The effect of differentintervals between observations on the estimation of the eating behavior of dairyheifers and lactating cows was evaluated. Twenty Holstein-zebu crossbred dairyheifers were distributed in a completely randomized design, with four levelsand five repetitions, fed isonitrogenous diets containing 71% sugar cane and29% concentrate. Also, 16 dairy crossbred cows were distributed in a completelyrandomized design, with four levels and four repetitions. They received isonitrogenousdiets, containing 85% sugar cane and 1% concentrate. For both heifers and lactatingcows, the sugar cane used was treated with doses of 0, 0.75, 1.5 and 2.25% CaO,and corrected with 1% of urea and ammonium sulfate mixture (9:1), at the momentof offering the diets. The experimental period was 21 days long, with observationsdone on the 19th and 20th days, during 24 hours, at intervalsof 5, 10, 15 and 20 minutes. For both heifers and cows, lower values were verifiedfor number of periods (nº/day) and higher values were obtained for averagetime spent per period of eating, rumination and idle activities, for 10-, 15-and 20-minute intervals. The mean dry matter and neutral detergent fiber withcorrections for ash and protein intake per period of eating was also lower for10-, 15- and 20-minute intervals. The intervals between observations of 10,15 and 20 minutes lead to underestimation of the number of periods (nº/day)and to overestimation of the average time spent per period of eating, ruminationand idle (min) on dairy heifers and cows, resulting in fallacy estimations.The use of 5-minute intervals for studying cattle eating behavior is recommended.
