Direct production losses and treatment costs from bovine viral diarrhoea virus,bovine leukosis virus,Mycobacterium avium subspecies paratuberculosis,and Neospora caninum

Our purpose was to determine direct production losses (milk loss, premature voluntary culling and reduced slaughter value, mortaliy loss, and abortion and reproductive loss) and treatmetn costs (veterinary services, medication cost, and extra farm labour cost) due to four infectious diseases in the maritime provinces of Canada: bovine viral diarrhoea (BVD), enzootic bovine leukosis (EBL), Johne's Disease (JD), and neosporosis. We used a partial-budget model, and incorporated risk and sensitivity analyses to identify the effects of uncertainty on costs. Total annual costs for an average, infected, 50 cow herd were: JD$ 2472; BVD$ 2421; neosporosis $ 2304; EBL$ 806. The stochastic nature of the proportion of infected herds and prevalence of infection within a herd were used to estimate probability distributions for these ex post costs. For all diseases, these distributions were right skewed. A sensitivity analysis showed the largest effect on costs was due to milk yield effects. For example, changing milk production loss from 0 to 5% for BVD increased the costs for the disease by 266%.     

The economic value of days open in Holstein cows in Japan based on simulated changes in conception rate

Increasing herd‐life length and culling parity with increasing conception rate (CR) is necessary to increase lifetime profit from dairy cow production. Economic values of days open (DO) were determined by calculating changes in fertility traits, herd‐life length, and milk yield when the simulated CR were changed in increments of 1% from ?5% to 5% from the basal levels, which were obtained for Hokkaido and regions other than Hokkaido separately. When CR increased, number of artificial inseminations, DO, and milking length decreased. Furthermore, culling parity, and annual milk yield increased. Herd‐life length increased in Hokkaido and decreased in the other regions. The economic values of CR were 1,623.8 to 946.8 yen and of DO were 857.4 to 399.0 yen. Relative economic values of milk yield to days open per genetic standard deviation were higher in the other regions than in Hokkaido where the economic effect of selection for DO was expected to be equal to selection for 305‐day milk yield and herd life. If the survival rate of multipara cows in the other regions increases, then the economic value of DO would similarly increase in Hokkaido.     

Effects of seropositivity for bovine leukemia virus, bovine viral diarrhoea virus, Mycobacterium avium subspecies paratuberculosis, and Neospora caninum on culling in dairy cattle in four Canadian provinces

The purpose of this research was to determine the effects of seropositivity for exposure to bovine leukemia virus (BLV), bovine viral diarrhoea virus (BVDV), Mycobacterium avium subspecies paratuberculosis (MAP) and Neospora caninum (NC) on overall and reason-specific culling in Canadian dairy cattle. Serum samples from, approximately, 30 randomly selected cows from 134 herds were tested for antibodies against BLV, MAP and NC using commercially available ELISA test kits, while 5 unvaccinated cattle over 6 months of age were tested for antibodies to bovine viral diarrhoea virus (BVDV). For analyzing the time (in days) to culling of cows after the blood testing, a two-step approach was utilized, non-parametric (Kaplan-Meier survival graphs) visualization and then semi-parametric survival modelling (Cox proportional hazards model), while controlling for confounding variables and adjusting for within herd clustering. For all reasons of culling, MAP-seropositive cows had a 1.38 (1.05-1.81, 95% C.I.) times increased hazard of culling compared to MAP-seronegative cows. Seropositivity for the other pathogens was not associated with an increased risk of overall culling. Among cows that were culled because of either decreased reproductive efficiency or decreased milk production or mastitis, MAP-seropositive cows were associated with 1.55 (1.12-2.15, 95% C.I.) times increased hazard compared to MAP-seronegative cows. Among cows that were culled because of reproductive inefficiency, NC-seropositive cows had a 1.43 (1.15-1.79, 95% C.I.) times greater hazard than NC-seronegative cows. Among cows that were culled because of decreased milk production, cows in BVDV-seropositive herds had a 1.86 (1.28-2.70, 95% C.I.) times increased hazard compared to cows in BVDV-seronegative herds. BLV-seropositive cows did not have an increased risk of reason-specific culling as compared to BLV-seronegative cows. No significant interaction on culling among seropositivity for the pathogens was detected, but only a limited number of cows tested seropositive for multiple pathogens. Results from our research will help in better understanding the economic impacts of these pathogens and justification for their control.     

