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Effects of Saccharomyces cerevisiae boulardii (CNCM I-1079) on feed intake, blood parameters, and production during early lactation

Open AccessPublished:November 07, 2022DOI:https://doi.org/10.3168/jds.2021-21740

      ABSTRACT

      The periparturient period is a metabolically demanding time for dairy animals because of increased nutrient requirements for milk yield. The objective of this study was to investigate the effect of feeding Saccharomyces cerevisiae boulardii (CNCM I-1079), a commercial active dry yeast (ADY), in dairy cows on productive and metabolic measures during the periparturient period. Primiparous (n = 33) and multiparous (n = 35) cows were fed a close-up total mixed ration (TMR) before calving and a lactation TMR postpartum. Three weeks before expected calving time, animals were blocked by parity and body weight and then randomly assigned to either control group (control; n = 34) or treatment (ADY; n = 34). All animals were housed in a tie-stall barn with individual feed bunks; the ADY animals received supplementary Saccharomyces cerevisiae boulardii (CNCM I-1079), top dressed daily at a predicted dosage of 1.0 × 1010 cfu (12.5 g) per head. Blood samples were collected weekly along with milk yield and milk composition data; feed intake data were collected daily. Serum samples were analyzed for glucose, nonesterified fatty acid, β-hydroxybutyrate, haptoglobin (Hp), and the cytokines tumor necrosis factor-α, IL-6, and IL-18. Colostrum samples collected within the first 6 to 10 h were analyzed for somatic cell score and IgG, IgA, and IgM concentrations. Data were analyzed using PROC GLIMMIX in SAS with time as a repeated measure; model included time, parity, treatment, and their interactions. The ADY groups had greater milk yield (39.0 ± 2.4 vs. 36.7 ± 2.3 kg/d) and tended to produce more energy-corrected milk with better feed efficiency. There was no difference in plasma glucose, serum nonesterified fatty acid, serum β-hydroxybutyrate, Hp, IL-6, or IL-18 due to ADY treatment. The tumor necrosis factor-α increased in ADY-supplemented animals (1.17 ± 0.69 vs. 4.96 ± 7.7 ng/mL), though week, parity, and their interactions had no effect. Serum amyloid A tended to increase in ADY-supplemented animals when compared to control animals and was additionally affected by week and parity; there were no significant interactions. No difference in colostrum IgG, IgA, and IgM was observed between treatments. Supplementing transition cow TMR with ADY (CNCM I-1079) improved milk production and tended to improve efficiency in early lactation; markers of inflammation were also influenced by ADY treatment, though the immunological effect was inconsistent.

