CASE NOTES


The Economic Impacts of Bovine Viral Diarrhoea Virus (BVDV) Infection on a South Coast Dairy Herd

Mike Healy, Genevieve Chin (Vet Interns, Sydney University) and Ian Lugton (SDV, South East LHPA, Bega)

Posted Flock & Herd August 2007

INTRODUCTION

BVDV (bovine pestivirus) is a viral infection that affects dairy and beef cattle and is estimated to be prevalent in 90% of herds in Australia (McGowan, 2009). Transient infection of previously unexposed breeding females 9 days prior to breeding or up to day 175 of pregnancy results in transplacental infection and can cause extensive reproductive losses, as well as a plethora of problems related to the birth of persistently infected (PI) calves (Grooms, 2004).

Economic losses are more extensive in previously unexposed herds but do occur to a lesser extent in herds with endemic BVDV. Modelling of the economic impacts of BVDV infection has been performed previously, but such modelling can suffer from considerable inaccuracies due to lack of reliable field information on the impact of the disease. This study attempts to investigate a real outbreak, gather information on observed losses and to quantify these in dollar terms.

AIMS

This case study examines the economic loss to a dairy operation affected by BVDV near Bega, New South Wales, Australia from March 2008 to October 2009. This report aims to cover the likely and measurable sources of loss on this property. Eight different areas of economic loss have been identified: abortions; conception rates; total milk production and mastitis; PI calf-associated problems; PI bull-associated problems; selling and buying stock; veterinary services and; long-term ongoing losses. The costs of future preventative measures have also been considered. The costs associated with each category have been listed and details regarding the calculations can be found in the Appendix. Epidemiological aspects of the BVDV outbreak are also discussed.

MATERIALS & METHODS

Information relating to financial and epidemiological aspects of the BVDV outbreak was obtained through multiple meetings and phone interviews with the herd managers, reference to computerised herd records, consultation with practitioners involved in this case and reviewing clinical records kept at Bega/Cobargo Veterinary Clinic and the South East Livestock Health and Pest Authority (SELHPA). Additional resources such as relevant peer-reviewed literature, the 'In Calf' Project and personal communication with experts involved with economic studies and BVDV were also utilised.

Herd Description

The affected herd is a year-round calving herd milking 950 cows. Breeding is performed by artificial insemination (AI). Bulls are run in with the herd to 'mop-up' any cows non-pregnant to AI. Bulls are replaced approximately every 2 years. Annual injections of Ultravac '7-in-1' (Pfizer) is used to immunise the herd against leptospirosis and clostridial diseases. The entire herd is kept on three separate properties: The milking herd at Angledale; the calf-rearing unit at Numbugga and; heifers at a property at Cann River, Victoria where they are joined. Cattle are moved between properties as they progress in their life cycle e.g. springing heifers are moved from Cann River to the dairy at Angledale, where they remain until culled from the herd.

The heifers at Cann River have all been born and reared in the Bega Valley. However, some mature cows are purchased on occasions.

The last cow herd introductions occurred in June 2007; at this time, a total of 125 cows from two herds in Shepparton and Cobargo were introduced to the milking herd. A high proportion of these cows were in-calf.

Case history

From July to November 2008, abnormally high numbers of early returns to service and mid-term and early abortions were identified. In November 2008, 32 first and second calving cows were tested for BVDV antibody with the AGID test. Five were negative, whereas 7, 10, and 10 cows had scores of 1, 2 and 3 respectively. This suggests that 6 to 9 months earlier that at least 15/32 (47%) of the young cows were naive to infection with BVDV.

One calf died at 3 weeks of age in November 2008 from bronchopneumonia showed histological lesions consistent with recent BVDV infection. As part of a consignment of export heifers around 12 months of age, 46 heifers were PACE tested on 19/12/2009. Two of 46 heifers were identified as PIs. This result retrospectively confirmed that PI calves were being born in November/December 2008.

