Effects of peripartal yeast culture supplementation on lactation performance, blood biomarkers, rumen fermentation, and rumen bacteria species in dairy cows.

Discipline: feeding; Keywords: transition cow, yeast culture, rumen bacteria.

The transition period is a critical period for dairy cows, characterized between three weeks before and three weeks after calving. This is a challenging period for dairy cows because of milk genesis, uterine contraction, as well as metabolic and hormonal changes associated with negative energy balance. Yeast products and yeast-containing feed ingredients can be used as a nutritional feed additive to improve health and performance during the transition between pregnancy and early lactation. Yeast culture is a complex fermentation product that contains yeast biomass and fermentation metabolites produced during specific fermentation process, including vitamins, peptides, amino acids, nucleotides, lipids, organic acids, oligosaccharides, esters, and alcohols. The main effects of yeast products are related to rumen fermentation, benefiting key microbial populations and their metabolism, and consequently increasing fibre degradation and stabilizing rumen pH. The objective of the study by Dr N. A. Carpinelli and colleagues was to evaluate the effects of this yeast culture product (Culture Classic HD; Phibro Animal Health) on performance, blood biomarkers, rumen fermentation, and ruminal bacteria population in dairy cows during the transition period from -30 until + 50 days in milk. The hypothesis was that feeding such a complex product (containing yeast, yeast components, and fermentation metabolites originating from a Saccharomyces cerevisiae yeast strain) during the transition period would affect performance and ruminal characteristics. The results were published in the Journal of Dairy Science, Volume 104 of 2021, page 10727 to 10743. The title of the paper is: Effects of peripartal yeast culture supplementation on lactation performance, blood biomarkers, rumen fermentation, and rumen bacteria species in dairy cows.

Forty Holstein dairy cows were enrolled in a randomized complete block design from 30 to 50 days in milk and blocked according to expected calving day, parity, previous milk yield, and genetic merit. At 30 days in milk, cows were assigned to either a basal diet plus 114 g per day of ground maize (control; n = 20) or a basal diet plus 100 g per day of ground maize and 14 g per day of yeast culture (n = 20), fed as a top dress. Cows received the same close-up diet from 30 day pre-calving until calving [5.82 MJ net energy for lactation {NEL} kg of dry matter (DM) and 12.3% crude protein (CP)], and a lactation diet from calving to 50 days in milk (6.69 MJ NEL per kg of DM and 15.6% CP). Blood samples and rumen fluid were collected at various time points from 30 to 50 days relative to calving.

Cows fed yeast culture compared with control showed a trend for increased energy-corrected milk (+3.2 kg per day). Lower somatic cell counts were observed in yeast culture cows than in control. We detected a treatment × time interaction in non-esterified fatty acids (NEFA) that could be attributed to a trend for greater NEFA in yeast culture cows than control at 7 days in milk, followed by lower NEFA in yeast culture cows than control at 14 and 30 days in milk. In the rumen, yeast culture contributed to mild changes in rumen fermentation, mainly increasing post-calving valerate while decreasing pre-calving isovalerate. This was accompanied by alterations in the rumen microbial population, including a greater abundance of cellulolytic (Fibrobacter succinogenes) and lactate-utilizing bacteria (Megasphaera elsdenii).

In conclusion: Yeast culture products have been fed to pre-calving dairy cows for many years to improve milk yield and milk efficiency. The findings of this study revealed that yeast culture promoted positive responses in performance, such as milk yield, SCC, and energy-corrected milk. In the rumen, yeast culture contributed to increased valerate soon after calving. The latter was accompanied by increments in rumen microbial populations such as cellulolytic and lactic acid-utilizing bacteria. The supply of the yeast culture product and its fermentation metabolites in the rumen could be a source of substrates for ruminal bacteria that can promote improvements in fermentable characteristics and optimize the abundance of microbial species. Overall, the results describe the potential benefits of supplementing yeast culture during the transition period through early lactation, at least in terms of rumen environment and performance.