Immunosuppression: Postpartum diseases of dairy cows

Abstract

Periparturient period in dairy cows is accompanied by numerous physiological, metabolic and nutritive changes. The way in which they occur and develop have a great influence on lactation performances, subclinical and clinical postparturient diseases and reproductive disorders, thus affecting the profitability as well. During periparturient period dairy cows may subject to the immune system function disorders. This immunosuppression leads to increased number of severe cases of infections (mastitis, metritis, retained placenta and other health disorders). The cause of periparturient immunosuppression is unknown, although it is a subject of numerous studies which suggest that immune disfunction may be provoked by both metabolic and endocrine factors. Numerous authors suggest that negative energy balance, non-esterified fatty acids (NEFA), ketone bodies and hypocalcaemia play a significant role in the development of immunosuppression. It is well known that glucocorticoids exert an immunosuppressive action. The changes in the levels of estradiol and progesterone may have either a direct or indirect influence on immune defence. However, their effect on the development of this immunofunction is not long, since the changes in their concentrations are short-lasting. Some nutrients are involved in the function of immune cells thus minimizing the inflammatory damages, due to more efficient immune response. Numerous tissue damages during the infection are possible, as a consequence of oxidative stress - reaction of unstable oxidised molecules with tissue lipids, proteins and DNA. A great number of antioxidants are important for animal health, however, optimal concentrations and forms of these supplements for maximizing the immune function and tissue protection are still unknown.

Peripartalni period kod mlečnih krava prate brojne fiziološke, metaboličke i nutritivne promene. Način na koji se one dešavaju i kako se odvijaju imaju veliki uticaj na laktacione performanse, subklinička i klinička postpartalna oboljenja, reproduktivne poremećaje, a sami tim utiču i na rentabilnost. U toku peripartalnog perioda mlečne krave podležu poremećaju funkcije imunskog sistema. Ova imunosupresija dovodi do povećanja broja i ozbiljnosti infekcija (mastitis, metritis, zadržavanje posteljice i drugi zdravstveni poremećaji). Uzrok peripartalne imunosupresije nije poznat, ali je predmet brojnih istraživanja koja sugerišu da je imunska disfunkcija uzrokovana metaboličkim i endokrinim faktorima. Brojni autori navode da negativni energetski bilans, nezasićene masne kiseline (NEFA), ketonska tela i hipokalcemija, imaju značajnu ulogu u razvoju imunosupresije. Poznato je da glukokorikosteroidi imaju imunosupresivno dejstvo. Promene nivoa estradiola i progesterona takođe mogu imati direktan i indirektan uticaj na imunsku odbranu. Međutim, oni nemaju dugotrajan uticaj na razvoj ove imunodisfunkcije, jer promene njihovih koncentracija kratko traju. Pojedini nutricienti su uključeni u funkciju imunskih ćelija i tako minimiziraju inflamatorna oštećenja, zahvaljujući efikasnijem imunskom odgovoru. Moguća su brojna oštećenja tkiva za vreme infekcije, kao posledica oksidativnog stresa - reakcije nestabilnih oksidisanih molekula sa tkivnim lipidima, proteinima i DNA. Brojni antioksidansi su važni za zdravlje životinja, međutim optimalne koncentracije i forme ovih suplemenata za maksimiziranje imunske funkcije i zaštite tkiva, su još uvek nepoznate.