      Key words

      INTRODUCTION

      During the transition period, beginning 3 wk before parturition, drastic metabolic and immunological changes occur in the dairy cow (
      • LeBlanc S.
      Monitoring metabolic health of dairy cattle in the transition period.
      ). Due to the high energy demand of lactation and inability of DMI to keep pace, cows enter negative energy balance associated with body condition score loss, risk of metabolic disorders, and immune function changes. In cattle, parturition induces an acute phase response, which is also linked to energy balance (
      • Tóthová C.
      • Nagy O.
      • Kovác G.
      Changes in the concentrations of selected acute phase proteins and variables of energetic profile in dairy cows after parturition.
      ). Further, negative energy balance is linked to decreased neutrophil function and uterine disease (
      • Hammon D.S.
      • Evjen I.M.
      • Dhiman T.R.
      • Goff J.P.
      • Walters J.L.
      Neutrophil function and energy status in Holstein cows with uterine health disorders.
      ). Overall, the parturition transition creates great metabolic and immunological stress that must be mitigated to optimize cattle health.
      Direct-fed microbial products such as bacteria and fungi are one possible avenue to improve animal health during the parturition transition. A subset of direct-fed microbials, active dry yeasts (ADY), which commonly include Saccharomyces cerevisiae, are a supplement group of particular interest. Active dry yeasts have been found to act as a growth promoter (
      • McAllister T.A.
      • Beauchemin K.A.
      • Alazzeh A.Y.
      • Baah J.
      • Teather R.M.
      • Stanford K.
      Review: The use of direct fed microbials to mitigate pathogens and enhance production in cattle.
      ), influence the immune system in several species (Sanchez et al., 2021), and improve milk production in dairy cows (
      • Schlabitz C.
      • Neutzling Lehn D.
      • Volken de Souza C.F.
      A review of Saccharomyces cerevisiae and the applications of its byproducts in dairy cattle feed: Trends in the use of residual brewer’s yeast.
      ). To our knowledge, the impact of ADY on transition cows is poorly understood. One S. cerevisiae strain decreased HSP-70 and increased lymphocyte proliferative response (
      • Nasiri A.H.
      • Towhidi A.
      • Shakeri M.
      • Zhandi M.
      • Dehghan-Banadaky M.
      • Pooyan H.R.
      • Sehati F.
      • Rostami F.
      • Karamzadeh A.
      • Khani M.
      • Ahmadi F.
      Effects of Saccharomyces cerevisiae supplementation on milk production, insulin sensitivity and immune response in transition dairy cows during hot season.
      ). Additionally, yeast cultures or hydrolyzed yeast mixtures increased milk production (
      • Faccio-Demarco C.
      • Mumbach T.
      • Oliveira-de-Freitas V.
      • e Silva-Raimondo R.F.
      • Medeiros-Gonçalves F.
      • Nunes-Corrêa M.
      • Burkert-Del Pino F.A.
      • Mendonça-Nunes-Ribeiro Filho H.
      • Cassal-Brauner C.
      Effect of yeast products supplementation during transition period on metabolic profile and milk production in dairy cows.
      ), fecal IgA concentrations, and tended to increase bacteria-killing abilities of whole blood (
      • Yuan K.
      • Mendonça L.G.D.
      • Hulbert L.E.
      • Mamedova L.K.
      • Muckey M.B.
      • Shen Y.
      • Elrod C.C.
      • Bradford B.J.
      Yeast product supplementation modulated humoral and mucosal immunity and uterine inflammatory signals in transition dairy cows.
      ). Together, these studies suggest a possible immunological response of dairy cows to ADY supplementation.
      Mechanisms of action for ADY are wide and varied. Active dry yeasts have been shown to affect lactate and lactic acid production, increase feed digestibility and efficiency, and decrease oxygen and improve fermentation and feed breakdown dynamics in the rumen (
      • Seo J.K.
      • Kim S.W.
      • Kim M.H.
      • Upadhaya S.D.
      • Kam D.K.
      • Ha J.K.
      Direct-fed microbials for ruminant animals.
      ). In beef steers, ADY have been shown to improve immune response via increased TLR-4 expression (
      • Lopreiato V.
      • Mezzetti M.
      • Cattaneo L.
      • Ferronato G.
      • Minuti A.
      • Trevisi E.
      Role of nutraceuticals during the transition period of dairy cows: A review.
      ). In the lower gut, ADY may inhibit growth of pathogens, stimulate an immune response, and balance microbial growth (
      • Seo J.K.
      • Kim S.W.
      • Kim M.H.
      • Upadhaya S.D.
      • Kam D.K.
      • Ha J.K.
      Direct-fed microbials for ruminant animals.
      ). The positive effects of ADY supplementation are dependent on the diet, formulation, and amount of supplementation and therefore can vary from farm to farm (
      • Elghandour M.M.Y.
      • Salem A.Z.M.
      • Castañeda J.S.M.
      • Camacho L.M.
      • Kholif A.E.
      • Chagoyán J.C.V.
      Direct-fed microbes: A tool for improving the utilization of low quality roughages in ruminants.
      ). Results on ADY have been inconsistent across a range of studies with a wide variety of variables examined (
      • Lynch H.A.
      • Martin S.A.
      Effects of Saccharomyces cerevisiae culture and Saccharomyces cerevisiae live cells on in vitro mixed ruminal microorganism fermentation.
