title: The effects of the brown ear-tick, Rhipicephalus appendiculatus, on milk production of Sanga cattle.
abstract: Lactating Sanga cows of the Mashona breed from Zimbabwe, receiving either a low or high level of nutritional supplement, were exposed to two levels of infestation of adults of the brown ear-tick, Rhipicephalus appendiculatus in the highveld of Zimbabwe. The effect of the ticks on the milk yield was measured over an 11-week period during the rainy season from January to April 1986. A technique in which calves were weighed before and after suckling was used to estimate milk yield. There were significant treatment effects of ticks (P < 0.05) on milk production but no significant differences in liveweight gain between calves from tick-free and tick-infested dams. The loss in milk production was poorly related to the number of female ticks that engorged, being 9 g (SEM 4) per tick. A Friesian x Hereford (Bos taurus) reference group of cattle carried 50% more ticks than the Mashona cows, illustrating a difference in resistance between the breeds. Thirteen screw-worm (Chrysomya bezziana) strikes were recorded amongst the thirty-two Mashona cows compared with twenty-one amongst the ten Friesian x Hereford animals between January and the end of March.
authors.affiliation: Veterinary Research Laboratory, Harare, Zimbabwe.
authors.forename: R A
authors.initials: RA
authors.lastname: Norval
authors.forename: R W
authors.initials: RW
authors.lastname: Sutherst
authors.forename: J
authors.initials: J
authors.lastname: Kurki
authors.forename: J D
authors.initials: JD
authors.lastname: Kerr
authors.forename: J D
authors.initials: JD
authors.lastname: Gibson
mesh_terms: D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000469:parasitology* / Q000502:physiology; D005260:Female; D007774:Lactation; D013984:Tick Infestations / Q000662:veterinary; D013987:Ticks; D015030:Zimbabwe