Effect of parity, stage of lactation, and intramammary infection on concentration of somatic cells and cytoplasmic particles in goat milk.

Aseptic foremilk samples (about 15 ml) were collected biweekly for four samplings and then monthly throughout lactation from 35 does in three herds on Dairy Herd Improvement test. Bacteriology, direct microscopic somatic cell counts, and cytospin differential cell counts were performed on all samples. Milk yield was obtained from monthly Dairy Herd Improvement records. Thirty-nine percent of udder halves were infected, and coagulase negative staphylococci were the most frequent isolates (201 of 205). Somatic cell counts were influenced by lactation number, stage of lactation, and intramammary infection. Also, infection of one udder half increased somatic cells in the corresponding uninfected mammary half of the same animal. Cytoplasmic particles were not affected by stage of lactation or by intramammary infection but were greater for goats in first lactation. Milk yield was influenced by lactation number, stage of lactation, and intramammary infection.