      ;
      • Seo J.K.
      • Kim S.W.
      • Kim M.H.
      • Upadhaya S.D.
      • Kam D.K.
      • Ha J.K.
      Direct-fed microbials for ruminant animals.
      ; Sanchez et al., 2021), likely due to the variability in efficacy among different strains of the same species.
      Yeast phenotypes in S. cerevisiae alone are diverse, encompassing at least 74 phenotypes grouped into 10 categories including environmental condition sensitivity, lipid and carbohydrate metabolism defects, carbon catabolite repression, and nitrogen utilization defects (
      • Hampsey M.
      A review of phenotypes in Saccharomyces cerevisiae..
      ). Whether S. boulardii is a substrain of S. cerevisiae or a separate species entirely is still unsettled (
      • Pais P.
      • Almeida V.
      • Yilmaz M.
      • Teixeira M.C.
      Saccharomyces boulardii: What makes it tick as successful probiotic?.
      ). Saccharomyces cerevisiae boulardii (SCB) is known to impact intestinal mucosa, modulating immune response, gene expression, and protein synthesis (
      • Buts J.P.
      • De Keyser N.
      Effects of Saccharomyces boulardii on intestinal mucosa.
      ). In ruminants, different S. cerevisiae strains can change rumen fermentation profile to a more acidotic and glucogenic state (
      • Chung Y.-H.
      • Walker N.D.
      • McGinn S.M.
      • Beauchemin K.A.
      Differing effects of 2 active dried yeast (Saccharomyces cerevisiae) strains on ruminal acidosis and methane production in nonlactating dairy cows.
      ) or impact fiber digestion (
      • Newbold C.J.
      • Wallace R.J.
      • Chen X.B.
      • McIntosh F.M.
      Different strains of Saccharomyces cerevisiae differ in their effects on ruminal bacterial numbers in vitro and in sheep.
      ). Among 7 strains of S. cerevisiae, there exists considerable strain-to-strain variation between in vitro rumen ammonia production and fiber degradation (
      • Chaucheyras-Durand F.
      • Walker N.D.
      • Bach A.
      Effects of active dry yeasts on the rumen microbial ecosystem: Past, present and future.
      ). Beyond S. cerevisiae, other yeast species such as Kluyveromyces marxianus, Candida tropicalis, and Candida utilis (
      • Shurson G.C.
      Yeast and yeast derivatives in feed additives and ingredients: Sources, characteristics, animal responses, and quantification methods.
      ) have shown positive impacts on rumen fermentation (
      • Wang Z.
      • He Z.
      • Beauchemin K.A.
      • Tang S.
      • Zhou C.
      • Han X.
      • Wang M.
      • Kang J.
      • Odongo N.E.
      • Tan Z.
      Evaluation of different yeast species for improving in vitro fermentation of cereal straws.
      ) and fiber digestion (
      • Jiao P.X.
      • He Z.X.
      • Ding S.
      • Walker N.D.
      • Cong Y.Y.
      • Liu F.Z.
      • Beauchemin K.A.
      • Yang W.Z.
      Impact of strain and dose of live yeast and yeast derivatives on in vitro ruminal fermentation of a high-grain diet at two pH levels.
      ). Additionally, neurological, immunological, and endocrinological effects, as well as bioactives production, are currently understood to be highly strain-dependent (
      • Hill C.
      • Guarner F.
      • Reid G.
      • Gibson G.R.
      • Merenstein D.J.
      • Pot B.
      • Morelli L.
      • Canani R.B.
      • Flint H.J.
      • Salminen S.
      • Calder P.C.
      • Sanders M.E.
      The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic.
      ). Due to the known strain-to-strain variation, it is important to distinguish the strains used in studies so that findings for 1 strain are not confounded with findings from other strains or isolates.
      One strain of ADY holding considerable promise is SCB, of which, a substrain (CNCM I-1079) is known to affect the small intestine and colon of calves. Specifically, SCB has been found to decrease crypt depth and width in dairy calves, increase goblet cell number in pre- and postweaned calves (
      • Fomenky B.E.
      • Chiquette J.
      • Bissonnette N.
      • Talbot G.
      • Chouinard P.Y.
      • Ibeagha-Awemu E.M.
      Impact of Saccharomyces cerevisiae boulardii CNCMI-1079 and Lactobacillus acidophilus BT1386 on total lactobacilli population in the gastrointestinal tract and colon histomorphology of Holstein dairy calves.
      ), and increase growth in postweaned dairy calves (Renaud et al., 2019). Protective effects on the small intestine in calves show promise in reducing inflammation and immune response by reducing pathogen load (
      • Ma T.
      • Renaud D.
      • Skidmore A.
      • Aguilar A.
      • Chevaux E.
      • Guan L.
      • Steele M.
      Alteration of fecal bacterial composition in pre-weaned veal calves by supplementation of Saccharomyces cerevisiae boulardii in milk replacer.
      ). Currently, the effects of SCB (CNCM I-1079) on health and productivity in the dairy cow parturition transition is unknown. The objectives of this study were to examine the effects of SCB (CNCM I-1079) on individual DMI, milk production, and markers of immune response and inflammation during the transition period and into early lactation. We hypothesized that SCB supplementation would improve milk production in early lactation and improve immune response of transition and early lactation dairy cattle.

