Consequences of reduced vitamin A administration on mammary health of dairy ewes

The study was carried out in Mytilene breed dairy ewes, which were allocated into two groups, 2 months before their first mating. All animals were given a diet based on dried alfalfa hay and concentrate compound feed with no added vitamin A or copper, hence making the diet poor in β-carotene and vitamin A. Ewes in group A were administered intramuscularly 150,000 IU of vitamin A at 3-month intervals, whilst animals in group B remained untreated. After lambing and on five occasions in total during their first lactation period, milk samples were collected from animals for somatic cell counting. Samples with somatic cell counts ≥0.5 × 106 cells mL−1, as well as samples from clinical cases of mastitis were examined bacteriologically. Significantly (P < 0.05) fewer cases of clinical or subclinical mastitis were recorded in group A animals, compared to group B ones. Coagulase negative staphylococci were the most frequently isolated bacteria from secretion samples of ewes with clinical or subclinical mastitis. Somatic cell counts of milk of group A ewes were significantly smaller than those of group B on the first four sampling occasions (P < 0.05), but not on the one at the end of the lactation period (P > 0.05). It is suggested that vitamin A deficiency may lead to increased incidence risk of clinical and subclinical mastitis in and to increased milk somatic cell counts in dairy ewes.