It was not until February that PACE testing on ear notch samples for PI status was undertaken in recently born calves. Calves returning a positive result on the first PACE ear notch test were re-tested 3 weeks later to confirm persistent infection. The results of this testing are depicted in Figure 1.

PACE test results
Figure 1. Results of 402 PACE tests on calves born from November 2008 and September 2009

Number of negative results = 346, and positive = 56

Ill-thrifty and small PI calves have been born from November 2008, through till July 2009. These births included a small number of 'dummy' and premature animals; a high proportion of PI calves died in the neonatal period. Uninfected calves that were reared alongside PI calves have shown a high rate of respiratory infection and scours. Property owners began managing newborns differently from May 2009 by housing them individually in hutches until they were PACE tested. Most PIs are destroyed, but some have been kept to autovaccinate heifers at the Cann River property.

Only cows in the milking herd have aborted or given birth to PIs or other BVDV-affected calves. Pregnant heifers sourced from the Cann River property have not suffered from reproductive losses associated with BVDV.

On 27 July 2009, one of the herd bulls purchased from outside the district was tested and subsequently identified as a PI (Figure 2). He had been the only bull in with the milking herd from March to June 2008 and subsequently one of two bulls run in with the herd during 2009. This bull was known to have sired 27 calves and they have all been tested BVDV-negative. This bull was removed from the cows immediately after his PI status was established.

The bull responsible
Figure 2. The PI bull which was the likely cause of the outbreak of BVDV infection in the herd

RESULTS

Sources of economic losses associated with BVDV:

1. ABORTIONS

Between July 2008 to May 2009, an approximately 60 cows exhibited early return to service after being pregnancy tested in-calf, indicating early embryonic death and resorption. These cows were rejoined.

Cost of early abortions = 60 x $699 = $41,940

Twenty-nine mid-term abortions (5-7 months gestation) were recorded between July 2008 and May 2009, with a peak of 6 occurring in the 2 weeks from 26/10/2008 and 8/11/2008. Based on the normal incidence of mid-term abortions in the herd due to other causes being less than 2%, an estimated 25 of these were attributed to BVDV infection of the cows. These abortions occurred in cows that had been born and reared in this herd, as well as in the introductions.

Cost of mid-term abortions = 25 x $850 = $21,250

2. CONCEPTION RATE IN COWS

A herd fertility report prepared in September 2008 revealed that average first service conception rate was 25%. At the same time the previous year, it was 35%. This decrease is likely to be directly related to BVDV and possibly indirectly related to an increase in the incidence of mastitis related to BVDV infection (ABS Global, Inc.). Cows that are transiently infected with BVDV around the time of mating are known to have conception rates reduced by up to 44% (Fray, Paton and Alenius, 2004; Kirkland et al., 1997).

Cost of decreased conception rate = $38,124

TOTAL HERD MILK PRODUCTION

The number of cows in the milking herd has not been reduced, since surplus heifers have replaced the 25 aborting cows. However, a good heifer will produce only 83% of the milk yield of a mature cow over a whole lactation (Dairy Australia, 2003).

Cost of lost milk production = 25 x 1615 x $0.42 = $16,957.50

There had been an ongoing mastitis problem in this herd that commenced prior to March 2008. In May 2008, there was an increase in the number of unresolved and new infections. It is likely that the introduction of the PI bull to the herd (in March 2008) was related to this increase in cases due to the induced immunosuppression.

Cost of increased mastitis in the herd through discarded milk = 300 x 30 x $0.42 = $3,780

3. PERSISTENTLY INFECTED CALF-ASSOCIATED PROBLEMS

From February to July 2009, herd managers have been identifying PIs by PACE testing and destroying all of the weaker individuals. Records examined have shown that 58 calves were found to be PIs. Interestingly two of these were found retrospectively in a November 2009 test of 46 yearling heifers destined for export. A total of 55 heifer calves have died or been destroyed due to illness or because they were PIs. At least 20 heifer calves with neurological abnormalities (dummies) and 5 premature heifer calves that showed patchy baldness were destroyed.

