Synovial fluid changes in induced infectious arthritis in calves

The objective was to develop an experimental model of septic arthritis in calves and to evaluate the effect of treatment on cytologic and bacteriologic variables of synovial fluid. The right tarsus of 7 healthy Holstein bull calves were inoculated with 10(8) colony-forming units of viable Escherichia coli of a pap-positive strain (day 1). On day 2, joint lavage was performed and antibiotic treatment was instituted. Cytologic examinations, bacterial cultures, and pap factor determinations by polymerase chain reaction (PCR) were performed on synovial fluid samples that were collected daily until day 4, then every 4 days until day 24. Results of physical examination, the severity of lameness, and swelling were recorded. Clinical signs of septic arthritis appeared on day 2 and persisted until day 9 for all calves. Bacterial cultures from all calves were positive for E. coli on day 2, and remained positive until day 3 for 1 calf and until day 4 for 5 calves. In addition, PCR results were positive for all calves, with 6 positive through day 3 and 1 positive through day 4, after which a positive result was again obtained on day 24. Synovial fluid neutrophil counts and white blood cell counts were significantly increased on days 2-4; however, synovial total protein concentrations were increased (P < .05) throughout the experiment in comparison to day 1. Results of all bacterial cultures were negative on day 8, although clinicopathologic signs of inflammation persisted until day 20. This model successfully induced acute septic arthritis in calves. Rapid recovery occurred within 1 week when an appropriate treatment was instituted early in the course of the disease.     

营养盐产品达可~预防新生犊牛腹泻的效果

利用24头新生荷斯坦犊牛母犊,研究营养盐产品达可R防治新生犊牛腹泻的效果。选择1～2周龄荷斯坦健康犊牛16头和腹泻犊牛8头,随机分为健康对照组(A组)、健康处理组(B1组)和腹泻处理组(B2组),每组8头。A组给饲新鲜常规牛奶,B1组和B2组分别给饲达可300g,分3次进行,每次间隔8h。试验犊牛分别在给饲前后直肠取粪,对其评分,并测定含水量和细菌(大肠杆菌、沙门氏菌)计数,同时记录生理指标和血液学参数。结果表明,达可产品能够显著(P0.01)降低健康犊牛和腹泻犊牛粪便中大肠杆菌和沙门氏菌的数量,表明具有预防和治疗犊牛腹泻的效果,而对犊牛生理和血液指标及血液pH没有不利影响。     

Evaluation of progesterone treatment to create a model for equine endometritis.

To investigate a model for equine endometritis, 12 mares with normal reproductive tracts were divided into 2 groups. All mares received progesterone in oil, 250 mg im, daily. At 5 days after initiation of progesterone administration, the uteri were inoculated with 10(6) colony forming units of Pseudomonas aeruginosa. The day of inoculation was designated Day 0. On Day 6, endometrial swab samples yielded P. aeruginosa in 5 mares; samples from the other 7 mares yielded heavy growth of Escherichia coli, Streptococcus zooepidemicus, Klebsiella pneumoniae, Enterobacter spp., Citrobacter diversus, Staphylococcus epidermidis and Streptococcus morbillorum. On Days 6, 7 and 8, Group A mares received intrauterine infusions of 6 g ticarcillin disodium and 0.2 g clavulanate potassium in 100 ml sterile saline. Group B mares received infusions of saline only. The incidence of swab specimens yielding no bacterial growth was significantly higher in Group A than Group B mares on Days 8 and 13 (4/6 vs 0/6). Swab samples from 5 of the 6 mares in Group A yielded growth of fungi on Days 13 and 19. Mares in Group B were then similarly treated with ticarcillin/clavulanate infusions, on Days 19, 20 and 21. The incidence of swab specimens yielding no bacterial growth was 2/6 and 1/6 on Days 21 and 26, respectively; fungi were not recovered from these mares at any time. The incidence of no-growth swabs after antibiotic treatment tended to be higher in Group A and incidence of fungal recovery after antibiotic treatment was significantly higher in Group A.(ABSTRACT TRUNCATED AT 250 WORDS)     

Health and performance of young dairy calves vaccinated with a modified-live Mannheimia haemolytica and Pasteurella multocida vaccine.

