Effects Of N-hydroxymethyl Methionine Calcium On Rumen Fermentation, Performances And Serum Biochemical Parameters Of Lactating Dairy Cows

The experiment was to determine the effect of N-hydroxymethyl methionine calcium (N-HMM-Ca) supplementation levels on rumen fermentation, productivity and serum biochemical indexes of lactating dairy cows.30 lactating Holstein dairy cows were blocked according parity, milk yield and lactation stage, and randomly assigned to 5 supplementation levels of N-HMM-Ca [0%(control),0.15%,0.30%,0.75%,1.50% of the diet(on DM basis)]. The experiment was continued up to 56 d, including 14 d of adaptation period and 42d of experimental period. The results were showed as follows.1. Effects of variety dosages of N-HMM-Ca supplementation on rumen parameters and bacterial abundance of dairy cows. The results indicated that, rumen pH value, Volatile Fatty Acid (VFA) and rumen microbial protein (MCP) concentration were not affected by treatments. NH3-N concentration declined linearly with N-HMM-Ca addition, TVFA production tended to increase and was greater in 0.75% level (P< 0.05). Furthermore, dietary N-HMM-Ca had positive impact on the abundance of R.amylophilus, P.brevie and B.fibrisolvens, and significantly increased in 1.50% level; and the relative abundances of F.succinogenes, R.flavefaciens, R.albus were increased in 0.15% supplementation, however, the abundance of P.ruminicola was declined.2. Effects of variety dosages of N-HMM-Ca supplementation on production performance and nutrition digestibility of dairy cows. The results showed as follows:1) Daily supplementation of 0.15% and 0.30% N-HMM-Ca in dairy cows increased DMI significantly (P < 0.001), while there was decreased on 0.75% and 1.50% levels (P< 0.001).2) There was no effect on the milk total solids percentage. Milk yield were increased in 0.15% level (P< 0.05), and supplemented 0.15-0.75% N-HMM-Ca also had positive effect on the milk lactose and milk protein percentage (P< 0.05); however, milk lactose and milk fat percentage were decreased in 1.50% group (P< 0.05); milk urea nitrogen concentration was decreased with the supplementation of N-HMM-Ca, and 1.50% group was the lowest (P< 0.05).3) The digestibility of CP、EE were no difference between control and treatment groups; dietary ADF and NDF digestibility increased with supplementation levels of N-HMM-Ca, respectively, except the 0.75% dosage (P< 0.01).3) There were no effect on the urine pH value and UN concentration (P>0.05).3. Effects of graded levels of N-HMM-Ca on serum biochemical indexes of dairy cows. The results showed as follows.1) Supplemented 0.75% dosage of N-HMM-Ca on the diet improved the serum ALT and AST concentrations.2) Blood urea nitrogen (BUN) concentration decreased linearly with increasing N-HMM-Ca levels, among which 1.50% group was the lowest. On the 14th day of experimental period, after supplemented 1.50% N-HMM-Ca the serum creatinine (CRE) content was significantly declined, meanwhile, triglyceride (TG) concentration was increased (P< 0.01). Serum urine acid (UA) concentration in 0.75% treatment was significantly increased, especially on the 42th day (P< 0.01); serum high-density lipoprotein (HDL) and β-hydroxybutyricacid (β-OHB) concentration were increased with N-HMM-Ca supplementation, nevertheless, serum non-esterified fatty acid (NEFA) was decreased linear.3) Serum IgA concentration was increased in 0.15%-0.30% groups, and significantly on the 42th day.4) Serum T4 concentration was tended to be improved in 0.15% level; and serum T3 concentration was significantly increased in 1.50% level on the 14th day (P< 0.01). Insulin (INS) concentration was significantly increased in 1.50% level, especially on the 14th and 28th days (P< 0.01); whereas serum parathyroid gland (PTH) concentration was significantly declined in 1.50% level (P< 0.01).5) on the 28th day, serum catalase (CAT) concentration was significant higher in 0.15% and 0.30% level than other treatments (P< 0.01).6) There were positive effect on the Glu, Met, Cys and Tyr concentrations with the N-HMM-Ca addition, and significantly in 0.30% level (P< 0.05); moreover, the Ser, Val, Lys and total free amino acid (TFAA) were increased in 0.15% and 0.30% level, significantly (P< 0.05); the serum Leu concentration trended to increase with 0.15-0.75% addition (P< 0.01); in addition, supplemented 0.15% N-HMM-Ca improved the serum Leu and Arg concentrations significantly (P< 0.05).Conclusion:the experiment indicated that 0.15% N-HMM-Ca supplementation in the diet is beneficial to improve the performance, nutrient digestibility and health of dairy cows; the most favorable level for improve the rumen performance is 0.75%; While 1.50% level is most effective dosage to the abundance of proteolytic bacteria.