Loss due to 80 dead heifer calves = 80 x $150 = $12,000.

Around 35 PI calves are being kept to be reared and act as immunisers for the herd. These will have a cost burden since they won't be bred or sold and have a low likelihood of living beyond 2 years of age (Figure 3).

Calf comparison
Figure 3. This PI heifer (red arrow and tag) is indistinguishable in size from other weaners that are 3 months younger

Loss due to immuniser PI calves = $26900

Seven heifer calves have been reared to 3-4 months of age and a few more at 6-8 months of age before dying of respiratory infection.

Cost of rearing and losing 7 calves = $1,365

To initially rear calves in isolation to prevent contact between PI and non-PI calves, 25 calf hutches were purchased (Figure 4). Only after PI test results were reported were calves placed into the automated calf feeding system.

Cost of 25 hutches @ $300 each = $7,500

1. PERSISTENTLY INFECTED BULL-ASSOCIATED PROBLEMS

The semen quality of the PI bull was checked in November 2008 as the bull was siring good calves. The semen was found to be of poor quality and unable to be frozen. PI bulls can still sire calves. However, they tend to have a reduced breeding efficiency (Grooms, 2004). This bull had a conception rate of approximately 56.8%. This is below the expected average conception rate of 65%.

Cost of a reduced conception rate = $1,200

The PI bull was culled 7 months prematurely and the owners had to acquire a new bull costing $1,750. The PI bull was sold for slaughter for $800 rather than $1,000 that could have been obtained if sold as a herd bull to another dairy.

Change over cost for new bull = $419

Calf units
Figure 4. Calf hutches outside the automated calf rearing facility

1. SELLING AND BUYING STOCK:

The BVDV outbreak has not affected the owners ability to sell animals. However, herd managers have had to decline offers to rear calves for clients due to the high risk of BVDV transmission and additional time needed to implement treatment and control measures for BVDV in their own herd.

Cost of lost contracts = 100 x $278 = $27,800

2. VETERINARY SERVICES:

Veterinary bills in the last few years (including costs of treatments) have been approximately $60,000 per annum. Associated with this BVDV outbreak, additional veterinary services required additional farm visits, travel fees, autopsies, purchase of antibiotics and other medications, purchase of consumables and laboratory testing fees.

Total cost of veterinary bills associated with BVDV outbreak = $9,791.70

3. REDUCED FUTURE INCOME:

BVDV is an insidious disease that causes economic losses that may carry forward for up to 13 years due to the continued production of PI cattle in the herd and the likelihood of a second, less severe outbreak of disease after approximately 4 years from initial one (Holmes and McGowan, 2008). Additionally, the death of so many calves means that in the next year or two, there will be fewer replacement heifers available. This will result in less scope for voluntary culling cows.

There will also be fewer surplus heifers sold.

Non-PI calves were also impacted by this disease due to the initial mixing of PI and non-PI calves. Non-PI heifer calves that suffered respiratory or gastrointestinal infections will have had setbacks to their growth rate. There is also likely to be some suffering permanent gastrointestinal damage, leading to reduced lifetime production. The slow growth will contribute to delayed onset of puberty and delayed calving to conception interval as affected heifers may not be at their optimum weight (85% weight of mature cows) at first milking (Dairy Australia, 2003). However, the cost of a delay of 2 months in joining the milking herd would be modest (J. Morton 2009, pers. comm., 17 June).

TOTAL ESTIMATED CURRENT ECONOMIC LOSS FROM OUTBREAK
Total costs = Abortions ($41,940 + $21,250)
+ Reduced conception rates ($38,124)
+ Lower milk production ($16,957.50 + $3,780)
+ PI calves ($12,000 + $26,900+ $1,365 + $7,500)
+ PI bull ($1200 + $419)
+ Lost calf rearing opportunity ($27,800)
+ Veterinary services ($9791.50)
= $20,9027 or $220 per milking cow

DISCUSSION

Transmission of BVDV within the herd occurs via close contact with a PI animal, which sheds the virus in bodily secretions e.g. faeces, urine, nasal discharge (Radostits et al., 2007). Infection of a previously unexposed cow nine days prior, or up to 175 days after insemination or mating, results in an array of reproductive problems. This may include reduced conception rates, early embryonic failure, early or mid-term abortions, congenitally abnormal calves, or the birth of PI calves if they survive an infection that was contracted from 40 to 125 days (Duffell and Harkness, 1985; McGowan et al, 1993).

