Experimental designs such as Latin square, crossover, and switchback have been used extensively in nutritional studies to assess behavioral, intake, and digestibility responses to diet. A critical consideration when using these designs is the necessary length of an adaptation period to accurately measure treatment effect and to minimize potential confounding influence of carry-over from previous treatment. The objective of this review was to determine typical time required for adaptation of these responses based on research evidence primarily with dairy cattle. We focused on (1) eating, ruminating, and resting behavior, (2) dry matter intake (DMI), and (3) total-tract nutrient digestibility. Animal response to dietary treatment integrates response to physicochemical properties of the diet being studied as well as the feeding environment, and so the environment must be similar among treatments. For example, competition for feed can profoundly affect eating behavior and DMI. Response to diet for eating, ruminating, and resting behaviors usually stabilizes within 1–7 d. Consequently, DMI response to diet reflects the pattern of change in eating behavior. This time course is affected by physical and chemical attributes of the diet such as particle size, carbohydrate fermentability, and fat or protein content and characteristics. Most research indicates that ruminant total-tract digestibility ordinarily adjusts to diet within 10 to 14 d. Meta-analysis reveals that change-over designs are as accurate as continuous designs in assessing DMI. However, diets of extremely high or low digestibility may cause lingering effects on digestive and metabolic processes related to ruminal function or dynamics of body fat and protein that may confound interpretation of response to diet in subsequent experimental periods. Examples of expected time to adaptation and potential carryover in lactating dairy cattle will be illustrated using Latin square studies that evaluated diets with considerable range in forage amount and carbohydrate fermentability. In summary, adaptation periods of approximately 7–14 d are usually adequate for measuring response in eating behavior and DMI, but potential consequences of carryover effects in change-over designs are less clear.