Ranch-management factors associated with antibody seropositivity for Neospora caninum in consignments of beef calves in Texas, USA

A study was conducted with a 1998 retained-ownership population of Texas (USA) beef calves to determine the ranch-management practices associated with calf seroprevalence to Neospora caninum. Management practices of 76 Texas ranches that consigned 760 calves to a retained-ownership feedlot program were reviewed from a mailed questionnaire. Ninety-nine of 760 (13%; 95% CI, 9.4%, 17.7%) calves were positive to N. caninum and 59% of the ranches consigned at least one positive calf. In the logistic multiple-regression model which controlled for overdispersion, increased odds of calf-level seropositivity was associated with seasonal calving patterns, with stocking>1cow/calfunit/2.2ha, using a round-bale feeder, allowing wildlife access to the weaning supplement, and self-reared replacement heifers. However, decreased odds of seropositivity was associated with using a cattle-working dog and with using a self-contained cattle feeder. There was substantial overdispersion due to ranch.     

The value of DNA paternity identification in beef cattle: examples from Nevada's free-range ranches

The feasibility and economic value of DNA paternity identification were investigated and illustrated using Nevada beef cattle operations. A panel of 15 microsatellites was genotyped in 2,196 animals from 8 ranches with a total of 31,571 genotypes. Probabilities of exclusion for each marker within ranch and across ranches were computed. Joint probabilities of exclusion for the 15 microsatellites were also determined, resulting in values over 0.99 for any individual ranch and across ranches. Dropping 1 or 2 microsatellites with the lowest probabilities of exclusion resulted in joint probabilities greater than 0.99 and with marginal reduction compared with the probabilities with 15 microsatellites. Formulas for benefit-cost analysis for a DNA paternity identification program in beef cattle were derived. Genotyping 15 microsatellites with 20 calves per sire resulted in benefits of $1.71 and $2.44 per dollar invested at bull culling rates of 0.20 and 0.30, respectively. The breakpoints for the program to be profitable occurred when the ratio of the price of 1 kg of calf liveweight over the cost of genotyping 1 microsatellite was greater than 1.1 for a bull culling rate of 0.30. Benefit-cost analysis was also derived under incomplete DNA paternity identification using a lower number of DNA markers than necessary to achieve joint probabilities of exclusion of 0.99. Approximately a 20% increase in the benefit-cost ratio was achieved using 10 vs. 12 microsatellites with incomplete paternity identification. The greater the number of bulls in the operation, the lower the benefit-cost ratio of the paternity testing program. Low probabilities of exclusion and a high number of bulls in the beef operation reduced the benefit-cost ratio dramatically. The DNA paternity identification programs are feasible and may be profitable for free-range beef cattle operations.     

A field trial to evaluate the efficacy of a commercial Pasteurella haemolytica bacterial extract in preventing bovine respiratory disease

A double blind, random, controlled field trial was conducted to ascertain the efficacy of a Pasteurella haemolytica bacterial extract (Presponse, Langford Inc., Guelph, Ontario) in the prevention of bovine respiratory disease and/or its effects. Calves from 13 ranches (n = 1140 calves) were assigned to one of four groups, namely: vaccinated at the ranch three weeks prior to shipping to the feedlot; vaccinated only on arrival at the feedlot; vaccinated at both locations; or not vaccinated at either location. Four replicates of auction calves (n = 731) were also assigned to either receive or not receive the vaccine on arrival at the feedlot.

The vaccine did not effect a change in morbidity rates or weight gain. Total mortality rates were increased significantly, and mortality rates from respiratory disease tended to be increased in ranch calves that were vaccinated with Presponse at the ranch. In auction calves, the relapse rates were significantly lower in vaccinated calves. There was a tendency towards a reduction of respiratory disease-related mortality, however there appeared to be no sparing against death from fibrinous pneumonia in auction calves.

     

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.     

