Braeburn Dairies Limited v McGregor & White Electrical Limited HC Dunedin Civ-2009-412-000668
[2011] NZHC 1402
•6 October 2011
IN THE HIGH COURT OF NEW ZEALAND DUNEDIN REGISTRY
CIV-2009-412-000668
BETWEEN BRAEBURN DAIRIES LIMITED Plaintiff
ANDMCGREGOR & WHITE ELECTRICAL LIMITED
Defendant
Hearing: 14-17, 21 & 22 February, 13 & 14 June 2011
(Heard at Christchurch (February), Invercargill (June))
Appearances: ADG Hitchcock for Plaintiff
R W Raymond and S Isherwood for Defendant
Judgment: 6 October 2011
RESERVED JUDGMENT OF HON JUSTICE FRENCH
Introduction
[1] In May 2007 Braeburn Dairies contracted with McGregor & White Electrical to install a Varivac in its milking shed. A Varivac (variable frequency drive) is an electronic device which, in cow sheds, is used to control the speed of the vacuum pumps.
[2] Contrary to the manufacturer‟s instructions, and in breach of its contract with Braeburn, McGregor failed to use screened cable when installing the Varivac. This resulted in the Varivac producing stray voltage in the cow shed.1
[3] During the 2007/2008 dairy season, Braeburn‟s herd suffered unprecedented
health problems. Braeburn attributes the problems to the stray voltage and seeks to recover damages from McGregor for production and other associated losses.
1 Stray voltage has been defined as “a small voltage (less than 10 volts) measured between two points that can be contacted simultaneously by an animal”.
BRAEBURN DAIRIES LIMITED V MCGREGOR & WHITE ELECTRICAL LIMITED HC DUN CIV-2009-
412-000668 6 October 2011
[4] The key issues for determination are:
i)Did the stray voltage cause health problems and have an effect on milk production?
ii)If there is a causal nexus, what are the recoverable heads of damage and how is the loss to be quantified?
Factual background
[5] Braeburn owns and operates a 306 hectare dairy farm located near Balclutha in South Otago.
[6] The farm is what is known as a high input system farm, meaning that while it is still pasture-based, there is extensive use of high quality food supplements.
[7] The farm is managed by the company‟s directors and shareholders, Mark and Andrea Shore. It was clear from the evidence that the Shores are highly successful farmers, hard-working, dedicated and progressive. Their farm is the top producing farm per hectare in the region.
[8] Braeburn commenced the 2007/2008 season with a 940-cow spring calving herd. There were expectations it would be the farm‟s most productive season yet.
[9] Milking started in late July, with milk supply to Fonterra commencing on
7 August 2007.
[10] There is a conflict in the evidence as to whether the Varivac was operating throughout August 2007.
[11] According to Mr Shore‟s brief of evidence,2 the Varivac was operating from the first milking, and by mid-August it had become very apparent that Braeburn had
a major problem. The cows were noticeably agitated and restless throughout the
2 Mark Robert Shore, brief of evidence dated 1 December 2010.
entire milking routine. Amongst other things, they were not letting their milk down and there was increased defecation and urination in the shed.
[12] Mr Shore testified that he was nonplussed as to what could be wrong. As the weeks went by, he became further concerned due to an increased incidence of clinical mastitis, elevated somatic cell count in the milk3 and a significant level of severe teat end damage.
[13] He contacted the farm‟s veterinary consultants, and on 10 and 11 September
2007 two vets visited the farm. The vets followed up their inspection with a report which made a number of recommendations.4
[14] Mr Shore implemented all of the recommendations. However, according to his evidence there was no improvement, and if anything the problems got worse. The cows were becoming even more agitated and the number of cows in the mastitis herd was steadily increasing to a point where, in his words, it was reaching epidemic proportions.
[15] In late October/early November 2007, Mr Shore learnt of the possibility that the Varivac could be creating stray voltage.
[16] On 22 November 2007 the Varivac was rewired with the correct type of cabling.
[17] In evidence, Mr Shore said that immediately the correct cable was installed, there was a dramatic improvement.
[18] By March 2008, milk production had recovered to be similar to previous seasons. However, production was never able to reach the anticipated levels.
[19] Braeburn‟s milk solids production had shown a steady upwards trend over the
seasons prior to the 2007/2008 season. Production in 2005/2006 was just short of
3 Somatic cells are white blood cells produced by a cow‟s immune system. A high somatic cell
count is an indication of the presence of a mastitis infection.
