Constraints for nutritional grouping in Wisconsin and Michigan dairy farms

A survey was conducted in Wisconsin (WI) and Michigan (MI) to quantify the proportion of farms that use a single diet for all lactating cows and to better understand the reasons for current grouping strategies and the limitations to grouping for better nutritional management. A questionnaire was mailed to all WI dairy farmers with ≥200 lactating cows (971 farms) and to a random sample of grade-A MI dairy farmers (800 farms) of varying herd sizes. The survey return rate was 20% in WI (196 farms) and 26% in MI (211 farms; 59 of them had ≥200 lactating cows). Feeding 2 or more different diets to lactating cows was predominant: 63% in WI (124 farms, all ≥200 lactating cows), 76% in MI farms with ≥200 lactating cows (45 farms), and 28% in MI farms with