Epidemiological study of parasite infection in a cow-calf beef herd in Quebec.

The patterns of gastrointestinal and pulmonary nematode infections in a previously untreated Aberdeen Angus cow-calf herd were observed between May 1988 and December 1990. The cow-calf herd and replacement heifers were on separate pastures. The relatively high mean faecal egg counts of cows and heifers at the time of turnout were mainly owing to the maturation of hypobiotic worms. The strongyle egg counts of calves began to rise soon after turnout onto pasture and reached peak levels at the end of the grazing season. The number of infective larvae on pasture was highest during September/October. Ostertagia, Cooperia and Nematodirus were the most prevalent genera found at necropsy and on pasture. Larvae of these nematodes were able to overwinter on pasture and Ostertagia larvae, additionally, were able to overwinter in the host as arrested early fourth stage larvae. The high egg output of cows at the time of turnout may serve as a source of infection for their calves and be responsible for the late-season rise in pasture larval counts.     

Importance of Escherichia coli in young beef calves from northwestern Quebec.

The objectives of this study were: (i) to investigate the prevalence of Escherichia coli producing F5 (K99), F41, or F165 fimbriae and STa enterotoxin; (ii) to determine serum antibody levels against these fimbriae; (iii) and to examine the association between bacteriological and serological results and the presence of diarrhea, in beef calves from northwestern Quebec. A total of 373 live three to four week old calves and 27 dead calves were sampled between January and March 1991. No isolates positive for F5 were detected in live calves, and only one E. coli producing STa and F41 was isolated. Escherichia coli producing F41-like surface antigens or F165 fimbriae were isolated from 17.43% and 5.63% of live calves, respectively. Antibodies against F5, F41 and F165 were low. Escherichia coli isolates positive for F41-like surface antigen were most often observed in calves born between January and March. No association was found between bacteriological and serological findings, nor between these findings and diarrhea. Calves born from dams vaccinated against E. coli had higher median antibody levels than those born from unvaccinated dams. No E. coli positive for F5 or F41 fimbriae were isolated from dead calves. Escherichia coli with F41-like surface antigen or F165 were found in 55.56% and 11.11% of ileal samples; 4% and 16% of cecal samples, and 0% and 7.4% of colon samples, respectively. Escherichia coli positive for F41-like surface antigen were detected significantly more frequently in the ileum (chi (2)2df = 31.01, p < 0.001).     

Prevention of lameness in cow-calf operations.

Lameness is a significant cause of economic loss, premature culling, and loss of genetics in cow-calf operations. In recent years, attention to treatment and prevention of lameness has increased. Veterinarians must be aware of factors associated with lameness such as genetics, environment, and nutrition so that preventive measures can be instituted in consultation with ranchers.     

Prevalence of antimicrobial resistance in fecal generic Escherichia coil isolated in western Canadian beef herds. Part II--cows and cow-calf pairs.

The objective of this study was to describe antimicrobial resistance in fecal generic Escherichia coli isolated from cows and cow-calf pairs from western Canadian beef herds. Susceptibility testing was completed on 1555 E. coli isolates (n = 533 cows from 69 herds) harvested from fresh fecal samples in the spring of 2002, and 630 isolates (n = 105 cow-calf pairs from 10 herds) collected in the spring of 2003. Only 1 cow isolate was resistant to an antimicrobial classified by Health Canada as being of very high importance to human medicine. Resistance to at least 2 antimicrobials was detected in 7.1% of the 2002 cow isolates, in 3.4% of the 2003 cow isolates, and 23.2% of the 2003 calf isolates. In the cows, resistance to at least 1 antimicrobial was not associated with cow breed (P = 0.16), cow age (P = 0.14), or previous cow treatment (P = 0.56). In the calves, resistance to at least 1 antimicrobial was not predicted by whether or not its dam was resistant to at least 1 antimicrobial (P = 0.36).     