Bovine coronavirus (BCV) infections in transported commingled beef cattle and sole-source ranch calves

This study investigated bovine coronavirus (BCV) in both beef calves direct from the ranch and commingled, mixed-source calves obtained from an auction market. The level of BCV-neutralizing antibodies found in the calves varied among ranches in 2 different studies in a retained-ownership program (ROP), from the ranch to the feedlot. Calves with low levels of BCV-neutralizing antibodies (16 or less) were more likely to be treated for bovine respiratory disease (BRD) than those with higher titers. In 3 studies of commingled, mixed-source calves, BCV was recovered from calves at entry to the feedlot and the infections were cleared by day 8. The BCV was identified in lung samples [bronchoalveolar lavage (BAL) collection] as well as in nasal swabs. Calves with low levels of BCV-neutralizing antibodies at entry were most likely to be shedding BCV. Bovine coronavirus was isolated from both healthy and sick calves, but not from sick calves after 4 d arrival at the feedlot. Bovine coronavirus (BCV) should be considered along with other bovine respiratory viruses in the diagnosis of etiologies in bovine respiratory disease, especially for animals that become sick shortly after arrival. If approved vaccines are developed, it would be best to carry out vaccination programs before calves are weaned, giving them sufficient time to gain active immunity before commingling with other cattle.     

Udder health in beef cows and its association with calf growth

Background

Studies outside the Nordic countries have indicated that subclinical mastitis (measured by milk somatic cell count or the California Mastitis Test), intramammary infections (IMI), or blind quarters in beef cows may have negative effects on beef calf growth. Knowledge on prevalence of such udder health problems in Swedish beef cows is scarce. Therefore, the main aim of this study was to investigate subclinical mastitis, IMI and udder conformation in a number of beef cow herds. Production of β-lactamase in staphylococci was also investigated. Associations between certain cow factors and subclinical mastitis and IMI, and associations between cow and calf factors and 200 day calf weaning weight were also studied. The herds were visited once within a month after calving and once at weaning. Udder examination and quarter milk sampling, for somatic cell count and bacteriology, were performed in 8 to 12 cows per herd and occasion.

Results

Approximately 50%, 40% and 10% of the cows had subclinical mastitis, IMI, and at least one blind quarter, respectively, but the prevalence varied markedly between herds. Intramammary infections (mainly due to staphylococci) were identified in 13-16% of the milk samples. Less than 5% of the staphylococcal isolates produced β-lactamase. Approximately 11% of the cows sampled twice had the same IMI (mostly Staphylococcus aureus) at both samplings. Cow factors of importance for subclinical mastitis and/or IMI were teat and udder shape, breed, parity, presence of blind quarters, and cow hygiene. No significant associations were found between udder health parameters studied and calf weaning weights.

Conclusions

Subclinical mastitis and IMI, but not blind quarters, were common in beef cows, but the prevalence varied markedly between herds. Most IMI were caused by staphylococci and more than 95% of those were sensitive to penicillin. Cows with large funnel-shaped teats or pendulous udder after calving, and cows with blind quarters were at risk of having subclinical mastitis and/or IMI. Poor hygiene was also a risk factor for udder health problems. No significant associations were found between udder health and calf weaning weight. More studies on risk factors are warranted to improve advisory services on awareness and prevention of mastitis in beef cows.     

Newborn calf welfare: A review focusing on mortality rates

Calf mortality control is vitally important for farmers, not only to improve animal welfare, but also to increase productivity. High calf mortality rates can be related to larger numbers of calves in a herd, employee performance, severe weather, and the neonatal period covering the first 4 weeks of life. Although the basic premise of preventing newborn calf mortality is early detection and treatment of calves at risk for failure of passive transfer of immunoglobulins, calf mortality due to infectious diseases such as acute diarrhea increases in the presence of these physical and psychological stressors. This suggests that farmers should not ignore the effects of secondary environmental factors. For prevention rather than cure, the quality of the environment should be improved, which will improve not only animal welfare but also productivity. This paper presents a review of the literature on newborn calf mortality and discusses its productivity implications.     

