[Risk and economics of disease introduction to dairy farms]

A more closed farming system will enhance the success of disease eradication programmes, because the introduction or re-introduction of infectious diseases is less likely. The objective of the study was to obtain input for the development of an on-farm decision support model to calculate the economic consequences of a more closed farming system. The input was based on bovine herpesvirus 1 (BHV1), since there were numerous data on this disease, but a more closed farming system will prevent introduction of other diseases as well (i.e. bovine virus diarrhoea virus (BVDV), L. hardjo, and S. dublin). Direct animal contacts, such as purchase of cattle, participation in cattle shows, and cattle that escape and mingle with other cattle, were found to be important risk factors for the introduction of BHV1. Furthermore, the use of protective farm clothing was found to be an important preventive factor. The effect of an IBR outbreak at an IBR-free farm on milk production caused limited losses of on average 0.9 kg per cow per day during 9 weeks, but the variability was high (95% CI 0-2 kg). Nine percent of Dutch IBR-free dairy farms that were also at risk for BVDV, L. hardjo or S. dublin had one introduction per year of one of these four diseases. All these results were incorporated in the economic model. Management measures to reduce the probability of introduction of BHV1, the costs of these measures, and the risk reduction after these measures were obtained from other sources. The calculations showed that the implementation of a more closed system will be profitable for most farms. The profitability will increase when a farm is at risk for more diseases, but will decrease when farms are limited in their facilities to rear replacement heifers or when a large proportion of pasture adjoins pasture of other cattle farms.

Spirometric performance in Belgian Blue calves: I. Effects on economic losses due to the bovine respiratory disease complex

The aim of this study was to determine whether high spirometric performances in calves are associated with low economic losses due to the bovine respiratory disease complex (BRDC). Five spirometric variables (SV) were measured in 909 double-muscled Belgian Blue calves from 15 to 60 d of age. Afterward, calves were monitored for 6 mo to determine whether they developed BRDC and to determine the costs due to BRDC (i.e., medicine costs and veterinarians' fees, plus estimated financial losses due to mortality in case of death). To analyze the effects of spirometric performances on BRDC cost, a fixed linear model was used for each SV. In addition to SV, each model included the effects of sex, dam's parity, vaccination status, muscular development score, herd-period, and BW. Only herd-period and the maximal ventilation and the vital capacity had significant effects on costs due to BRDC, indicating that these two SV are major physiological determinants of economic losses associated with BRDC. Accordingly, it is assumed that an amelioration of maximal ventilation and vital capacity could result in increased resistance to BRDC in calves.

[Integrated disease control in dairy herds. A case study from the veterinarians' viewpoint]

Integrated control of bovine virus diarrhoea virus, bovine herpesvirus-1, Leptospira interrogans serovar hardjo subtype hardjobovis, Mycobacterium avium subsp. paratuberculosis, and Salmonella dublin in dairy herds may provide economic benefits superior to those obtained by sequential disease control, because, among other things, it allows optimization of voluntary culling. However, in practice there are no adequate instruments to establish priorities in voluntary culling. Therefore, in this study the priorities in decision-making for voluntary culling of infected cattle, as indicated by more than 300 cattle veterinarians, were analysed. Based on our results and supplementary considerations, the priorities for voluntary culling in the Netherlands can be ranked as: 1st. cull S. dublin carriers, 2nd. cull persistently infected BVDV carriers, 3rd. cull paratuberculosis faecal culture positive cattle and their last offspring, 4th. cull, in paratuberculosis infected herds, paratuberculosis ELISA positive cattle and their last offspring and cull, in low prevalence herds, BHV1 gE-positive cattle, and 5th. cull leptospirosis seropositive cattle. Since this ranking was based on one case study only, other priorities may prevail in other herds.

