Method: eFeederRab: A new electronic feeder to measure individual feed intake−related traits on growing rabbits raised in collective cages

Measuring individual intake in animals raised in groups is a paramount aspect for different fields of animal production, both with a direct implication and relevance on the production itself, i.e. within breeding programmes for the improvement of feed efficiency; or for research in different disciplines such as animal behaviour or animal nutrition. The rabbit is one of the few species for which there is no device for measuring this trait. Thus, we aimed to design and manufacture a feeding device (eFeederRab) allowing such recording. In the present study, we describe the methods behind the tool we have developed, accompanying the description with a set of descriptive statistics showing the performance of the tool. We use records from 430 animals belonging to lines selected for different feed efficiency criteria − some of them raised using the eFeederRab -, as well as from their control unselected population. Measurements were taken from 35-38 to 56–59 days of age. The lines selected for reducing residual feed intake clearly show a lower daily feed intake, 8–15% when the lines were compared using eFeederRab, and 7–10% when the lines were compared using conventional feeders. These are clear indications about the validity of the device for recording data to be used in selection to improve feed efficiency, i.e., biologically meaningful records. In spite of the biological relevance of the recorded data, when comparing performances of the lines raised using eFeederRab or conventional feeders, it was evident that feed intake was reduced by around 12–20% when using the electronic feeder, with the subsequence growth penalization. Note however that this penalty is proportional to the intake; therefore, the feed conversion ratio remains fairly similar (2.99–3.13) between the two types of feeders also reflecting the expected tendency according to the different selection criteria across lines. We hypothesise that this reduction in the intake is a consequence of the less comfortable eating posture that eFeederRab imposes: each animal must eat alone and inside a tunnel for leading the animals one by one towards the feeder to grant their proper identification by radio frequency. We can conclude that although the eFeederRab is a device with different animal feeding conditions than those on conventional feeder, the records, despite being noisy, can be successfully used to improve the genetic selection of feed efficiency in rabbits.