Metritis complex in Michigan Holstein-Friesian cattle: incidence,descriptive epidemiology and estimated economic impact

Twenty-two Michigan dairy herds participating in a computerized herd health program were studied to determine the incidence and epidemiologic characteristics of metritis. Of 3773 lactations studied, 18% of the cows developed metritis at least once during the lactation. Metritis was reported most frequently immediately following calving. No clear pattern of association with age or season was demonstrated. A estimate was made of the extra cost associated with a cow treated for metritis. After including the effect on reproductive efficiency, milk production, cost of medication and losses due to culling, the total cost estimate was $106.00 for a lactation with metritis.     

Effects of different dry period lengths on production and economy in the dairy herd estimated by stochastic simulation

A range of preplanned dry period lengths in a dairy herd was evaluated, at different culling strategies and feeding regimes, by means of a dynamic stochastic model simulating the production at herd level. Dry period lengths were studied in the range of 4 to 10 weeks. The culling strategies exhibited two different rates of voluntary culling for reproductive failure and milk production, and the feeding regimes consisted of grass silage ad lib. and either 8 or 12 kg of concentrates/day in the first 24 weeks of lactation. The economic result was studied under a herd size and a milk quota constraint, respectively. A dry period of seven weeks appeared to be preferable under most circumstances. The net revenue per unit of milk sold was less sensitive to dry period length than the net revenue per cow per year. No major interactions between dry period length and culling strategy or feeding regime were found. The conclusions were fairly insensitive to price changes, and to variation in the assumed effect on lactational performance of dry period lengths from 6 to 8 weeks.     

An economic model to calculate farm-specific losses due to bovine respiratory disease in dairy heifers

This paper describes a personal-computer-based model estimating the economic losses associated with clinical bovine respiratory disease in replacement heifers raised on individual dairy farms. The model is based on the partial-budgeting technique, and calculates the losses for two types of the disease separately: calf pneumonia and a seasonal outbreak. Model input includes farm-specific data such as the incidence of bovine respiratory disease, prices, and effects of the disease on the heifers' productivity. The input database was linked directly with the economic model. For all input parameters, default values used are available to the user and can be modified easily.Losses considered by the model include treatment expenditures and costs associated with increased mortality, increased premature culling, reduced growth, reduced fertility and reduced milk production in first lactation. Uncertainty is taken into account for parameters related to disease incidence, mortality and culling.Basic calculations for a typical Dutch dairy farm with 60% of the heifers (<3 months) affected, indicated total annual losses due to pneumonia average 31.2 per heifer present on the farm (range 18.4-57.1). The estimated losses for one seasonal outbreak with heifers up to 15-months old affected were 27.0 per heifer present (range 17.2-43.1). For both BRD types, the model's outcome was most sensitive to the number of heifers affected. Most of the parameters that had a major impact on the total losses were related to treatment or to the effects on the heifers' productivity.The model is user-friendly and flexible, and can be used as an interactive tool by farmers and veterinarians in the (economic) decision-making process regarding on-farm prevention and control of bovine respiratory disease.     