OBJECTIVE: To evaluate the health and performance of young dairy calves vaccinated with a commercial Mannheimia haemolytica and Pasteurella multocida vaccine. DESIGN: Randomized clinical trial. ANIMALS: 358 Holstein dairy calves between 14 and 20 days of age on 8 farms. PROCEDURE: Calves were randomly assigned to a control or vaccinated group. The vaccine used was a commercial modified-live M. haemolytica and P. multocida vaccine that was administered on days 0 and 14. Calf weight was measured on day 0 and monthly for 3 months. Farmers were asked to record any treatment given to the calves and the reason for treatment during the 4 months of the study. Blood was collected from all calves on days 0 and 28, and titers of antibodies to M. haemolytica were determined by means of direct bacterial agglutination. RESULTS: Mean daily gain was not significantly different between vaccinated and control calves. Vaccinated calves had a significantly greater increase in antibody titers (5.3-fold increase), compared with control calves (3.6-fold increase). There was no significant difference between vaccinated and control calves for any of the treatment outcomes (number and duration of treatments and age at first and last treatments). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the M. haemolytica and P. multocida vaccine, given twice 2 weeks apart, was effective in increasing titers of antibodies against M. haemolytica in young dairy calves but did not improve calf performance or health.     

Effects of weaning age and milk feeding frequency on dairy calf growth, health and rumen parameters

Various methods can be used to feed dairy calves that may influence calf performance and these include changing frequency of feeding or age at weaning. Two trials were conducted to determine effects of feeding frequency and weaning age on calf growth, health and rumen development, where 124 Holstein heifer and bull calves were weaned at 3, 4, 5 or 6 weeks of age. During Trial 1, milk replacer (12.5% DM; 22% CP, 15.6% fat) was fed at 10% BW twice per day until 1 week prior to weaning when intake was reduced to 5% BW. During Trial 2 calves were fed at 10% BW in two feedings until 14 days, then at 10% BW once daily until 1 week prior to weaning when milk replacer was reduced to 5% BW. Blood glucose and urea nitrogen, BW 4 h post-feeding, heart girth, hip height, and withers height 4 h post-feeding were obtained weekly. Growth and structural measurements were similar for all treatments up to 8 weeks of age in both trials. Blood constituents and health observations were not different between trials. Similar growth and performance between treatments in both trials through 8 weeks of age indicate that calf performance is not affected by weaning early and feeding once daily.     

Effect of antibiotics in milk replacer on fecal shedding of Escherichia coli O157:H7 in calves

The objective of this study was to compare the concentration and duration of fecal shedding of Escherichia coli O157:H7 between calves fed milk replacer with or without antibiotic (oxytetracycline and neomycin) supplementation. Eighteen 1-wk-old Holstein calves were orally inoculated with a strain of E. coli O157:H7 (3.6 x 10(8) cfu/calf) made resistant to nalidixic acid (NA). Rectal samples were obtained three times weekly for 8 wk following oral inoculation. Fecal shedding of NA-resistant E. coli O157:H7 was quantified by direct plating or detected by selective enrichment procedure. Eight weeks after inoculation, calves were killed, necropsied, and tissues (tonsils, retropharyngeal and mesenteric lymph nodes, and Peyer's patches) and gut contents (rumen, omasum, abomasum, ileum, cecum, colon, and rectum) were sampled to quantify or detect NA-resistant E. coli O157:H7. The percentage of calves shedding NA-resistant E. coli O157:H7 in the feces in the antibiotic-fed group was higher (P < 0.001) early in the study period (d 6 and 10) compared with the control group fed no antibiotics. There was no difference between treatment and control groups in the concentration of E. coli O157 in feces that were positive at quantifiable concentrations. A comparison of the duration of fecal shedding between treated and untreated calves showed no significant difference between groups. At necropsy, E. coli O157:H7 was recovered from the rumen and omasum of one calf in the control group and from retropharyngeal lymph node and Peyer's patch of two calves in the antibiotic group. Supplementation of milk replacer with antibiotics may increase the probability of E. coli O157:H7 shedding in dairy calves, but the effect seems to be of low magnitude and short duration.     

