Table 3.

Literature summary of effect of REE supplementation in ruminants

Dose	Results and conclusions	Reference
REE-citrate at 100, 200, and 300 mg/kg DM (having Ce 57.9%, La 34.0%, and Pr 6.5%) in the diet of fattening bulls.	Non-significant effect in feed-to-gain ratio, ME-to-gain ratio and digestibility of nutrients due supplementation of REE	Schwabe et al [7]
REE-citrate at 100, 200, and 300 mg/kg DM (having Ce 57.9%, La 34.0%, and Pr 6.5%) in the diet of fattening bulls.	Significantly linear increase the concentrations of REE (lanthanum [La], cerium [Ce], and praseodymium [Pr]) in the liver, kidneys and rib bone While, the concentration in muscle was not influenced Risk to humans from consuming of edible tissue of REE supplemented animals can be regarded as negligible	Schwabe et al [19]
REE-citrate (Ce 56.8%, La 35.0%, and Pr 6.5%) at 100, 200, and 300 mg/kg DM in diet of sheep	Significantly decrease in ruminal pH Quadratically decreased in ruminal ammonia content with increasing REE supplementation Other ruminal parameters like total volatile fatty acids concentration and acetate to propionate ratio were also affected by REE supplementation Negative effect on growth of several rumen bacteria Digestibility of various nutrients and urinary excretion of purine derivatives were also increased with increasing REE addition	Xun et al [53]
LaCl3, CeCl3, or PrCl3 at 204 mg/kg DM to the basal ration of beef cattle	Linear increase in NDF digestibility and reduced enteric CH4 emissions Significant decreased in total N excretion and urinary N excretion, increased N retention Total urinary PD were linearly increase Non-significant effect in N retention, urinary PD, microbial N flow and plasma biochemical parameters	Lin et al [54]
Cerium chloride (CeCl3) at 0, 80, 160, and 240 mg/kg DM in beef cattle	Significant increase in NDF digestibility and N retention Significantly decreased the molar ratio of rumen acetate to propionate, total N excretion, urinary N excretion and CH4/kg DMI	Lin et al [55]
Lanthanum oxide at 100, 200, and 300 mg/kg in the diet of sheep	Significant improvement in daily weight gain and total weight gain Non-significant effect on AST, ALT, cholesterol, urea, total protein, albumin, and globulin	Adu et al [56]
In-vitro addition of REE chloride mixture (LaCl3 380 mg/kg; CeCl3 521 mg/kg, PrCl3 30 mg/kg and chlorides of other REE 69 mg/kg) at 400 and 800 mg/kg	No effect on ruminal VFA concentration Impact on VFA profile was marginal Linear increase in ruminal true digestibilities of organic acid, acid detergent fibre and crude protein with increasing REE supplementation	Yang et al [34]

REE, rare earth elements; ME, metabolizable energy; NDF, neutral detergent fiber; PD, purine derivatives; DMI, day matter intake; AST, aspartate amino transferase; ALT, alanine amino transverse; VFA, volatile fatty acid.