4 The recommendations were to reduce the ACR settings, change from automatic to manual teat spraying, change concentration of spray and change liner.
428,000 kg MS, and in 2006/2007 it was 442,532 kg MS. The 2007/08 season, however, was a disappointing 402,561 kg MS.
[20] A comparison of the 2007/2008 season with the previous season reveals a three-fold increase in the proportion of cows with clinical mastitis within lactation, while the number of cows with sub-clinical intra-mammary infections increased by nearly 50 per cent. Further, a much greater number of cows died or had to be culled that season than usual because of mastitis and teat end damage.
[21] Braeburn is adamant the stray voltage was responsible for these losses and seeks compensation.
The competing cases
[22] It was common ground that in order to succeed in its claim, Braeburn must prove on the balance of probabilities that the installation of the unscreened cable was a material and substantial cause of its loss.
[23] As I have mentioned, McGregor admits that its failure to use the correct cable was a breach of its contractual obligations to Braeburn.5 It admits, too, that the use of unscreened cable produced stray voltage at a level much greater than would otherwise have been the case had screened cable been used.6
[24] It is also accepted that the Braeburn herd did suffer significant health problems with clinical and sub-clinical mastitis and severe teat end damage that particular season, although not poor milk let down. McGregor also accepts that the increase in the incidence and prevalence of mastitis that season would have caused loss.
[25] What McGregor strongly disputes is the existence of any causal nexus between those health problems and the stray voltage.
5 Breach of implied term to use reasonable care and skill in the installation of the Varivac.
6 There was unchallenged evidence that the use of the unscreened cable would have increased the stray voltage measured at the platform by a factor of 11: Mark Empson brief of evidence, paragraph 60.
[26] It contends there were a number of other factors independent of the Varivac which, in combination, are more likely to have caused the problems, including a decision by Mr Shore to increase the vacuum levels in the shed early on in the season, poor weather, automatic teat spraying with insufficient emollient, and aggressive ACR settings.7 All of those things can cause, or contribute to cause, teat end damage, which is in turn a risk factor for mastitis. McGregor also points to incontrovertible evidence that mastitis has been a significant issue historically in the herd, as well as a report from Braeburn‟s own nutrition expert dated December 2007.
The report attributes the production deficit to two factors – the elevated somatic cell count, and a drop in the pasture metabolisable energy as a result of a “cold, blustery spring”. Of the two factors, the report identifies the drop in metabolisable energy as the main factor.
[27] As a fall-back position, McGregor also contends that Braeburn has greatly over-stated its losses.
[28] For its part, Braeburn argues that while there had always been mastitis in the herd, there was a statistically significant increase in both its incidence and prevalence compared with other seasons. The vacuum levels were high, but no higher than previous seasons. The weather was bad, but no worse than other seasons, and because the farm is a high input system, it is not as vulnerable to climatic changes as are other farms. The only thing it says was different that season was the new Varivac. Braeburn says the problems encountered were textbook symptoms of stray voltage. Further, in terms of timing, the emergence of the problems coincided with the operation of the Varivac and the problems only abated once the Varivac was rewired. Subsequent seasons saw a resumption of the upward production trend. In those circumstances, it is submitted there can be no doubt that the Varivac must have been a material and substantial cause of the loss.
Discussion
[29] In determining the question of causation, I have found it convenient to analyse the evidence under the following headings:
Was the Varivac operating throughout August 2007? When was the vacuum level increased?
What was the extent of the problem observed before 10 September 2007
(the date of the vets‟ visit)?
Changes in the herd after the correct cabling was installed. The expert evidence regarding causation.
An overall assessment of the evidence.
Was the Varivac operating throughout August 2007?
[30] In evidence, Mr Shore stated that the problems caused by stray voltage were evident from the first milking in late July/early August, and continued throughout August.
[31] McGregor, however, says the Varivac was not operational in the first half of
August. Therefore, the problems could not have been caused by the Varivac. [32] The Varivac was installed in late May 2007.
[33] When it was operating in variable speed mode, there was a vibration problem which McGregor was unable to rectify until 13 August 2007. The Varivac was not fully commissioned until 18 August 2007.
[34] It was common ground that it was possible for milking to take place without the Varivac operating.
