Free-Choice Feeding of Trolene for Reduction of Cattle Warble Infestations (Oestridae: Diptera)

Abstract

The systemic insecticide Trolene reduced the numbers of cattle grubs by 83 to 95 per cent when total doses of 180 and 250 mg. per kg. of animal weight were fed to calves in supplementary feed at daily doses of 10 and 15 mg. per kg. These reductions were significantly greater than those produced by lower daily or total doses including Trolene boluses at 105 mg. per kg. However, very high grub infestations survived in individual animals in all test groups except the two highest dosage groups. This is attributed to variation in feeding behaviour that resulted in the slower feeding animals receiving low doses of insecticide. This factor is apparently an inherent flaw in treatments based on free-choice feeding.Grubs were not eradicated by any of the test treatments and only the 250 mg. per kg. total dosage reduced them below the level of infestation annually observed in two semi-isolated, untreated herds. Studies of the significance of this level of survival in the perpetuation of the treated infestations are necessary.Transitory toxicity-symptoms were observed in the bolus-treated calves but not in the feed-treated calves.

The Use of Organophosphorus Compounds in Veterinary Medicine

“…Here the aim is that the insecticide should act against the larva of hypoderma during their migration through the body (Adkins 1957, MacGregor & Bushland 1957). Etrolene has been found to be effective when given orally as a bolus or as a suspension in water, and free-choice feeding to cattle has been suggested by Kohler et al (1959) and Rich (1960). Etrolene does not appear to be effective as a systemic insecticide when applied to intact skin.…”