Individual trade-offs between nutrition and risk of interspecific transmission of disease by grazing: cows, badger latrines and bovine tuberculosis.

摘要

This study was conducted to correlate individual cow characteristics and physiological state (age, milk output, milk composition and genetic merit) with the levels and type of contact they have with areas of contaminated pasture. Dairy cattle were used as model system for the risks of tuberculosis (TB) transmission posed by pasture contaminated with badger excreta (via the faecal-oral route). The contact behaviour of ~150 dairy cattle at pasture contaminated with badger excreta (faeces and urine) were monitored and correlated this with measures of current and genetic production. Cows producing milk with lower milk solids (percentage protein and fat) had higher contact with faeces-contaminated swards. In contrast, genetic merit for milk protein and fat content, and overall genetic merit were not correlated with contact at faeces-contaminated swards. Individuals with higher somatic cell counts (SCC) had less contact with badger faeces. In general, the cattle behaved similarly at non-contaminated swards and those contaminated with badger urine, but differently at badger latrines (which contain both faeces and urine). Current animal state is a better indicator than genetic potential of the contact behaviour with environmental distributions of excreta (and thus, disease risk). Individual physiological characteristics, regularly monitored, may have a value in predicting behaviour and thus, exposure to and risks from disease..