Immune response, udder health and productive traits of machine milked and suckling ewes

Twenty Comisana ewes, with no history of mastitis, were divided into 2 groups of 10 and housed separately in 2 rooms within the same building. Ewes in the machine milked (MM) group were removed from their lambs 48 h postpartum and subjected to machine milking twice daily thereafter. Lamb suckled (LS) ewes were suckled by their lambs throughout the trial. The concentrations of the main microbial groups (mesophilic bacteria, pyogenic streptococci, total coliforms, total staphylococci, yeasts and moulds) were measured weekly from both the air and potential sources of udder contamination such as room surfaces, lambs’ mouths, milking operators and milking equipment. The cell-mediated immune response in vivo of ewes to phytohemagglutinin (PHA) injection was evaluated at days 7, 21 and 35 of the study period. At days 7 and 21, ewes were intravenously injected with chicken egg albumin (OVA). Antibody titers were determined immediately before the first antigen injection and then again at days 21 and 35. On each sampling day, an aliquot of blood was analyzed for white blood cell (WBC) differentials. Individual milk samples were analyzed weekly for somatic cell (SCC) and polymorphonuclear neutrophil leukocyte count (PMNLC), and for bacteriological characteristics and composition. The main carriers of milk contamination were the hands of milking operators and mouth of suckling lambs. The MM ewes displayed a lower (P<0.05) immune response to PHA than the LS animals at day 21. However, no significant differences were found in WBC differentials and antibody titers to OVA. The MM ewes had higher concentrations of PMNL (P<0.05) and staphylococci (P<0.01) in their milk than the LS ewes. Milk yield and protein content were not affected by treatment, whereas the fat content was lower (P<0.01) in the milk of the LS ewes. Results suggest that early transition to machine milking may impair the responsiveness of the ewe immune system. Maximum care should be taken to control the hygiene of the udder, milking equipment and personnel in order to minimize the risk of intramammary infections.