Animal and farm influences on the dynamics of antibiotic resistance in faecal Escherichia coli in young dairy calves

It is believed that the intensive use of antibiotics in the management of disease in pre-weaned calves contributes to high levels of antibiotic resistance in commensal and pathogenic bacteria. We described the temporal dynamics of antibiotic-susceptibility patterns seen in bovine enteric Escherichia coli in pre-weaned calves on dairy farms and dedicated calf-rearing facilities. Cohorts of 30 calves at each of six farms were sampled at 2-week intervals during the pre-weaning period. Faecal E. coli isolates were analyzed for antibiotic susceptibility to 12 antibiotics with the disk-diffusion method and grouped using cluster analysis of inhibition-zone patterns. The influences of calf age, farm-type, and individual-calf antibiotic therapy on the clusterings were assessed using stratified analyses and cumulative multinomial logistic regression using generalized estimating equation with antibiotic-resistance cluster as an ordinal-dependent variable. The model controlled for farm and cohort by a nested design and included a repeated measure on calf at each sampling occasion. E. coli from calves 2 weeks of age were more likely to be increasingly multiply resistant than E. coli from day-old calves (OR = 53.6), as were 4- and 6-week-old calves (OR = 29.8 and 16.4, respectively). E. coli from calves on dedicated calf-rearing facilities were more likely to be increasingly multiply resistant than E. coli from dairy-reared calves (OR = 2.4). E. coli from calves treated with antibiotics within 5 days prior to sampling were also more likely to be increasingly multiply resistant than E. coli from calves not exposed to individual antibiotic therapy (OR = 2.0).     

A longitudinal field trial assesing the impact of feeding waste milk containing antibiotic residues on the prevalence of ESBL-producing Escherichia coli in calves

A longitudinal field trial was carried out on a farm known to harbour cefotaximase (CTX-M)-positive Escherichia coli, in order to assess the impact of feeding waste milk containing antibiotic residues (WM + AR) on the prevalence of these bacteria in the faeces of calves. Fifty calves were alternately assigned to one of two groups at birth and fed either milk replacer (control group) or WM + AR (treatment group). Faecal samples were collected from all calves daily for the first week after enrolment, twice weekly until weaning, then weekly for a further six weeks. Environmental samples from the calf housing were collected weekly. WM + AR and powdered milk samples were examined for antibiotic residues and CTX-M-positive E. coli. Total E. coli and CTX-M-positive E. coli in faecal samples were enumerated using selective media. Regression analyses were performed on the bacterial count data using a population-averaged approach based on generalised estimating equations (GEE) to account for repeated measurements on individual calves over time.     

Fecal Escherichia coli O157:H7 shedding patterns of orally inoculated calves.

To assess the duration of fecal shedding upon initial infection, the duration of shedding after subsequent re-infection and the effects of dietary restriction and antibiotic treatment on shedding recrudescence, four, one-week-old calves were orally inoculated on three separate occasions with 5x10(8) cfu of Escherichia coli O157:H7 strain 86-24 Nal-R. Fecal shedding was followed by serial culture three times weekly. Following the first inoculation, the calves shed E. coli O157:H7 in their feces for a mean of 30 days, with a range of 20 to 43 days. Following the second and third inoculations, the calves shed E. coli O157:H7 in their feces for 3-8 days. In each of the three inoculations, feed was withheld from the calves for 24 h after they had become fecal culture negative. Two calves resumed shedding, one for 1 day and the other for 4 days, after food was withheld after the third inoculation, but not in the first two inoculations. In the third inoculation, one calf resumed shedding for one day after treatment with oxytetracycline. No E. coli O157:H7 strain 86-24 Nal-R was found in the calves at necropsy. These calves did not exhibit persistent low-level shedding, and did not appear to be persistently colonized with E. coli O157:H7.     