Trends in the reproductive performance of Holstein dairy cows in Iran

The study was undertaken to determine the trends in the reproductive performance of Holstein dairy cows in Iran during 1994 to 2008. Reproductive performance data for 528,034 lactations of 246,132 cows in 1,822 Holstein dairy herds of Iran were used. The potential effect of calving season, herd, parity, calving year, as well as herd size and 305-day milk production on reproductive performance traits was investigated using multiple regression models. The least squares means of age at first calving decreased by 3.1 (±0.06) days per year from 806.5 (±96.3) days in 1994 to 788 (±89.9) days in 2008. The least squares means of calving interval increased 1.02 (±0.03) days per year from 394.1 (±65) days in 1994 to 413.2 (±81) days in 2008. Greater 305-day milk production was associated with an average increase of 6.55 (±0.08) days in calving interval per 1,000-kg increase in milk yield. Larger herd size was associated with an average decrease of 0.22 (±0.02) days in calving interval per 50 cows per herd. The mean number of days dry was 88.6 (±51.3) days and increased by 0.82 (±0.02) days per year. In conclusion, reproductive performance in Holstein dairy herds has generally decreased, whereas herd size and milk production have increased over time. Producers may make significant improvements in herd reproduction by reviewing management strategies including the sire selection, reproductive management, inseminator training and techniques, and improved estrous detection. Moreover, it may be advisable for the fertility traits to be included in the genetic selection indices to reduce the rate of reproductive decline.     

Quantification of economic losses consecutive to infection of a dairy herd with bovine viral diarrhoea virus

Production losses and treatment expenditures consecutive to bovine viral diarrhoea virus (BVDV) infection in a dairy herd were calculated by partial budgeting based on published estimates of production effects. Overall costs (losses plus expenditures) resulted in a decreased gross margin of 10.7 euros and 19.0 per 1000 l of milk for an average and severe infection, respectively. With a milk quota system allowing no lease of quota, assuming adjustment of the herd size by the farmer to produce the quota, decrease in gross margin was limited to 7.9 euros and 13.9 per 1000 l of milk.     

Economic consequences of postponed first insemination of cows in a dairy cattle herd

The purpose was to analyse the economic consequences of postponed first insemination of cows in dairy herds with different reproduction management, and to analyse the sensitivity of the results to a further decrease in beef prices, using a model simulating production and health in a dairy cattle herd. Three different period-to-first-insemination scenarios were analysed. Period to first insemination was defined as days post partum for initiating insemination at observed heat. The three scenarios consisted of a short period to first insemination (70 days for primiparous and 35 days for older cows), a 70 days postponed first insemination of primiparous cows and a scenario with 70 days postponed first insemination for all cows. At a 70 days postponed first insemination for primiparous cows a decrease in annual herd profit of 1% were found. A 70 days postponed first insemination for all cows led to a decrease in annual herd profit by 3% at good reproductive efficiency and 4% at poor reproductive efficiency. The herd profit was calculated as the profit to cover labour costs and fixed costs. Postponed inseminations might reduce labour per cow-year. The reduction in labour per cow-year need to be 3.2 h at good reproductive efficiency and 4.3 h at poor reproductive efficiency to counterbalance the reduction in herd profit by postponing first insemination for all cows by 70 days. In a situation with a 50% decrease in beef prices in a herd constrained by a milk quota (optimising profit per kg milk) herd profit was increased by 0.8% at good reproductive efficiency and 0.3% at poor reproductive efficiency by postponing first insemination for all cows by 70 days.     

Association between bovine-leukosis virus seroprevalence and herd-level productivity on US dairy farms

Bovine-leukosis virus (BLV; also termed ‘bovine-leukemia virus’) is a retrovirus that primarily affects lymphoid tissue of dairy and beef cattle. Our objective was to investigate the association between BLV infection and annual value of production (AVP) on dairy herds within the United States, as part of the USDA National Animal Health Monitoring System’s 1996 dairy study. 1006 herds (in 20 states) with at least 30 dairy cows were interviewed during 1996. The agar-gel immunodiffusion test was used to detect serum antibodies to BLV. 10–40 cows from each herd were tested and each tested cow was classified as negative or positive based on results of a single test.

A multivariable regression model was used with the 976 herds with complete data for analysis. When compared to herds with no test-positive cows, herds with test-positive cows produced 218 kg per cow (i.e. 3%) less milk. The average reduction in AVP was $ 59 per cow for test-positive herds relative to test-negative herds. For the dairy industry as a whole, BLV seropositivity was associated with loss to producers of $ 285 million and $ 240 million for consumers. Most of this $ 525 million industry loss was due to reduced milk production in test-positive herds.     

