Ingestive behaviour of grazing ruminants: meta-analysis of the components of bite mass

Bite mass (BM) is the main parameter determining intake, production level and efficiency for grazing ruminants. Various data have been published concerning BM and its components bite diameter, bite area, bite depth and bite volume (BDiam, BA, BD and BV). However, it was not yet possible to have a clear quantitative view of the relationships between BM and its related components. The sward factors and animal traits influencing BM have only partially been studied previously. To progress on this topic, we performed a meta-analysis of a large set of 96 publications (776 treatments). Bite volume is closely linked with BM, and when linear components of BV are considered, BDiamis much more determining than BD. Among the sward characteristics, sward height (SH) is a key factor of BM through its strong and almost linear influence on BD and BV. On this aspect, SH is more determining than herbage mass/ha. Herbage bulk density (HBD) is also an influencing factor, notably at low HBD, which induces an adaptive behaviour consisting of increasing BDiam and BA. A significant interaction was observed between SH and HBD in determining BM;for low values of SH, the positive influence of HBD on BM was distinct. The measured parameters were diversely scaled with BW. For BM, the power coefficient was 1, while it was 0.346 for incisor arcade (IA) and of 0.20 for bite depth. Incisor arcade is an accurate determining factor for BM via BDiam and BA. Analysis of the various factors of variation in bite mass and its components studied in the literature facilitates our understanding of the adaptive strategies of the animals.