Blood Fatty Acids and Glycerol Response to Diet and Norepinephrine

Twelve mid-lactating Holstein cows divided equally into two groups were given either a normal diet or restrictedroughage high grain diet.During the 5th week, blood plasma glycerol and free fatty acids response of each group to 3.75 milligrams L-norepinephrine or saline were compared at 0, 10, 20, 30, and 40 minutes after intravenous injection.Mean control (saline) values (micromolar) for cows fed normal and restricted-roughage high grain diets were glycerol, 95 and 102 and free fatty acids, 394 and 467.Following norepinephrine injection, mean values (micromolar) for cows were glycerol, 112 and 127 and free fatty acids, 507 and 523.Glycerol response to norepinephrine was greater and free fatty acids apparently lower in cows fed restricted-roughage high grain diets than cows fed a normal diet.Diet appeared to alter capacity of adipose tissue to respond to norepinephrine.Feeding the restricted roughage-high grain depressed milk fat from 3.8 to 2.65 without affecting milk production.