Effect of a trainer cow on health, behavior, and performance of newly weaned beef calves

Experiments were conducted to investigate the effects of the presence of a trainer cow on behavior, performance, health, and feeding patterns of newly weaned beef calves. In Exp. 1,252 weaned calves (270+/-18 kg) were allocated to 22 pens (11 to 15 calves per pen). A trainer cow was randomly assigned to each of 11 pens. Calves were weighed prior to feeding on d 0, 3, 7, 14, 21, and 28. Rectal temperatures were taken on each of these days (except d 28) and blood samples were collected on d 0, 3, and 7 and subsequently analyzed for serum haptoglobin and leukotoxin antibody titers. Instantaneous scan observations of calf behavior were made at 10-min intervals between 0730 and 1730 on d 1, 2, 4, 5, and 6. A similar protocol was used in Exp. 2, in which 297 calves (258+/-17 kg) were allocated to 24 pens. Blood analyses included haptoglobin, white blood cell counts (WBC), and neutrophil:lymphocyte (NL) ratios. In Exp. 3, the above protocol was followed and patterns of feed bunk attendance of individual calves were also monitored using radio frequency identification by passive transponder ear tags. Trainer cows did not influence (P > .10) calf rectal temperatures, requirements for antibiotic therapy, WBC, NL ratios, or leukotoxin antibody titers. Pooled across treatments, NL ratios were lower (P < .01) on d 0 (.31) than on d 3 (.36) or d 7 (.39). Although differences in weight gain were detected in some periods within the three experiments, there were no differences (P > .10) overall (d 0 to 28). Trainer cows did not affect (P > .05) frequency or duration of bunk visits by the calves. Averaged across treatments, frequency and duration of bunk visits increased (P < .001) from 9.6 visits/d and 56.7 min/d between d 0 and 3 to 12.3 visits/d and 108.9 min/d between d 15 and 21. The number of calves observed eating during scan sampling observations also increased from 16.4% on d 1 to 25% on d 4 (P < .10) and 29% on d 5 and 6 (P < .05). More (P < .05) calves were observed lying on d 1 (41.7%) and d 2 (45.3%) than on d 4 (37.5%), d 5 (34.8%), or d 6 (36.2%). With a trainer cow present, fewer (36.7% vs 41.5%; P < .001) calves were observed lying and more (11.7% vs 10.2%; P = .08) were observed walking than when no cow was present. Trainer cows did not improve calf health, time spent at the feed bunk, or performance of newly weaned calves.     

Intrauterine infection with bovine virus diarrhoea virus on alpine communal pastures in Switzerland

This study involved 13 calves, one to 50 days of age, born to first calf heifers that had been pastured on one of seven alpine communal pastures in the canton of St. Gallen during the summer of 1995. Of a total of 993 cattle pastured, 61 were pregnant heifers that were negative for bovine virus diarrhoea (BVD) antigen and for BVD antibodies at the start of pasturing. Seroconversion occurred in 26 of these pregnant heifers during the pasture period. Blood samples and skin biopsy specimens of calves born to 13 of these were examined for BVD antigen by antigen-ELISA and by an immunohistochemical technique, respectively. Blood samples were positive for BVD antigen in four calves, questionable in one calf, negative in seven and missing in one prematurely born calf. The four calves that were positive for BVD antigen in the blood were also positive in skin biopsies. Of the seven calves with a negative or missing blood test, six had positive and two had negative skin samples. Based on the combined results of blood and skin testing, 11 of 13 calves were positive for BVD antigen. Of the 11 infected calves, six were normal at birth, four were smaller than normal and one was premature and weak and was euthanized on humane grounds. Of the four small calves, two developed diarrhoea and died within the first month of life. The two calves that were negative for BVD antigen were clinically normal. The results of this study not only demonstrate the occurrence of in-utero infection with BVD virus, but also stress the importance of alpine communal pasturing in the spread of BVD virus. Because the prevention of infection with BVD virus on communal pastures does not seem feasible, it is recommended that all calves born to cows from such pastures be tested for BVD antigen.     

