Pre-calving energy density and rumen protected lysine impacted blood metabolites and biomarkers of liver functions in dairy cows during the transition period.

Dairy cows usually face negative energy balance and disorders of normal organ function due to a mismatch between energy intake and energy demand. Negative energy balance directly affects liver function and blood metabolites because the liver is used as source of energy supply and a center of metabolic activity. This study was aimed to determine the effect of pre-calving energy density and rumen-protected lysine on blood metabolites and biomarkers of liver functions in the dairy cows during the transition period. Forty 3rd lactation Holstein cows going to enter their 4th lactation were randomly allocated to one of the four dietary treatments (high energy with rumen-protected lysine (HERPL) = 1.53NEL plus 40 g Lys, high energy without lysine (HECK) = 1.53NEL, low energy with rumen-protected lysine (LERPL) = 1.37NEL plus 40 g Lys, and low energy without lysine (LECK) = 1.37NEL arranged in a 2 × 2 factorial design. Blood samples were collected during the transition period, and concentrations of blood metabolites and biomarkers of liver function were measured. Interaction between pre-calving high-energy diet and rumen-protected lysine tended to increase plasma albumin, numerically increased glucose, decreased triglyceride, total bilirubin, and aspartate aminotransferase concentrations. The result revealed that pre-calving high-energy density increased insulin, albumin and decreased blood urea nitrogen and total bilirubin concentrations and substantial favor liver functions during the transition period.

Screening and characterization of lipase from a metagenome library of dairy rumen microflora / 生物工程学报

Using lipase segregation agar containing trioleoylglycerol, we obtained 18 lipase positive clones by screening from a metagenome library of dairy rumen microflora containing 15,360 clones. The average insert size of lipase positive clones was about 60 kb. Lipase enzyme activity analysis by p-NPP method indicated that Lipase6, Lipase7 and Lipase8 had higher lipolytic activities to substrates of p-nitrophenyl palmitate (C16), p-nitrophenyl alaurate (C12) and p-nitrophenyl palmitate (C16) respectively. The optimum pH of Lipase 6, Lipase 7 and Lipase 8 were 7.5. The halflife period of Lipase 8 with the value of 15 min in 70 degrees C decreased with the increase of temperature. In conclusion, the lipases screened in this study had different substrates specificity and good thermo stability, which laid a basis for large-scale industrial application.