High prevalence of Cryptosporidium bovis and the deer-like genotype in calves compared to mature cows in beef cow-calf operations

Recent studies have identified the novel, host adapted Cryptosporidium bovis and the deer-like genotype in dairy cattle from farms in the United States, China, India and Europe. This novel species and genotype appear to be more prevalent in older, post-weaned dairy cattle than previously thought. However, little information is available on their prevalence in beef cow-calf operations. In the present study, we determined the prevalence of Cryptosporidium species in 98 calves (6-8 months old) and 114 cows (>2 years old) in seven beef cow-calf herds in western North Dakota. DNA was extracted from fecal samples and Cryptosporidium spp. were identified by amplification of the 18S rRNA gene followed by sequencing or RFLP analysis. All seven herds tested positive for Cryptosporidium. Overall, 43/212 (20.3%) animals were positive. Only five of these positives were from cows. C. bovis, the deer-like genotype and C. andersoni were identified in 9.4, 6.6 and 1.4% of animals sampled, respectively. C. parvum was not identified in any of the positive samples. C. bovis, the deer-like genotype and C. andersoni were detected in 6/7, 5/7 and 2/7 herds, respectively. C. bovis and the deer-like genotype were primarily detected in calves, while C. andersoni was only detected in cows. Six isolates could not be typed. These results show a relatively high prevalence of C. bovis and the deer-like genotype in 6-8-month-old beef calves compared to cows older than 2 years in the seven herds studied.     

A seroepidemiological study of bovine pestivirus in Queensland beef and dairy herds conducted in 1994/95

OBJECTIVE: To describe the distribution and prevalence of cattle herds with detectable antibody to bovine pestivirus in Queensland in 1994/95. MATERIALS AND METHODS: The study used 7,838 serum samples collected from 250 herds in Queensland, as part of a structured animal health surveillance program conducted in 1994 and 1995. Samples were collected from female cattle bred on the property. In each herd, 10 to 20 heifers less than two years of age and 10 to 15 older cows were sampled giving a 95% probability of detecting one or more seropositive animals if the seroprevalence was approximately 10% or greater. Sera were analysed for antibodies to bovine pestivirus using a virus neutralisation test. RESULTS: Total cattle numbers in sampled herds varied from 62 to 24,600 head, while total area of properties sampled varied from 50 to 395,400 hectares. Eleven percent of herds contained no seropositive animals among those sampled, and in 38% of herds, all sampled cattle aged one to two years of age were seronegative. There was a trend for larger herds to have one or more animals seropositive for bovine pestivirus (chi-squared for Linear trend = 3.656, p = 0.056). Herds with more than 500 head of cattle were significantly more likely than herds with less than 500 head to contain one or more seropositive animals in any age group (prevalence ratio = 1.12; 95% confidence interval 1.01 - 1.23; p = 0.026). Age specific seroprevalence increased from around 10% in heifers, to between 75% and 85% in cows aged 10 years. The average annual incidence risk for bovine pestivirus infection varied from 0.12 to 0.24 seroconversions per cattle year at risk, and did not vary with age. The overall crude seroprevalence adjusted for herd size was 45%. There was a wide range of seroprevalence recorded for each level of stocking intensity. CONCLUSIONS: This survey provides valuable baseline data on bovine pestivirus infection in Queensland cattle herds.     

A comparison of crossbred and straightbred cow-calf pairs. I. Heterosis effects on total feed efficiency

Records of 104 crossbred and 33 straightbred individually fed cow-calf units were used to study the effects of heterosis on total cow-calf feed efficiency in the production of weight of calf at weaning, 168 d postweaning, slaughter and in the carcass. The cows were Angus, Hereford, Charolais and reciprocal crosses of these breeds. The calves were straightbred and all possible two-breed backcrosses and three-breed crosses produced from first cross cows. The efficiency of the cow-calf unit was defined as kg of calf produced per kg of total TDN (total digestible nutrients) consumed by the cow-calf pair. Total feed consumed by the cows was for an average period of 315 d, from approximately November 21 to October 2. Total calf TDN consisted of creep to weaning and feed during the postweaning fattening period to slaughter. For all measures of cow-calf unit efficiency studied, the heterosis estimates were small but generally positive, ranging from -.8 to 2.1%. The average advantage of all crosses over the straightbred parents for the conversion of total feed consumed by cow-calf pair to calf weight at weaning was 2%. Heterosis effects, individual and maternal combined, on the average, among two-breed backcrosses and the three-breed crosses were essentially the same. Among the three groups of first-cross cows compared, the study indicated that a slight advantage in total cow-calf efficiency was exhibited by the Angus X Hereford cross.(ABSTRACT TRUNCATED AT 250 WORDS)     

Investigation of causative agents of bovine respiratory tract disease in a beef cow-calf herd with an early weaning program.

