This article first appeared in our sister publication, Dairy Farmer.
Sound recordings of livestock doing (or not doing) their usual activities could provide valuable insights into their health, welfare and environmental impact, research shows.
Scientists at Crown Research Institute AgResearch have been investigating the potential of compact, non-invasive acoustic sensors as a tool to monitor the animals’ behaviour and assist farmers. These sensors are composed of a digital voice recorder, placed in a custom-made housing and strapped to the cow’s rear leg or collar.
“What we’ve found is that use of these sensors is potentially a very accurate way of automatically differentiating between the activities of the cows, such as grazing, breathing, walking, lying down, vocalisation (mooing) and `dung events’,” says AgResearch senior scientist Dr Paul Shorten.
“For example, the respiration rate of cows can be accurately determined by automatically identifying periods of inhalation and exhalation from the acoustic recordings. This provides a non-invasive automated alternative to methods that require sensors to be inserted in or near the nostril or require labour-intensive identification of respiration rate from visual observation or video recording of animals.
“The pattern of breathing is a key predictor of heat stress, and this acoustic technology provides an opportunity to identify animals that are heat stressed.”
Researchers drew on recordings obtained from sensors attached to more than 150 dairy cows at multiple locations and times of the year. Hundreds of representative “acoustic signals” were obtained, representing different classes of activity, along with background events that included the sound of birds, insects, weather, traffic and passing aircraft to broaden the data set.
“When we analysed the recordings to check their accuracy against the actual behaviours we are trying to detect, we found a very high level of accuracy in the classification model,” Shorten says.
“What it means is this technology could eventually be used as a non-invasive method of monitoring cows to detect any abnormal behaviours or change in behaviours that could indicate a problem, such as the animal being unwell or heat stressed. This could potentially then alert farmers to do some further investigation, adjust management practices or seek further advice.”
Research by AgResearch scientists has previously looked at use of these acoustic sensors as a tool to monitor the urination patterns of cattle, to provide insight into nitrogen loss through urine and assist farmers in managing it. That research found that while the total amount of nitrogen excreted in urine per day can be similar between individual cows, there is large natural variation between cows in urination frequency and volume per “urination event”. This provides an opportunity to identify cows that excrete lower amounts of nitrogen per urination event and therefore present a lower risk to the environment.
While various other sensor technologies have been trialled on cows, acoustic sensors offer unique advantages. For example, the acoustic technology provides the ability to detect the vocalisation of cows, which provides information on the welfare and state of the animal.
“There is more work to do to refine these acoustic models we are using, and in particular to investigate the role of the environment on animal behaviour,” Shorten says.
“But we’re making progress towards proving this is a viable technology that could be available to use on-farm and could contribute to tools available to farmers.”