[35] It was also common ground that if the Varivac was operating in the first half of August, it would not have been in variable mode (because of the vibration problem) but would have been in constant speed mode.
[36] In support of its contention that the Varivac was not operating at all in early August, McGregor relies on a job sheet (packing slip) completed by one of its staff who did some work in the Braeburn shed on 3 August. The packing slip reads:8
To by pass vari vac and put on doil and test ok. Find fuses kept blowing,
40A fuse with three 63A HRC fuses, leave hanging in switchboard and test ok.
[37] McGregor says what this packing slip means is that the Varivac was bypassed. It was not in service, but the vacuum pumps were running. The power was disconnected from the Varivac and connected directly to the motor circuit breakers.
[38] As a general rule, where there is a conflict of evidence, contemporaneous documents such as the packing slip carry significant weight and are often conclusive. However, in this case I am not prepared to attach the weight to this document which McGregor seeks to attach. I say that for the following reasons:
i)McGregor did not call the staff member who wrote the jobsheet, and there was no evidence that person was unavailable or unable to recall the events in issue.
ii) McGregor‟s interpretation of the jobsheet involves the
addition of the word „motors‟ after direct on line (“doil”).
iii)On the evidence, the jobsheet is also capable of another interpretation, namely that „direct on line‟ relates to the Varivac and that it was still part of the electrical system and operating. It was bypassed by leaving it on constant speed and not allowing it to operate on variable mode.
iv)Mr White, of McGregor, who tested the Varivac on variable mode on 10 August, was unable to recollect whether it was operating when he arrived and whether at the conclusion of his testing he took it out of the system altogether or left it on constant speed.
v)In contrast, Mr Shore was adamant that the machine was operating throughout August. He had a clear recollection of the computer light display and the humming noise.
[39] For reasons which I shall explain, I found some aspects of Mr Shore‟s evidence unreliable. However on this issue, given all the circumstances, I accept his evidence and so find the Varivac was operating throughout August 2007.
When was the vacuum level increased?
[40] In August 2007, Mr Shore instructed a McGregor employee called Jared Cowley to increase the vacuum levels in the shed. The central gland gauge was faulty, and although Mr Cowley thought he was increasing the level from 38 kPa to
42 kPa, he was in fact increasing it to 46 kPa.9
[41] McGregor discovered the correct levels during a routine plant test on 24
August 2007, but had no reason to advise Mr Shore because the farm had operated at similarly high levels in previous seasons.
[42] According to the evidence of Braeburn‟s vet however, the desirable level was somewhere between 40 and 44 kPa. At 46 kPa the level was too high, and as a result the vet assumed it must have been the primary cause of the severe teat end damage that he observed in September 2007.
[43] The level was not reduced until 10 September, the day of the vet‟s first visit.
[44] While the date the level was reduced is agreed, what is disputed is the date that it was first increased by Mr Cowley.
[45] In evidence, the vet testified that subject to certain qualifications teat end damage generally takes weeks rather than days to develop.10 Therefore, the earlier the level was increased, the stronger McGregor‟s argument that the vacuum levels may have caused or contributed to causing the problems.
[46] McGregor says that Mr Cowley increased the vacuum levels on 4 August to fix a perceived problem with the wash.
[47] Mr Shore, however, says that it happened later, on 21 or 22 August, and was requested by him as a means of attempting to resolve slow milking and poor milking out.
[48] Mr Shore‟s version of events was largely corroborated by Mr Cowley.
[49] Regrettably, I did not find Mr Cowley a reliable witness. He is no longer employed by McGregor, but is in business on his own account, Braeburn being one of his clients. At the time of the hearing, Mr Cowley was in fact working for Mr Shore. It was clear that he and Mr Shore had recently discussed his evidence and that as a result Mr Cowley has changed what he was previously saying. Previously, in a written statement made in March 2008, Mr Cowley had stated that he increased the vacuum levels on 4 August 2007. The written statement was obviously made at a time when he would have had better recall than he does now, and at a time when the significance of the increased levels was not fully appreciated. There were some very long, telling silences in Mr Cowley‟s evidence when answering questions, especially when asked what it was that had made him realise his 2008 statement was wrong. He eventually conceded that, given other work commitments, it would have been impossible for him to have attended at the Shore farm between 18 and 24
August.
[50] There is no record of Jared Cowley attending the Shore farm between
4 August and 18 August.
[51] The evidence also established that although increasing vacuum levels to fix a wash problem would not be the ordinary way to solve that problem, it is not unknown and it does help the wash.
