The causation issue
71The parties agree it is necessary for the plaintiff to establish that any breach of agreement that he propounds is a cause of the loss of the sheep (defendant's written submissions, paragraph 19; plaintiff's written submissions, paragraph 12). The defendant relied upon two experts, Mr Curran and Mr McCann. Only Mr McCann was required for cross-examination.
72Mr Curran, a veterinary officer with the Department of Primary Industries, is the technical specialist for the western division, which incorporates the arid and semi-arid areas of western New South Wales including the Coolabah area where the defendant's property at Killawarra is situated. Mr Curran's knowledge of the Killawarra property goes back to the 1980s (paragraph 3 of affidavit). The plaintiff submits that this must mean that he cannot comment on conditions at Killawarra at the relevant time, but there is no material before me to suggest that there is any significant change in relation to the climate or country conditions in this area over this period of time. As a specialist in diseases affecting sheep and other areas particularly in respect of arid areas, Mr Curran's expertise relates to his work in this area over a number of decades and in the absence of evidence of any significant change to the environment or to diseases in the area, it would be wrong for me to disregard or place little weight on his evidence simply because he has not been to this particular farm since the 1980s. His description of the property is consistent with its current condition, and while he may not have visited this particular farm, he says that he knows the general area well.
73Mr Curran describes his role as an expert in these areas to advise both farmers and the Department about diseases, management and welfare of sheep. This includes diseases which are more common where there is heavy or above average rainfall. Mr Curran recites that he has checked the records for the rainfall in the area and he notes that in 2009 in May, September and October, there was heavy or above average rainfall, and in particular in early 2010, when the rainfall could again be described as very heavy or greater than usual. It is in these circumstances that the risk of blowfly-strike increases. He explains blowfly problems in his affidavit sworn 21 July 2011 as follows:
"6. Blowflies get into the fleece of the sheep or the faecal material around the perineum, and this is particularly evidence after rainfall in the spring and autumn. Blowflies are able to survive and infest sheep because of the good shrub cover. Sick blown sheep are much more difficult to see than normal healthy sheep because they are either moving little or they lie down, hence the difficulty of spotting them on a property. Deaths from blowflies infesting sheep in this way can produce death in something like 2-5 days." (Affidavit of Mr Curran sworn 21 July 2011, paragraph 6)
74Mr Curran goes on to explain other health problems for sheep in wet weather as follows:
"8. The losses of sheep in woody weed areas particularly where the woody weed area is heavily infested with undergrowth is 8 per cent across all the years. Where there is additional rainfall, that percentage would be expected to be larger. I would not regard a 20 per cent loss of sheep from all causes as exceptional. At about this time, there were similar or greater losses from sheep blowfly in Western NSW and Northern South Australia.
9. The problem of intestinal parasites is particularly acute in wet weather. I would not rate the significance of internal parasites in this area to be as great as flystrike in causing the death of sheep. It is very difficult to talk specifically about this but where there is heavier rainfall or where there is a pattern of rainfall and heavy rainfall on limited areas where the sheep graze, the problem can be greater." (Affidavit of Mr Curran sworn 21 July 2011, paragraphs 8 and 9)
75Mr Curran also explains why it is that if a sheep falls victim to disease or to a predator, there is little left to the sheep after scavenger have struck:
"7. A further problem is that if a sheep dies pigs, foxes and birds rapidly scavenge the carcasses, often leaving very little, and it is much more difficult to see a carcass than it is to see a healthy or even a sick sheep. I say this particularly in respect of scrubby country." (Affidavit of Mr Curran sworn 21 July 2011, paragraph 7)
76This is relevant because the fact that those who attended for mustering saw only smaller numbers of dead sheep. Mr Curran's evidence explains that such carcasses are quickly disposed of by predators.
77In particular, Mr Curran expresses an opinion as to the percentage of sheep likely to die from natural predation at paragraph 8, namely that loss of sheep in woody weed areas such as the land on the defendant's property would be 8% across all ewes, but where there is additional rainfall and additional problems caused by disease, a 20% loss of sheep would not be regarded as exceptional; there was similar or greater losses in sheep blowfly in western New South Wales or northern South Australia generally. In other words, the plaintiff's evidence of a loss of sheep over the period of 23% would fall within expected parameters.
78The evidence of Mr Curran, who was not cross-examined and whose expertise is directly relevant, is something to which great weight should be given. The defendant draws my attention to the statement to this effect by Gibbs J in Precision Plastics Pty Ltd v Demir (1975) 132 CLR 362 at 370-371 and to Ellis v Wallsend District Hospital (1989) 17 NSWLR 553 at 586 and 607.
79The fact that an expert is not required for cross-examination does not, mean, given current case management practices, that his or her evidence should be accepted uncritically. In Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705 evidence of an expert was considered unreliable for other reasons.
80However, none of those reasons apply to the opinion of this expert. He clearly has the appropriate expertise, and he has exposed his reasons and provided information in support of the factual material upon which his opinion is based.
81The principal basis upon which Mr Curran's evidence is attacked is that, although he knows the general areas in which the defendant's farm is situated well, he has not specifically visited the defendant's farm since the 1980s. However, the counsel for the plaintiff has not articulated what specific geographical changes have occurred since that time. As to his knowledge of predators in the areas, the mobile and secretive nature of predators is such that even if Mr Curran had visited the defendant's farm, he would not have been in any better position to say whether these predators were on the farm, and in what number.
82In addition, the opinion of Mr Curran was corroborated by the evidence of Mr McCann, who swore affidavits of 19 and 21 July and 2 September 2011, and who was cross-examined.
