Development of Cattle Grubs in Oklahoma Cattle Imported into Canada

Abstract

Infested weanling heifer calves were imported into Alberta from Oklahoma in October of 1956. The subsequent seasonal incidence curve of their cattle grubs was characteristic of Oklahoma and not of Alberta infestations. Hypodermal grubs of Hypodermalineatum (de Villers) were found in these cattle earlier than in control Alberta cattle and the grubs dropped over a longer period of time. Grubs of H. bovis (L.) in the Oklahoma cattle formed a discrete second peak in the seasonal incidence curve. They occurred in the backs and dropped out at the same time as those in the Alberta cattle. Results of artificial infestations of Alberta cattle with H. lineatum eggs of Oklahoma origin indicated that the rate of development or grubs was not influenced by atmospheric temperatures. Published autecological results and soil temperature records suggested that only a small number or late-season Oklahoma puparia of H. lineatum would survive in Alberta, but that H. bovis would surive as well as the native ones. It is suggested that when northern cattle are imported into Oklahoma the relatively high temperatures would accelerate development of puparia, so their offspring would appear progressively earlier in subsequent years This would be particularly noticeable for H. bovis infestations. A group of late-born Oklahoma calves, imported into Alberta in 1961, carried grubs of H. bovis, which occurred in the backs earlier in the season than in the cattle examined in 1956-57. Apparently adaptation to the Oklahoma seasons had taken place in the intervening 5 years. H. bovis seems to be establishing itself in Oklahoma and adjusting to the seasons through adaptation in the puparial stage.