Changing Meal Patterns and Suppression of Feed Intake with Increasing Amounts of Dietary Nonprotein Nitrogen in Ruminants

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Abstract
Goats were injected intraruminally during spontaneous meals with ammonium chloride, urea, ammonium lactate, or sodium lactate arranged in a Latin square experimental design randomized for order of treatments. Urea and ammonium injections shortened meal length by 20-30%. Rate of eating and meal frequency were reduced. Sodium lactate injections reduced meal size. In cows, meal length and meal size also were measured. Grain concentrate, corn silage and chopped hay were fed as complete mixed rations. In the concentrates 58% of the N was either from soybean meal or urea. Length of the 1st meal after feeding was reduced from 24.3 min with soybean meal to 12.4 with urea. Meal size was reduced from 3.2-1.8 kg when urea was fed. Total feed intake was similar, 12.0 kg/day (soybean meal) and 11.6 kg/day (urea) since spontaneous meal number and size were 17 and .30 kg for soybean meal but increased to 23 and .36 kg for urea. The physiological basis for the limit on meal length with urea rations is unknown but is an important factor in successful feeding of urea when eating time is limited for cows.