Mammary Defences and Immunity against Mastitis in Sheep

Abstract

Simple SummaryThe article reviews the defence mechanisms and the relevant processes that occur in the udder of sheep. Due to the importance of the udder in milk production, animals display many defences to protect the organ. These include the teats, the epithelial and the white-blood cells in the udder, the immunoglobulins and chemical substances that all participate in the various processes. These are influenced by many factors, animal- or management-regulated, which must be taken into account in the formulation of prevention schemes against mastitis in sheep.AbstractThe objectives of this review paper are to present udder defences, including teat of the udder, mammary epithelial cells, leucocytes, immunoglobulins, complement system and chemical antibacterial agents, to describe cooperation and interactions between them and to elaborate on potentials regarding their significance in mammary immunisation strategies. The teat of the udder provides initial protection to the mammary gland. The mammary epithelial cells synthesise antibacterial proteins and the leucocytes produce various inflammation mediators (cytokines or chemokines), phagocytose bacteria and recognise antigenic structures. In the mammary gland, four immunoglobulins (IgG1, IgG2, IgM and IgA) have important roles against bacterial pathogens. The complement system is a collection of proteins, participating in the inflammatory process through various pathways. Other components contributing to humoral mammary defence include lactoferrin, lysozyme and the lactoperoxidase/myeloperoxidase systems, as well as oligosaccharides, gangliosides, reactive oxygen species, acute phase proteins (e.g., haptoglobin and serum amyloid A), ribonucleases and a wide range of antimicrobial peptides. Management practices, genetic variations and nutrition can influence mammary defences and should be taken into account in the formulation of prevention strategies against ovine mastitis.

Size of supernumerary teats in sheep correlates with complexity of the anatomy and microenvironment

“…Therefore in spite of the considerations described above, the spectrum of anatomical variants of supernumerary teats we have described is likely to be applicable to other groups of sheep, although it is possible that differences in microenvironment may be observed in sheep managed in differing types of production system. That said, much of the work on inducible lymphoid follicles in ewe teats has been carried out in dairy breeds (Fragkou et al ; Katsafadou et al ) and yet we observed very similar follicle‐like structures in a subset of the supernumerary teats from the suckler ewes detailed here, hinting that the teat microenvironment may be similar even in animals from different production systems.…”

Mortality of Dairy Sheep during the Peri-Parturient Period: Results of a Field Investigation in Greece

“…It is also possible, given the immunocompromise present during that period, that the affected ewes were unable to counteract a mammary infection, and so suffered acute clinical mastitis and death [ 24 , 25 ]. Moreover, in animals with increased concentrations of β -hydroxybutyrate (which occurs in pregnancy toxaemia), Galvao et al [ 26 ] found reduced blood neutrophil numbers, an issue that can clearly predispose a ewe to mastitis, given the importance of neutrophils in the defence mechanisms of the mammary gland [ 27 ].…”

Mastitis in Small Ruminants

“…2) Nutritional deficiency adversely affects the animal host defense mechanism, and may promote disease progression to clinical mastitis. Katsafadou et al [14], associated nutritional deficiencies with impaired leucocyte function or mammary defense. Here nutritional elements such as Selenium, Zinc, vitamin E and Vitamin A deficiencies have been linked to an increased risk of mastitis in ewes [14][15][16].…”