PI calves are often illthrifty and suffer from lower weaning weights. They usually have reduced survival rates due to an increased susceptibility to BVDV-related respiratory disease or mucosal disease leading to severe gastrointestinal lesions. These calves rarely survive beyond 2 years, but on occasion they do, and continue to be an important reservoir of the virus (Lawson, 2009) as was the case with this PI bull which appeared clinically normal (Figure 2).

When a PI calf is born, we can generally surmise that its dam was infected between 5 to 8 months prior. In this case BVDV could have first entered the herd anytime between March and June 2008. This coincides with the introduction of the PI bull to the herd in early March 2008. The introduction of a mop up PI bull into a herd after AI presents an ideal circumstance for BVDV transmission and associated reproductive problems. Since the last cows were introduced cows in June 2007, it is unlikely that a PI cow initiated the cascade of problems in 2008.

However, other sources of BVDV cannot be ruled out e.g. cattle could have been exposed to the disease from BVDV-positive semen for AI, over boundary fences from PI animals on neighbouring farms or from straying animals in the herd. However, it is probably reasonable to assume that most, if not all, of the BVDV-associated issues in this incident related to the introduction of the PI bull. It is likely, however, that if a greater proportion of the herd had been BVDV-naive prior to this bull's introduction the outbreak and its economic effects would have been considerably worse.

The mid-term abortion outbreak was identified to affect this herd from July 2008 through to May 2009, with a peak incidence in October and November 2008.

This suggests that from December 2008 onwards there were few pregnant cows remaining which had not been exposed to BVDV infection. This estimate is supported by the August 2009 birth of the last identified PI calf. BVDV is a highly contagious disease that spreads in a herd environment even if no physical contact is made between infected and non-infected cows e.g. the virus can spread by contaminated pens and through the air (Niskanen and Lindaberg, 2003).

Transient infection of cattle from a PI animal usually results in initial immunosuppression, predisposing animals to secondary infections within weeks of exposure, but confers life-long immunity after this initial period. In this herd, there was suspicion that BVDV resulted in immunosuppression in milking cows, leading to an increased incidence of persistent and new mastitis cases 2 months after the PI bull was introduced.

BVDV is reported to be able to cause up to a 7% increase in clinical mastitis in the year a herd is exposed (Wagge, 2000). However, in this herd, an increase in the incidence of mastitis due to BVDV was not able to be confirmed due to a pre-existing mastitis prior to the introduction of the PI bull.

Acute outbreaks of BVDV infection in naive herds are termed 'wrecks' as they can cause significant economic losses which span many years. Endemically infected herds are also impacted by BVDV infection. However, these are termed 'mini wrecks' which may occur every few years.

The economic impact is reduced because there is a lower proportion of naive females in the breeding herd (Holmes and McGowan, 2008). Impacts experienced on affected farms is largely a matter of chance. Costs will vary greatly depending on such factors as the type of production enterprise, stage of pregnancy during which exposure occurs, number of exposed animals and strain of BVDV (Lawson, 2009).

Costs that were not estimated in this study due to difficulty of calculation include the impact of having fewer cows to voluntarily cull in the years to come. This may result in an increased incidence of mastitis, reduced milk yields and other health and production issues.

Labour costs related to dealing with the outbreak e.g. rearing of calves in calf hutches, increased labour required to deal with mastitis etc. were also not considered by this study. The incidence of recurrent mastitis in BVDV herds is also likely to be elevated, but no account has been taken of this likelihood. As a consequence the estimated total cost of $211,727 or $223 per cow should be considered a conservative estimate of the true losses.