      MATERIALS AND METHODS

      Animal Management

      This study was approved by the Institutional Animal Care and Use Committee at the University of Idaho (AUP# IACUC-2017-63). Dairy heifers (n = 34) and multiparous dairy cows (n = 38 total; n = 19 for second lactation, and n = 16 for third lactation) from the University of Idaho Dairy Center were moved into individual stalls at University of Idaho Research Barn and assigned to either control (CTRL; n = 36) or a top-dressed, direct-fed microbial SCB (CNCM I-1079; ADY; n = 36) at 12.5 g/d, predicted dosage of 1.0 × 1010 cfu. Treatment assignments were balanced for BW, parity, and previous lactation milk yield (multiparous cows only) with cows blocked by seasonal calving dates. Figure 1 depicts a visual representation of the experimental design. The experimental unit was the cow. Two animals (one from the group CTRL-P, primiparous control animals; and one from the group CTRL-M, multiparous control animals) were removed from the study within 2 d for failure to adapt to the tie-stall research barn; any data obtained from these 2 animals were not used in this study. Two additional animals were removed from the study due to left-displaced abomasum (CTRL-M) and recurring mastitis (ADY-M). Thus, the final animal numbers per treatment were CTRL-P (n = 16), ADY-P (n = 17), CTRL-M (n = 17), and ADY-M (n = 18).
      Figure thumbnail gr1
      Figure 1Experimental design. Primiparous and multiparous cows were fed a close-up TMR until lactation, when all animals were transitioned to a lactation diet. Animals were assigned to either no supplementation or supplementation with Saccharomyces cerevisiae boulardii (CNCM I-1079) top dressed from 3 wk preparturition until 9 wk postparturition. After calving cows were milked 4 times/d for the first 4 wk and 2 times/d for the last 5 wk.
      Dose of ADY was based upon manufacturer recommendations; no vehicle or flavoring was used as the ADY was top dressed and mixed directly into the top 6 inches of the TMR in each individual bunk. Treatments were consumed within the first 30 min after feeding. Cows were fed a TMR daily at 0700 and 1700 h. The ADY treatment was top dressed in morning feeding, and as such, the yeast was given as a pulse dose each morning. Diets were fed to target 5 to 10% orts daily. Actual orts were 4.9 ± 4.5 kg/cow per d or 11.9 ± 10.3% of the total amount fed. For approximately 3 wk before the expected calving date (18.5 ± 6.3 d), cows were housed in the tie-stall research barn and were fed a TMR with (multiparous) or without (primiparous) anionic salts with a 90:10 forage:concentrate ratio (Table 1). At calving, all cows were moved into maternity pens where they were fed alfalfa hay and water free choice. After 24 h, they were moved to a bedded pack barn for up to 48 h to ensure adequate movement and successful expulsion of placenta. Cows were then returned to the tie-stall research barn and fed a lactation diet with a forage:concentrate ratio of 45:55 (Table 1). From wk 1 to 4 postcalving, cows were milked 4 times per d at 0700 h, 1100 h, 2000 h, and 0000 h. From wk 5 to 9, cows were milked 2 times per d at 0700 h and 2000 h. Table 2 provides information on the nutritional analysis of the close-up and lactation diets; Table 3 displays main effect and interaction P-values for all data analyzed.
      Table 1Diet formulations fed during the calving transition period
      Ingredient (% of DM)Close-up

