Lactating Cow Feeding Study

Animal care and experimental procedures were conducted according to the guidelines of the University of Nebraska-Lincoln (UNL) Animal Care and Use Committee. Five ruminally cannulated Holstein lactating cows averaging 6.2 ± 0.70 (mean ± SE) years of age (range = 3.9 years) and four Jersey lactating cows (not cannulated) averaging 4.5 ± 0.39 years of age (range = 1.9 years) were used in the experiment. All Holstein cows had been part of the UNL dairy herd throughout their lives, whereas Jersey cows were purchased from a commercial dairy farm and had been part of the UNL dairy herd for 230 days under the same management as the Holstein cows before the start of the experiment. Cows were housed in a temperature-controlled room in individual tie stalls, and were fed the same diet once daily at 1000 h for ad libitum consumption at 110% of expected intake for four weeks. On a dry matter (DM) basis, the diet was comprised of 51% forage and 49% concentrate and was formulated to meet or exceed the requirements of a lactating cow (Table S1).