[52] In all the circumstances, I consider it more likely than not that the vacuum levels were increased on 4 August 2007, and I so find.
What was the extent of the problems observed before 10 September 2007 (the date of the vets’ visit)?
[53] While it is accepted that during the 2007/2008 season, the Braeburn herd suffered an increased incidence of teat end damage and mastitis, McGregor contends that Mr Shore has exaggerated the extent of the behavioural problems, including poor milk let down.
[54] Milk let down is the physiological release of the milk from the cow‟s alveoli into the udder. It is a hormonally-driven process under the influence of the hormone oxytocin. Poor let down reduces milk yield and leads to over milking.11
[55] Milk let down is to be distinguished from incomplete milk out. The latter may be caused by poor let down, but can also occur independently.
[56] Failure to let down is another risk factor for mastitis.
[57] In his brief of evidence, Mr Shore had this to say about his observations of the herd in August:12
54.It was very clear that things were not right in the shed right from the very first milking with the Varivac…
55.Problems with the cow‟s [sic] behaviour and the difference to previous seasons were evident right from the first milking.
11 The machine tries to extract milk that is not presenting.
12 Mark Robert Shore, brief of evidence, 1 December 2010.
56.The cows were not at ease on the milking platform, being agitated and trying to avoid contact with the bum rail. (They normally rest against this.) …
57.The cows were noticeably restless and unsettled throughout the entire milking routine. They were not happy being milked, jumping with contact of milker or milking equipment and not letting their milk down. They were also defecating considerably more than usual
– the ultimate sign of discontent.
…
59.By mid-August 2007, after the first few milkings with the Varivac installed, it was very apparent we had a major problem.
…
62.We were also getting very slow milking which is also a significant problem as it is a major contributor to teat end damage and udder health.
…
64.An optimal target for complete milk-out is 5-7 minutes. What we were finding was that cows were there for much longer than 5-7 minutes and still had not milked out completely…
…
77. Despite the reported clean bill of health given by the plant test [24
August 2007] the problems in the shed were steadily getting worse. The problems Shore had with the cows in the milk shed included:
a. Reluctance of the cows to enter the milking stalls.
b.Extreme nervousness with cows refusing to lean against the bum rail.
c. Increased defecation by cows.
d. Rapid exit by cows from the milk shed. e. Lengthened milking times.
f. Incomplete milk let down. g. Reduced milk production.
h. Increased incidence of mastitis.
i. Elevated somatic cell count in milk.
…
93… with the benefit of hindsight, the Varivac was the obvious cause of the cows withholding milk, the slow milkings and the terrible animal behaviour during milking.
[58] Evidence was also given by Darlene Cross, who has been employed by
Braeburn as a milk harvester since August 2006:13
6. … The cows were very clearly agitated and restless, kicking often.
They were unhappy, stressed, hesitant to walk onto the platform and extremely eager to get off the platform. The cows were also defecating on the platform and on staff a lot more than normal.
…
8.The other problem we were experiencing was the cows were not milking out…
[59] My general assessment of this evidence is that it does significantly overstate the problems. I also gained a clear impression that much of what Mr Shore in particular was saying had been coloured by information he has subsequently obtained about problems associated with stray voltage.
[60] I have come to that conclusion for the following reasons.
[61] First, in cross-examination, or at least one part of it, Mr Shore resiled from what he had said in chief about the differences in the cows‟ behaviour from previous seasons being evident “right from the very first milking”.14 Instead, he conceded
“probably it didn't seem out of the norm, but when we look back in time it does”.15
[62] When it was pointed out to him that the farm‟s records suggest that only two cows had been treated for milk let down and that he did not have a record of the numbers where there was a failure of milk let down, he stated “I cannot tell you how many cows, there might have only been two cows, I don‟t know”.16
[63] Secondly, if the problems were as bad in August as Ms Cross and Mr Shore claim, I am confident he would have sought professional help earlier. As I have
mentioned, the Shores impressed as progressive and dedicated farmers. In addition
13 Darlene Mary Cross, brief of evidence, 1 December 2010.
14 Brief of evidence at 54.
15 Notes of evidence, page 53, line 3.
16 Notes of evidence, page 62, line 25.
to the vet, the Shores employed a nutrition specialist, Ms Murphy, whom they trusted and consulted on a regular basis. Yet Mr Shore did not consult either of those two advisers during August, even although according to his evidence it had become apparent to him by mid-August that he had a major problem. Even when Mr Shore did consult the vet in September, he did not consult him about behaviour
issues.17 Nor for that matter did he ever tell Mr White of McGregor about them. All
he mentioned to McGregor was mastitis.