      (PP
      PP = primiparous.
      )
      Close-up

      (MP
      MP = multiparous.
      )
      Lactation
      Grass hay18.917.92.0
      Alfalfa hay5.0
      Alfalfa silage29.828.23.0
      Triticale silage39.737.633.4
      Corn, ground0.90.94.3
      Barley, rolled2.62.515.5
      Canola meal1.81.79.5
      Corn DDGS
      DDGS = dried distillers grains.
      0.90.913.1
      Soybean meal4.7
      MagnaFat
      MagnaFat = rumen protected fat supplement, produced by Energy Feeds International.
      3.9
      Liquid mineral mix
      Mineral mix: custom mineral mix containing 4.00% Ca, 0.16% P, 1.07% Mg, 3.28% K, 0.59% S, 2.02% Na, 2.66% Cl, 193 ppm Fe, 416 ppm Mn, 651 ppm Zn, 178 ppm Cu, 11 ppm Co, 11 ppm I, 4.6 ppm Se, 440 ppm Zn (organic), 92,664 IU/kg vitamin A, 28,572 IU/kg vitamin D, and 990 IU/kg vitamin E.
      4.94.65.0
      Vitamin A, D, E0.30.20.5
      Salt0.10.10.1
      Anionic salt supplement5.4
      1 PP = primiparous.
      2 MP = multiparous.
      3 DDGS = dried distillers grains.
      4 MagnaFat = rumen protected fat supplement, produced by Energy Feeds International.
      5 Mineral mix: custom mineral mix containing 4.00% Ca, 0.16% P, 1.07% Mg, 3.28% K, 0.59% S, 2.02% Na, 2.66% Cl, 193 ppm Fe, 416 ppm Mn, 651 ppm Zn, 178 ppm Cu, 11 ppm Co, 11 ppm I, 4.6 ppm Se, 440 ppm Zn (organic), 92,664 IU/kg vitamin A, 28,572 IU/kg vitamin D, and 990 IU/kg vitamin E.
      Table 2Nutritional analysis of close-up and lactation diet; weekly samples were composited by month
      Analyte (% of DM)
      Unit is % of DM unless otherwise indicated.
      Close-up, MP,
      MP = multiparous.
      and PP
      PP = primiparous.
      Lactation
      DM (% as fed)51.3 ± 4.250.3 ± 2.5
      CP15.9 ± 1.918.2 ± 0.4
      Soluble protein (% of CP)41.3 ± 3.839.2 ± 1.2
      aNDF49.6 ± 1.841.2 ± 0.8
      ADF33.9 ± 1.725.6 ± 0.6
      Lignin5.4 ± 0.34.7 ± 0.4
      NFC21.4 ± 2.626.4 ± 0.8
      Starch3.5 ± 1.213.0 ± 0.3
      Crude fat2.5 ± 0.15.0 ± 0.3
      Ash10.7 ± 0.69.3 ± 0.2
      TDN (%)58.8 ± 0.866.7 ± 0.7
      1 Unit is % of DM unless otherwise indicated.
      2 MP = multiparous.
      3 PP = primiparous.
      Table 3P-values for all variables by main effects and interactions
      Trt = treatment; NEFA = nonesterified fatty acids; TNF-α = tumor necrosis factor-α.
      ItemTrtWkParityTrt × WkTrt × ParityWk × ParityTrt × Wk × Parity
      Animal productivity
       DMI (kg)0.47<0.01<0.010.200.810.080.01
       BW (kg)0.05<0.01<0.010.560.89<0.010.21
       Daily milk yield (kg)0.02<0.01<0.010.490.990.960.32
       ECM (kg/d)0.08<0.01<0.010.300.950.920.14
       Feed efficiency (kg of milk/kg of DMI)0.08<0.01<0.010.130.920.180.17
       Peak milk yield (kg/d)0.28<0.010.18
      Colostrum
       IgG (mg/dL)0.930.760.44
       IgA (mg/dL)0.50<0.010.46
       IgM (mg/dL)0.660.980.50
      Milk composition
       Fat (%)0.44<0.010.450.900.790.640.18
       Protein (%)0.50<0.010.560.940.340.04<0.01
       Lactose (%)0.75<0.010.070.960.330.850.23
       MUN (mg/dL)0.28<0.01<0.010.650.880.340.21
       SCS0.100.030.770.930.660.900.81
      Energy metabolite
       Glucose (mg/dL)0.63<0.01<0.010.620.380.140.14
       NEFA (mEq/L)0.87<0.01<0.010.050.950.22<0.01
       BHB (mg/dL)0.68<0.010.020.590.470.060.61
      Cytokine
       IL-6 (pg/mL)0.430.350.620.780.090.950.70
       IL-18 (pg/mL)0.570.500.420.720.110.280.90
       TNF-α (ng/mL)<0.010.930.970.870.330.210.59
      Acute phase protein
       Haptoglobin (mg/mL)0.560.240.480.740.500.410.49
       Serum amyloid A (ng/mL)0.06<0.01<0.010.410.710.370.57
      1 Trt = treatment; NEFA = nonesterified fatty acids; TNF-α = tumor necrosis factor-α.