Herd managers have PACE tested all new-born calves in 2009 and some of their dams. The dams of PI calves have a 10% chance of being PI (Lawson, 2009). However, no PI dams were found in this investigation. None of the calves sired from the PI bull were PACE-positive. This is consistent with the literature as PI bulls tend to cause reproductive losses by infecting naive dams rather than through infection of foetuses via semen.

It is clear that this is a disease in which prevention is far better than cure. Modelling of the disease predicts that a severe BVDV outbreak costs $41 per annum for every breeder when considered over a span of 13 years. This takes into account 'mini-wrecks' and long-term effects of the disease (Holmes and McGowan, 2008).

A combination of control measures on this herd could be implemented. The herd managers have already taken a few steps in the right direction such as culling of all identified PI animals and maximising the likelihood of BVDV exposure of young heifers well before joining by keeping PI heifers to autovaccinate the heifer herd. Regular surveillance will help to monitor the immunity of groups within herd will provide data on the susceptibility of those groups and detect early signs of any renewed unwanted transmission or act as a trigger for vaccinating younger stock.

This outbreak is a reminder to suppliers and farmers of the importance of PACE testing cattle before introduction. New introductions should also be quarantined from the herd for a couple of weeks to allow any newly acquired infection to run its course safely. However, it is sometimes possible for PI bulls to be PACE-negative but still store a reservoir of the virus in their reproductive tissues due to the 'blood-testes barrier' that develops if the bull was infected at puberty (Voges et al., 1998). Therefore, thorough testing of bulls requires testing of ejaculates in addition to PACE testing of blood, hair or skin (Fray et al., 2000).

Bulls should be quarantined for 4 to 6 weeks before mixing with the herd. Introduction of pregnant cows should be avoided as there is the possibility that they may carry a PI calf - the so called 'Trojan Cows'. Calves born to such introduced cows should always be PACE tested after birth, especially if the dam has high levels of BVDV antibodies (Fray et al., 2000).

Prevention of cattle mixing between properties e.g. over the fence, or by straying cattle, can be performed by double-fencing or using electrified outriggers along property boundaries. In known endemic herds there is also an ethical responsibility on the manager to minimize risk of infection escaping to neighbouring stock. Any cattle that will be transported off-farm then later returned should be vaccinated, this commencing 8 weeks beforehand. Mixing of groups around the time of mating should be avoided. Screening of a proportion of the breeding herd before mating with the AGID test may be warranted to assess the level of seroconversion in different age groups.

Vaccine use is common overseas, but has only recently been gaining in popularity in Australia. Its adoption has been hampered due to perceptions of limited efficacy and questionable cost-effectiveness.

However, modelling results show that vaccination is cost-effective in naive herds as the cost and likelihood of a 'wreck' greatly outweighs cost of annual vaccination. However, vaccination is of some benefit (0-34%) in endemically infected herds, depending on how many susceptible cows remain in the herd (Holmes and McGowan, 2008). To reduce the cost of vaccination while maximising its benefits, agar gel immunodiffusion (AGID) testing could be done on a proportion of each mob of breeding females to estimate the level of naivety (Lawson, 209). Those mobs with a low level of prior exposure to BVDV should be selectively vaccinated.

CONCLUSION

Bovine Viral Diarrhoea Virus is prevalent in cattle herds around Australia and often goes unrecognised. However, this real-life case study outlines the devastating effect it can have, especially when the factors are ideal for transmission e.g. introduction of PI bull at joining and following AI, and having a high proportion of previously unexposed breeders. It has been shown that the economic impact of a severe outbreak far outweighs the cost of preventative control. There is a need for veterinarians and cattle producers alike, to be aware of the epidemiology of BVDV and institute adequate control and preventative measures e.g. regular diagnostic testing of the herd, vaccinations and pre-purchase testing

ACKNOWLEDGEMENTS

The authors wish to thank the Kimber family, particularly Matt and Annabel, for their open cooperation and assistance in providing the information which formed the basis for this study.

