Effect of Streess on Blood Leucocyte and Milk Somatic Cell Counts in Dairy Cows

Open Access
Publisher Website
Google Scholar
Abstract
Physiological stressing conditions act via the hypothalamic-pituitary-adrenal axis and are associated with a number of responses including blood neutrophilic leukocytosis. Blood and milk samples from Holstein cows were examined for total blood leukocyte count, differential blood leukocyte count, milk quality test and somatic cell count in milk while the cows were stressed by i.m. porcine corticotropin injection, confinement in a heat-humidity chamber, or environmental-heat stress by exposure during the hot summer months of June through Nov. in S Arizona [USA]. All 3 stressing conditions resulted in a moderate blood leukocytosis. Modest increases in somatic cell counts of milk were associated with corticotropin injection and environmental-heat stress. Positive correlations were recorded between blood leukocytes and somatic cell counts of milk in mastitis-free cows injected with corticotropin and between percent blood neutrophils and somatic cell counts of milk in environmental-heat stressed cows with no evidence of current mastitis.