Short communication: Effects of dietary fat supplements and forage:concentrate ratio on feed intake, feeding, and chewing behavior of Holstein dairy cows

Feed intake and feeding behavior of dairy cows fed diets that varied in fat supplementation and forage:concentrate (F:C) ratio were investigated. Eight multiparous Holstein dairy cows were used in a replicated 4 × 4 Latin square experiment with 21-d periods. Treatments were 1) no supplemental fat and 34:66 F:C ratio; 2) 2% hydrogenated palm oil and 34:66 F:C ratio; 3) 2% yellow grease and 34:66 F:C ratio; and 4) 2% yellow grease and 45:55 F:C ratio. Cows were fed ad libitum twice daily as total mixed ration with free access to water. Dry matter intake (DMI) was not affected by fat supplementation regardless of fat source, whereas increased F:C ratio (from 34:66 to 45:55) lowered DMI by 7.5%. Meal interval, eating rate, and meal size were lower for cows fed yellow grease, and eating rate was less for cows fed the 45:55 F:C ratio diet. Chewing activity was not affected by fat supplementation, but was greater for cows fed the 45:55 F:C ratio diet. Results suggest that supplementation of 2% hydrogenated palm oil or 2% yellow grease had little effect on DMI and chewing behavior of Holstein dairy cows fed a 34:66 F:C ratio diet. The 2 fat sources can replace each other, depending on the availability or cost. Results also showed that DMI and chewing activity can be effectively manipulated by changing the F:C ratio of diet.