      Sampling

      Blood and feed were sampled weekly, and cows were weighed between morning and evening feedings on an in-ground livestock scale. Blood samples were taken on the same day weekly until calving, at which point a sample was taken within 24 h of calving (wk 0). Then cows were assigned to 1 of 3 sampling groups according to the day of the week in which they calved. For example, a cow that calved on a Monday would have her blood sampled for 7 DIM the following Monday, along with all other Sunday and Monday calvers. Tuesday, Wednesday, and Thursday calvers would be sampled on Wednesdays, and Friday and Saturday calvers would be sampled on Fridays. This ensured that all cows were sampled ± 2 d from each other for each weekly sample.
      Milk production and DMI was averaged weekly; milk was sampled twice weekly and DMI thrice weekly. Samples from all milkings were pooled together and DMI were averaged for the week. Feed samples were taken from the whole TMR (not individual feed bunks), dried, ground through a 2-mm screen, sent to a commercial laboratory (Dairy One Labs), and analyzed via established wet chemistry techniques for DM (
      • AOAC International
      Official Methods of Analysis.
      ), CP (
      • AOAC International
      Official Methods of Analysis.
      ), soluble protein (
      • Licitra G.
      • Hernandez T.M.
      • Van Soest P.J.
      Standardization of procedures for nitrogen fractionation of ruminant feeds.
      ), aNDF (
      • Van Soest P.J.
      • Robertson J.B.
      • Lewis B.A.
      Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition.
      ), ADF (
      • AOAC International
      Official Methods of Analysis.
      ), lignin (
      • AOAC International
      Official Methods of Analysis.
      ), starch (
      • AOAC International
      Official Methods of Analysis.
      ), crude fat (
      • AOAC International
      Official Methods of Analysis.
      ), and ash (
      • AOAC International
      Official Methods of Analysis.
      ). Calculations of NFC and TDN were carried out according to
      • NRC
      Nutrient Requirements of Dairy Cattle.
      .
      Postcalving, milk composite samples were taken weekly with equal amounts from all milkings and analyzed for milk components using wet chemistry at Dairy One Labs. Colostrum was sampled at first milking after calving (within 8 h) and analyzed via radial immunodiffusion assay for total IgA, IgG, and IgM at TripleJ Farms in Washington. Briefly, samples were added to an agar plate containing IgG, IgA, or IgM antigens. Upon addition of a sample of precipitate ring forms on the plate, the diameter of which was compared with the supplied standards, the amount of immunoglobulin in the sample was determined.
      Blood was drawn from the coccygeal vein into Vacutainer tubes (Greiner Bio-One) containing sodium heparin. Blood was centrifuged at 3,000 × g at 4°C for 20 min to separate plasma and was stored at −20°C until analysis. Samples were analyzed for glucose and β-hydroxybutyric acid (BHBA) using in-house enzymatic assays (
      • Laarman A.H.
      • Ruiz-Sanchez A.L.
      • Sugino T.
      • Guan L.L.
      • Oba M.
      Effects of feeding a calf starter on molecular adaptations in the ruminal epithelium and liver of Holstein dairy calves.
      ) and for nonesterified fatty acids (NEFA) using a commercially available enzymatic and colorimetric assay (Fujifilm, Wako Diagnostics USA). Blood was also analyzed for the acute phase proteins and cytokines using commercially available bovine-serum-reactive kits (MyBiosource); specifically, for serum amyloid A (MBS2024318; limit of detection: 6.25 ng/mL), haptoglobin (MBS1603719; limit of detection: 3 µg/mL), tumor necrosis factor-α (TNF-α; MBS2609886; limit of detection: 15.6 pg/mL), IL-6 (MBS2882335; limit of detection: 78 pg/mL), and IL-18 (MBS2022718; limit of detection: 15.6 pg/mL). Samples below limit of detection were denoted as 0.5 × limit of detection to minimize skew; no samples were above maximum range of standard curve. Interassay coefficients of variation were 15% or less and intraassay coefficients of variation were 10% or less for all samples.

      Statistics

      Normality of data was analyzed using a Shapiro-Wilks test in PROC UNIVARIATE of SAS (v. 9.4, SAS Institute Inc.). Not all variable residuals were normally distributed, and as such, all data were analyzed using PROC GLIMMIX with a lognormal distribution with identity link. Least squares means and standard error of the mean (SEM) were then back-transformed for manuscript readability. Week was used as the repeated measure with 5 variance/covariance structures [unstructured, variance components, compound symmetry, autoregressive (1), and heterogeneous autoregressive (1)] to determine Akaike information criterion values, the lowest of which was used. Interaction of treatment × week × parity was sliced post hoc by parity × week to focus on biologically relevant comparisons: comparison of ADY vs. control with each parity × week grouping. Wherever a treatment × week × parity interaction was significant, only post hoc slices that were significantly different were discussed.
      Repeated and nonrepeated measures data were analyzed according to the respective predictors:
      Y = µ + Pi + Tj + Wk + P × Wik + P × Tij + T × Wjk + P × T × Wijk + εijkl


      and
      Y = µ + Pi + Tj + P × Tij + εijk,


      where µ = overall mean, P = effect of parity (i = primiparous or multiparous), T = effect of treatment (j = CTRL or ADY), W = effect of week (k = −3 to 9 for nonlactation parameters or 0 to 9 for lactation), and εijkl and εijk = residual error. Random effects of cow and block were included.
      Significance was declared at P < 0.05 and tendencies were declared at 0.05 ≤ P < 0.10. Data reported throughout are back-transformed means ± SEM. The main effects and their interactions are denoted in P-values only to improve readability of the manuscript.

