Effects Of Linseed And Cottonseed On Milk Quality In Lactating Dairy Cows

Conjugated linoleic acid (CLA) has attaracted people much interests in view of its many potential benefits in the animal nutrition in recent years.Ruminant fats are the major source of CLA, it is derived from two sources that are biohydrogenation of dietary polyunsaturated fatty acids (PUFA) by microorganisms in the rumen and endogenous synthesis in the mammary gland (or fat tissues) by △ 9dehydrogenation enzyme. Supplemention of whole oilseeds containing enrichment C18:2 and C18:3 fatty acids in ruminant diet can also increase CLA content in milk fat and meat. Many experiments indicate that fat content of ruminant diet can't be beyond 8%, otherwise which can effect on rumen fermentation and subsequently lead to reduction of NDF digestibility etc .The thesis study that the effect of different doses of cottonseed , linseed and supplemention of their mixture up diet fat proportion to 4% ,6% and 8% respectively, on fermintation parameters in invitro experiment and found 6% of cottonseed and linseed's mixture is the most best treatment according to all parameters, furthermore study the effect of treatment on milk yield, milk fat, milk protein and CLA content in milk etc. by feeding experiment, the result indicate that: 1. In vitro experiment, the supplemention of cottonseed up diet fat proportion to 4%-8% can increase BCP content and reduce A:P ratio (P<0.05), there is a decreasing tendency of infusorians' numbers, and the infusorians' numbers in 8% cottonseed treatment are decreased significantly (P<0.05); there is a increasing tendency of acetate,propionate,butyrate,total VFA,DM and NDF digestibility of all cottonseed treatment, but the difference is not significant (P>0.05); the effect on pH and NH3-N have not evident rules; 2. In vitro experiment, the supplemention of linseed up diet fat proportion to 4%-8% can increase BCP content and reduce A:P ratio (P<0.05), there is a tendency of increasing acetate,propionate,butyrate,total VFA,DM and NDF digestibility and decreasing infusorians numbers of all cottonseed treatment, but the difference is not significant (P>0.05); there is a increasing tendency of pH and NH3-N concentration; 3. In vitro experiment, the supplemention of cottonseed and linseed mixture up diet fat proportion to 4%～8% can increase BCP concentration and reduce A:P ratio (P<0.05); there is a tendency of decreasing infusorians' numbers, and the infusorians' numbers in 8% mixture treatment are decreased significantly (P<0.05); there is a increasing tendency of pH, NH3-N, acetate, propionate, butyrate, total VFA, DM and NDF digestibility of all mixture treatments, but the difference is not significant (P>0.05); 4 Supplemention of their mixture up diet fat proportion to 6% can increase milk yield, milk fat, milk protein, CLA content in milk, in addition, there is a alteration in milk fatty acid composition characterized as an increase in long chain PUFA and decrease short chain fatty acid, but the difference is not all significant (P>0.05).