Effects Of Rare Earth Elements Lanthanum, Cerium,praseodymium On Rumen Fermentation, Nutrient Digestion And Plasma Biochemical Parameters Of Beef Cattle

The objectives of the thesis was to study the effects of REE LaCl3, CeCl3, PrCl3on CH4and VFA production in vitro and rumen fermentation, nutrient digestion, CH4production, N balance and plasma biochemical parameters in beef cattle.Experiment1.The objectives of the trial were to study the combination effects of REE La, Ce, Pr on CH4, total gas, VFA production using feed mixtures as substrates.Three levels of LaCl3, CeCl3, PrCl3, i.e.0,0.40,0.80mmol/kg DM were allocated in a three-factor3x3x3randomized design. The results showed that supplementing LaCl3group or CeCl3group decreased CH4production (P<0.05), increased molar ratio of propionate (P<0.05), decreased the molar ratio of acetate to propionate (P>0.05) and CH4/TVFA (P<0.05),whereas did not affect total gas production, CO2production and TVFA production. Supplementing PrCl3group did not affect CH4, CO2, total gas and VFA production. There were no interaction effects between LaCl3, CeCl3, PrCl3on CH4production, CO2and total gas production. There were interaction effects between LaCl3, CeCl3, PrCl3on TVFA, acetate, propionate and ratio of acetate to propionate.Experiment2. The objectives of the trial were to investigate the effects of supplementing REE Ce on rumen fermentation, nutrient digestibility, CH4production, N balance and plasma biochemical parameters in beef cattle. Four Simmental male cattle, aged at14months, with initial liveweight of355±8kg and fitted with permanent rumen cannulas, were used as experimental animals. The cattle were fed with a total mixed ration composed of concentrate mixture and corn silage. Four levels of cerium chloride (CeCl3·7H2O, purity99.9%), i.e.0,80,160and240mg CeCl3/kg DM, were added to basal ration in a4×4Latin square design. Each experimental period lasted15days, of which the first12days were for pre-treatment and the last3days were for sampling. The results showed that supplementing CeCl3at160or240mg/kg DM increased NDF digestibility (P<0.05) and tended to increased ADF digestibility (P=0.083). Supplementing CeCl3at160or240mg/kg DM decreased the molar ratio of rumen acetate to propionate (P<0.05) and decreased total N excretion, urinary N excretion and increased N retention (P<0.05), increased excretion of total urinary PD (P<0.05) and decreased CH4/kg DMI (P<0.05). In conclusion, supplementing CeCl3at160or240mg/kg DM in the ration of beef cattle increased the digestibility of NDF, decreased the molar ratio of rumen acetate to propionate, increased N retention and microbial N flow and decreased CH4/kg DMI. Supplementing CeCl3at240mg/kg DM increased plasma concentration of albumin.Experiment3. The objectives of the trial were to compare the effects of dietary supplementation of LaCl3, CeCl3and PrCl3on rumen fermentation, nutrient digestion, N balance and plasma biochemical parameters in beef cattle. Four12month-Simmental male cattle, with initial average liveweight of333±9kg and fitted with rumen cannulas, were fed with a basal ration composed of concentrate mixture and maize silage. Three treatments, i.e. supplementing204mg LaCl3/kg DM,204mg CeCl3/kg DM or204mg PrCl3/kg DM to the basal ration and the control (basal ration without REE) were allocated in a4x4Latin square design. The purity of LaCl3, CeCl3or PrCl3was99.9%. Each experimental period lasted15 d, consisting of12d for pre-treatment and3subsequent days for sampling rumen fluid, faeces, urine, blood and gas exhaled from the cattle and the samples were analysed for related parameters. Results showed that supplementing204mg LaCl3/kg DM,204mg CeCl3/kg DM or204mg PrCl3/kg DM tended to increase NDF digestibility (P=0.064) and tended to decrease rumen CH4production (P=0.056). Supplementing204mg LaCl3/kg DM and204mg CeCl3/kg DM decreased total N excretion and urinary N excretion, increased N retention (P<0.05), tended to increase total PD (P=0.053) and microbial N flow (P=0.095) whereas supplementing204mg PrCl3/kg DM did not affect N retention, urinary PD and microbial N flow(P>0.05). No differences were found in nutrient digestibility, CH4production and plasma biochemical parameters among treatments of LaCl3, CeCl3and PrCl3.In summary, under the conditions of the present trial, supplementing LaCl3groups or CeCl3groups decrease CH4production and increase the molar ratio of acetate to propionate in vitro. Supplementing160mg or240mg CeCl3/kg DM or supplementing204mg LaCl3,204mg CeCl3/kg DM increase NDF digestibility, N retention and microbial N flow and decrease CH4production in beef cattle.