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B.H.C. Residues in a North Coast Piggery
J.M. WILSON., B.V.Sc., Veterinary Inspector, Lismore NSW 2480
INTRODUCTION
This is not a scientific paper. Rather, it is an account of some aspects of the detection, control and management of a major level of pesticide contamination in a large piggery.
The piggery had about 150 breeding sows, about 3000 pigs on the property, and turned off 50 - 100 baconers each week. Management, housing and nutrition are of a high order, and the product regularly commands a premium price from its client, a large supermarket operator.
The detection of B.H.C. residues led to a complex chain of events, involving financial loss to the owner and others; disposal of unsaleable pigs and feed; tracing the source of contamination; the involvement of a second, larger piggery; and the evolution of a management system designed to get the unit back into commercial production as quickly as possible.
A major frustration has been the lack of available information on B.H.C. half lives in pigs, and the failure of B.H.C. levels, in many cases, to decay as predicted.
Looming over the whole episode is a chain of litigation involving the Department of Agriculture, the pig producers and their customers, and the supplier and grower of the contaminated grain; together with their respective insurers.
HISTORY
On 3rd June, 1986 a veterinary practitioner submitted a 5 months old cadaver to the Regional Veterinary Laboratory at Wollongbar for autopsy. Suspected causes of death were campylobacteriosis or swine dysentery. The piggery manager who actually delivered the cadaver to the laboratory remarked to the receiving Veterinary Research Officer, that there was a peculiar odour associated with the feed. On the basis of this remark, fat, and stomach contents were forwarded to the analyst for pesticide screening.
Verbal advice (confirmed in writing several days later) was received by the Veterinary Inspector, that fat showed 2.8 mg/Kg B.H.C. and stomach contents contained 3.0 mg/Kg B.H.C. As the M.R.L. for B.H.C. is 0.3 mg/Kg in fat, immediately on receipt of the verbal advice, a visit was made to the property on 12th June, 1986. Feed samples were collected for analysis, and were processed within 24 hours. Prepared grower, finisher, and sow meals all had in excess of 3.0 mg/Kg B.H.C. 2 samples of barley stored in a silo had levels of 0.12 and 2.5 mg/Kg.
On 14th June, 1986 Veterinary Inspector and Senior Field Veterinary Officer visited the property. Form 1 Detention was imposed and we were informed that 100 pigs had been booked in for slaughter the following week. 64 pigs had been consigned for slaughter the week before.
Immediate action was directed towards:
* Preventing pigs already sold from being consumed by humans.
* Tracing the contamination source, and determining when it had occurred.
* Determining the distribution of contamination in live pigs according to age groups.
1. PIGS ALREADY SOLD AND SLAUGHTERED
It was possible, with the co-operation of the supermarket chain, the Meat Inspection Service, and the Health Commission, to detain the 64 pigs already slaughtered, together with a large part of the edible offal. B.H.C. levels in this material were 0.35 - 1.7 mg/Kg. This resulted in withdrawal from sale and condemnation of the pigs and by-products.
2. TRACING THE SOURCE AND TIME OF CONTAMINATION
All grain had been supplied by one wholesaler. The piggery manager had, for three months, been keeping samples from each delivery of grain for retrospective analysis in case of an emergent pesticide problem.
Unfortunately, because of his incorrect sampling technique, analysis of these samples was unrewarding. Departmental computer records were consulted on past monitoring, and revealed no B.H.C. in pigs sampled as late as 13th January, 1986. Retrospective sampling of pork from the owner's deep freezer confirmed that contamination had occurred subsequent to 15th May, 1986. Armed with delivery dockets for the suspect period, we approached the grain wholesaler. In the first instance, acting on legal advice, he was not prepared to co-operate.
However, a few days later he was more amendable. In the meanwhile, an intensive sampling campaign was mounted through the Regional Pesticides Inspector, Agricultural Inspectors, and the Queensland Department of Primary Industries, taking samples from all possible sources of contamination. His sampling involved not only grain storages on farms, but also vehicles used in grain transport. Within a few days it became clear that the contaminated barley originated from a silo on a Casino district property, delivered to the piggery on 22th May, 1986.
Unfortunately, it was also learned that a second load of the pesticide affected grain had been delivered to a second, larger piggery in the same area as the first property involved. Fortunately, this grain had not been fed out. However, it did result in a substantial loss because it had mixed with other grain held in storage.