Phenotypic trends in incidence of stillbirth for Holsteins in the United States

The objectives for this study were to determine 1) if there was a trend in stillbirths for the U.S. Holstein population, 2) if stillbirths are the same trait in primiparous and multiparous cows, and 3) what was the role of dystocia in stillbirths. A sample of 666,341 births from the MidStates Dairy Records Processing Center and the National Association of Animal Breeders was used to examine the influence of sire, herd, year, season, sex of calf, parity of dam, calving ease, and gestation length on the survival of the calf. Parity was scored as an ordered variable (1, 2, 3+). Calving ease was scored on a scale of 1 (no assistance) to 3+ (needed assistance). An increasing trend in stillbirths was found in primiparous and multiparous cows. The percentage of stillborn calves in primiparous cows increased from 9.5 in 1985 to 13.2 in 1996. Stillbirths in multiparous cows increased from 5.0 to 6.6% from 1985 to 1996. Variation about the trend was greater in primiparous cows than in multiparous cows. Dystocia was a major determinant of stillbirth incidence, but the association was stronger in primiparous cows. Sex of calf had different associations with stillbirth incidence in primiparous and multiparous cows. Gestation length and season of birth also had significant associations with stillbirth incidence. Logistic regression models with fixed and random effects were fit to the data to preserve the binary nature of the stillbirth response. The expected probability of stillbirths for an average herd and sire was 10% for primiparous cows and 5% for multiparous cows. Replacement of stillborn calves is a substantial cost to the dairy industry at more than $125.3 million per year. Because of the increasing incidence of stillbirths, these costs have increased by $75.9 million from 1985 to 1996.

[Extensivity of infection of Fasciola hepatica L. in cattle in Lublin's voivodship in the years 1993-2001]

Extensivity of infection of Fasciola hepatica L. among cattle in Lublin's voivodship from 1993-2001. Aim of the work was to determine extensitivity of appearance of hepatica among catlle put to slaughter in slaughtershouses in Lublin's voivodship from 1993 to 2001. Substance for the work was braught from the annual reports of official examination of slaughtered animals, reached from both main Inspectorate (department) of Veterinary in the Ministry of Agriculture and from Regional Institute of Veterinar's Hygiene in Lublin. Results of researches are as follow: extensivity of infection of Fasciola hepatica among cattle in Lublin and voivodship between 1993 - 1999 oscillates about 5%. In 2000 extensivity of invasion reached 10,9%.

[Occurrence and economic importance of congenital hernia in German Fleckvich calves]

The frequency of congenital hernia was investigated in German Fleckvieh calves being driven up for sale on livestock markets for breeding and fattening calves in Miesbach and Traunstein. Data were collected on 77 livestock auctions in the years 1996 and 1997. Altogether 53,105 calves were examined and 1.8% of these calves showed a congenital umbilical hernia. The incidence of umbilical hernia was significantly influenced by the sex of the calf, the occurrence of multiple births, the market place/market date, the sire and the sire line. Red Holstein blood proportion, lactation number, duration of pregnancy and 305 day milk performance were not of significant importance. Herd milk level did not influence the incidence of congenital umbilical hernia, however, herdmate averages for calves differed significantly in their incidence. The average difference of the market price between male calves affected by congenital umbilical hernia and not affected male calves amounted to 75 DM, in female calves, however, only to 38 DM. The risk, that a congenital umbilical hernia is not closing within an age of 15 months, depends on the width of the hernial opening in the newborn calf. An opening of 4 cm and more has only a healing chance of 50% and less. However, negative effects on fattening and carcass traits could be not found. The genetic influence on congenital umbilical hernia was obvious. The analyses indicated that the incidence of congenital umbilical hernia observed could not be explained by one autosomal recessive gene locus, but it seemed much more likely that more than one gene locus is involved or a mixed multifactorial monogenic mode of inheritance may be the underlying genetic mechanism. Breeders should be aware of the implications of congenital hernias and thus, congenital hernia should get more attention in the selection process of young sires.

Fasciola hepatica: a review of the economic impact in cattle and considerations for control

To understand the rationale behind recommended control programs for liver flukes in cattle, the economic impact and the complex life cycle of Fasciola hepatica need to be appreciated. Fluke-infected cattle rarely demonstrate clinical disease, but subclinical impairment of feed efficiency, growth, and fertility can have an important impact on productivity. Although the precise benefit from controlling liver flukes is unknown due to the inherent variability between studies, most investigations demonstrate a considerable economic advantage to treatment. In addition, recent studies have demonstrated that liver flukes may cause a decrease in host fertility by altering normal metabolism and/or balance of sex hormones. This review focuses on these issues and how to best use available drugs to implement optimal fluke control programs.

Progress in national control and assurance programs for bovine Johne's disease in Australia

Cattle strains of Mycobacterium paratuberculosis are known to infect cattle, goats and alpaca in southeastern Australia, where there are also significant numbers of farmed deer. Although sheep strains have recently been identified in some cattle in Australia, epidemiological evidence to date supports the distinction (between bovine Johne's disease (JD), caused by cattle strains in cattle, goats and alpaca, and ovine JD, caused by sheep strains in sheep and goats) for the purposes of control and assurance programs. The National Johne's Disease Control Program is coordinated by the Australian Animal Health Council, working with the livestock industries and with the Commonwealth, state and territory governments. The council also brokers industry and government funding for the program. The National Johne's Disease Market Assurance Program for Cattle was launched in 1996 as the first of a suite of voluntary national market assurance programs (MAPs) to assess and certify herds as negative for JD. By December 1998, over 550 herds had achieved an assessed negative status. A MAP was also launched for alpaca in 1998 and a program for goats should be finalized in early 1999. National standards for state control of JD through zoning, movement controls and procedures in infected and suspect herds have also been developed. The paper covers factors affecting development and implementation, uptake of and improvements to national control and assurance programs for bovine JD in Australia.