Serum samples were collected from early weaned fall calves shortly after the onset of respiratory tract disease. Antibody titers to infectious bovine rhinotracheitis (IBR) virus, parainfluenza type 3 (PI-3) virus, bovine viral diarrhea (BVD) virus, bovine adenovirus type 3 (BAV-3), and bovine respiratory syncytial virus (BRSV) were determined on paired (acute and convalescent) serums. Seroconversion rate (a fourfold or greater rise in antibody titer) for IBR virus was 4.3%, PI-3 virus--16.3%, BVD virus--9.6%, and BAV-3--2.2%. Seroconversion for BRSV was 45.4%. An increased rate of seroconversion for IBR, PI-3, and BVD viruses and BAV-3 was observed in the presence of BRSV seroconversion. These results suggest that BRSV may facilitate infection by other viruses. Results of virus isolation procedures from these calves were negative.     

Epidemiology and effects of nematode infections on beef cow-calf systems of Argentina's western pampas.

The epidemiology and the effects of nematode infections on cow-calf systems were followed from 3 weeks before calving to 7 months afterwards. Two groups, each of 15 cow-calf pairs grazed on separate lucerne pastures. Group I (GI) were treated monthly with oxfendazole (4.5 mg kg-1), cows being dosed from calving and calves starting 45 days later. Animals in Group II (GII) were not treated. The egg output of the cows was very low. An increase was recorded 2 months after parturition, consisting mainly of Ostertagia spp. The egg output and worm burdens of calves remained low until late summer and reached a peak in autumn. Ostertagia, Cooperia and Haemonchus were the main genera recovered from slaughtered calves. The pasture contamination and tracer calf worm counts remained consistently low until autumn when they began to increase. Inhibited early fourth stage larvae of Ostertagia were recovered during spring. After calving, the live-weight gains (LWG) of treated GI cows were significantly higher (P less than 0.004) than those of GII cows, whereas the LWG of GI calves were significantly higher during December (P less than 0.037) and March (P less than 0.029) than those of GII calves. There were significant (P less than 0.04) cumulative LWG responses between GI and GII calves with no differences in cow cumulative LWG at the end of the trial. For spring-born calves, these results suggest that strategic deworming programs in cow-calf systems may produce benefits.     

Prediction of enteric methane emission from beef cattle in Southeast Asia

We conducted a meta‐data analysis to develop prediction equations to estimate enteric methane (CH₄) emission from beef cattle in Southeast Asia. The dataset was obtained from 25 studies, which included 332 individual observations on nutrient intakes, digestibilities, and CH₄ emissions. Cattle were provided tropical forage or rice straw, with or without concentrates in individual pens equipped with indirect open‐circuit head hood apparatus. The simplest and best equation to predict daily CH₄ emission was CH₄ (g/day) = 22.71 (±1.008) × dry matter intake (DMI, kg/day) + 8.91 (±10.896) [R² = 0.77; root mean square error (RMSE) = 19.363 g/day]. The best equation to predict CH₄ energy as a proportion of gross energy intake (CH₄‐E/GEI, J/100 J) was obtained using DMI per body weight (DMIBW, kg/100 kg), content (g/100 g DM) of ether extract (EE) and crude protein (CP), and DM digestibility (DMD, g/100 g); CH₄‐E/GEI = ?0.782 (±0.2526) DMIBW ? 0.436 (±0.0548) EE ? 0.073 (±0.0218) CP + 0.049 (±0.0097) DMD + 8.654 (±0.6517) (R² = 0.39; RMSE = 1.3479 J/100 J GEI). It was indicated that CH₄ emissions from beef cattle in Southeast Asia are predictable using present developed models including simple indices.     

Reproductive efficiency and calf survival in Ontario beef cow-calf herds: a cross-sectional mail survey.

A survey of the efficiency of production of Ontario beef cow-calf herds was conducted using a stratified systematic random sample of Ontario producers. In general, about 87% of females exposed to breeding produced a live calf and 6% of these died before reaching four weeks of age. The herd to herd variation in these rates was quite large, the coefficient of variation being about 17%. The stillbirth rate was 1.7% and the abortion rate 1.2%. In general, herds in northern Ontario and herds whose owners kept breeding and calving records, had reduced livebirth rates, the latter probably reflecting accuracy of data. Herds with a restricted (less than three months) breeding season had increased livebirth rates. Herds using injectable vitamins ADE, and prophylactic antibiotics, had increased neonatal losses. Herds with a restricted calving season (less than or equal to 3 months) and/or feeding free choice salt to cows had decreased neonatal losses. Herdsize and calf mortality rate were directly related, but this did not appear to be due to increased density of cows at calving time. In herds, where calving occurred during the spring, using scour vaccines in calves was associated with increased calf mortality.     

