New insights: Effect of live yeast on dairy cows

The transition period in dairy cows spans 3 weeks pre-calving to 3 or 4 weeks following calving. It represents a critical time for the cow with major dietary, metabolic and physiological changes.

Photo: Henk Riswick

In particular, the transition from a high-fibre diet to a diet high in rapidly fermentable carbohydrates represents important challenges for rumen health. It can also have a negative impact on the cow’s inflammatory status. A trial was conducted in partnership with Professor Alex Bach’s team (IRTA, Spain) at the Blanca Experimental Farm (Spain), on the impact of transition challenges on rumen health and microbiota profiles as well as the effect of live yeast.

The trial was conducted on 21 Holstein dairy cows from 21 days before calving until 21 days after calving. The diet changed from 28% concentrate before calving (51.2% neutral detergent fibre, NDF, 13.2% crude protein, CP) to 64% concentrate after calving (34.8% NDF, 15.2% CP).

Understanding metagenomics data

Metagenomics is the genetic identification of the whole microbiota of a host and their relative abundance. These technologies generate millions of genetic sequences. Thanks to biostatistics analysis, this data could be pooled together according to bacteria genus — which shows more than a hundred of different bacteria types. Such analysis can help microbiologists have a better understanding of the complex composition of the microbiota, like that found in the rumen.

In the case of transition cows, the goal was to focus on the relative abundance of functionally relevant bacteria. Results from 2 main categories of microbes were combined: bacteria that degrade complex carbohydrates, such as fibre; and bacteria that degrade rapidly fermentable carbohydrates, like starch (Figure 1).

Figure 1 – Results from 2 main categories of microbes were combined.

The data shows that:

• Before calving, the relative proportion of the fibre-degrading bacteria is higher than the ones thriving on rapidly fermentable carbohydrates.
• Post-calving, there is a rapid shift towards a higher proportion of bacteria degrading rapidly fermentable carbohydrates.

The first part of the study published in 2018 showed that feeding S. cerevisiae CNCM I-1077 from 3 weeks pre-calving positively improved the rumen dynamics by:

• Reinforcing rumen epithelium integrity, thanks to higher tight junction gene expression before the challenge.
• Increasing resistance to a LPS challenge leading to a lower inflammation after calving
• The metagenomics data further indicate the protective role for the live yeast:
• Pre-calving, the relative proportion of fibre-degrading populations is significantly higher (P<0.05).>
• Post calving, the live yeast group showed higher dry matter intake, leading to a 1.21 kg/day increase in non-fibre carbohydrates. This would have negatively impacted rumen pH and microbial balance leading to a higher proportion of rapidly carbohydrate degraders. Instead, there was no statistical difference with the control group that consumed less fermentable carbohydrates.

Dr Bach explains: “Because LEVUCELL SC cows consumed more feed, a lower rumen pH and greater relative abundance of Prevotella (rapidly fermentable carbohydrate degrader) would have been expected, unless LEVUCELL SC had exerted a positive effect on rumen pH.”

In conclusion, the live yeast — by stabilising the rumen pH despite a higher non-fibre intake — limits the burst of rapidly fermentable carbohydrates degraders.

Source and for more info: www.lallemandanimalnutrition.com.