Direct and correlated responses to selection for milk yield: results and conclusions of regional project NC-2, "improvement of dairy cattle through breeding, with emphasis on selection". NC-2 Technical Committee

Measurement of direct and correlated responses to single-trait selection for milk yield was the major objective of regional project NC-2. The NC-2 Technical Committee included representatives from Alaska, Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Nebraska, South Dakota, Wisconsin, and the USDA. All representatives, except Illinois, Kansas and Nebraska, maintained a selection line formed by using AI sires selected for high estimated transmitting abilities for milk and a second line that served as some type of a control. Stations varied in criteria for selection of bulls for control lines. Farms were managed similarly, including feeding and management of selection and control lines as one herd, random mating within line, and restricted culling policies. Selection for milk yield effectively increased milk production. All selection lines increased milk and net income per lactation more than control lines. Realized gains matched or exceeded gains expected from estimates of breeding values. Yields of milk components increased, but component percentages decreased appreciably for selection lines. Reproduction of nulliparous animals was not affected, but days open for lactating selection cows increased in some of the individual projects. Selected cows tended to have larger health costs, specifically for mammary treatment. Udder and conformation traits did not deteriorate for selection lines, although control lines with selection of sires on genetic evaluations for type received higher type scores. There should be few reservations about undesirable responses correlated with selection for milk yield.

Estimating the economic effects of cystic echinococcosis: Uruguay, a developing country with upper-middle income

Cost-benefit analyses, run before the commencement of a programme to control a parasitic disease, should include estimates of the economic losses attributable to the disease. Uruguay, a middle-income, developing country, has a recent history of persistent problems with cystic echinococcosis, in both its human population and livestock. The economic effects in Uruguay of this disease, caused by the larval stage of the canine tapeworm Echinococcus granulosus, have now been evaluated. Data on the incidence of the disease, in humans and livestock, were used to construct cost estimates. The estimated minimum cost (U.S.$2.9 million/year) was based on the condemnation costs of infected offal together with the actual costs of the hospital treatment of the human cases. The estimate of the maximum cost (U.S.$22.1 million/year) also included the production losses resulting from lower livestock efficiency and the reduced income of individuals with morbidity attributable to the disease.

Relative cost-effectiveness of treatment of feedlot calves with ivermectin versus treatment with a combination of fenbendazole, permethrin, and fenthion

OBJECTIVE

To compare growth performance, animal health characteristics, and carcass characteristics of feedlot calves treated with ivermectin topically with that of feedlot calves treated with a combination of fenbendazole orally and permethrin and fenthion topically.

DESIGN

Clinical trial.

ANIMALS

14,184 British crossbred steer calves (mean weight, 286 kg [630 lb]) in 30 pens at a commercial feedlot in Nebraska.

PROCEDURE

On arrival at the feedlot, calves were randomly assigned to be treated with ivermectin topically or with a combination of fenbendazole orally and permethrin and fenthion topically (control). At the time of assignment to treatment groups, fecal samples were collected from 5% of the calves. Growth performance, carcass characteristics, and health information were recorded.

RESULTS

Geometric mean fecal egg counts at the time of arrival at the feedlot were not significantly different between groups. Final weight, weight gain, average daily gain, and the dry matter intake-to-gain ratio were significantly improved for calves in the ivermectin group. The percentage of carcasses classified as quality grade choice was higher for the ivermectin group than the control group; however, the percentage of carcasses classified as yield grade 1 and the dressing percentage were higher for the control group than for the ivermectin group.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that topical administration of ivermectin to feedlot calves is relatively more cost-effective than administration of a combination of fenbendazole orally and permethrin and fenthion topically.

