Effect of yeast culture (Saccharomyces cerevisiae) on adaptation of cows to postpartum diets and on lactational performance

Multiparous (n = 26) and primiparous (n = 18) Holstein cows were fed prepar tum and postpartum total mixed diets that were, or were not, supplemented w ith a yeast culture (YC) for approximately 23 d prepartum and 56 d postpart um. Multiparous cows supplemented with YC selected a prepartum diet higher in CP than did unsupplemented cows, although prepartum performance of cows of both parities, as assessed by DMI and measures of body status, was not i nfluenced by YC. The extent of the prepartum DMI depression was not influen ced by YC supplementation in cows of either parity. An intake behavior stud y with six multiparous cows suggested that cows supplemented with YC exhibi ted repeated diurnal feed intake patterns until approximately 7 d prepartum , vs 10 d prepartum for unsupplemented cows. Cows of both parities suppleme nted with YC had numerically higher DMI and production of milk and milk com ponents, although only DMI for multiparous cows and milk production for pri miparous cows approached statistical significance. Intake behavior results suggested that cows supplemented with YC achieved repeated diurnal feed int ake patterns by approximately 14 d postpartum, vs 20 d postpartum for unsup plemented cows. Concentrations of ruminal metabolites and pH did not differ between treatments, although ruminal fluid collection occurred while diurn al feed intake patterns were repeated (regular). Overall, our results can b e interpreted to support a trend toward a modest postpartum improvement in performance of primiparous and multiparous cows supplemented with this YC f or 23 d prepartum and 56 d postpartum. However, primiparous cows seemed to achieve this modest overall improvement primarily through enhanced postpart um DMI, whereas in multiparous cows it was due almost equally to enhanced p ostpartum DMI and higher energy density of the diet.