Review: Precision Livestock Farming technologies in pasture-based livestock systems

Material and methods

Screening

An extensive literature screening, as shown in Fig. 1, was performed to evaluate the state of the art application of PLF in pasture-based farming systems. The search was conducted on Google Scholar and Scopus databases, without any limits on the date, country, or climate.
Three consecutive approaches were used to carry out the screening process:

1. 
   use of combined keywords, such as ‘‘PLF” AND parameter ofinterest (e.g., temperature, BW, virtual fencing, etc.) AND ‘‘extensive” OR ‘‘grazing” OR ‘‘pasture”;
   
2. 
   use of the specific PLF technology as keyword (e.g., Globalpositioning system (GPS), accelerometer, etc.) AND the animal species (‘‘cattle,” ‘‘bovine,” ‘‘sheep,” ‘‘goat,” ‘‘beef,” ‘‘dairy,” ‘‘pig,” ‘‘swine,” ‘‘Sus scrofa,” ‘‘chicken,” ‘‘poultry”);
   
3. 
   examination of the references reported both in the reviewson PLF and in the articles selected in steps (i) and (ii). This third screening phase was carried out to check whether additional articles were considered suitable for the chosen topic.
   

Selection

After the screening phase, articles were grouped according to the technologies used and the objective of each PLF application (e.g., GPS for location, tracking, or behavioural studies; accelerometers for health monitoring, oestrus detection, etc.). This grouping established the main structure of the present work, as described in Section 3.
Among the articles resulting from the screening phase, an initial selection was performed by examining every Material and Methods section. This phase was mainly aimed at ensuring that the PLF technologies reported were actually applied in pasture-based systems, and the devices were tested under field conditions. Then, the remaining articles were examined in greater depth to identify the ones most representative of each selected technology. Since the objective of the present work was to perform a focused literature review, a further and final selection step was carried out using the publication year as the preferential criterion to choose the most recent studies between similar ones, especially for those technologies that are more widespread, such as GPS.
A summary of the articles selected for the type of device and animal species is presented in Table 1.
Precision Livestock Farming applications in pasture-based systems
The applications of PLF in pasture-based systems were reviewed, considering both precommercial research technologies and commercial solutions. PLF technologies were organised according to the aim for which they were used and the parameters they assessed. Some are already used in intensive livestock systems but have also been applied in pasture-based systems, while others are specifically thought to address specific issues related to pasture-based systems. The variable development stages were also noted. Some devices developed for scientific research were also reported because of their indirect contribution to outlining novel management practices with effective applications in rangelands.