Feeding supplemental dried distiller's grains increases faecal shedding of Escherichia coli O157 in experimentally inoculated calves

Escherichia coli O157 is an important foodborne pathogen and asymptomatic cattle serve as major reservoirs for human infection. We have shown a positive association between feeding distiller's grains and E. coli O157 prevalence in feedlot cattle. The objective of this study was to determine the effect of feeding dried distiller's grain (DDG) on faecal shedding of E. coli O157 in calves experimentally inoculated with E. coli O157. Holstein calves (five per treatment group), fed steam-flaked corn-based high-grain diets supplemented with 0% (control) or 25% DDG, were orally inoculated with a five-strain mixture (6 x 10(9) CFU/calf) of nalidixic acid-resistant (NalR) E. coli O157. Faecal samples were taken three times per week for 6 weeks to determine the prevalence and concentration of Nal E. coli O157. At the end of the study (day 43), calves were euthanized and necropsied. Ruminal, caecum, colon, and rectal contents, and rectoanal mucosal swab (RAMS) samples were collected at necropsy to determine NalR E. coli O157 concentration. There was a trend for an interaction between treatment and faecal sampling day. The concentration of NalR E. coli O157 in the faeces was significantly higher in faecal samples from calves fed DDG compared with control calves on days 35, 37, 39 and 42. At necropsy, the concentration of NalR E. coli O157 was higher in the caecum (P = 0.01), colon (P = 0.03) and rectum (P = 0.01) from calves fed DDG compared with control animals. The number of sites at necropsy positive for NalR E. coli O157 was higher in calves fed DDG compared with calves in the control treatment (P < 0.001). Our results indicate that E. coli O157 gut persistence and faecal prevalence increased in calves fed DDG, which potentially have important implications for food safety.     

Antimicrobial use in the treatment of calf diarrhea

Calves with diarrhea often have small intestinal overgrowth with Escherichia coli bacteria, regardless of the inciting cause for the diarrhea, and 30% of systemically ill calves with diarrhea have bacteremia, predominantly because of E coli. Antimicrobial treatment of diarrheic calves should therefore be focused against E coli in the small intestine and blood, the 2 sites of infection. Fecal bacterial culture and antimicrobial susceptibility testing is not recommended in calves with diarrhea because fecal bacterial populations do not accurately reflect small intestinal or blood bacterial populations and because the break points for susceptibility test results have not been validated. Antimicrobial efficacy is therefore best evaluated by the clinical response of a number of calves to treatment, with calves randomly assigned to treatment groups. Amoxicillin, chlortetracycline, neomycin, oxytetracycline, streptomycin, sulfachloropyridazine, sulfamethazine, and tetracycline administered PO are currently labeled in the United States for the treatment of calf diarrhea. On the basis of published evidence for the oral administration of these antimicrobial agents, only amoxicillin can be recommended for the treatment of diarrhea. Dosage recommendations are amoxicillin trihydrate (10 mg/kg PO q12h) or amoxicillin trihydrate-clavulanate potassium (12.5 mg combined drug/kg PO q12h) for at least 3 days; the latter constitutes extra-label drug use. Parenteral administration of broad-spectrum beta-lactam antimicrobials--ceftiofur (2.2 mg/kg IM or SC q12h) and amoxicillin or ampicillin (10 mg/kg IM q12h)--or potentiated sulfonamides (25 mg/kg IV or IM q24h) is recommended for treating calves with diarrhea and systemic illness; both constitute extra-label drug use. In calves with diarrhea and no systemic illness (normal appetite for milk, no fever), it is recommended that the health of the calf be monitored and that oral or parenteral antimicrobials not be administered.     