Association between milk production, somatic cell count and bacterial dermatoses in three dairy cattle herds

OBJECTIVE: To determine the correlations between three bacterial dermatoses in cattle, milk production and bulk-milk somatic cell count (BMSCC). DESIGN: Field observations in three dairy cattle herds. METHODS: Milk production, BMSCC, fertility and all herd diseases were recorded by computerised dairy management systems. Each herd was visited twice weekly and the clinical signs, course of diseases and morbidity and culling rates were noted. Bulk-tank milk was sampled twice monthly and analysed for somatic cell count. Bacteriological and histological examinations were carried out from samples collected from affected animals in the respective herds. RESULTS: The acute exudative form of dermatophilosis was diagnosed only in first-calving cows. The morbidity rate was 53% and the culling rate was 16% of the affected animals. The BMSCC increased by a factor of 2.4 times, and there was an average loss of milk production of 30%/cow/day in affected animals. Ulcerative lymphangitis was diagnosed in first-calving cows (22%) and older cows (15%). The culling rate was 28%. The BMSCC increased by a factor of 17.3 times, and the average loss of milk production was 5.5%/affected animal/day. Papillomatous digital dermatitis (PDD) was diagnosed in first-calving cows (25%) and in older cows (18%). The culling rate was 8%. The BMSCC increased by a factor of two times, and the average loss of milk production was 1.7%/affected animal/day. CONCLUSIONS: The correlations between three skin diseases (ulcerative lymphangitis, dermatophilosis, papillomatous digital dermatitis), milk production and BMSCC have been found to be unfavourable.     

Characterization of Minnesota dairy herds participating in a Johne's disease control program and evaluation of the program risk assessment tool

The objectives of this study were to: (1) characterize Minnesota dairy herds participating in a Johne's disease control program (JDCP) based on herd size, milk production, and clinical Johne's disease (JD) history, (2) evaluate if change in farm management practices, expressed in risk assessment (RA) total score, is associated with the change between the first and most recent ELISA test herd seroprevalence or change in clinical JD culling rate, and (3) identify farm factors associated with ELISA seroprevalence. A total of 1234 RA, performed between January 2000 and February 2004, were available for analysis from 714 dairy herds. ELISA test results from herd sampling between 2000 and 2004 were obtained from the Minnesota board of animal health (MBAH) database, and were available for 474 herds. Both the first and the most recent ELISA test results for herds with more than one RA were available for 262 herds. Mean herd size and mean annual milk production per cow was higher in JDCP dairy herds (161 milking cows) than either all Minnesota dairy herds or Minnesota dairy herd improvement association (DHIA) herds. For herds with more than one RA available, the most recent RA total score was significantly lower (mean 11% less) than the first. The change in RA total score (and any RA subtotal scores) between the first and most recent RA was not associated with the change between the first and the most recent ELISA within-herd seroprevalence or the change in JD culling rate between the first and most recent RA. The most recent ELISA test results were positively associated with postweaned heifer score and JD culling rate. The RA score was not found to be an effective tool for the prediction of ELISA seroprevalence.     

Technical and Economic Effects of Culling and Reproduction Strategies in Dairy Cattle Herds Estimated by Stochastic Simulation

Abstract

The objective of this study was to create operational replacement guidelines under various conditions concerning reproductive performance, supply of replacement heifers and individual milk yield. Nine culling strategies were defined by three average insemination periods and by three discrimination policies between high- and low-yield cows. The effect of the nine culling strategies was analysed with combinations of heat detection rate and time of initiation of breeding after calving under two replacement heifer purchase policies: purchase (open herd) and no purchase (closed herd). The strategies were evaluated using a stochastic simulation model that simulated production and reproductive status in herds composed of dual-purpose cattle with additional young stock. The evaluation of the strategies was made in a situation without a milk quota under typical Danish conditions in 1993. Results showed that discriminating between high- and low-yield cows improved net revenue significantly in open herds but not in closed herds. Irrespective of the purchase policy, using longer insemination periods increased net revenue significantly in herds with poor reproductive performance; whereas net revenue in herds with good reproductive performance tended to increase by using shorter insemination periods. The culling rate is a poor figure when evaluating culling strategies and culling strategies should be assessed at herd level rather than per cow.     