Economic aspects of outbreaks of dermatophilosis in first-calving cows in nine herds of dairy cattle in Israel

Outbreaks of dermatophilosis in nine herds of dairy cattle in Israel were studied retrospectively. The outbreaks might have been associated with the exposure of the animals to intense showering during the spring and summer months of May to October, in addition to calving and postcalving stress. The acute exudative form of dermatophilosis occurred in the first-calving cows during the six weeks after they calved. The morbidity rate ranged from 10.0 to 66.6 per cent and the period of morbidity ranged from eight to 19 days. Mortality or culling occurred in four of the herds and ranged from 1.6 to 17.1 per cent. The disease also resulted in a gradual loss of condition, a decrease in milk production and marked increases in the somatic cell counts in milk.

A stochastic model simulating the feeding-health-production complex in a dairy herd

A dynamic, stochastic, and mechanistic Monte Carlo model, simulating a dairy herd with focus on the feeding-health-production complex is presented. By specifying biological parameters at cow level and a management strategy at herd level, the model can simulate the technical and economic consequences of scenarios at herd level. The representation of the feeding-health-production complex is aimed to be sufficiently detailed, to include relationships likely to cause significant herd effects, and to be sufficiently simple to enable a feasible parameterization of the model and interpretation of the results from the model. Consequently, diseases are defined as four disease types: two metabolic disease types, an udder disease type, and a reproductive disease type. Risk factors for the diseases were defined as parity, yield capacity, disease recurrence, disease interrelationships, lactation stage, and season. Direct effects of the diseases were defined according to milk yield, feed intake, feed utilization, conception, culling, involuntary removal, and death. Scenarios differing in base risks of milk fever and ketosis, heat detection rate, and culling strategy were simulated for describing the model behavior. Annual milk yield per cow was decreased by increased risk of ketosis and by increased risk of milk fever, even though no direct effect of milk fever on milk yield was modeled at the cow level. The indirect effect from milk fever is a consequence of increased replacement rate (relatively lower milk yield from younger cows). By ignoring the history of milk fever in insemination and replacement decisions, a significantly reduced net income per cow was found in some herds. We concluded that important benefits from using such a herd model are the capability of accounting for herd management factors and the advantage of avoiding to double count the indirect effects from disease, such as increased risk of other diseases, poorer reproduction results, and increased risk of culling and death.

A stochastic partial-budget analysis of an experimental Pasteurella haemolytica feedlot vaccine trial

A field trial compared a modified Pasteurella haemolytica biotype A serotype 1 leukotoxin vaccine to a commercial vaccine during March-July 1995 in a Natal Midlands, South African, feedlot. Weaners/long weaners purchased by the feedlot were allocated systematically into test vaccine and control vaccine groups of 1241 and 1240 head, respectively, and fed in groups of approximately 200 head. Morbidity and mortality were monitored until the animals were marketed. Details of pleuritis and pneumonia at veterinary meat inspection were recorded for 409 test-vaccinated and 424 control-vaccinated cattle. An increase in morbidity but not mortality risk of respiratory disease was shown between test (13.8% morbidity) and control (11.4% morbidity) groups. Cattle with a processing weight <245 kg were 1.4 times more likely to develop respiratory diseases than cattle with a processing weight > or =245 kg. Cattle bought on auction were 1.6 times more likely to develop respiratory disease than cattle bought at private sales. A partial farm budget incorporating Latin Hypercube sampling of uncertain variables was done to obtain the distribution of possible financial outcomes if the test vaccine were used. Impact (sensitivity) analyses indicated that median weight of carcass cut away had the greatest impact on the profit margin. The partial farm budget highlighted the importance of reducing sub-clinical lesions in a feedlot.

Vaccination against ticks (Boophilus spp.): the experience with the Bm86-based vaccine Gavac

The control of tick infestations and the transmission of tick-borne diseases remain a challenge for the cattle industry in tropical and subtropical areas of the world. Traditional control methods have been only partially successful and the parasites continue to result in significant losses for the cattle industry. Recently, vaccines containing the recombinant B. microplus gut antigen Bm86 have been developed. Our vaccine formulation (Gavac, Heber Biotec S.A., Havana, Cuba) has been registered and is commercially available in Cuba, Colombia, Dominican Republic, Brazil and Mexico. In controlled pen trials, Gavac has been effective for the control of artificial infestations of B. annulatus, B. decoloratus and chemical-sensitive and resistant B. microplus strains from Australia, Africa, America and Iran. In controlled field trials in Cuba, Brazil, Argentina and Mexico, Gavac has shown a 55-100% efficacy in the control of B. microplus infestations in grazing cattle 12-36 weeks after the first vaccination. Field trials under production conditions have been conducted in Cuba, Colombia, Brazil and Mexico in pure and cross-bred cattle herds. The application of Gavac has increased the time between acaricide treatments by an average of 32 /-21 days (P = 0.0005) resulting in important savings for the cattle industry. In Cuba, a cost-effectiveness analysis was conducted in more than 260000 animals. The cost-effectiveness analysis showed a 60% reduction in the number of acaricide treatments, together with the control of tick infestations and transmission of babesiosis, which resulted in savings of 23.4 dollars animal(-1) year (-1). These results clearly demonstrate the advantage of vaccination and support the application of Gavac for the control of Boophilus spp. infestations.