Effects of parenteral supply of iron and copper on hematology, weight gain, and health in neonatal dairy calves

The objective of the present study was to examine the effects of parenteral administration of iron and copper on hematological parameters, weight gain, and health of neonatal dairy calves in the period when iron and copper deficiency could be existed. Twenty-four Holstein calves were used for the experiment and randomly assigned to four different treatments. Treatments consisted of (1) control (no injections of Fe and Cu), (2) test 1 (1000 mg Fe as fe-dextran was injected to each calf at day 2 of age), (3) test 2 (160 mg Cu as methionine-copper complex was injected to each calf at day 14 of age), and (4) test 3 (Fe and Cu were injected to each calf as mentioned previously). Blood samples were collected from all of the calves within 24-48 hours after birth and at 7, 14, 21 and 28 days of age for measuring hematological parameters and within 24-48 hours after birth and at 14, 21 and 28 days of age for the determination of iron, copper, TIBC concentrations, and AST activity. Anti-coagulated blood was analyzed shortly after collection for: number of red blood cell (RBC), hemoglobin (Hb), heamatocrit (HCT), total leukocyte count (WBC), Platelet (Plt), MCH, MCV, MCHC, and differential leukocyte counts. The amounts of iron, copper, TIBC, and AST were measured in serum. Group had significant effects on the amounts of HCT, RBC, hemoglobin, MCV, neutrophil, weekly weight gain, and daily gain during each week (p < 0.05). Sampling time had significant effects on the amounts of RBC, MCV, MCH, MCHC, WBC, neutrophil, lymphocyte, monocyte, platelet, fibrinogen, copper, TIBC, AST, weight, weekly gain and, daily gain during each week (p < 0.05). significant interactions between sampling time and group were seen for HCT, RBC, hemoglobin, MCV, platelet, total protein, fibrinogen, iron, and TIBC (p < 0.05). Improved RBC parameters and MCV were seen in calves of group 4 (test 3) in comparing with control group. Total and daily gains were also significantly improved in test groups in comparing with control group (p < 0.05). No significant difference was seen for the days of treatment between groups.     

Resistance of neonatal calves given colostrum diet to oral challenge with a septicemia-producing Escherichia coli.

Twenty Holstein-Friesian male calves were obtained within 4 hours after bith (colostrum deprived) and allotted to 1 of 4 groups, each given a different feeding: colostrum, milk replacer, polyvinylpyrrolidone (PVP), and saline solution (0.85% NaCl). Each calf was fed 2 L of the respective diets every 12 hours. Rectal temperatures were recorded and blood samples were collected immediately before each feeding. At approximately 27 hours of age, all calves were inoculated orally with 1.5 X 10(10) viable organisms of a septicemia-producing Escherichia coli serotype O26: K60:NM. Within 8 hours, all calves had diarrhea. Coli-septicemia (E coli cultured from liver, spleen, and cardiac blood) was present in 1 of the 5 calves fed colostrum, in 5 or the 5 calves fed milk replacer, in 5 of the 5 calves fed PVP, and in 4 of the 5 calves fed saline solution. At necropsy of the calves (12 to 48 hours after oral inoculation), the same organism was isolated by cultural technique from small intestines of 19 of the 20 calves. Serum immunoglobulin G concentrations increased (P less than 0.01) in calves fed the colostrum diet in sharp contrast to the agammaglobulinemia occurring in calves fed the milk replacer, PVP, or saline solution. Results indicate that colostrum fed to the calf soon after birth provides protection from colisepticemia, but does not prevent the diarrhea of colibacillosis.     

