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This article was published in 1997
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DIP YARDS AND CHEMICAL RESIDUES - Case Histories
Ian R. Harradine - District Veterinarian Grafton
Introduction
There has been wide publicity regarding the risks of residues in cattle obtained from dip yards. Despite this, cases continue to occur causing economic loss to the people concerned not to mention the effects on the cattle industry as a whole. This paper gives a brief account of two such cases that occurred in the Grafton district during 1996.
Case I. - Morgan's Dip
The original notification of a residue found on a random test at Casino abattoir on 24 July 1996 was for a total DDT level of 21.18mg/kg in a C4 steer. The MRL, for DDT is 5.0mg/kg. There was only one companion animal sold and this was tested clear.
Action was quickly taken to establish the source of the DDT and to detain the remaining 18 head of cattle on the property.
Fat biopsy samples were collected from 4 animals with the following results:
| Animal | Total DDT (mg/kg) |
|---|---|
| 1 | 1.6 |
| 2 | 0.18 |
| 3 | 8.1 |
| 4 | 36.0 |
| Soil | Location | DDT (mg/kg) |
|---|---|---|
| 1A | Dip splash area | 1510 |
| 1B | Scoop mound | 558 |
| 2 | Outside Race | 52 |
| 3A | Inside front race | 3.4 |
| 3B | Inside back race | 2.7 |
| 4 | Dip shed | 15 |
| 5 | In bottom yard | <2.0< /td> |
| 6 | In top yard | <2.0< /td> |
| 7 | Forcing pen | <2.0< /td> |
| 8 | Out yard | <2.0< /td> |
| 9 | Creek bed below rubbish tip | 0.45 |
The herd had been mustered the day before at 10am into the dip yard, with drenching, vaccination and eartagging done. It was decided to sell the two steers so they were not treated and left overnight in the yard with the rest of the herd. The two steers were then taken to sale at 3pm the next day and the remaining herd was released back in the paddock.
This gave an exposure time of approx. 29 hours. The cattle had been mustered into these yards before, but not for approx. 6 months prior to this episode.
The cattle were not handfed during the 29 hours in the dip yard as there was an abundance of kikuyu grass and this was grazed off.
The remaining cattle have been placed in detention and are to be sampled after the expiration of 12 months to allow for depletion of residues.
Case 2 - Palmers Island Dip
The original notification of a residue found on a random test at Casino abattoir on 11 September 1996 was for a total DDT level of 13.0mg/kg in a cow. The MRL for DDT is 5.0mg/kg. There were 7 companion animals sold and their results were 18.0, 17.0, 12.0, 9.8, 6.0, 5.1, and one that passed at 4.9mg/kg DDT.
27 other cattle were sold at the same sale around the state and interstate (Victoria) and all were traced and the new owners informed of the contamination, as were the relevant veterinary officers.
All 35 head of cattle had been fed in the dip yard, with access to a 10 Ha paddock outside, for a period of 8 weeks prior to sale. There were other cattle on the property in other paddocks that had no access to the yards and fat biopsy testing confirmed this as all results were negative.
The 35 head of cattle were fed a ration of lucerne hay on the ground of the holding yards and a ration of feedlot finisher was fed from a grain bin placed directly over the location of the since demolished dip yard shed.
Soil sampling results:
| Animal | Total DDT (mg/kg) |
|---|---|
| 1 | 1.6 |
| 2 | 0.18 |
| 3 | 8.1 |
| 4 | 36.0 |
| Soil | Location | DDT (mg/kg) |
|---|---|---|
| 1 | Scoop mound | 5.1 |
| 2 | Dip bath inside yard | 300 |
| 3 (feed trash) | From ground feeding area | 13 |
| 4 | Old tin site near drain pen | 290 |
| 5 | Dip shed, feeder on top | 290 |
| 6 | Loading ramp area | 1.0 |
Conclusions
It is recommended that cattle not be held or fed in dip yards and this has been widely publicised. Even short exposures have the potential to produce residues exceeding the MRL.
Producers often only have dip yards as their only set of yards and need to use the yards for management procedures like drenching and also for despatch and delivery of stock. These two cases highlight the necessity for such producers to move stock through these dip yards without delay.
Cattle should never be fed, weaned or held in dip yards. If it is necessary to use the yards then capping the ground with a minimum 300mm of gravel may be an option. Fencing out ofthe most heavily contaminated areas may be useful, especially around the dip bath and scoop mound.
Stockowners who have dip yards on their properties should check the chemical history of these yards with the Cattle Dip Community Information program. If residues are likely, serious thought should be given to formulating a management plan that will lesson the risk of contamination of livestock.