts at puberty. However, CTC feeding may have influenced a trend to-ward an increased ovulation rate and increased number of live embryos in gilts.

Effects of Dietary Additives on B-Vitamin Production and Absorption in Steers

Eight Hereford-cross steers (470 kg), each with T cannulae in the duodenum and ileum, were used in four trials to measure effects of monensin and chlortetracycline on thiamin, niacin, riboflavin and biotin production and absorption. Steers were fed at 2-h intervals and Cr-EDTA and acid-insoluble ash were used as markers. Diets were fed in pelleted form. Effects of monensin were tested (trial 1) using a diet that contained 90% corn + 22 mg monensin/kg feed. Feed, duodenal and ileal quantities of thiamin in steers fed the basal diet were 12.6, 7.4 and .8 mg/d, respectively. Steers fed the monensin diet had thiamin quantities of 14.0, 9.3 and 1.7 mg/d for the three sites. Dietary niacin quantities did not differ among diets; however, duodenal, ileal and fecal quantities of niacin were lower in monensin-fed animals. Riboflavin and biotin quantities were not affected by monensin supplementation. Apparent ruminal organic matter digestibility was lower for steers fed monensin. In trial 2, chlortetracycline (7.8 mg/kg diet) did not affect quantities of duodenal or ileal thiamin. Chlortetracycline tended to reduce flow of niacin to the duodenum. Duodenal or ileal riboflavin was not affected by feeding chlortetracycline. In trial 3, chlortetracycline (70 mg·head−1 ·d−1) did not affect duodenal quantities of thiamin, but increased ileal (P<.01) and fecal (P<.10) quantities of thiamin. Chlortetracycline did not affect quantities of duodenal or ileal niacin or riboflavin. Quantities of riboflavin were greater in feces of control steers than in steers fed chlortetracycline. In trial 4, effects of feeding chlortetracycline (1 g/d) for 3 d were investigated during the post-antibiotic feeding period. Samples were collected on d 1 and 2, 5 and 6, and 9 and 10 following withdrawal of chlortetracycline feeding (samples from adjacent days were pooled). Chlortetracycline resulted in increased quantities (P<.005) of duodenal thiamin during d 1 and 2 (13.7 vs 6.7 mg/d). This effect decreased with time. Chlortetracycline tended (P<.25) to decrease duodenal, ileal and fecal riboflavin throughout the collection period. Niacin and biotin quantities at the various sites were not greatly affected by feeding chlortetracycline in this manner.