Inverse relationship between skimmed milk progesterone and somatic cell counts during gestation and postpartum periods in Bunaji Zebu COWS

Abstract Variations of milk somatic cell counts and milk progesterone concentrations were investigated during the periods of artificial insemination (A.I.), pregnancy, parturition and postpartum, in 30 pregnant and 68 postpartum Bunaji Zebu cows. Milk somatic cell counts for the 30 pregnant cows were 75 000 ± 12 000 per ml at A.I. but decreased gradually to 21 000±6000 per ml 30 days after A.I. and remained low throughout the gestation period. Skimmed milk progesterone concentrations were low (0.2±0.1 ng/ml) at A.I. but increased gradually to 11.2±3.8 ng/ml during the first month of gestation and remained high (13.8±4.6 ng/ml) throughout the gestation period. After parturition, somatic cell counts increased sharply from 19 000±8000 per ml to 250 000±18 000 per ml throughout the 90-day postpartum period, during which the skimmed milk progesterone concentrations were below 1 ng/ml. It is concluded that there is an inverse relationship between milk progesterone and somatic cell counts during the gestation and postpartum periods in lactating Bunaji Zebu cows, and that this inverse relationship may have no single cause because these two responses differ with gross physiological states. Therefore, the occurrence of somatic cells may be under no regulatory control of the hormone progesterone and vice versa.