Resistance to penicillin of Staphylococcus aureus isolates from cows with high somatic cell counts in organic and conventional dairy herds in Denmark

Table 1 Herd size, production and herd health in Danish dairy herds. Characteristics of herd groups in the study.

	No. herds	End of one year study period	Herd size Cow years/year	Calculated bulk tank somatic cell count	Milk production Kg ECM/day	Mastitis treatments % cows treated/cow year	% of cows with infection risk > 50%
Conventional	20	03–2000	83	283	25.7^a	74^a	42
Organic before 1995	18	03–2000	88	296	22.1^c	48^b	38
Converting herds before conversion	19	04–1999 or 04–2000	87	317	24.6^a,b	61^a,b	42
Converting herds first year after conversion	19	04–2000 or 04–2001	101	337	23.3^c	52^a,b	44
Converting herds second year after conversion	19	04–2001 or 04–2002	107	327	23.8*	48^a,b	45
Conventional herds in full research project	109	03–2000	85	309	24.4^b	55*	43

ISSN: 1751-0147