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15/12/20 |   Research, Development and Innovation  Animal production

Researchers listen to cows in new method to assess thermal comfort

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Photo: Rafael Rocha

Rafael Rocha - Digital recorders are attached to halters and make accurate, non-invasive measurements of cattle behavior in the pastures

Digital recorders are attached to halters and make accurate, non-invasive measurements of cattle behavior in the pastures

  • Research has developed an unprecedented bioacoustics method to measure the respiratory rate (RR) of cattle in pastures.

  • The technique consists in attaching digital recorders to halters and assessing RR with the help of open software.

  • The analysis is accurate, non-invasive and dispenses with human interference.

  • Thermal comfort is fundamental to increase cattle production performance.

  • It can directly help animal assessment in ICLF systems define shading and herd management.

  • The new methodology gained international recognition as it was considered one of the top ten works at the Temple Grandin Animal Welfare Workshop.

Losses in productivity due to animals being exposed to high temperatures and humidity may not be as silent as they appear. And research by Embrapa Rondônia entailed literally listening to cows, as it used bioacoustics, that is, the sounds emitted by the animals, to measure respiratory rate (RR). The team of scientists validated a new method to assess such parameter of thermal comfort, which uses digital recorders attached to the animals' halters to measure the behavior of grazing cattle in a practical, accurate and non-invasive way.

The work, in partnership with the Federal University of Pelotas (UFPel) and the Federal University of Rondônia (Unir), is supported by open software for the analyses: it allows obtaining acoustic data for a period of up to 48 hours and without human interference. The methodology was validated for the Girolando dairy herd - a cross between the Dutch Friesian and Gyr breeds -, both for heifers and lactating cows.

According to UFPel professor Eduardo Schmitt, this is a methodology that can become a strong ally in the assessment of systems like Integrated Crop-Livestock-Forestry Systems (ICLFS) as it makes it possible to identify the level of comfort to which animals are subjected. By listening to the animals' breathing, it is possible to know if they are spending more energy with heat dissipation mechanisms and, later, correlate this information with performance. "In a practical view, this measure can assist in research that helps to define, for example, how many square meters of shade should be offered so that animals produce more, how that shade should be outlined in the pasture, among other factors," Schmitt states.

The professor explains that when bovines are exposed to high temperatures, they need to activate mechanisms for heat dissipation like increasing blood circulation in the skin, sweat and respiratory rate. All of this represents an energy cost for the animal, which leads to decreased productivity, increased susceptibility to diseases, which can also result in interferences in fertility. “To assess losses and whether we need to interfere to improve the animals' environmental conditions, the assessment of the respiratory rate of cows can say a lot,” Schmitt adds.

 

Method brings innovation to the measurement of animal comfort

Respiratory rate has been used for decades as an indicator of heat stress in animals, a factor that directly influences the herd's production and reproduction. But the difficulty has always been to keep monitoring throughout the day, since the traditional (visual) method consists in observing the animals by counting their flank movements. The visual assessment has a few limitations, such as the difficulty in doing it at night or in extensive pasture areas with the presence of obstacles (e.g. trees). There is also the possibility of interference from observers during the assessment period.

Classification of heat stress in light of bovine respiratory rate (RR)

Heat Stress Level Respiratory Rate (movements/ minute)*
Low 40-60
Medium 60-80
High 80-120
Severe >120

 

*Recorded by visual observation of flank movements. Source: Silanikove (2013) (DOI: 10.1016/S0301--6226(00)00162-7).

Bioacoustics has also been used to characterize cattle behavior, as a measure of grazing time, rumination, rest and water intake. But this is the first time that the methodology has been validated to measure respiratory rate. According to Embrapa Rondônia researcher Ana Karina Salman, it is a valuable tool for researchers who study the effect of heat stress on cattle grazing. “We have successfully validated a new and unprecedented method, in which the respiratory rate is measured from the audio files of animals captured by MP3 recorders, and that is very practical and simple to use. The acoustic method can replace the conventional flank movement count by visual observation ”, says Salman.

 

Innovation in the method earns international recognition

The novelty of the methodology has made it gain national and international prominence. The study was published in the journal Livestock Science in September 2020 and it was one of the top ten selected works at the Temple Grandin Animal Welfare Workshop, held in 2018, in São Paulo, which gathered renowned experts in the topic, researchers, scholars, farmers and private sector. The findings were part of the dissertation by the animal scientist Giovanna de Carvalho, presented in July 2019 at UNIR's Postgraduate Program in Regional Development and Environment.

The researcher explains that in order to assess the thermal comfort of the animals, it is necessary to simultaneously monitor environmental parameters, such as temperature and relative humidity, and physiological parameters like body temperature and respiratory rate. According to her, there are few studies on bovine physiological response to heat stress and with unreliable results, given the difficulty of continuous visual monitoring throughout the day. Other methods were developed to automatically measure respiratory rate, but they were restricted to animals in stables and with equipment that requires an internet connection, that is, they were not suitable for animals on pasture or in places without internet access.

Another interesting point is that for the Girolando breed, which is responsible for approximately 80% of the milk produced in Brazil, there is still no scientific definition of their thermoneutrality zone, that is, the room temperature range in which the cattle are in thermal comfort. This scenario demonstrates the need for more studies and data so that researchers, technicians and farmers, based on more accurate indicators, can make decisions in their properties about which measures to adopt and how to minimize heat stress in the production system, making it more efficient.  

 

How the new methodology works 

Collecting audio or acoustic data used to measure respiratory rate requires an MP3 recorder, halters, TNT fabric, PVC film and packaging tape. The most expensive item on this list is the recorder, which costs, on average, R$ 450.00 on retail without shipping. The audio analysis is performed with the aid of Audacity, an open (free)software that reproduces the audio files captured by the recorders. The software generates oscillograms from the audio files that are specific to every activity performed by the animals, making it possible to identify when os tempos de início e fim de cada uma. each starts and ends. Embrapa Rondônia has made a manual for bioacoustic data colletion and analysis for the characterization of grazing cattle behavior available for free. 

Watch a video of the process, step by step:

 

The analysis of audio data (identification and count of breathing sounds) is laborious and requires a trained person. Animal scientist Giovanna de Carvalho, who performed the analysis of respiratory rates (RR) in the study, explains that the same technique described in the bioacoustic manual is used. The difference is that the RR required further depth, as it occurs during the entire assessment, whether the animal is eating or not, which can cause the sounds to overlap. 

Breath count with Audacity

In 15 seconds: 16 breaths
In 60 seconds: 16 x4 = 64 breaths/minute

 

Thus, the mere visual analysis of the sound waves generated by the program is not enough. “A headset is essential for the analysis, as well as a dose of patience and not being afraid to redo the analysis or ask for a second opinion, as there may be doubts about the sounds throughout the process”, Giovanna recommends.

Due to the characteristic pattern of breathing sounds, it should be possible, in the future, to develop an artificial intelligence algorithm that allows the automation of this step of the methodology. In addition, this method is not recommended for a herd formed by animals with aggressive temperament, as they can damage the recorders, or for studies that require assessing RR for over 48 hours, due to the battery life of the recorders.

Watch the video that demonstrates how to analyze the audio files to assess respiratory rates:

 

 

Renata Silva (MTb 12361/MG)
Embrapa Rondônia

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Mariana Medeiros (Translation - English)
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