Table 4.

Summary of population at risk, incident cases, and time at risk of Anaplasma marginale infection for cattle followed up to determine rate of A. marginale infection.

Age group	Group 1 heifers	Group 2 heifers∗		Cows
Pasture	C§	A†	B‡	C§
Population at risk	31	37	10	5
Incident cases	18	26	3	2
Days at risk	80	70	123	80

^∗Group 2 heifers were grazed on pasture A for the first 70 study days and on pasture B for the remaining 123 study days.

^†Annual rangeland pasture, approximately 160 m elevation, Tehama County, CA.

^‡Valley irrigated pasture, approximately 120 m elevation, Tehama County, CA.

^§Mountain meadow irrigated pasture, approximately 1060 m elevation, Plumas County, CA.