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

Abstract

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 beta-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 x 10(6) 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. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.