Risk factors for calf mortality in large Swedish dairy herds

The aim of this study was to identify possible risk factors for 1-90 day calf mortality in large Swedish dairy herds. Sixty herds with a herd size of ≥160 cows were visited once between December 2005 and March 2006. Thirty herds were known to have low mortality (LM) and 30 were known high mortality herds (HM). Upon the visit, data about housing and management was collected from interviews with personnel responsible for the calves. The herd status regarding the calves' passive transfer (total protein), levels of α-tocopherol, β-carotene and retinol, and excretion of faecal pathogens (Cryptosporidium spp., Escherichia coli F5, rota and corona virus) was evaluated based on targeted sampling of high risk calf groups; in each herd, blood and faecal samples were collected from calves 1-7 and 1-14 days old, respectively. Similarly, the herd status regarding clinical respiratory disease in calves and history of respiratory virus exposure was evaluated based on lung auscultations and blood samplings of calves 60-90 days old. The median calf mortality risk (in calves 1-90 days of age) among HM herds was 9% (Range: 6-24%) and among LM herds 1% (Range: 0-2%). LM and HM herds were compared using five logistic regression models, covering potential risk factors within different areas: "Disease susceptibility", "Factors affecting the gastrointestinal tract", "Factors related to transmission of infectious disease", "Hygiene" and "Labour management". The percentage of calves, 1-7 days old, with inadequate serum concentrations of α-tocopherol and β-carotene were significantly higher in HM herds compared to LM herds and also associated with higher odds of being a HM herd (OR=1.02; p=0.023 and OR=1.05; p=0.0028, respectively). The variable "Average number of faecal pathogens in the sampled target group" was significantly associated with higher odds of being a HM herd (OR=4.65; p=0.015), with a higher average in HM herds. The percentage of calves with diarrhoea treated with antibiotics was significantly higher in HM herds and was associated with higher odds of being a HM herd (OR=1.08; p=0.021). The median age at death of calves in the age interval 1-90 days that died during a one-year period was significantly lower among HM herds (13 days) than in LM herds (24 days) (p=0.0013) The results indicate that gastrointestinal disorders may be an important cause of calf mortality in large Swedish dairy herds. Furthermore, our study provides additional indications that fat soluble vitamins might play an important role for calf health.     

Evaluation of diagnostic tests for Johne's disease in young cattle

OBJECTIVE: To investigate the development of immune responses in calves experimentally and naturally infected with Mycobacterium paratuberculosis and to evaluate the potential for diagnostic tests to detect infected calves. DESIGN: Sequential testing of four treatment groups of calves over a 2 year period. PROCEDURE: Twenty-nine calves were allocated to four groups. Group D calves were orally dosed with M paratuberculosis, group N calves naturally exposed to M paratuberculosis, group V calves vaccinated for M paratuberculosis, and group C were control calves (not infected or vaccinated). Blood and faecal specimens were collected from each calf at monthly intervals to 18 months of age and then every 2 months until they were slaughtered between the ages of 21 and 29 months. Specimens were tested using absorbed EIA, IFN-gamma EIA and faecal culture. The infection status of the calves was confirmed by extensive histopathological examination and tissue culture. RESULTS: M paratuberculosis infection was confirmed in 10 calves, comprising six of eight orally dosed calves, three of five naturally exposed calves and one of nine vaccinated calves. The six artificially infected calves and one naturally infected calf were detected shedding M paratuberculosis in their faeces. Results with positive absorbed EIA were obtained from one artificially infected calf, one naturally infected calf and three vaccinated calves. All calves including controls had positive results on at least one occasion using the IFN-gamma EIA. In addition, seven calves had positive bovine tuberculosis results using the IFN-gamma EIA, even though bovine tuberculosis has been eradicated from Australia. CONCLUSION: Detection of M paratuberculosis infection in young cattle continues to be difficult using current tests.     

The effect of monensin on performance and selected biochemical and hematological parameters in the blood of calves]

