Mammary tissue damage during bovine mastitis: Causes and control1

Abstract

Mastitis, an inflammatory reaction of the mammary gland that is usually caused by a microbial infection, is recognized as the most costly disease in dairy cattle. Decreased milk production accounts for approximately 70% of the total cost of mastitis. Mammary tissue damage reduces the number and activity of epithelial cells and consequently contributes to decreased milk production. Mammary tissue damage has been shown to be induced by either apoptosis or necrosis. These 2 distinct types of cell death can be distinguished by morphological, biochemical, and molecular changes in dying cells. Both bacterial factors and host immune reactions contribute to epithelial tissue damage. During infection of the mammary glands, the tissue damage can initially be caused by bacteria and their products. Certain bacteria produce toxins that destroy cell membranes and damage milk-producing tissue, whereas other bacteria are able to invade and multiply within the bovine mammary epithelial cells before causing cell death. In addition, mastitis is characterized by an influx of somatic cells, primarily polymorphonuclear neutrophils, into the mammary gland. With more immune cells migrating into the mammary gland and the breakdown of the blood-milk barrier, damage to the mammary epithelium worsens. It is well known that breakdown of the extracellular matrix can lead to death of the epithelial cells. Meanwhile, polymorphonuclear neutrophils can harm the mammary tissue by releasing reactive oxygen intermediates and proteolytic enzymes. In vitro and in vivo studies suggest that the use of antioxidants and other protective compounds in mastitis control programs is worth investigating, because they may aid in alleviating damage to secretory cells and thus reduce subsequent milk loss.

Intramammary administration of platelet concentrate as an unconventional therapy in bovine mastitis: First clinical application

“…Indeed, in addition to decreased production, economic losses associated with clinical mastitis include cost of treatment, extra labor, and an increased rate of cow replacement (Bartlett et al, 1990). Although antibiotics are very useful to treat infections, they do not directly protect the gland from being damaged (Zhao and Lacasse, 2008). Moreover, mastitis, besides being an animal welfare issue, is also a food safety problem because it should be taken into account that dairy cows produce milk for human consumption.…”

“…This assumption makes urgent to expand the prophylaxis interventions based on management, livestock hygiene, respect for animal welfare, and the development of alternative remedies that can replace or support those currently in use. In addition to the use of antibiotics, other therapies, aimed at reducing udder tissue damages, may be a cost-effective way to reduce the losses caused by mastitis (Zhao and Lacasse, 2008).…”

Mediation analysis to estimate direct and indirect milk losses associated with bacterial load in bovine subclinical mammary infections

“…On the one hand, bacteria release toxins that may destroy mammary epithelial cells and damage milk-producing tissues. They may also invade and multiply within the bovine mammary epithelial cells before causing cell death (Zhao and Lacasse, 2008). A therapeutic approach against such damages is to milk cows and to give them antibiotic treatment.…”

Associação genética entre ocorrência de mastite clínica e produção de leite em vacas Holandesas

“…A primeira se caracteriza por sinais visíveis de inflamação: aumento de volume e temperatura do quarto mamário afetado, dor, vermelhidão e mudanças na aparência e constituição do leite. Na mastite subclínica (MSC), não há alterações visíveis no leite e no úbere, o processo inflamatório da glândula mamária pode ser detectado por exame laboratorial, em que se observam alterações na composição físico-química do leite e elevação da contagem de células somáticas (CCS) no leite e, neste caso, também ocorre diminuição da produção (ZHAO & LACASSE, 2008).…”