Effects of breeding date,weaning date,and grazing season length on profitability of cow-calf production systems in southeastern Montana

Production data from 11 southeastern Montana ranches were used to parameterize a bio-economic computer model of cow/calf range production. Effects of changes in breeding date, weaning date, and range removal date on system performance for a ranch with a fixed forage resource base (3,060 animal unit months of range forage and 744 t of hay) were simulated. Input costs were locally established in 1994. Cattle prices were determined by week from 13-yr averages. For the base scenario, breeding season was 66 d with breeding starting on June 9. Weaning, range removal, and calf sales occurred on November 3. Cows were fed stored forages from November 3 until turnout to grazing (May 1). Five replications were simulated for combinations of breeding, weaning, and range removal dates in a factorial design. Each factor was deviated from the base scenario by +/- 14 and 28 d. Production efficiency was measured by break-even steer price. Gross margin (gross revenue - variable costs) was used as a measure of profitability. Increasing calf age (and weight) at sale time, by decreasing breeding date and(or) increasing weaning date, improved ranch efficiency and profitability. Increasing range removal date improved system performance even though extending the grazing season led to decreased herd size. Compared to the base system, the best system increased gross margin by approximately 17%. Responses for gross margin reflect the dynamics of herd size, purchased feed expense, and production efficiency. Results suggest that for range-based cow-calf enterprises in the northern Great Plains, production efficiency and profitability may be improved by increasing calf weaning age and extending the grazing season, even if herd size must be reduced.     

The pattern of fatal fibrinous pneumonia (shipping fever) affecting calves in a large feedlot in Alberta (1985-1988).

Data from a retrospective field study were used to describe the epidemiology of fatal fibrinous pneumonia as it affected beef calves entering a large commercial feedlot in southwestern Alberta during the fall months of y 1985 to 1988. A chute-side computer system was used to record processing and health data on 58885 calves during this period. The large annual variation (10%-57%) in the proportion of total mortality due to fibrinous pneumonia indicated that crude mortality cannot be used in epidemiological studies as a surrogate measure of fibrinous pneumonia mortality. Yearly epidemic curves for fatal fibrinous pneumonia were very similar, with a short time interval (median, 19-22 d) between arrival and fatal disease. Fully 75% of the calves that died of fibrinous pneumonia already were sick within 2 weeks of arrival. Studies of the biological, environmental, and population factors that are present before and shortly after arrival at the feedlot are needed to identify strategies for reducing the incidence of fatal fibrinous pneumonia.     

Determining the IgG concentrations in bovine colostrum and calf sera with a novel enzymatic assay

Background: Immune protection in newborn calves relies on a combination of the timing,volume and quality of colostrum consumed by the calf after birth.Poor quality colostrum with inadequate immunoglobulin concentration contributes to failed transfer of passive immunity in calves,leading to higher calf morbidity and mortality.Therefore,estimating colostrum quality and ensuring the transfer of passive immunity on farm is of critical importance.Currently,there are no on-farm tools that directly measure immunoglobulin content in colostrum or serum.The aim of this study was to apply a novel molecular assay,split trehalase immunoglobulin G assay(STIGA),to directly estimate immunoglobulin content in dairy and beef colostrum and calf sera,and to examine its potential to be developed as on-farm test.The STIGA is based on a split version of trehalase TreA,an enzyme that converts trehalose into glucose,enabling the use of a common glucometer for signal detection.In a first study,60 dairy and64 beef colostrum and 83 dairy and 84 beef calf sera samples were tested with STIGA,and the resulting glucose production was measured and compared with radial immunodiffusion,the standard method for measuring immunoglobulin concentrations.Results: Pearson correlation coefficients between the methods were determined and the sensitivity,specificity,and accuracy of the test were calculated for different colostrum quality and failed transfer of passive immunity cut-off points.The correlations of the STIGA measured by colorimetric enzymatic reaction compared to radial immunodiffusion for dairy and beef colostrum were 0.72 and 0.73,respectively,whereas the correlations for dairy and beef sera were 0.9 and 0.85,respectively.Next,STIGA was tested in a blinded study with fresh colostrum and serum samples where the correlation coefficient was 0.93 and 0.94,respectively.Furthermore,the performance of STIGA followed by glucometer readings resulted in correlations with radial immunodiffusion of 0.7 and 0.85 for dairy and beef colostrum and 0.94 and 0.83 for dairy and beef calf serum.Conclusions: A split TreA assay was validated for measurement of the immunoglobulin content of colostrum and calf sera using both a lab-based format and in a more user-friendly format compatible with on-farm testing.     

Nursing disease in mink: individual-level epidemiology

A cross-sectional study on the epidemiology and pathology of nursing disease in mink was undertaken in 1990 on 64 ranches in southern Ontario, Canada. A subset of 14 of these ranches also was involved in a prospective case-control study, exploring the effects of several individual-level factors on the probability of nursing disease occurrence. The outcome of interest was generally mortality due to nursing disease, as determined by gross post-mortem examination; on six ranches, however, morbidity data also were collected. The factors examined were: dam age, color phase, date of parturition, number of kits raised, and date of death.