Association between anti-F. hepatica antibody levels in milk and production losses in dairy cows

This study was conducted to determine: (1) the associations between anti-Fasciola hepatica antibody levels in milk and some productive and reproductive parameters in dairy cattle, and (2) the threshold antibody level associated with loss of productivity, at both herd and individual level. Anti-F. hepatica antibodies were analysed by MM3-SERO ELISA in milk samples from the bulk tanks of 490 dairy farms and from 686 lactating cows. The results of general linear model analysis revealed a significant (P<0.05) negative association between the F. hepatica infection status at herd level, determined by analysis of specific antibodies in bulk tank milk, and the average herd milk production. Highly positive herds (MM3-SERO ELISA result>0.405) produced an average of 1.5 kg milk/cow per day less than the negative herds. At cow-level, the mixed model analysis also revealed a significant (P<0.05) association between anti-F. hepatica antibody levels and milk yield. A significant (P<0.05) average reduction of 2 kg milk/day was observed in cows with highly positive ELISA results (>0.762) in relation to cows with negative results. The results of the study led us to conclude that MM3-SERO ELISA is a powerful tool that can be successfully applied, if appropriate "economic thresholds" are established, to identify herds and cows suffering from milk production losses associated with natural infection by F. hepatica.     

Economic implications of bovine leukemia virus infection in mid-Atlantic dairy herds

OBJECTIVE: To determine the baseline costs of bovine leukemia virus (BLV) infection, including costs of clinical disease and subclinical infection, in a dairy herd representative of the mid-Atlantic region and compare these costs with the cost of a test-and-manage BLV control program. DESIGN: Stochastic spreadsheet model. SAMPLE POPULATION: A commercial Holstein dairy herd with 100 milking cows. PROCEDURES: A spreadsheet model was developed. The overall cost of infection included the cost of clinical disease (ie, lymphosarcoma [LS]) and the effects of subclinical infection on milk production and premature culling. Model input values and distributions were designed to reflect economic conditions in the mid-Atlantic region. Relative costs of infection and control were calculated for infection prevalences of 20, 50, and 80%. RESULTS: Estimated mean cost to the producer per case of LS was 412 dollars; for a herd with a 50% prevalence of BLV infection, annual incidence of LS was 0.66. Mean annual cost of subclinical infection at a 50% prevalence of infection was 6,406 dollars. Mean annual cost of a test-and-manage control program was 1,765 dollars. The cost of clinical disease and subclinical infection varied substantially with the prevalence of infection, whereas the cost of control varied with herd size. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that a basic BLV control program may be economically beneficial in herds in which the prevalence of BLV infection is > or = 12.5%. Farm-specific considerations may factor prominently when weighing the costs and benefits of an individual BLV control program.     

Economic impact of an epizootic of pseudorabies in a commercial swine herd in Ohio, achieving test negative status and quarantine release by use of vaccination and test and removal.

The effect of pseudorabies in a commercial farrow-to-finish operation on selected production and economic values was estimated. Pseudorabies was first diagnosed in this herd by circle testing done in March 1988, as a required part of follow up from another herd that had been diagnosed with pseudorabies in the area. A pseudorabies virus vaccination program was initiated in the herd at that time. The mean litter size of pigs born alive varied from 9.26 to 10.02 pigs/litter throughout the study period; however, there was a twofold increase in suckling pig mortality and a 2.6-fold increase in nursery pig mortality when the months of the epizootic were compared with pre-epizootic months. In the 6-month period following the epizootic, suckling pig mortality was three-fold higher than that reported in the preepizootic months. Total net loss for this operation was estimated at $99,700 from when the epizootic started until eradication, when calculating losses directly. The major economic losses (76.5% of total loss) were related to suckling pig mortality, which was $16,240 during the epizootic or $24/inventoried sow/week; $19,395 in the 6 months following the epizootic or $3.8/inventoried sow/week; and $40,628 thereafter until eradication 26 months later or $0.37/inventoried sow/week. Nursery pig mortality losses were 12.6% of total net losses; $754 during the epizootic, $357 in the 6 months after the enzootic, and $11,444 thereafter until eradication 26 months later. Sow culling and deaths accounted for 9.4% of net losses that took place from 6 months after the epizootic until eradication.(ABSTRACT TRUNCATED AT 250 WORDS)     

