title: A farming systems study of abortion in dairy cattle on the Atherton Tableland. 3. Metabolic factors.
abstract: An association with a rank correlation of 0.55 (p = 0.06) was obtained between monthly rainfall and monthly abortions for a group of 24 farms in tropical Australia where cows grazed predominantly summer rain-dependent pasture. A similar association was found among cows grazing nitrogen-fertilised, irrigated pasture in winter in the same area. On farms with irrigated pasture the first service conception and abortion rates in herds which grazed intensively during the night (abortion 8.9%; first service conception 42.9%) differed significantly from those which grazed during the day (abortion 6.4%; first service conception 52.9%), and this suggested that increased abortion rates and decreased first conception rates may be part of the one syndrome. An hypothesis was developed that the feeding of immature nitrogen-fertilised pasture, rich in protein and stimulated by rain or irrigation, is associated with an increased abortion rate and a depressed conception rate. Other evidence included an increased susceptibility of first lactation cows to abortion, a lower abortion rate in late pregnant dry cows fed more mature pasture, a 20% repeat abortion rate in the population sampled and the lack of conclusive evidence for infectious and selected non-infectious agents. There were no other observed clinical signs in most aborting cows.
authors.affiliation: Queensland Department of Primary Industries, Oonoonba Veterinary Laboratory, Townsville.
authors.forename: J H
authors.initials: JH
authors.lastname: Norton
authors.forename: W P
authors.initials: WP
authors.lastname: Tranter
authors.forename: R S
authors.initials: RS
authors.lastname: Campbell
authors.forename: R K
authors.initials: RK
authors.lastname: Shepherd
mesh_terms: D000034:Abortion, Veterinary / Q000453:epidemiology / Q000209:etiology*; D000383:Agriculture; D000818:Animals; D002417:Cattle / Q000502:physiology*; D002418:Cattle Diseases / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D005308:Fertilizers; D009584:Nitrogen; D011247:Pregnancy; D011270:Pregnancy, Animal; D011793:Queensland; D011891:Rain; D012621:Seasons; D012820:Silage; D013997:Time Factors; D014329:Tropical Climate
chemical_list: D005308:Fertilizers; D009584:Nitrogen