The aim of this study was to find out the influence of monensin, a ionophore antibiotic, on calf performance and selected physiological parameters. Monensin is a product of Streptomyces cinnamonensis. It has effects on all Gram-negative microbes, such as Escherichia coli, salmonellas, pseudomonads and vibria. It has a small effect on Gram-positive microbes. At the beginning of the experiment eight young crossbred bulls (C x N) at the age of three weeks were weighted and divided into two groups, experimental and control ones. Calves were kept in individual boxes and fed acidified whole milk (2 ml of 85% formic acid per 1 litre of milk). They had a free access to concentrates (COT), hay and drinking water. The calves received 3 lt. of whole milk twice a day until the age of eight weeks. 0.5 mg of monensin per 1 kg live weight were served orally to calves of the experimental group every day. Monensin was made by the Spofa Corporation, Prague. Daily intake of feed was recorded and the calves were weighted once a week. Blood samples were taken from the jugular vein before the beginning of the experiment, and in the period from the fifth to the tenth week of age, always before morning feeding. The average daily live weight gain was 0.452 kg and 0.471 kg for the control and experimental group, respectively, during the milk feeding period, the index being 104.2 (Tab. I). Tab. II shows the average feed intake per 1 kg live weight gain.(ABSTRACT TRUNCATED AT 250 WORDS)     

The hematocrit values and hemoglobin content of blood and the level of total protein, free fatty acids, glucose, lactate, Ca, Mg, Na, K, Pa, Fe, Fe-binding capacity, Cu and Zn in the blood plasma of newborn calves and their mothers immediately after birth

Blood samples were collected from 22 calves in three weight classes (A: 29.3 +/- 0.5 kg, B: 36.0 +/- 1.3 kg, C: 42.7 +/- 3.7 kg), 1-3 minutes after parturition and prior to uptake of foremilk as well as 24-26 hours after parturition. Other blood samples were collected from 45 calves, 5-60 minutes after parturition, and from their mothers, 3-5 or 5-60 minutes from calving. Haematocrit and haemoglobin in the blood of the calves, immediately after parturition, were higher the values recorded from adult cattle. Major differences were found to exist between individual calves regarding total protein of blood plasma. Protein levels in 14 calves were below 50 g/l, within 24-26 hours from parturition. Free fatty acids in blood plasma of calves were lower than those in cattle, 1-3 minutes from parturition, and were higher, 5-60 minutes from parturition. Glucose levels in Group C were higher than those in A and B, 1-3 minutes postpartum. Lactate in Group C was higher than that in B. An account is also given of blood plasma levels of Ca, Pa, Mg, Na, K, Cu, and Zn.     

The effect of group size on health and growth rate of Swedish dairy calves housed in pens with automatic milk-feeders

Group pens equipped with automatic milk-feeding systems are increasingly being used for young dairy calves in Sweden. The system is, however, associated with an increased risk of clinical respiratory-tract disease and a reduced growth rate. In an experimental study we compared the health and growth rate of two different group sizes of calves (6-9 versus 12-18) kept in pens with automatic milk-feeders. The experiment was performed from September 2002 to February 2004, in nine commercial dairy farms in south-west Sweden. Each farm was equipped with two pens with automatic milk-feeders and no possibility of direct contact between calves from different pens. The calves were housed individually until 3-35 (median, 12) days of age, and then were allocated to one of the two group pens by random-number lists. Altogether 892 calves were studied: 297 in the small- and 595 in the large-sized groups. The calves' heart girths were measured at birth and at 56 days of age. Blood samples for analysis of serum haptoglobin concentration (S-Hp) were collected once for each calf, at four to eight weeks of age. Diseases were recorded by the farmers and by a veterinarian, who visited the farms every third week and physically examined all the calves. The effects of group size on the risks of diarrhoea, clinical respiratory-tract disease and increased respiratory sounds, and on the growth rate and S-Hp were evaluated using multiple logistic- and linear-regression models with herd as fixed effect. Age at transfer to group pen, breed, immunoglobulin concentration of colostrum received, parity of the dam and presence of diarrhoea before transfer to the group pen, season, sex, year, and, in the analysis of growth rate, birth heart girth were extra explanatory variables. Calves in pens for 12-18 calves had a higher incidence of respiratory illness (OR: 1.4) and grew 0.022 cm/day less than calves housed in groups of 6-9 animals (equivalent to approximately 40 g/day). We detected no differences between calves kept in the small-sized versus the large-sized groups in terms of risk of diarrhoea or mean S-Hp. We concluded that housing calves in groups of under 10 calves is preferable from a health and growth perspective.