      RESULTS

      Animal Productivity

      Dry matter intake was affected by treatment × week × parity (P = 0.01; Figure 2); in wk −1, 1, and 7, ADY-P had greater DMI than CTRL-P (P = 0.02, 0.05, 0.03). The DMI was unaffected by main effect of treatment (P = 0.47). For parity, multiparous cows had greater DMI than primiparous cows (P < 0.01), and week intake increased as lactation progressed (P < 0.01). Body weight was affected by a week × parity interaction (P < 0.01) with ADY-P tending to have greater BW at wk 1 and 8 (P = 0.08, 0.09). Body weight was positively affected by treatment (P = 0.05) with ADY-supplemented cows having higher BW after calving (563.7 ± 12.2 vs. 588.3 ± 13.5 kg, CTRL vs. ADY).
      Figure thumbnail gr2
      Figure 2Dry matter intake (A) and BW (B) of primiparous and multiparous cows with or without diet supplementation with top-dressed Saccharomyces cerevisiae boulardii. CTRL-P: control diet, primiparous cows; active dry yeast (ADY)-P: ADY-supplemented diet, primiparous cows; CTRL-M: control diet, multiparous cows (lactation 2 or 3); ADY-M: ADY-supplemented diet, multiparous cows. Error bars are ±SEM.
      Daily milk yield increased with ADY supplementation (36.7 ± 2.3 vs. 38.9 ± 2.4 kg/d, P = 0.02 Figure 3) and was also affected by week (P < 0.01) and parity (P < 0.01). Energy-corrected milk tended to increase with treatment (P = 0.08) and it was affected by week (P < 0.01) and parity (P < 0.01). Feed efficiency also tended to be positively affected by treatment (1.84 ± 0.09 vs. 1.93 ± 0.1 kg milk/kg DMI; P = 0.08, CTRL vs. ADY) and was affected by week (P < 0.01) and parity (P < 0.01). Peak milk yield was higher for multiparous cows than primiparous cows (P < 0.01) but was unaffected by ADY treatment (P = 0.28; Figure 3). Other than the interactions noted above, no other interactions were significant.
      Figure thumbnail gr3
      Figure 3Milk production (A), ECM (B), feed efficiency (C), and peak milk yield (D) of primiparous and multiparous cows with or without dietary supplementation with top-dressed Saccharomyces cerevisiae boulardii. CTRL-P: control diet, primiparous cows; active dry yeast (ADY)-P: ADY-supplemented diet, primiparous cows; CTRL-M: control diet, multiparous (lactation 2 or 3); ADY-M: ADY-supplemented diet, multiparous cows. Error bars are ±SEM.

      Colostrum and Milk Composition

      Colostrum IgG, IgA, and IgM concentrations were unaffected by treatment × parity interactions or by treatment (Figure 4). The only exception to this trend was IgA, which was greater in multiparous cows than primiparous cows (1,011 ± 37 vs. 749 ± 38 mg/dL, P < 0.01). The most abundant immunoglobulin was IgG (5,800–7,000 mg/dL), followed by IgA (749–1,028 mg/dL), then IgM (540–585 mg/dL).
      Figure thumbnail gr4
      Figure 4Colostrum IgG (A), IgA (B), and IgM (C) concentrations of primiparous and multiparous cows with or without dietary supplementation with top-dressed Saccharomyces cerevisiae boulardii. CTRL-P: control diet, primiparous cows; active dry yeast (ADY)-P: ADY-supplemented diet, primiparous cows; CTRL-M: control diet, multiparous cows (lactation 2 or 3); ADY-M: ADY-supplemented diet, multiparous cows. Error bars are ±SEM.
      Milk protein % was affected by treatment × week × parity interaction (P < 0.01), but no post hoc slice was significant. Milk protein % was also affected by week × parity (P = 0.04). No other interactions were significant for any milk component. Milk components were unaffected by main effect of ADY supplementation (fat %, P = 0.44; protein %, P = 0.50; lactose %, P = 0.75; MUN, P = 0.28; Figure 5). Week of lactation affected all components (P < 0.001). Lactose tended to be affected by parity (P = 0.07), and MUN (P < 0.01) was affected by parity with lactose and MUN being greater in primiparous cows. Milk SCS was unaffected by ADY supplementation (P = 0.10) but was affected by week (P = 0.03; Figure 6).
      Figure thumbnail gr5
      Figure 5Milk fat percentage (A), protein percentage (B), lactose percentage (C), and milk urea nitrogen concentration (D) of primiparous and multiparous cows with or without dietary supplementation with top-dressed Saccharomyces cerevisiae boulardii. CTRL-P: control diet, primiparous cows; active dry yeast (ADY)-P: ADY-supplemented diet, primiparous cows; CTRL-M: control diet, multiparous cows (lactation 2 or 3); ADY-M: ADY-supplemented diet, multiparous cows. Error bars are ±SEM.
      Figure thumbnail gr6
      Figure 6Milk SCS of primiparous and multiparous cows with or without dietary supplementation with top-dressed Saccharomyces cerevisiae boulardii. CTRL-P: control diet, primiparous cows; active dry yeast (ADY)-P: ADY-supplemented diet, primiparous cows; CTRL-M: control diet, multiparous cows (lactation 2 or 3); ADY-M: ADY-supplemented diet, multiparous cows. Error bars are ±SEM.