[64] Thirdly, the contemporaneous written records do not support the claims now being made about the extent of the behavioural problems.
[65] On 10 August 2007 Ms Murphy visited the farm and provided a report. There is no mention in that report of any concerns about cow behaviour during milking.
[66] On 21 August 2007, in an email, Ms Murphy asked the Shores whether the cows were happy, and the answer was “… in general well”.18 I did not find the attempts to explain away that email convincing.
[67] Curiously, although Mr Shore keeps a diary for every year, he has lost his diary for the 2007/2008 season.19 Mrs Shore, however, has a diary, and there are no entries in it about problems with the cows in August.
[68] Even in a formal written statement made in December 2008 at the request of McGregor‟s insurer, the Shores did not make the claims being made now. All the statement says is:20
We started calving in early August and found our cows were not milking out as well as we felt they should.
17 The reason for the vets‟ visit was because of concerns expressed to them regarding the high level of clinical mastitis, high BMSCC count and cows not milking out.
18 Agreed bundle of documents, page 1236.
19 His explanation that he had lost this particular diary (and only this diary) while subsequently shifting house was unsatisfactory, especially given the importance of that season.
20 Agreed bundle of documents, page 823.
[69] The only other behavioural matters mentioned are in the context of what happened after the correct cabling was installed – once again leaning on the bum rail and three weeks later the cow flow and mess in the shed was back to normal.
[70] This suggests that any behavioural issues were at the lower end of the spectrum.
[71] Mr Shore said in evidence that the vets “thoroughly inspected both the shed and our herd”.21 On the second visit on 11 September 2007, the vets were also there at milking time. Yet their written report makes no mention whatsoever of any behavioural concerns other than slow milking and the fact that the cows were fidgeting before the cups were taken off, which is consistent with the ACR settings being too aggressive.
[72] Significantly, too, the vets‟ report says absolutely nothing about poor milk let down, which should have been readily apparent, especially if it was widespread across the herd. As for incomplete milk out, the report states the opposite and says milk out was complete.
[73] I accept this is only one day, and it is possible that the cows may have behaved differently because the vets were strangers, but when taken in conjunction with all the other matters I have mentioned it leads me to the clear view that the behaviour was at a lower level than is now being claimed, and that while problems with let down and milk out may have existed, they were not widespread.
[74] I am reinforced in this conclusion by my general impressions of Mr Shore as a witness. At times his evidence demonstrated a clear propensity to exaggerate which resulted in contradictions and inconsistencies. In addition to the matters I have already mentioned, Mr Shore claimed for example to be “very confident” about the date the Varivac had been commissioned,22 but was eventually forced to concede
he was wrong and had been in his own words “a wee bit loose”.23 Another claim
which he was forced to modify was that Mr White of McGregor had given him all
21 Brief of evidence, paragraph 85.
22 Brief of evidence, paragraph 53.
the performance guarantees. Mr Shore said in chief that Mr White was “very clear” about that, but in cross-examination conceded Mr White only talked about some of the performance guarantees and none of those pertained to milk production.
[75] Another claim made by Mr Shore was that Mr White had assured him he would do a stray voltage test when installing the Varivac. Mr Shore stated that getting a test done was “one thing that was really, really enforced to me” by the supplier of the Varivac:24
I talked to him [the supplier], he said this is one thing that you need to get done.
[76] Then, when it was pointed out to Mr Shore that this contradicted his claim that he did not know anything about stray voltage, he attempted to downplay his conversation with the supplier and even suggested he did not know whether what the supplier was saying related to the Varivac or other equipment within the shed – a suggestion which I consider fatuous in the circumstances.
[77] It was also apparent that Mr Shore had grossly over-stated the number of extra hours he was claiming in damages. Another over-statement was a claim made in chief that the Shore farm is “possibly unique in New Zealand” when in fact it transpires that 10 per cent of dairy farms nationally use a high input system.
[78] Another unsatisfactory aspect of Mr Shore‟s evidence was his attempt to downplay the discussions he had entered into with Mr Cowley about the latter‟s evidence.
