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 prepartum and postpartum total mixed diets that were, or were not, supplemented with a yeast culture (YC) for approximately 23 d prepartum and 56 d postpartum. 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 influenced by YC. The extent of the prepartum DMI depression was not influenced by YC supplementation in cows of either parity. An intake behavior study with six multiparous cows suggested that cows supplemented with YC exhibited repeated diurnal feed intake patterns until approximately 7 d prepartum, vs 10 d prepartum for unsupplemented cows. Cows of both parities supplemented with YC had numerically higher DMI and production of milk and milk components, although only DMI for multiparous cows and milk production for primiparous cows approached statistical significance. Intake behavior results suggested that cows supplemented with YC achieved repeated diurnal feed intake patterns by approximately 14 d postpartum, vs 20 d postpartum for unsupplemented cows. Concentrations of ruminal metabolites and pH did not differ between treatments, although ruminal fluid collection occurred while diurnal feed intake patterns were repeated (regular). Overall, our results can be interpreted to support a trend toward a modest postpartum improvement in performance of primiparous and multiparous cows supplemented with this YC for 23 d prepartum and 56 d postpartum. However, primiparous cows seemed to achieve this modest overall improvement primarily through enhanced postpartum DMI, whereas in multiparous cows it was due almost equally to enhanced postpartum DMI and higher energy density of the diet.