Control of Sheep lick And Eradication in One Year

Poverty Bay Herald, Volume LX, Issue 18255, 25 November 1933, Page 14

Control of Sheep lick And Eradication in One Year

pOMI’LGTE freedom from sheep licit is possible in one year, according to the half-yearly; report of Lincoln College presented to the board of governors. The report., states:— “ll is estimated that in New Zealand approximately £1 SO,OOO is spent annually in dipping sheep to control beds aiid lice.” This amount does not include labor costs, •depreciation in wool, or losses duo to deaths lollowing dipping. ’ , , “From what knowledge we possess of the control and eradication of these parasites it is possible to state that by a combined effort freedom from Ji’ce and keds could be achieved in one year with a total expenditure of not more than three times the amount that is at present spent every year. In arriving at this conclusion we have considered the possible value of dipping in preventing attacks by blow dies, but are not satisfied that it is al all effective.”

The report consists of a review of the present knowledge of the life history of the sheep ke:l (tick) and its control, and certain data which havo been collected during an investigation by the entomological and vetferili&ry departments of the college. Effect of Rain.

“Irrespective of the nature of the dip used,” continues the report, “it was found that the greater the growth of wool on the sheep about to 1 be dipped the more effective and lasting was the parasiticidal action. Tills' is supported by an observation under field conditions, that the greater too amount of dip removed by each sheep the moro efficient tho dipping appeared. “Rain following dipping is generally considered to reduce the parasiticidal properties of the dip by dilution and washing out. By spraying newlydipped sheep carrying different growth of fleece with' known quantities of water it was found that the efficacy of the dip may be only ' slightly affected by rain after dipping if a good growth of wool is present at dipping time. The dilution and washing out due to spraying were most marked in newly shorn sheep and least in well-fleeced one case spraying with water, equivalent to half an- inch of rain, after dipping, did not affect the killing power of an arsenic dip used on sheep carrying seven months’ flceec. To obtain this information similarly clad sheep of the same breed were dipped but not sprayed and then allowed to depasture with those sprayed. “Under ordinary conditions at Lincoln during February, March and April of this year, a dipped sheep shorn on one side and carrying a 16-month, fleece on the other could bo reinfested In 2*l days on the shorn sido but not until 62 days on the unshorn side.

More Frequent Dipping. “Judging from the comparative ease with which newly-shorn dipped sheep may be reinfested artificially, it is concluded that dipping on top of the shears or very soon after is not the best time to securo ked control and eradication. It is for this reason that lambs and ewes dipped early at’ten require dipping before being disposed of fat. We suggest that if circumstances necessitate early dipping a second or third dipping should be given late in the season. In suggesting the cooler months of lute summer or early autumn we have taken into consideration the popular belief in New Zealand that losses from chill, etc., may follow dipping at this time. Experience here and elsewhere recommends later dipping where possible. “To find out if infestation could tako place during dipping, a clean, long-woolled seven-months-old lamb was put through the dip following tne dipping of heavily-infested sheep. The lamb was examined after dipping, and pupae were found in the fleece along the back. These were obtained from the surface of the dipping fluid. The lamb was isolated and later found to be infested with keds. “Trials were conducted to dctcnminc whether the length, of time in tho dip influenced the efficiency of dipping, it was found that thorough immersion was more important than time. Satisfactory results wore obtained from a half minute period with thorough immersion, whereas it minute or more without proper immersion was ineffective. Experience indicates . that a time limit of one minute should aimed at in preference to a shorter time and risks associated with hurried immersions.”