The aim of this study was to investigate differences in disease incidence between organic and conventional herds. The study was based on data from the Norwegian Dairy Herd Recording, which includes the Norwegian Cattle Health Recording System. All herds certified for organic farming in 1994 with a herd size of more than five cow-years were included. Conventional herds were matched on size and region, and from these, three herds were randomly selected for each organic herd. This resulted in a study group of 31 organic and 93 conventional herds with data from 1994 through 1997. The study unit was the cow within a lactation. Factors influencing disease incidence were studied by means of a generalized linear model approach. Management system had a highly significant effect on disease incidence. Odds ratios for organic compared with conventional herds were as follows: mastitis, 0.38; ketosis, 0.33; and milk fever, 0.60. Other significant factors that emerged in modeling the three diseases were year and lactation category for mastitis; lactation category, maximum milk yield, and season for ketosis; and lactation category and milk yield for milk fever. There was no marked difference in milk somatic cell count (SCC) between organic and conventional herds. However, cows in organic herds had lower SCC in lactation two and greater counts in lactations six and higher.
The use of synthetic pyrethroids in pour-on formulations reduced tick infestations and the incidence of tick-associated diseases in lambs more than dipping in organophosphate acaricides. Though the use of pyrethroids did not prevent the lambs from being infected with tick-borne fever (TBF), the incidence of lambs with lameness (tick pyaemia) or lambs suddenly found dead (Pasteurella haemolytica septicaemia), which often are seen in association with TBF, was reduced. The use of pyrethroids for three years did not seem to affect the prevalence of TBF.
Summary
Twenty Norwegian Red cattle, aged 8–10 months were used. Ten animals were inoculated intravenously with 3 ml of a whole blood dimethyl sulphoxide stabilate of a bovine strain of Ehrlichia (Cytoecetes) phagocytophila. The animals were observed on a daily basis for clinical symptoms and rectal temperatures were recorded daily for 36 days post inoculation. Blood and serum samples were collected regularly during the observation period. All infected animals developed fever of 2–4 days duration within a week. Six out of 10 animals had secondary temperature rises of 1–2 days duration. Three animals showed swellings in the hind limbs and a stiff gait. Compared with the control group, there was a 10% decrease in the mean haematocrit and a leukopenia that initially was due to a lymphopenia and later to a neutropenia. A monocytosis occurred after the subsidence of the primary fever period. A thrombocytopenia occurred during the early phase of infection. Granulocytic inclusions were detected for 18–32 days. All infected animals developed antibodies ≥ 1: 4096 to E. phagocytophila within 14 days post infection.
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