Prevalence and importance of endoparasites in calves raised in Swiss cow-calf farms]

A longitudinal study was performed to establish estimates of prevalence of selected endoparasites in Swiss cow-calf operations and to investigate the importance of an infection with endoparasites on diarrhea and weight gain until weaning. Three hundred and eighty-six calves raised in 67 larger cow-calf herds were included in the study. Faecal samples were collected during the first three months of life and at weaning. Parasitological analyses were performed according to standard procedures including specifically the detection of Eimeria spp., Cryptosporidium parvum, Strongyloides papillosus and Trichostrongylida. The effects of an infection with endoparasites on weight gain were analyzed with a linear model accounting for effects of farm, breed, sex, calving month and weight at birth. The average prevalences of endoparasites within the first three months of life were: E. bovis 36%, E. zuernii, 19%, C. parvum 16.8%, S. papillosus 22.3% and Trichostrogylida 1.5%. The prevalence of diarrhea within the same time period was 13%. Prevalences at weaning (at the end of the grazing period) were: E. bovis 56.5%, E. zuernii 4.6%, C. parvum 3.7%, S. papillosus 14.4% and Trichostrogylida 84.5%. With the exception of E. zuernii, endoparasites were more frequently observed in healthy calves than in diarrheic calves. Weaning weights were available from 190 calves (33 herds). Statistical analyses of weaning weights revealed no evidence that an infection with helminths and/or protozoa within the first three months of life or at weaning had a negative influence on individual weight gain.     

Prevalence of Giardia duodenalis assemblages in weaned cattle on cow-calf operations in the United States

To determine the prevalence of Giardia duodenalis in weaned beef calves on cow-calf operations in the United States, fecal specimens were collected from 819 calves (6-18 months of age) from 49 operations. After cleaning and concentration procedures to maximize recovery of cysts from feces, DNA was extracted from each of the 819 specimens. The presence of G. duodenalis was determined by nested PCR of a fragment of the SSU rRNA gene. All positive PCR products were subjected to sequence analysis. The overall sample level prevalence of Giardia was 33.5% with prevalence ranging from 0 to 100% among operations. The highest within herd prevalence of infected beef calves was found in one cow-calf operation from the South region (100%), followed by a cow-calf operation from the West region (90%), and three cow-calf operations from the Midwest region (87.5, 85, and 85%). Giardia was not detected in samples from 7 operations including 5 cow-calf operations from the South region, and 1 cow-calf operation each from the Midwest and West regions. Molecular analysis of the Giardia-positive samples identified assemblage E (or E-like) in 31.7% of all samples (260/819) and assemblage A in 1.2% (10/819). A mixed infection with assemblages A and E was observed in four calves from an operation in Midwest region. The potentially zoonotic assemblage A was detected in specimens from four operations in Midwest region. These findings indicate that most G. duodenalis found in weaned beef calves was assemblage E which represents no known zoonotic threat. However, the presence of assemblage A in a small number of animals poses a potential risk of infection to humans.     

The importance of by-products to the US beef industry.

The use of by-products as nutrient sources for beef cattle will continue to be driven by economics. As landfill prices continue to escalate, more by-product will become economically viable as cattle feed. These considerations will be counter-balanced by safety concerns. American consumers are becoming increasingly concerned with the production aspects of their food. The environmental concerns associated with additional landfills will have to be balanced against which by-products consumers will accept in the production of the beef that they consume. These will most assuredly heighten over the coming years.     

A stochastic model to assess the risk of introduction of bovine viral diarrhea virus to beef cow-calf herds

A spreadsheet model using Monte Carlo simulation was designed to evaluate the introduction of bovine viral diarrhea virus (BVDV) to cow-calf farms and the effect of different testing strategies. Risks were modeled to include imports to the cow-calf herd and stocker calves imported to adjacent pastures. The number of persistently infected (PI) animals imported and the probability of BVDV introduction were monitored for three herd sizes, four import profiles, and six testing strategies. Importing stockers and importing pregnant heifers were the biggest risks for introduction of BVDV. Testing for PI animals in stockers decreased the risk they posed, but testing pregnant heifers was not sufficient to decrease risk unless their calves were also tested. Test sensitivity was more influential than PI prevalence on the likelihood of BVDV introduction, when all imports were tested. This model predicts the risk of BVDV introduction for individual herds based on management decisions, and should prove to be a useful tool to help cow-calf producers in controlling the risk of importing BVDV to a na?ve herd.     

