Effects of supplementing a Saccharomyces cerevisiae fermentation product during the periparturient period on performance of dairy cows fed fresh diets differing in starch content.

A fermentation product of the yeast Saccharomyces cerevisiae (SC), has been widely used in diets of dairy cows with the aim of increasing production performance and stabilizing rumen pH. Several studies have reported positive effects such as increased DMI and milk production when cows were fed SC, but the results are inconclusive. Also,  the possible interaction between the fermentability of the basal diet and SC supplementation on DMI has not yet been addressed. Therefore, the objective of a study by Dr W. Shi and co-workers was to evaluate the effect of SC supplementation during the pre-calving period on DMI, milk production and post-calving ovulation of dairy cows fed diets varying in starch content. They hypothesized (1) that feeding high-starch diets during the fresh period would negatively affect performance of dairy cows compared with feeding low-starch diets, and (2) that supplementing SC during the transition period would mitigate the negative effects of feeding high-starch diets and enhance production performance of dairy cows. They published their results in the Journal of Dairy Science Volume 102 of 2019, page 3082 to3096, the title being: Effects of supplementing a Saccharomyces cerevisiae fermentation product during the periparturient period on performance of dairy cows fed fresh diets differing in starch content.

The effect of supplementing Saccharomyces cerevisiae (SC) was studied during respectively the pre-calving period (day −28), day -3 to 44 days post-calving and day +3 relative to calving. Measurements were dry matter intake (DMI), milk production and post-calving ovarian activity. The cows were fed diets varying in starch content. A total of 117 Holstein cows were divided into those receiving SC (n = 59) or not receiving SC, the control (CON; n = 58). The pre-calving diet was calculated to contain 1.43 Mcal per kg DM net energy for lactation (NEL) and 13.8% starch. Cows within each treatment (CON or SC) were fed either a low-starch (LS; 22.1%) or high-starch (HS; 28.3% starch) diet from day 1 to 23 after calving (fresh period), resulting in four treatment groups: LS-CON (n = 30), LS-SC (n = 29), HS-CON (n = 28), and HS-SC (n = 30). All cows were fed the HS diets from day 24 to 44 after calving (post-fresh period). Milk yield was higher for cows fed the LS diets compared with those fed the HS diets during the fresh period (34.1 vs. 32.1 kg per day), whereas DMI and 3.5% fat-corrected milk yield (FCM) were not affected by feed starch content. Low starch cows tended to lose more body condition than HS cows (−0.42 vs. −0.35 per 21 days) during the fresh period. Overall, DMI during the close-up and fresh periods did not differ between SC and CON cows. However, SC supplementation transiently increased DMI on days 1 (13.0 vs. 11.9 kg per day) and 5 (15.5 vs. 14.1 kg per day) after calving compared with CON. During the post-fresh period, SC cows tended to eat less than CON cows (19.8 vs. 20.6 kg per day) but had similar 3.5% FCM (44.9 vs. 43.6 kg per day), resulting in greater feed efficiency for SC cows (FCM /DMI; 2.27 vs. 2.13). Neither starch content of fresh diets nor SC supplementation affected the interval from calving to first ovulation or the incidence of double ovulation.

These results suggest that feeding low-starch diets during the fresh period can increase milk production of dairy cows during the fresh period, and that supplementation of Saccharomyces cerevisiae may increase feed intake around calving and feed efficiency in the post-fresh period.