Economics of theileriosis control in Zambia

For an economic analysis of theileriosis control, we adopted the total economic cost (TEC) method, which calculates the sum of output losses from tick damage, theileriosis mortality and morbidity, and expenditures for treatment or prevention of the disease. At farm level, the TEC can be minimized by a specific combination of vector control and/or immunization and an acceptable level of losses. Expenditures for vector control include acaricides, construction of dipping or spraying facilities and their maintenance, and variable costs such as those for water and labour. Economics of vector control depend on the herd size and the method of application of the acaricide. Morbidity, mortality and tick damage losses are effectively reduced by correct and intensive vector control programmes. Expenditures for vector control are estimated at US$ 8. 43, 13.62 and 21.09 per animal per year for plunge dipping, hand spraying and pour-on, respectively. Immunization costs comprise production of parasite stabilates, storage and application, delivery and treatment. At US$ 9.5 per animal, immunization limits losses caused by Theileria parva, but ticks still may reduce the productivity of the animals. Expenditures for treatment after natural infection involve drugs, transport, veterinary fees and farm labour costs. Treatment has a moderate success rate, hence both morbidity and mortality remain important factors. Equally, it does not affect the vector, which may continue to reduce overall productivity of cattle. Expenditures for treatment range between US$ 9.04 and US$ 27.31 per animal. To compare different TECs in relation to different control strategies, assumptions have to be made on disease occurrence, case fatality, value and productivity of the cattle, reductions in productivity due to morbidity and number of animals under a specific control regime. Calculations based on data from Southern Province, Zambia show that large-scale immunization reduces the TEC by 90% compared to no intervention. Treatment, which is the second-best option, reduces the TEC by 60%. Appendix 1 Summary of factors influencing total economic cost

The economic impacts of endemic diseases and disease control programmes

The authors discuss the evaluation of the economic impacts of endemic livestock diseases, and economic issues in control of these diseases. Particular attention is focused on helminths and on endemic vector-transmitted infections (particularly ticks and tick-borne diseases). Decisions relating to disease control have to be made by government and by the producer. Government requires information on the level of control to adopt, the extent of involvement needed, and how to fund animal health programmes (particularly how to share costs between taxpayers and livestock producers). Individual producers require information as to how much effort to invest in disease control, including information collection effort, and how to design control strategies. Economics can shed light on these issues. However, experience suggests that animal health policies are particularly difficult to evaluate from an economic viewpoint, with complex relationships between animal health, production impacts, market access, and non-production benefits of livestock. While little information is available concerning the cost of helminth diseases, many estimates have been made of the costs of ticks and tick-borne diseases at a regional and national level, sometimes demonstrating that eradication is warranted.

Estimating the costs associated with endemic diseases of dairy cattle

A number of endemic diseases of dairy cattle cause significant losses to the dairy industry in the mainland UK (England, Scotland and Wales), both in terms of the reductions in output levels or wastage of resources incurred and the resource costs of disease prevention and treatment (Esslemont & Spincer, 1993; Esslemont & Kossaibati, 1996). Various studies have estimated the costs associated with different diseases (Bennett, 1992). However, these studies use different methods of assessment, relate to different populations at risk, refer to different points in time and utilize different ways of measuring disease and valuations of the effects of disease on production. Thus, it is difficult to use these studies for any comparative assessment of the magnitude of output losses and resource wastage incurred as a result of different diseases. Such information is useful in exploring both the economic consequences of diseases and the potential benefits of research on improved disease control (Howe, 1991; McInerney, 1996).

This paper presents analyses of the impacts on production of five endemic diseases and conditions of dairy cattle in mainland UK: bovine viral diarrhoea (BVD), fasciolosis, lameness, leptospirosis and mastitis (including summer mastitis). These analyses follow from a preliminary economic study of the impacts on livestock production of some 30 non-notifiable diseases and conditions of farm animals (Bennett et al. 1997). The study was funded by the Ministry of Agriculture, Fisheries and Food in the UK, with the (eventual) aim of providing information to policy makers that might help them to reach decisions on allocating funds to research into livestock diseases. Full details of the analyses are available from the website address given at the end of this paper.