The most stressful time for a dairy cow is from late gestation to calving and into the first four weeks of lactation. Dairy scientists call this the transition period. The transition period lasts about eight weeks and it is during this time that the cow can experience metabolic stress. The transition period is characterized by substantial metabolic stress, inflammation and altered immune function. This combination of metabolic
stress, inflammation and altered immune function can contribute to the elevated incidence of health disorders in early lactation dairy cows. All cows during the transition period have an increase in inflammation, a decrease in immune function and experience metabolic stress due to negative energy balance. Most cows get through this period without any visible problems.

We need to think of problems during the transition period like an iceberg. There is the part of the iceberg that we see above the water. This visible part of the problems would be the clinical health events we observe during the transition period like mastitis, metritis, retained placenta, ketosis, and displaced abomasum. The part of the iceberg that is hidden under the water would represent the subclinical problems that do not show visible signs such as subclinical milk fever. It is the combination of clinical and subclinical health issues that cut into your profit per cow by reducing peak milk yield, and milk fat and milk protein synthesis while increasing involuntary culling in the first 60 DIM. Developing effective nutritional strategies that could modulate the immunity of these animals is therefore critical.

Three issues must be addressed.  First, dry cows must eat 2% of their bodyweight. A 1500- pound dry cow should eat 30 pounds of dry matter. A 1500- pound dry cow eating 1.8% of her bodyweight (27 lbs. DM) is susceptible to more stress. The second issue is fresh cow dry matter intake. A 1500-pound cow should eat 3.0% of her bodyweight (45 lbs. DM) during the first three weeks of lactation. If fresh cow dry matter intake is 40 pounds or less, you will have subclinical and clinical ketosis that is likely caused by subclinical or clinical infections of the uterus or mammary gland. The third issue is immune system suppression. This is a normal biological response but if it lasts more than a few days after calving, cows are at risk for metritis, mastitis, retained placenta and leaky gut. We must develop strategies that allow the cow to reach dry matter intake goals and boost immune function. When we accomplish these goals, we reduce systemic inflammation and metabolic stress on the cow.

When we reduce systemic inflammation and metabolic stress on the cow, more glucose becomes available for milk component synthesis. An increase in glucose supply to the mammary gland will increase milk yield, milk fat and milk protein synthesis. Lactose, which is milk sugar, can only be made from glucose. When lactose synthesis is increased, milk volume is increased. Glucose plus acetate and butyrate from rumen fiber digestion are needed for milk fat synthesis. Increasing the supply of glucose, acetate and butyrate to the mammary gland will increase milk fat yield. Glucose is also used as fuel to provide the energy needed for milk protein synthesis. Increasing the glucose supply to the mammary gland by reducing systemic inflammation and subclinical and clinical disease will increase milk component synthesis and increase the value of milk sold.

Yeast products derived from Saccharomyces cerevisiae have been shown to improve feed intake and milk yield in transition cows (Dann et al., 2000; Ramsing et al., 2009). Recent findings suggest refined yeast cell wall does boost immune function in dairy cows (Aung et al., 2020). One overlooked aspect of the response to yeast is the potential to influence mucosal immunity. Mucosal surfaces of the intestinal and reproductive tracts are among the most important routes of entry of microbial pathogens into the host. Epithelial cells that line mucosal surfaces are important mechanical barriers that prevent most pathogens and mycotoxins found in the environment from entering the cow. Yeast product supplementation modulated humoral and mucosal immunity and uterine inflammatory signals in transition dairy cows (Yuan et al., 2015). Proposed modes of action for yeast products in dairy cattle diets have expanded beyond alterations in digestive function and now include gut health, immune function and mucosal immunity.

Is there evidence that feeding yeast products on commercial operations during the transition period is effective at reducing metabolic stress and inflammation? Yes, in case study 1., a yeast probiotic (Actisaf HR+) was fed at 10 grams during the pre-fresh period and at 5 grams during the fresh period and throughout lactation. Blood BHBA concentration, a marker for ketosis and liver function, was lower (P=0.07) in
cows fed yeast probiotic pre-fresh and during the fresh cow period (Emanuele and Goodson, 2020 Phileo Report). When blood BHBA concentration is 1.4 mg/dL or higher, it indicates that the cow has ketosis. Feeding a yeast probiotic pre-fresh at 10 grams /cow and at 5 grams/cow to fresh cows, reduced cows with BHBA of 1.4 mg/dL or greater from 17.5% to 7.5%. Cows with blood BHBA concentration greater than 14 mg/dL were 1.8 times more likely to develop metritis; 4.8 times more likely to develop clinical ketosis and 3.9 times more likely to have a DA, compared to cows with lower BHBA concentrations (Suthar et. al. 2013). When refined yeast cell wall product (Safmannan) was fed at 10 grams per cow/day during the transition period on a commercial dairy operation, the incidence of fresh cow health events was reduced, SCC declined by 77,000 and milk fat yield was increased 0.04 pounds. (Emanuele, and Ydstie, 2020 Phileo report).

In summary, to reduce metabolic stress, systemic inflammation and enhance immune function, dry matter intake goals need to be achieved and yeast probiotics and yeast cell wall products can enhance dry matter intake and gut health, leading to a reduction in fresh cow health events. ◄

Aung, M., I. H. Ohtsuka and K. Izumi. 2020. Short communication: Effect of yeast cell wall supplementation on peripheral leukocyte populations and mRNA expression of cytokines in lactating dairy cows. J. Dairy Sci. 103:

Dann, H. M., J. K. Drackley, G. C. McCoy, M. F. Hutjems, and J. E. Garrett. 2000. Effects of yeast culture (Saccharomyces cerevisiae) on prepartum intake and postpartum intake and milk production of Jersey cows. J. Dairy Sci. 83:123–127

Ramsing, E. M., J. A. Davidson, P. D. French, I. Yoon, M. Keller, and H. Peters-Fleckenstein. 2009. Effect of yeast culture on peripartum intake and milk production of primiparous and multiparous Holstein cows. Prof. Anim. Sci. 25:487–495.

Suthar, V.S., J. Canelas-Raposo, A. Deniz and W. Heuwieser. 2013. Prevelance of subclinical ketosis and relationships with postpartum diseases in European dairy cows. J. Dairy Sci. 96:2925

Yuan, K., L. G. D. Mendonça , L. E. Hulbert , L. K. Mamedova , M. B. Muckey , Y. Shen , C. C. Elrod , and B. J. Bradford. 2015. Yeast product supplementation modulated humoral and mucosal immunity and uterine inflammatory signals in transition dairy cows. J. Dairy Sci. 98 :3236–3246