PERFORMANCE AND PROFILES OF MILK FATTY-ACIDS OF COWS FED FULL-FAT, HEAT-TREATED SOYBEANS USING VARIOUS PROCESSING METHODS

Twenty-four multiparous Holstein cows (48 d in lactation) were used in an 8-wk trial employing a completely randomized block design to deter mine the effect of heat treatment of full fat soybeans on the fatty ac id composition of milk fat. Treatments consisted of a total mixed rati on supplemented with 1) ground raw, 2) extruded, 3) micronized, or 4) roasted soybeans included at 17.5% of the dry matter of the total mixe d ration. Dietary treatment had no effect on body weight, yields of mi lk or solids-corrected milk, fat percentage, or yield of milk fat or p rotein. Cows fed ground raw soybeans had a higher dry matter intake an d a higher percentage of protein in milk than those fed heat-treated s oybeans. The concentrations of saturated fatty acids from C-8:0 to C-1 6:0 were lower, and cis-Delta-9-C-18:1 tended to be higher, in the mil k fat of cows fed heat-treated soybeans than in the milk fat of cows f ed ground raw soybeans. The concentration of trans-Delta-11-C-18:1 was lowest for cows fed ground raw soybeans, intermediate for cows fed mi cronized and roasted soybeans, and highest for cows fed extruded soybe ans. Cows fed extruded soybeans had lower concentrations of C-18:2 and C-18:3 than did cows fed micronized or roasted soybeans; cows fed gro und raw soybeans had intermediate concentrations of C-18:2 and C-18:3.