Prevalence of enteric pathogens in the feces of healthy beef calves

Fecal specimens from 136 healthy beef calves (1 day to 12 weeks of age) were examined for the presence of infectious agents known to cause enteric disease in calves. The calves were selected from 22 herds in which all calves were free of clinically apparent enteric disease. Salmonella sp, enterotoxigenic Escherichia coli, Cryptosporidium, and coronavirus were not detected in any of the calves. Three calves were infected with rotavirus and 1 calf was infected with Yersinia enterocolitica. Campylobacter-like bacteria were isolated from 50 of 130 calves, with 36 of the calves positive for C jejuni. Seemingly, clinically normal calves may be infected more often with enterotoxigenic E coli, Cryptosporidium, coronavirus, or rotavirus in herds in which some calves have enteric disease than in herds free of major enteric disease. Campylobacter jejuni was well adapted to the bovine host and was of similar prevalence in diarrheal and nondiarrheal calves. The K99 positive, nonenterotoxigenic E coli was isolated from the feces of 16 healthy calves. Information in addition to the presence of K99 antigen is useful when diagnosing enterotoxic colibacillosis in calves.     

A longitudinal study of bovine coronavirus enteric and respiratory infections in dairy calves in two herds in Ohio

This prospective longitudinal study examined the epidemiology and disease syndrome associated with bovine coronavirus (BCV) infections in a cohort of 8 conventional calves from 0 to 120 days of age, in two dairy herds in Ohio. The periods of respiratory shedding of BCV were determined by direct immunofluorescent (DIF) staining of nasal epithelial cells and ELISA of nasal swab supernatant fluids. The periods of fecal shedding of BCV were determined by ELISA and immunoelectron microscopy (IEM). The isotype-specific antibody titers to BCV in serum (at selected intervals between 0 and 120 days of age) and the post-suckling (24 to 48 h after birth) total immunoglobulin levels were examined by ELISA and zinc sulfate turbidity tests, respectively. Of the 8 calves studied, 4 had evidence of BCV respiratory (by DIF or ELISA) or enteric infections (by IEM or ELISA) in association with diarrhea or rhinitis, even though 7 of 8 calves showed increases in one or more serum antibody isotypes to BCV and 6 of 8 calves showed BCV respiratory or enteric antigen shedding by ELISA. Serological antibody titer increases occurred in 3 calves before 30 days of age and in 4 calves after 30 days of age; two of the latter calves had a second rise in serum antibody titers to BCV after the initial rise. A serological antibody titer increase was not observed in one calf. This suggests that BCV infections may be very common in a closed herd and may occur in older calves, although many may be subclinical and some may be recurrent. There were no statistically significant correlations between total serum immunoglobulin levels or BCV antibody isotype titers in serum (24-48 h after birth) and clinical disease or infection by BCV; however, calves with low levels of IgA BCV antibodies in serum (24-48 h after birth) had a significantly greater average number of days with diarrhea than those calves having high levels of IgA BCV-specific antibodies in serum.     

Lack of associations between air emissions from sour-gas processing plants and beef cow-calf herd health and productivity in Alberta,Canada

This paper describes a large-scale investigation into the effects of licensed air emissions from sour-gas processing plants on the health and productivity of beef cow-calf herds in the province of Alberta, Canada. In conjunction with a geographical information system, two atmospheric-dispersion models were used to assess historical exposures at 5726 beef cow-calf farm-sites from 1987 to 1990. We did secondary analyses of health, productivity, and management data, from a government-extension survey previously administered to beef cow-calf producers across the province. Statistical models (adjusted for potential confounding and clustering within herd and over time) were used to determine associations with estimates of sour-gas emission exposure. All analyses were conducted at the herd-level. There were no significant (P>0.05) detrimental associations of exposure and the annual herd risk for culling, calf-crop delivered, calf-crop season profile, stillbirth and twinning, calfhood mortality, or calf-crop weaned.