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Chemical Composition of Mammary Gland During Experimental Mastitis

Dairy Cattle Research Branch, U.S.D.A., Beltsville, Maryland

ABSTRACT

Water, fat, Na, K, Cl, DNA, RNA, histamine, and glyeogcn were determined on sheep mammary gland samples to characterize the tissue changes occurring during the experimental induction of mastitis with Escherichia coli and Staphylococcus aureus. Inoculations were made on one-half of the udder and chemical changes determined during initial stages of inflammation. One-half to five hours after inoculation treated udder halves showed great increases in size and weight. This inflammatory response resulted in dilution of adipose tissue from 20% of total weight in the control to 10% in mastitic glands. Water content increased markedly, from 83 to 88%. The response appeared to be very similar in glands from either estrous or luteal phases of the reproductive cycle, while ovariectomized ewes showed a lesser response. Na and Cl increased greatly and K decreased, indicating an inflammatory edema. Histamine concentration of the inoculated glands decreased. The most dramatic change occurred in glycogen content, which increased three- to fourfold in inoculated glands. This glycogen response appeared to he correlated with leukocytic invasion. Chemical changes induced by S. aureus were not as marked as those occurring after E. coli infection.