[79] In making these comments, I am not suggesting that Mr Shore was necessarily being deliberately dishonest. My sense was that Mr Shore believes so strongly in the rightness of his cause that he allowed himself to get carried away at the expense of accuracy.
Changes in the herd after the correct cable was installed
[80] In his brief of evidence, Mr Shore said:
110. Immediately the screened cable was installed, the problems we were experiencing with the cows improved dramatically. The change in the cows was unbelievable from the very next milking.
[81] Ms Cross stated in her brief of evidence:
19.After the wiring on the Varivac was screened the change in the mood and temperament of the cows was almost instant and it was apparent within a couple of weeks that the problem had been correctly identified and fixed.
20.The cows were a lot more relaxed and flowed in and out of the shed with ease. They were no longer defecating and kicking as they had been.
21.The change in the cows‟ udders was amazing. They changed to the nice pear-shaped udders you typically expect, they were milking out and milking flat, the cows were strolling on to the platform and were almost hesitant to walk off the platform (in stark contrast to a few weeks earlier when they were extremely eager to get off the platform and out again).
[82] Mr Hitchcock relied on this as strong evidence of causation. [83] However, there are a number of difficulties.
[84] First, it is unlikely there would be an immediate change in the cows‟ learned behaviour such as avoiding the bum rail. According to Dr Matthews, a leading animal behaviourist, typically if you remove an adverse stimulus it takes several episodes of no application for the animal to start to re-establish a new base line. There would still be an avoidance response because they remember that was an aversive place to be.25
[85] Secondly, if the stray voltage was affecting milk let down and somatic cell counts, and there was an immediate change in the cows‟ behaviour after the correct cable was installed, then in the view of Dr McDougall it would be reasonable to
expect the milk let down and somatic cell count effects to also reverse quickly. Yet
25 An alternative explanation is that the behaviours may have appeared to disappear because they
his analysis of the relevant data suggests that no substantive difference in either milk yield or bulk tank somatic cell count occurred following the rewiring.26 That would tend to support McGregor‟s position that while the stray voltage may have caused behavioural responses such as increased defecation and avoiding the bum rail, it did not have any effect on milk production.
[86] Thirdly, the evidence established that the improvement coincided with the confluence of other factors. By late November, the weather was improving, and there was an improvement in pasture quality, while the changes recommended by the vet would have been coming on stream. There was the fact, too, that cows calving after 11 September (250 cows) would have been in better shape than the cows calving earlier, as they were coming into a lower risk environment. All these changes were coming to a head in terms of improving the herd at about the time as the cable was replaced.
The expert evidence regarding causation
[87] It is at this juncture I now turn to a consideration of the expert evidence regarding causation.
[88] That evidence focused on two issues:
i)What was the electrical current which the Braeburn cows were likely to have been experiencing as a result of the stray voltage?
ii)Would it have had any effect on udder health and milk production?
[89] Braeburn called two experts who dealt with causation – Mr Empson, an electronics engineer; and Dr Sandles, a nutrition consultant. McGregor called
26 Dr McDougall accepted that as regards somatic cell count, the inferences to be drawn from the
Dr Matthews, who as I have said is a scientist specialising in animal welfare and behaviour.27
[90] Counsel for McGregor, Mr Raymond, objected to most of the opinion evidence given by Braeburn‟s experts on the grounds of lack of independence and/or lack of expertise.
[91] The objections were valid, although my preference is to deal with them as bearing on weight rather than admissibility. While neither Mr Empson nor Dr Sandles were animal behavioural experts, they did have extensive practical experience.
[92] Dr Sandles was not however a truly independent witness. He has been the
Shores‟ nutrition consultant since October 2008 and regards them as friends.
[93] His lack of independence was reflected in his evidence, which at times gave me the strong impression he was advocating for the Shores. His evidence at times also lacked the precision which is normally expected from an expert witness.
[94] In contrast, Dr Matthews was a particularly impressive witness. He is a senior scientist with an international reputation in the field of animal welfare and behaviour. He made concessions where that was appropriate, and generally showed a rigorous concern for precision and accuracy. Where there was a conflict between his evidence and that of the defendants‟ experts, I prefer Dr Matthews‟ evidence as modified by the agreements reached at the hot tub session.
[95] Following a hot tub session, the experts reached agreement on a number of important issues, but some key differences remained.