83Mr McCann is the Senior District Veterinarian at the Central West Livestock Health and Pest Authority (LHPA) and, like Mr Curran, has appropriate qualifications. He has not visited the defendant's property at all, but it falls within the areas administered by the adjoining authority, the Darling LHPA, and he knows the general areas well (paragraph 3). He describes the defendant's acreage of 27,000 acres as "reasonably large" within the area and notes that the area in general is constituted by trees and scrub.
84In his first affidavit of 19 July, he described the problem of activity during moist conditions, noting that the opportunity for sheep loss in these circumstances is "horrendous" (paragraph 7). He explains that it takes merely three days for the sheep to die. The only way that this can be avoided is by shearing or crutching and by the application of chemicals to prevent the flies laying eggs in the sheep's fleece. I note that this was the responsibility of the plaintiff, and agreed by him to be his responsibility, and further that it was not carried out by him during the whole of the time that the sheep were on the defendant's property.
85A second problem described by Mr McCann is the problem of intestinal worm; he notes in particular Haemonchus Contortus ("Barber's Pole"). Unless these worms are controlled by chemical drenches, they can cause the death of the host sheep within one week of the worms reaching adult status. Again, the plaintiff was the person obliged to carry out this work.
86As to loss of lambs and their mothers from childbirth-related problems, Mr McCann's affidavit of 2 September 2011 is particularly helpful. He explains at paragraph 7 that these losses are caused by the following:
"(a) Embryonic losses. These losses occur towards the end of a pregnancy and are believed to be due to foetal abnormalities. The losses routinely are in the order of 5%;
(b) Losses due to difficult births. If the ram that is used to mate the ewes produces lambs with high birth weights, then lamb losses - and possible ewe losses - will occur during the birthing process. I note that the ewes had been mated to rams of the SAMM breed. This breed has a tendency to have high birth weight lambs.
(c) Losses due to low birth weights are inadequate milk production. If the nutritional status of the pregnant ewe is inadequate to establish normal milk production or to ensure normal growth of the lamb towards the end of the pregnancy, then high lamb losses during the first week of life can be expected;
(d) Losses due to poor mothering ability. Merino ewes have not been selected for the quality of their mothering ability and some merino ewes are poor mothers. These poor mothers - usually about 10% - frequently abandon their lambs, especially a twin lamb, resulting in the loss of the lamb;
(e) Predation. Foxes and pigs can have a devastating effect on lamb survival. Unless eradication measures are undertaken, if the predator population is high, heavy lamb losses will occur; and
(f) Disease. Diseases such as Pulpy Kidney and Tetanus can cause significant losses in young lambs given the right conditions. Vaccination protects the lambs. Unvaccinated lambs are at risk from these diseases."
87In his affidavit, he goes on to state that taking into account potential losses from the provision of inadequate management, the normal loss rate for the area, the wet conditions experienced over the period that the sheep were agisted on the property, and the incomplete mustering carried out by the plaintiff, Mr McCann considers that the loss rate of 21% of all ewes and 23% of all lambs is at the lower end of the potential loss rate (paragraph 10).
88Mr McCann confirmed these views in cross-examination. Mr McCann's conclusions were challenged on the basis of there been insufficient exposure of his reasons. In particular, there was an objection to his stating "in my experience as a general rule" ( Majeau Carrying Co Pty Ltd v Coastal Rutile Ltd (1973) 129 CLR 48). I reject that objection on the basis that it was a summary of the material which he had referred to elsewhere in his report. In addition, this evidence was explained by the witness in cross-examination as being obtained by a comparison to losses which occurred in other properties in a similar area, local knowledge such as talking to district vets in the system and landowners, and in the case of the mothering habits of merino sheep, scientific reports (which were later called for by Mr Toomey, but have not been tendered).
89When considering the evidence of experts in relation to agricultural or husbandry issues, it is my view that courts should not be overly pedantic in requiring scientific evidence in relation to what is clearly a matter of expertise obtained through many years experience. Both Mr Curran and Mr McCann have worked in this area for decades. Both have many years of professional experience which in my view are just as important, if not more, than their provision of scientific reports.
90In his evidence, Mr McCann explained an additional problem in relation to predators, which is that it is in wet conditions that there is an influx of pigs as predators (T 254). He rejected the contention that a large part of their diet was vegetable, saying they were carnivores and in fact on occasions cannibals. Given a choice, they are mainly carnivorous and in particular young lambs are most at risk.
91As to predation by the pigs, he considered a serious predation problem would be a report of up to 70% lamb losses, and that the lamb loss that was suffered by the plaintiff in these proceedings "I wouldn't class as serious" (T 256).
92As to lamb losses from poor mothering, he referred to a study of 40,000 merinos in the Gulargambone area in the 1970s which was "not as hard a country" as the defendant's. The average result of losses was 30%. This was a loss in good conditions, not hard conditions or conditions of additional rain as had been the case in the present.
93Mr McCann was asked whether, if 600 stock were lost due to disease or other reasons, he would expect to find large numbers of dead animals or carcasses around the property, to which he replied that "you may not see too much left of the carcasses" (T 268). He agreed that you would have expected to see "something" but asked how big was the land over which they were dying. For a total of 600 carcasses to be spread over a 28 square mile area over a period of months, Mr McCann agreed that one would expect to see evidence of adult carcasses most likely to be found within a kilometre of the waterholes (T 270). However, that was as high as his evidence went in relation to the likelihood of discovery of carcasses.
94I do not accept the submissions of the plaintiff that evidence of losses would be "widespread and obvious" across the defendant's property. The expert evidence is to the contrary.
95The plaintiff called no evidence to respond to these experts. Their evidence is consistent with each other and confirms that the stock losses suffered by the plaintiff were well within the range of acceptable stock losses. The plaintiff has therefore failed to establish causation.