A Study On Approprioate Supplementary Level Of Zhongda Rumen By-pass Fat In The Diet Of Lactating Cows

The research contained three parts with the focus on the appropriate dosage of rumenbypass fat added to the diets of cows in early lactation. The effect of different dosage ofrumen bypass fat on the rumen fermentation in cows were studied using in vitro fermentationtests and modified nylon bag technique in Experiment One and Two respectively. Experiment3was focused on the effect of different dosage of rumen bypass fat on the productionperformance and blood biochemical indicators of cows in early lactation.Experiment one: the effect of rumen bypass fat on in vitro fermentationIn vitro fermentation tests were conducted. Two cows in early lactation with permanentrumen fistula were chosen as donors of rumen fluid. The effect of rumen bypass fat on in vitrofermentation was studied. Alfalfa was used as fermentation substrate. Six treatments weredivided according to the different dose of rumen bypass fat administration(2%、3%、4%、5%、6%of rumen bypass fat administration). Each treatment was quadruplicated. The resultsrevealed that less than3%rumen bypass fat administration did not cause adverse effects onrumen fermentation in cows when the data of the pH of rumen fluid, concentration ofammonia and volatile fatty acids, and gas production were compared.Experiment two: the effect of rumen bypass fat on the degradation rate of feed usingmodified nylon bag techniqueFour Holstein cows with similar production performance that were pre-fitted withpermanent rumen fistula were chosen as the experimental animal in this experiment. Theeffect of rumen bypass fat on the degradation rate of feed were studied using modified nylonbag technique Basal ration containing0g,300g,600g,900g fat were to feed each cows daily(Treament A, Treament B, Treament C, Treament D respectively). Degradation rate of theconcentrate18h in rumen and forage24h in rumen were recorded on the20day of formalexperiment. The results showed degradation rate of feed was not affected in the cow that wasadministrated with600g/day bypass fat. The cow that was administrated with900g bypass fateveryday showed normal degradation of feed, however, rumen fermentation of this cow wasaffected. Experiment three: the effect of different dosage of rumen bypass fat on the productionperformance and blood biochemical indicators of cows.80cows with similar conditions were evenly divided into four groups.200g,400g,600gbypass fat were added to the basal ration and feed20cows in the three groups. Basal rationwere to feed cows in the control group. Cows in the test group and control group were feedtwice and milk three times a day. Cows were pre-feed7days ad libitum with concentratedfeed mixed with bypass fat and this experiment lasted for24days. The result revealed milkproduction was significantly improved in the cows that were feed400g/day bypass fat. Milkfat percentage was improved by adding bypass fat. The content of milk protein and lactoseshows no difference among the four groups. NEFA levels in plasma were reduced and theconcentration of calcium in plasma rose by adding bypass fat. The total cholesterol was notaffected in the four groups. In addition, insulin levels were improved in the initial stage offeeding.