[96] All the experts agreed that the crucial biological measure is the current flow or ampage. The greater the current, the greater the severity of the behaviours that
can be expected, and the greater the numbers affected within a herd.
27 Dr McDougall, a mastitis expert, also participated in the hot tub discussion on causation.
[97] It was also agreed that current flow can be calculated by a formula known as Ohms Law. Ohms Law states that current (amps) = voltage (volts) ÷ resistance (ohms).
[98] The stray voltage generated by the use of the unscreened cable at Braeburn was able to be measured. The estimated voltage generated was agreed as being 1.3 volts zero to peak.
[99] Under Ohms Law, voltage is however only one part of the equation. In order to determine current levels, it is also necessary to calculate the cows‟ resistance.
[100] Resistance is measured in ohms, and within a cow is pathway-dependent. That is to say, the current flows will differ depending on which way the current is put through the cow.
[101] In a rotary dairy like the one at Braeburn, there will be multiple pathways, with the primary pathway being rump to rib. There have been studies which have measured other pathways such as rump to hooves, but none has considered rump to rib, nor have any studies considered multiple pathways in a rotary shed. Animal resistance is lower in pathways that do not include the hooves.
[102] The absence of any studies on multiple pathway resistance in a rotary shed was just one of several difficulties confronting the experts in this case.
[103] Other problems included:
The fact there is a wide variation in the sensitivity of cows to electrical
currents.
The absence of any evidence as to the numbers of cows exhibiting the
behaviours described by Mr Shore and Ms Cross.
The absence of any evidence as to the number of pathways in the
Braeburn shed.
The fact that cows are able to regulate the current and adopt avoidance tactics, giving rise to the possibility that some cows could have avoided
getting any shock at all, or reduced the current level.
In experiments that have measured resistance, the animals have typically been shaved and had gel applied, thereby minimising the resistance and
not reflecting real world conditions.
[104] In the hot tub session, the experts endeavoured to calculate the resistance by using two different methodologies.
[105] The first method was to use the published data on other pathways and devise some equations covering the resistance paths for three different pathways. That model resulted in a figure of between 13 and 20 mA. All agreed that the result was demonstrably wrong. As Dr Sandles graphically put it, if the current had been that high, there would have been deaths.
[106] The second method adopted was to use two pathways: hooves to rump and chest to rump. That resulted in a figure of 6.2 mA.
[107] The problem for Braeburn is that, according to all the published peer- reviewed scientific data, where the milking cups can be kept on a cow,28 there is no evidence for milk yield depression at up to 8 mA.29 At currents of up to 8 mA, the only effect of stray voltage is on behaviour, not milk production.
[108] Dr Sandles‟ response to that was two-fold.
[109] First, he pointed out that the 6.2 mA calculation was based on only two pathways out of a possible four or five. The effect of multiple pathways would be
28 There was no evidence that, at Braeburn, the cups had not been kept on.
29 This was agreed by the experts in the hot tub session, although Dr Sandles in my view wrongly attempted later to resile from it. There is one paper which found no production effect at up to 12 mA. However, because it was just one paper, Dr Matthews preferred not to attach significant weight to it.
cumulative.30 Therefore, in his view, there must be a very high probability that the actual current was significantly higher than 6.2.31
[110] Secondly, Dr Sandles and Mr Empson say the scientific studies are contrary to their own experience in the real world. They are also contrary to several real world field or observational studies which claim that stray voltage does inhibit milk let down and has an effect on milk out, speed of milking, somatic cell count and the incidence of mastitis. Dr Sandles and Mr Empson say further that the published peer review papers are funded by utility companies, and so should be viewed with
caution.32
[111] I do not accept those arguments.
[112] In my view, given all the imponderables in the calculations of current, the best approach is to examine the evidence of the actual behaviours exhibited by the Braeburn cows.
[113] That evidence shows the levels simply could not have been as high as Dr Sandles is suggesting. Even if one were to accept Mr Shore‟s evidence in its entirety (which for the reasons advanced I do not), the behaviours even he describes are not consistent with levels as high as those advocated by Dr Sandles. At those levels, the scientific data shows a significant proportion of the cows would have been exhibiting unusual and extreme behaviours such as falling down, jumping out of stalls, and avoiding eating and drinking. There was however no evidence of any
of those extreme behaviours.33
30 This was agreed by all the experts.
31 Dr Sandles also claimed that the fact the cows could regulate the current would not mean they were lowering it. However, this was contrary to the view taken by Mr Empson and Dr Matthews and is a matter on which I do not consider Dr Sandles has the necessary expertise.
