Health status of dairy cows on organic farms, with emphasis on ketosis S6
Olesen, Ingrid1, Strøm, Turid2; Ebbesvik, Martha3
1) Department of Animal Science, Agricultural University of Norway, N-1432 Ås, 2 and 3) Norwegian centre for Ecological Agriculture, N-6630 Tingvoll
|The objective of the present study was to
examine the health status of dairy cows on 11 farms with or in conversion to ecological
management. In order to study the tendency of ketosis, acetone level in milk was measured
in 8 herds from 1993 to 1995.
Records of veterinary treatments of approximately 175 cows per year were available from 1989 to 1995. Grass silage and hay were the main roughage fed during winter on all farms. None or very small concentrate rations were offered all cows 1-2 weeks before calving. Mean concentrate rations during the first 8 weeks after calving was 3.4 FEm in 1993-1995. Mean daily milk yield on the farms during the same period was 22.5 kg.
Percent cows treated for mastitis, ketosis and milk fever varied considerably between herds. However, the overall means were considerably lower in the organic farms studied compared to the means for the National herd recording system.
Analysis of variance of ketosis showed significant interaction effects between herd, year and calving month in addition to significant effects of lactation number, minimum concentrate ration and sire's breeding value for ketosis.
Category of hyperketonemia was defined by maximum level of aceton contents in the cow's milk samples. Of the cows with aceton measured of at least 5 milk samples per early lactation, 73.4 % were normal, 10.4 % showed light to moderate ketonemia, 7.8 % were in the interval of risk of clinical symptoms and 8.4 % showed values which almost always imply clinical symptoms.
The agreement between maximum aceton level and treatment for ketosis was found to be poor (corr=0.11). The low frequency of treatments for ketosis in spite of low concentrate rations may be due to the low concentrate feeding before calving, much pasturing and exercise, more diversed diet and low protein balance in the ration reducing the milk yield. These issues require further investigation.