APPENDIX (detail of calculations of economic loss)

1. ABORTIONS:

Late embryonic death: After 100 days post-calving in an average-yielding cow in a year-round calving herd, the cost of a delay in getting in-calf is ~ 4 British pounds for each day that the cow doesn't get in-calf (Esslemont et al, 2003). This is approximately $8 Australian. Cost of each early abortion = cost of semen straw (one straw is used per heat in this herd) + labour cost of AI and heat detection ($24/hour) + cost due to delay in start of next lactation (12 weeks or 84 days delay if takes average of two weeks to re-inseminate). = $15 (average cost of semen straws used in this herd) + $12 (half hour labour) + (84 x $8) = $699 Mid-term abortions: Cows having mid-term abortions were culled for slaughter. They were replaced with surplus in-calf heifers, so the number of animals in the milking herd was not reduced. However, potential profit from the sale of surplus heifers has been lost. Cost of each mid-term abortion = lost profit from sale of heifer - average price received per culled cow = $1500 - $650 = $850

2. CONCEPTION RATE:

On average, 75 inseminations are done per week in the milking herd, so a decrease of 10% in conception rate equates to an additional 7.5 unsuccessful inseminations per week. It is unclear how long the conception rate has been reduced due to BVDV circulating in the herd, but we estimate 24 weeks since the PI bull was introduced in March 2008 and the fertility report was performed in September 2008 (a conservative estimate since the birth of PI calves has been spread over a greater length of time than this). In this herd, average time to first joining in 2008 was around 100 days; it is then safe to assume that any failure to conceive results in cows being empty 100-days post-calving. As cows in this herd were high-yielding (averaging around 21L/day at 42c/L) the cost of a delay in conception of over 100-days post-calving is $7.60 for every day a cow is not in calf (Morton, J., pers comm 2009). Cost of each unsuccessful insemination = cost of semen straw + labour cost of AI and heat detection + cost of 21 delay to getting in-calf = $15 + $12 + (21 x $8.80) = $211.80 Cost of decreased conception rate = $211.80 x 7.5 x 24 = $38124

3. TOTAL HERD MILK PRODUCTION:

Heifer vs. Mature cow milk production: A good heifer will only produce 83% of the milk of a mature cow over a whole lactation (Dairy Australia, 2003). The average lactational milk yield per mature cow in this herd is 9500L. Therefore a heifer will yield 17% less than this (1615L). The price received per litre of milk has been around $0.42 for this herd. Cost of lost milk production = 25 x 1615 x $0.42 = $16957.50 Increased incidence of mastitis: During the peak incidence of persistent and new mastitis infections in May 2008, the amount of unusable milk increased from 500L to 800L daily; there was also an increase in use of intramammary antibiotic preparations (included under Veterinary services). This increase in mastitis cases is consistent with immunosuppression at the initial transient infection stage of BVDV. Volume of lost milk due to mastitis outbreak = Amount of wasted milk daily x number of days of mastitis =300L x 30 days = 9000L Cost of increased mastitis in the herd = 9000L x $0.42 = $3780

4. PERSISTENTLY INFECTED CALF-ASSOCIATED PROBLEMS

Dead or destroyed heifer calves: A total of 80 heifer calves have died or been destroyed (sickness, PIs, dummy calves, and premature calves). Newborn Friesian calves at this farm have an average replacement value of $150. Loss due to 80 dead heifer calves = 80 x $150 = $12000 Rearing PI calves which will not contribute to production: The cost to a dairy of rearing a heifer calf to 2 years of age has been estimated as $950, including feed, management and labour costs (Moss, 2005). Half of the PIs will die by 12 months of age, costing around $400 each to rear. Half of the remainder die by 2 years of age, costing an average of around $700 to rear. Loss due to 35 immuniser PI calves = value of neonatal Friesian calves + cost of rearing PIs to various ages up to 2 years = (35 x $150) + (17 x $400) + (9 x $700) + (9 x $950) = $5250 + $6800 + $6300 + $8550 = $26900 Calves dying at 3-4 months of age: Cost of rearing 7 calves to 3-4 months old, assuming pellets are consumed for 90 days is $45 per calf. Cost of rearing and losing 7 calves = (7 x $45) + (7 x $150) = $1365