32 Dr Sandles and Mr Empson were also critical of the peer reviewed papers on the grounds that the samples were too small. However, one of the key papers relied upon by Dr Matthews is a
meta-analysis which overcomes the problems of small samples in other studies. See Erdreich et
all, “Meta-analysis of stray voltage on dairy cattle” (2009) 92 Journal of Dairy Science 5951.33 In the hot tub session, the experts agreed that at high levels the cows would have physically been able, notwithstanding the confines of the Braeburn shed, to exhibit unusual and extreme behaviours such as kicking, scrabbling with their back feet down and potentially become recumbent. Dr Sandles appeared to attempt to resile from this agreement later in evidence.
[114] I therefore do not accept that the current levels were significantly higher than
6.2 mA, and certainly not higher than 8 mA.
[115] The behaviours described were at best for Braeburn what animal
behaviourists term „discomfort responses‟.
[116] As to what that signifies in terms of effect on milk production, I prefer to place greater weight on the published peer-reviewed scientific studies than the field studies.
[117] As Dr Matthews explained, while the methodology employed in the epidemological field studies is a valid scientific method, in the absence of a controlled experiment, it is not capable of establishing cause and effect. This is recognised in one of the studies itself.34
[118] I also accept Dr Matthews‟ evidence that the fact the peer-reviewed scientific literature has been funded by utility companies does not detract from the weight to be afforded those studies, particularly when they have been peer-reviewed.
[119] Further, and in any event, the field studies themselves are not consistent. The largest study ever undertaken, involving 4000 herds, found no correlation between stray voltage and milk production. Not only is this the largest field study ever undertaken, but it was undertaken by a public body. This study was not mentioned by either Dr Sandles or Mr Empson.
Overall assessment of the evidence
[120] On the face of it, Braeburn‟s argument that the problems were unprecedented and the only thing new was the Varivac has a certain superficial attraction.
34 Dewes et al, “The detection and measurement of stray electrical leakages on dairy farms: effects on performance” (1989) 37 New Zealand Veterinary Journal 117 at 118: “There are many causes of impaired production and cow behaviour. Voltage problems are simply one of them and it would be extremely difficult to establish a cause and effect relationship by means of field observations.”
[121] However, in my view, that argument is overly simplistic, failing as it does to take account of the complexities of the situation.
[122] Mastitis is a multi-factorial disease. The combined effect of a set of circumstances and the timing of those circumstances can all be important. As Mr Shore himself stated, there can be “a million factors” for a drop in production.35
[123] On the evidence before me, there are reasonable alternative explanations for the teat end damage and the mastitis as claimed by McGregor.
[124] When I combine those with the evidence of the hot tub session and Dr Matthews, I am driven to the conclusion that Braeburn has not discharged its onus of satisfying me on the balance of probabilities that the stray voltage did anything more than cause a behavioural discomfort response.
[125] It follows that Braeburn‟s claim must fail, and that it is not necessary for me
to consider quantum.
[126] I am acutely conscious of the impact this conclusion will have on Mr and Mrs Shore. It is impossible not to have a great deal of sympathy for them. They, I appreciate, are utterly convinced that stray voltage was responsible for what must have been a stressful season. However, in a court of law, the onus is on them to prove that claim, and in my assessment, looking at the evidence in its entirety, they have not been able to discharge that onus.
Outcome
[127] The claim is dismissed, and judgment entered for the defendant.
Costs
[128] As regards the costs of this proceeding, my expectation is that these will be able to be resolved by agreement between the parties.
35 Notes of evidence, page 78, line 5.
[129] If, however, agreement does not prove possible and a formal award is required, Mr Raymond is to file submissions first, followed by any submissions in reply ten working days thereafter.
Acknowledgement
[130] Finally, I wish to acknowledge the difficulties facing counsel, the parties and their witnesses as a result of the serious earthquake which struck partway through the hearing. Despite the difficulties, the hearing was however able to be resumed in Invercargill. I thank all concerned for their co-operation in ensuring that happened and also thank counsel for the quality of their respective presentations.
Solicitors:
AWS Legal, Invercargill
Duncan Cotterill, Christchurch
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