EFFECT OF ADDED DIETARY-FAT ON PERFORMANCE, RUMEN CHARACTERISTICS, AND PLASMA METABOLITES OF MIDLACTATION DAIRY-COWS

Effects of supplemental Jet-Sploded(R) canola seed in the diets of dai ry cows on milk yield and composition and blood metabolite concentrati ons were investigated. Twenty multiparous and 5 primiparous midlactati on Holstein cows were assigned to treatments following a 3-wk covariat e period; cows were then on the treatments for 70 d. Ten of the cows h ad previously been fitted with rumen cannulas. Five concentrate mixtur es containing 0, 7.5, 15, 22, or 29% Jet-Sploded(R) canola seed (Simon s Feed Co., Quimby, IA) (equivalent to 0, 2.66, 5.33, 7.81, and 10.30% added fat, respectively) were formulated by substituting Jet-Sploded( R) canola seed for barley and canola meal. Diets consisted of 25% alfa lfa silage, 25% whole-crop oat silage, and 50% of one of the concentra te mixtures (dry matter basis). An increase in the amount of dietary f at from Jet-Sploded(R) canola seed did not influence feed intake, milk yield or composition, or milk component yields. The inclusion of Jet- Sploded(R) canola seed in the diet increased long-chain fatty acids an d inhibited de novo synthesis of medium-chain fatty acids in milk. Mea n total volatile fatty acids in the rumen and propionate concentration were reduced in a linear fashion by treatment. The inclusion of Jet-S ploded(R) canola seed in the diets of midlactation cows altered rumen and blood metabolite concentrations; however, these changes had minima l effects on yield responses with the exception of milk fatty acid com position and milk protein content.