The risk of nuring disease increased with increasing litter size, though the effect tapered off somewhat in females with litters of more than seven kits. Color phase was highly significant on many individual ranches; however, the color with the greatest incidence was different from one ranch to the next. The mean time between parturition and onset of disease was 42 days (SD=3.9). This was remarkably consistent among ranches, even though their median calendar dates of parturition and disease onset varied. Age and date of parturition were not associated with nursing disease.     

Persistence of cattle grubs (Diptera: Oestridae) on a Canadian ranch with long-term, continuous therapeutic control

Sero-prevalence of cattle grubs (Diptera: Oestridae) was monitored on two large western Canadian ranches from 1992 to 1999. One ranch has had a long-term programme for therapeutic control of cattle grubs as required by legislation in the province of Alberta. The other ranch, located in southeast Saskatchewan, has not used any treatment for grub control for an extended period of time. Serum from calves was tested each fall for the presence of antibodies to Hypoderma spp. using an ELISA. Percent positive sera on the Ranch 1 ranged from 8.0 to 73.3%. There was substantial variation among years and among two separate herds maintained on the ranch. Percent infested calves on the Ranch 2 ranged from 76.5 to 99.0%. Improved surveillance for cattle grubs using serological techniques is the only effective means to monitor the status of this important parasite.     

Calving performance and calf mortality

The most important maternal factor influencing calving performance is parity. Among calf factors, birth weight seems the most important. There are large differences between breeds and, generally speaking, heavier beef and dual-purpose breeds present more problems than smaller cattle. Variation in calving performance and stillbirth may be attributed to characters of both the calf and the dam. Genetic variation in calving performance and stillbirth at first calving has been demonstrated in several investigations for both the direct (calf) and the maternal character.In a Swedish investigation a heritability of 10% was found for both the direct and the maternal character. For stillbirth values were on average 3%. A strong genetic relationship was found between calving performance and birth weight as direct characters (r_GD = 0.98) but for the maternal characters it was considerably weaker (r_GM = 0.60). Correlations between stillbirth rate and birth weight were generally weaker, because the relationship was non-linear. Estimations of the genetic correlations between direct and maternal effects gave values between zero and ?0.5 for the characters investigated, indicating an antagonistic relationship between the genetic make-up of the cow and the calf. This implies that, in the long run, selection will not be as effective as the heritabilities suggest.A substantial improvement in calving performance and calf mortality can be achieved, however, through selection within breeds, optimal organization of breeding structures, choice of appropriate beef breeds for cross-breeding on heifers and cows, respectively, and timing calving to occur at favourable ages and in favourable seasons.     

Randomly amplified polymorphic DNA (RAPD) analysis of Mycoplasma gallisepticum isolates from turkeys from the central valley of California.

Randomly amplified polymorphic DNA (RAPD) analysis was used to investigate the molecular epidemiology of 26 Mycoplasma gallisepticum (MG) isolates obtained from turkeys located in the central valley of California. The MG isolates were recovered from 5 different companies and 13 ranches. Each company had unique MG strains. No evidence of spread of MG between companies was detected. RAPD analysis of MG isolates within a ranch during an outbreak revealed only a single strain involved in each outbreak. RAPD analysis identified an isolate from 1 ranch with a banding pattern identical to that of the 6/85 vaccine strain, which had been used on that particular ranch. Similar RAPD banding patterns of isolates from different ranches within the same company suggested horizontal spread of MG between ranches. The use of 2 primer sets in RAPD analysis was critical to prevent misinterpretation of relationships between different isolates.     

Dairy calf mortality rate: influence of management and housing factors on calf mortality rate in Tulare County, California.

