Prospects of Rare-Earth Elements in Ruminant Production

The use of rare-earth elements (REE) has nowadays become critical due to their wider applications in numerous modern technologies. It has been effectively incorporated as an additive both in fertilizers and animal feeds from past centuries, especially in China. However, its usage outside China as a zoo-technical feed additive in livestock has been largely limited. Recently, myriads of health and production benefits specifically in non-ruminants have been observed with REE as a viable antibiotic-free growth promoter. Despite the limited studies available for ruminants, few beneficial effects such as improved gain in body weight of calves, enhanced fiber digestibility, and rumen fermentation characteristics have been reported in them. These might prompt further explorations of REE mixtures as feed additives in ruminants. Lastly, on the flip side, due to enhanced usage, REE are also now being recognized as emerging contaminants with implications on human and environmental health. This chapter introduces REE in animal nutrition and presents their prospects for ruminant production.