Effect of Introduction of Urea on Feeding Behavior of Holstein Heifers

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Abstract
Effects of introduction of urea upon feeding behavior were studied in dairy heifers that never had been exposed to urea. Dairy heifers (12, 158 .+-. 40 kg) exhibited no significant aversion or preference in 20 two-choice preference tests with tap water vs. tap water adulterated with urea (1-64 .times. 10-2 M). Ammonia intoxication was avoided by limiting liquid volumes offered so that urea intake would not exceed 0.35 g/kg body wt during the 30 min test period. In single stimulus preference tests with 5 pairs of heifers (156 .+-. 24 kg), animals fed urea vs. soy protein diet during the daily 6 h test period did not decrease consumption until day 3 of exposure. Heifers provided with urea diet spent as much time feeding, but the eating rate was decreased. They remained averse to the urea diet after eating a soy protein diet for 4 days. The decreased consumption of urea diets fed below toxic amounts apparently is not due to taste and/or odor but probably results from association of the flavor of urea diets with a malaise produced by ammonia.