Effect of Dietary Supplementation of Soybean Oil on Concentration of Conjugated Linoleic Acid in Milk Fat of Holstein Cows

• Main Authors: Po-An Yang, 楊博安
• Other Authors: Der-Fang Jan
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/66324227597058672536

碩士 === 國立中興大學 === 畜產學系 === 92 === The purpose of the study was to investigate the effect of dietary supplementation of soybean oil on the concentration of conjugated linoleic acid (CLA) in milk fat as well as on the plasma and ruminal characteristics of Holstein cows. The study included two trials. In trial 1, twelve lactating Holstein cows were randomly allotted into three dietary treatments, i.e., 0% (control), 2.0% (SO2), and 4.0% (SO4) soybean oil supplemented diets. The treatments were arranged in a 3×3 Latin square design with three periods of 21-d each. For each period, cows were allowed to adapt to the treatment diets for 2 weeks followed with a collection time for one week. The results indicated that the milk yield had no significant differences among the treatments. Both percentage of milk fat and 4% FCM were lowered for cows in SO4 (P < 0.05). Percentage of milk protein was lowered for cows in SO2 (P < 0.05). The concentration of CLA in milk fat of cows in SO4 was 1.58%, which was higher (P < 0.05) than those of the cows in control (0.58%) and in SO2 (0.92%). Cows in SO4 had higher (P < 0.05) concentration of C8:0, C10:0, C12:0, C14:0, and C16:0 fatty acids and lower (P < 0.05) concentration of C18:0, C18:1, and C18:2 fatty acids in milk fat than those in the other treatments. The concentration of blood urea nitrogen was not significantly different among the treatments. The concentration of blood cholesterol of the cows in SO4 was higher than those in the other treatments (P < 0.05). In trial 2, three non-lactating ruminally cannulated Holstein cows were randomly assigned into the same three dietary treatments as those in trial 2. Ruminal fluid was sampled for the last three days of each experimental period to analyze the pH and concentrations of ammonia nitrogen and volatile fatty acids. The results indicated that ruminal pH as well as the concentrations of ammonia nitrogen, acetate molar percentage and total volatile fatty acids had no significant differences among the treatments. Cows in SO4 had higher molar percentage of propionate (P < 0.05) and lower ratio of acetate:propionate than those in the other treatments (P < 0.05). It was therefore concluded that diets supplemented with soybean oil rich in C18:2 fed to cows significantly increased concentration of CLA in their milk fat. In comparisons with diets supplemented with none or 2% soybean oil, cows fed diets supplemented with 4% soybean oil had higher concentration of CLA in their milk fat.