The impact of environmental factors on the milk ejection and stress of dairy cows

Abstract

Farm breeding of cattle is organized so that the animals are kept in a controlled environment (an closed corner, feeding time, milking time, workers), where daily animal encounter with familiar sounds, smells, movements and equipment. Any positive or negative change of environment causes certain physiological reactions of cattle on it. Negative stimuli (relocation, new technological activities, unidentified sounds and people) disrupt the homeostasis of the animals and lead them into a state of stress. During stress in cattle appears central inhibition of milk ejection from the alveoli of the udder, causing its incomplete emptying which could lead to pathological changes. In stressful situation, there is a connection between nervous (SA system), endocrine (HPA-axis) and the immune system. Stimuli from the outside were obtained through sight, hearing, smell and touch, leading to nerve impulses which then activate the endocrine system (increased levels of cortisol, ?-endorphin, adrenaline, and reducing levels of oxytocin in the blood), whose actions over a long time lead to decline in immune response and susceptibility to disease. Many studies suggest an association between central inhibition of milk ejection and stressful situations (first milking of primiparious cattle, environment changes), but the very principle of inhibition is not fully understood. Some studies indicate an association between endogenous opioids (?-endorphin) and catecholamines (adrenalin) in the central inhibition of milk ejection, however, there is still no clear evidence and there is still plenty to do in this area.Farmsko gajenje goveda organizovano je tako da se zivotinje drze u kontrolisanom okruzenju (zatvoreni prostor, vreme obroka, vreme muze, radnici) gde se zivotinja svakodnevno susrece sa poznatim zvucima, mirisima, pokretima i opremom. Svaka pozitivna ili negativna promena okruzenja uzrokuje izvesne psiholoske reakcije goveda na nju. Negativni stimulusi ( promena lokacije, nove tehnoloske aktivnosti, nepoznati zvuci i ljudi) ometaju homeostazu zivotinja i uvode ih u stanje stresa. Tokom stresa kod goveda dolazi do centralne inhibicije ejekcije (ispustanja) mleka iz alveola vimena, prouzrokujuci njihovo nepotpuno praznjenje sto moze dovesti do patoloskih promena. U stresnim situacijama postoji veza izmedju nervnog (SA sistem), endokrinog (HPA-axis) i imunog sistema. Spoljasnji nadrazaji dobijeni culima vida, sluha, mirisa i dodira prenose se nervnim impulsima aktivirajuci endokrini sistem (povecava se nivo kortizola, ?-endorfina, adrenalina, a smanjuje nivo oksitocina u krvi), cija aktivnost tokom duzeg vremenskog perioda dovodi do pada imunog odgovora i sklonosti ka bolestima. Mnoge studije ukazuju na povezanost izmedju centralne inhibicije ejekcije mleka i stresnih situacija (prva muza prvotelki, promene u okruzenju), ali sam princip inhibicije nije u potpunosti objasnjen. Neke studije ukazuju na vezu izmedju endogenih opioida (?-endorfin) i kateholamina (adrenalin) u centralnoj inhibiciji ejekcije mleka ali ipak ne postoje jasni dokazi i jos mnogo toga treba uraditi u ovoj oblasti.