3. B.H.C. LEVELS IN THE PIGGERY
Barley from the contaminated silo had been fed for 32 days. Barley was fed to all pigs over 12 weeks of age. A wheat based diet was fed to pigs up to 12 weeks of age.
Unweaned piglets were exposed to residues, as B.H.C. was detected in sows' milk on day 27. Residues were detected in pigs less than 12 weeks old who were on wheat based diets. This included piglets whose mothers had not been on contaminated feed prior to weaning. It was thought that contamination of the wheat based feed had occurred through incomplete emptying of the mixer between ration formulations.
Grower pigs aged 14 - 24 weeks, and fed contaminated barley, had residues of approximately 10 times M.R.L. on day 27.
B.H.C. levels in pigs were established by fat biopsy, necropsy, and milking sows. One problem encountered was the difficulty in obtaining sufficient fat by biopsy, because of the very lean type of pig produced.
Restraint was a problem with large baconers, sows, and boars. In some cases 10 ml of 'Stresnil' was barely sufficient. The owner commented that in many cases, pigs became aggressive and difficult to manage following 'Stresnil' medication.
4. MANAGEMENT
Due to lack of information on half lives of B.H.C. it was difficult to predict the outcome of any management regime. It was postulated that pigs less than 12 weeks of age would probably outgrow their residues by the time they reached bacon weight. This in fact proved to be correct, and it was possible to release this group, and subsequent groups, for commercial sale.
Assuming a half life of B.H.C. of 40 days, and after consultation with Livestock Officer (Pigs), management elected to hold the pigs over 14 weeks of age on a maintenance ration. This was based on predictions that there would still be a margin of profit from sale as overweight pork or backfatters. However, by day 72 it was apparent that the break-even point had arrived, while the hoped for decline in residues had not!
132 of the best types of gilts were transferred to the breeding herd. The balance, totalling 406 growers and overweight baconers, together with 10 cull sows, were slaughtered and buried on the property.
Subsequently, as sows and boars have become eligible for culling, biopsy samples have been taken to determine whether they may be released for sale, or must be destroyed and buried on the property. As a result of this, an additional 50 breeders have been destroyed.
5. DISPOSAL OF UNSALEABLE PIGS
After carefully considering and ruling out options such as meatmeal manufacture, pet food, and disposal interstate, it was decided to slaughter and bury unwanted pigs on the property. Under the supervision of State Pollution Control Commission, a suitable site was selected and a large trench dug, using a hired excavator, to S.P.C.C. specification.
Pigs were run up a ramp onto a truck, and stunned using an electric stunner on loan from a local abattoir. The pigs were then shot through the brain with a single shot, sawn-off .22 rifle. They were then dragged onto a 4-wheel drive truck and trailer, for transport downhill to the excavation site. Here they were offloaded by Veterinary Inspector, Veterinary Officer and Ranger. Body cavities were slashed open, and fat samples were taken from selected age groups. Pigs were then pushed into the trench, the object being to have them stacked evenly about 3 deep along the length of the trench. Slaughtering started about 7.30 a.m. on a Saturday, and was completed by 4.30 p.m.
The hole was filled and consolidated by 6.30 p.m. on the same day.
6. DISPOSAL OF CONTAMINATED FEED
Pesticide affected barley and feed from 2 properties was involved, about 120 tonnes in all. Various options, including use for seed, were considered, and ruled out. Burning was not approved by State Pollution Control Commission. Because there was no suitable local site for burial, the grain from both properties was eventually taken to Lismore City Council garbage tip, where it was buried under supervision.
Grain and feed storage facilities on both properties were then thoroughly cleaned. Following swabbing and check testing by the Chemist, they were cleared for storage of clean feed.
7. COSTS
After slaughter-out of pigs and burial of feed, cost estimates were about $105,000.00 for direct losses to both properties. Subsequently, additional costs and losses incurred have substantially increased the damages bill, and litigation amongst the various parties is at present in progress.
A strong case was put by the pig industry for some form of financial support to affected owners, using Swine Compensation Fund moneys, but this was unsuccessful.
8. INFORMATION ON B.H.C. HALF LIVES
As previously mentioned, there is little information available. It is hoped that the sampling and trials set up in connection with the foregoing unfortunate episode will contribute something to our knowledge.
These findings will no doubt be published at a later date. However, at this stage we can say that the mean half life of B.H.C. in pigs is around 5 - 6 weeks.
CONCLUSION
With the benefit of hindsight, my advice to anyone encountering a B.H.C. problem, with levels exceeding twice M.R.L. in pigs, would be to start digging.