Data on calf mortality, calving site, calf-rearing facilities, and calf-management procedures were collected from 16 dairy farms in Tulare County, California. Discriminant analyses were used to test if any significant differences in these factors existed between farms with higher than average and farms with lower than average death losses. The average mortality rate over a period of at least 2 years on individual farms varied from a low of 3.5 +/- 1.1% to a high of 30.6 +/- 3.1%. Calf management personnel was the only factor significantly related to the mortality rate, with considerably fewer death losses on farms where the owner managed the calves than on farms where employees performed these duties. In general, other factor categories relating to size of the cow herd, calving site, and calf housing were not related significantly to calf deaths. The average number of heifer calves born each year on individual farms was increasing year by year, and on some farms, there seemed to be a concomitant increase in death losses. This, together with the tendency toward greater number of deaths on the larger owner-managed farms, indicated that calf care was diluted under these conditions.     

Use of arbitrarily primed polymerase chain reaction to investigate Mycoplasma bovis outbreaks

Colony lineages from three Mycoplasma bovis outbreaks representing different husbandry conditions in the United States were characterized with arbitrarily primed polymerase chain reaction (AP-PCR). Cases studied included a closed beef herd, a dairy calf ranch, and a feedlot. The DNA was obtained from colony lineages and used for AP-PCR with primers REP1R-I and REP2-I. Case A and C lineages were uniform by AP-PCR analysis. Lineages from case B showed heterogeneity with AP-PCR. Outbreaks A and C were therefore both infected by one source, while the ranch (case B) was infected by multiple calf shipments. The AP-PCR typing method provides genotypic epidemiological information to successfully characterize M. bovis from sequential sampling of outbreaks and different husbandry conditions.     

Gross postmortem and histologic examination findings from abortion losses and calf mortalities in western Canadian beef herds

Production losses from abortions, stillbirths, and early calf mortality were described for the 2002 calf crop in 203 beef herds in western Canada. A total of 1689 calves were examined. A summary diagnosis was reported for 64% of aborted calves, 78% of stillborn calves, 88% of neonatal calves, and 94% of the calves > 3 d of age. Diagnoses for aborted calves included: thyroid gland lesions, pneumonia, developmental anomalies, placentitis, and myocardial necrosis or myopathy. For stillborn calves, diagnostic findings included: dystocia, thyroid gland lesions, myocardial necrosis or myopathy, developmental anomalies, and skeletal myopathy or necrosis. The most common diagnoses for neonatal calves (≤ 3 d) were: pneumonia, skeletal myopathy or necrosis, myocardial necrosis or myopathy, accident or trauma, and septicemia. For older calves (3 d to 3 mo), the most common diagnoses included: starvation, abomasal ulcer or perforation, enteritis or colitis, pneumonia, and intestinal volvulus, obstruction, or perforation.     

Pericardial mesothelioma in a neonatal calf

We encountered an extremely rare tumor, a pericardial mesothelioma, in a neonatal calf. The patient calf showed severe abdominal distention, and died immediately after birth. The thoracic cavity was contained a huge heart with a large amount of pericardial fluid. A number of granular and cobblestone-like nodules were dispersed over the epicardium and pericardium. The nodules consisted of papillary proliferations of neoplastic cells, and the neoplasm occasionally showed mesenchymal proliferations. Immunohistochemistry revealed that they had the characteristics of mesothelial cells (cytokeratin-and vimentin-positive), and the neoplasm was diagnosed as mesothelioma.     

Biosecurity for neonatal gastrointestinal diseases.

Infectious diarrhea is an important cause of neonatal calf morbidity and mortality that results in significant economic losses in the beef and dairy industries. Although numerous risk factors related to the occurrence of neonatal diarrhea have been identified, they can all be categorized into those that are related to the calf, the pathogens involved, or the environment of the calf. The immune status of calves, specifically the level of passively acquired immunity through colostrum, is the major risk factor related to the calf and the occurrence of diarrhea. Although numerous pathogens have been implicated in the occurrence of neonatal diarrhea, only a relatively limited number are commonly involved. Most should be viewed as secondary opportunists rather than primary pathogens, because none are extraordinarily virulent, and with the exception of Salmonella spp., most are present within the gastrointestinal tract of many healthy, mature cattle. Important risk factors related to pathogens involved in neonatal calf diarrhea involve the size of the inoculum and the occurrence of multiple infections. Finally, when considering the environment and housing conditions in which beef and dairy calves may reside, it is clear that tremendous variations exist. Despite these variations, the risk factors associated with the environment of the calf are also those that are the most amenable to the implementation of general environmental control and monitoring strategies as well as specific biosecurity measures.