5. PERSISTENTLY INFECTED-BULL ASSOCIATED PROBLEMS

The PI bull sired 27 calves that were born over a period of 8 months. The conception rate to artificial insemination is approximately 90% on this property, leaving only 10% of the herd to be mopped up by the bull. Assuming that the PI bull was the only bull that was run in with the cows at certain times and approximately half of the 950 milking herd are mated each 6 months, Fertility rate = 27/ (0.1 x 0.5 x 950) = 56.8% It is possible that this bull had slightly decreased conception rate (of 8.2%), assuming average conception rate is 65%. The number of additional calves that could have been sired = 8.2% x 10% x 950 = 8 calves Cost of reduced conception rate = 8 x $150 = $1200 This bull was sold 7 months prematurely ie the owners lost 7 of his 24 months of useful work. The usual depreciation of the bull over the 24 months was $750 ie purchase price ($1750) less sale price to another dairy ($1000). The value of the lost useful work time was 7/24 x $750 = $219 Property owners were paid $800 for the bull at slaughter. This represented a loss of $200 over the price that could have been achieved if sold to another farm. Changeover cost of acquiring a new bull = $219 + 200 = $419

6. SELLING AND BUYING STOCK:

The herd managers rejected calf-rearing contracts for around 1 year, reducing the number of additional calves that could have been reared by around 100. Commonly, contracts are undertaken to rear Wagyu or Friesian calves to 12 weeks of age, at which point they fetch $460 per calf. Calves cost this farm around $100 to purchase initially. Calves are reared using whole milk from the dairy and calf pellets. Milk costs $0.42/L and each calf consumes 4L whole milk/day until weaning (Moran, 2002). If calves are weaned at 4 weeks of age, pellets cost $0.50/kg and are consumed at 1kg/day/calf. Therefore, one calf will consume milk that will cost 4 x 28 days x $0.42 = $47 and pellets which will cost 70 days x 1kg x $0.50 = $35 and Cost of lost contracts = 100 x ($460 - $100- $47 - $35) = $27800

7. VETERINARY SERVICES:

Farm visit for 2 aborting cows, including travel = $102.00
Farm visit for 2 sick calves, including travel = $115.50
Farm visit and autopsy of three calves, including travel = $304.00
Medications - The dairy manager estimates that as a result of treating PI calves, and sick immunosuppressed calves, one additional bottle of 'Micotil' has been used (cost $203.00) and one additional 250mL bottle of 'Engemycin' has been used (cost $187.00). A 5L 'Scourban Suspension' also had to be purchased (cost $176.00) to treat sick, scouring calves.
Purchase of vacutainers and needles = $161.50
Fees for PACE testing by DPI lab including collection and handling by private veterinarians and freight = $3268.50
Fees for miscellaneous tests by DPI lab (including foetal autopsy, BVDV AGID tests, leptospirosis antibody titre tests, histopathology and culture of aborted foetus) up to 15 June 2009 = $1539.00
Fees for BVDV PACE (ear notch and serum) tests from 15 June to 8 Sep 09 = 151 ear notch x $10 + 6 sera x $33.45 = $1710.70
Gribbles lab fees (Neospora IFAT and BVDV AGID) = $132.00
Fees for PACE testing by Swans Laboratory = $1447.00
Vet visit to teach farmer how to bleed calves for PACE testing = $145.50 including travel
Additional intramammary antibiotic treatment for mastitis treatment = $200 (1st month) + $100 (2nd month) = $300 Total cost of veterinary bills associated with BVDV outbreak = $9791.70

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