A stochastic model for the simulation of management decisions in dairy herds,with special reference to production,reproduction, culling and income

A stochastic simulation model was developed to study management decisions in dairy herds. The primary purpose of this model is to quantify the economic effects of different culling policies with respect to productive and reproductive failure.Each stimulated herd consists of a fixed number of up to 100 cows (with additional youngstock), individually generated according to various predetermined herd characteristics. Changes in the herd can be followed at 20-day intervals over 15 years. Calculations are repeated 20 times for each alternative, in order to obtain statistically reliable results. Milk production, fat and protein content of the milk, reproductive performance and involuntary disposal are stochastic variables in the model. The major deterministic variables are feed intake, live body weight (including normal carcass value) and number of youngstock.Calculations to test the model's behaviour have been carried out. Results obtained in the basic situation were consistent with averages observed in practice. A sensitivity analysis was used to compare the economic importance of different management issues under identical conditions. Some parameters commonly used as economic indicators, namely 305-day milk production and Fertility Status, were shown to have limited value. Moreover, the results showed again that improvements in fertility traits alone (such as oestrus detection and pregnancy rate) do not affect income greatly. Therefore, a broadening of the content of herd health programs to include other aspects is desirable from an economic point of view. Breeding and culling policy are particularly important. Income decreased considerably when the maximum allowable calving interval was reduced, despite the positive effect on the average calving interval of the herd. Strategic breeding, taking into account the productive capacity of the cows, was the most profitable policy.More precisely defined strategic breeding and culling policies will be evaluated and discussed in a subsequent paper. Meanwhile the present model is being adapted for interactive use in teaching of veterinary and agricultural students.     

Culling on low milk yield and its economic consequences for the dairy herd

Voluntary culling on low milk yield and the economic returns for herds with a stable number of milk cows was investigated for spring calving dairy herds in the Republic of Ireland. The analysis was conducted at annual involuntary removal rates: 15, 20 and 25% and replacement costs as percent of beef value 94, 126, 157%. Varying cow replacement rate above involuntary removal rate by voluntary culling increased milk sold per cow in year 16 to a maximum of +5 to +10% after practicing a fixed strategy for 16 years. Greatest absolute and relative gains in yield occur from voluntary culling at the lowest involuntary replacement rate. Voluntary culling up to 3 to 8 percentage units above involuntary cow replacement rate maximizes economic returns per cow in herd when the market price for replacement heifers exceeds 150% of their beef value. Maximum voluntary culling may be practiced for prices near or below beef value.     

Risk factors for herds to test positive for Mycobacterium avium ssp. paratuberculosis-antibodies with a commercial milk enzyme-linked immunosorbent assay (ELISA) in Ontario and western Canada

The objectives of this study were to identify risk factors associated with i) a Mycobacterium avium subsp. paratuberculosis (MAP)-antibody milk enzyme-linked immunosorbent assay (MAP milk ELISA)-positive herd status, and ii) the within-herd MAP milk ELISA-positive prevalence in Canadian dairy herds. This prospective cohort study was conducted between 2005 and 2009 on 226 herds in Ontario and western Canada, which participated in a voluntary risk assessment (RA)-based Johne’s disease control program. Two MAP milk ELISA and risk assessments and a previsit survey were available per herd. The overall farm RA scores alone could not be used to predict whether a herd would test positive for MAP antibodies. However, the results of this study indicated that increasing the likelihood of exposing calves to MAP through certain management practices, as assessed with the RA, increased the likelihood of a herd being test-positive for MAP antibodies.