Effect Of Urease Inhibitor On Production Performance, Blood Metabolism, Rumen Fermentation And Apparent Digestibility Of Nutrients In Lactation Holstein Dairy Cows

This study was aimed to determine the maximal safe dose of Urease Inhibitor(UI)as an additive in lactating cows. Effects of UI on production performance, bloodparameters, rumen fermentation parameters and nutrients apparent digestibility ofdairy cows were defined. Forty healthy Holstein cows with similar DIM (averageDIM=149d), milk yield (average milk yield=32kg/d) and parity (averageparity=1.2)were randomly divided into4groups(10cows/group). During the entireexperiment, cows in4groups(one control group and three treatment groups) were feda basal diet supplemented with0,45,225,450mg/kg UI respectively. After2-wk longadaptation period and2-wk long standardization period, the formal feeding was lastedfor6-wk. All cows were housed in free stall barn and received free access to waterand diet. Cows were milked3times daily(5:00,13:00,21:00) and fed3timesdaily(6:00,13:30,18:00) with total mixed ration(TMR).1Effects of Urease Inhibitor on production performance of dairy cowThere was no significant difference among treatment in milk yield (P>0.05).However, significant increae of dry matter intake was observed in45mg/kg and450mg/kg urease inhibitor feeding groups. Additionally,45mg/kg,225mg/kg and450mg/kg urease inhibitor increased4%-standard milk, energy-corrected milk, milkprotein yield, lactose yield and milk fat yield (P<0.01). Milk protein percentagelinearly increased, while the content of milk fat, lactose, total solids and somatic cellcount did not different compared with the control.2. Effects of urease inhibitors(UI) on blood biochemical indexes：The addition of225mg/kg and450mg/kg urease inhibitors in diets coulddecrease the triglycerides concentration in the blood (P <0.01) and at the same timeincrease the blood urea nitrogen concentration (P <0.05) linearly. There was nosignificant influence on other biochemical indexes.3. Effects of urease inhibitors(UI) on nutrients apparent digestibility The addition of225mg/kg and450mg/kg urease inhibitors in diets can improvethe digestibility of dry matter, crude protein, neutral detergent fiber, acid detergentfiber and the organic matter (P <0.05). With the increase of adding dose, digestibilityof dry matter, crude protein, neutral detergent fiber, acid detergent fiber and organicmatter had the tendency of linear increase, even not significantly.4. Effects of urease inhibitors(UI) on rumen fermentation parametersCompared with the control group, urease inhibitors has no effect on pH value,ammonia nitrogen, total volatile acid, acetic acid, propionic acid, butyric acid,pentanoic acid and ethylene propylene rati. Urease activity were no changedsignificantly among groups (P>0.05), even a trend of decrease along with theincrease of UI dosage was observed.