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

Discipline: nutrition/feeding; Key words: calving transition, dietary starch, Saccharomyces cerevisiae fermentation product, ovulation. 

Dairy cattle often experience negative energy balance during the calving transition period, because of reduced feed intake and a drastic increase in nutrient demands after the onset of lactation, thereby contributing to high risk of metabolic disease and low immunity. This implies that feeding strategies during the calving transition period should be designed to maintain feed intake to mitigate excessive fat mobilization. An increase in the starch content of post-calving diets is expected to reduce the extent of the negative energy balance and improve performance by increasing energy intake. However, this approach is risky as it may decrease dry matter intake (DMI) and expose dairy cows to sub-acute ruminal acidosis (SARA). The occurrence of SARA usually results in reduced feed intake and impaired animal health; therefore, feeding diets high in fermentable carbohydrate (e.g. starch) during the post-calving transition period may not necessarily improve dairy cow performance. A secondary problem is that cows in negative energy balance often experience an increase in the interval from calving to first ovulation. It has been shown that high-starch diets reduce or tend to reduce the interval from calving to first ovulation, but increase the incidence of double ovulation. Therefore, although shortening the interval from calving to first ovulation by feeding high-starch diets appears logical, the increased risk of associated double ovulations could have negative ramifications.

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.