      Blood Metabolites

      Serum NEFA was affected by treatment × week (P = 0.05) and treatment × week × parity interaction (P < 0.01) with ADY-P tending to have lower NEFA than CTRL-P at wk −2 (P = 0.06) and wk 9 (0.03) and ADY-M tending to have lower NEFA than CTRL-M at wk 8 (P = 0.07). Blood glucose, BHBA, and NEFA were unaffected by main effects of treatment (Glucose: P = 0.63, NEFA: P = 0.87, BHBA: P = 0.68; Figure 7) but were affected by week (P < 0.01) and parity (P = 0.02). Acute phase protein serum amyloid A tended to increase in ADY-supplemented animals (P = 0.06), but haptoglobin was not affected by ADY treatment (P = 0.56; Figure 8). As for cytokines, IL-6 tended to be affected by the interaction of treatment × parity (P = 0.09). The TNF-α was significantly increased by ADY supplementation (1.17 ± 0.69 vs. 4.96 ± 7.7 ng/mL, P < 0.01; Figure 9). Proinflammatory IL-18 (IFN-γ inducing factor) was unchanged by ADY supplementation, week, or parity (IL-18; trt P = 0.57, week P = 0.50, parity P = 0.42). Other than the interactions mentioned above, no interactions were significant.
      Figure thumbnail gr7
      Figure 7Blood glucose (A), nonesterified fatty acids (NEFA; B), and β-hydroxybutyric acid (BHBA; C) concentrations in primiparous and multiparous cows with or without dietary supplementation with top-dressed Saccharomyces cerevisiae boulardii. CTRL-P: control diet, primiparous cows; active dry yeast (ADY)-P: ADY-supplemented diet, primiparous cows; CTRL-M: control diet, multiparous cows (lactation 2 or 3); ADY-M: ADY-supplemented diet, multiparous cows. Error bars are ±SEM.
      Figure thumbnail gr8
      Figure 8Acute phase proteins haptoglobin (A) and serum amyloid A (B) in primiparous and multiparous cows supplemented with or without dietary supplementation with top-dressed Saccharomyces cerevisiae boulardii. CTRL-P: control diet, primiparous cows; active dry yeast (ADY)-P: ADY-supplemented diet, primiparous cows; CTRL-M: control diet, multiparous cows (lactation 2 or 3); ADY-M: ADY-supplemented diet, multiparous cows. Error bars are ±SEM.­
      Figure thumbnail gr9
      Figure 9Serum concentrations of cytokines tumor necrosis factor-α (TNF-α; A), IL-6 (B), and IL-18 (C) in primiparous and multiparous cows with or without dietary supplementation with top-dressed Saccharomyces cerevisiae boulardii. CTRL-P: control diet, primiparous cows; active dry yeast (ADY)-P: ADY-supplemented diet, primiparous cows; CTRL-M: control diet, multiparous cows (lactation 2 or 3); ADY-M: ADY-supplemented diet, multiparous cows. Error bars are ±SEM.

      DISCUSSION

      Broadly speaking, ADY are understood to improve competitive exclusion of pathogenic bacteria (
      • McAllister T.A.
      • Beauchemin K.A.
      • Alazzeh A.Y.
      • Baah J.
      • Teather R.M.
      • Stanford K.
      Review: The use of direct fed microbials to mitigate pathogens and enhance production in cattle.
      ;
      • Hill C.
      • Guarner F.
      • Reid G.
      • Gibson G.R.
      • Merenstein D.J.
      • Pot B.
      • Morelli L.
      • Canani R.B.
      • Flint H.J.
      • Salminen S.
      • Calder P.C.
      • Sanders M.E.
      The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic.
      ), improve immunomodulation through TLR-4 signaling (
      • Nasiri A.H.
      • Towhidi A.
      • Shakeri M.
      • Zhandi M.
      • Dehghan-Banadaky M.
      • Pooyan H.R.
      • Sehati F.
      • Rostami F.
      • Karamzadeh A.
      • Khani M.
      • Ahmadi F.
      Effects of Saccharomyces cerevisiae supplementation on milk production, insulin sensitivity and immune response in transition dairy cows during hot season.
      ;
      • Lopreiato V.
      • Mezzetti M.
      • Cattaneo L.
      • Ferronato G.
      • Minuti A.
      • Trevisi E.
      Role of nutraceuticals during the transition period of dairy cows: A review.
      ), and improve total-tract digestibility (
      • Desnoyers M.
      • Giger-Reverdin S.
      • Bertin G.
      • Duvaux-Ponter C.
      • Sauvant D.
      Meta-analysis of the influence of Saccaromyces cerevisiae supplementation on ruminal parameters and milk production of ruminants.
      ). Some studies suggest that ADY products compete with opportunistic bacteria in the intestine and keep them from overgrowing (
      • Krehbiel C.
      • Rust S.
      • Zhang G.
      • Gilliland S.
      Bacterial direct-fed microbials in ruminant diets: Performance response and mode of action.
      ;
      • Seo J.K.
      • Kim S.W.
      • Kim M.H.
      • Upadhaya S.D.
      • Kam D.K.
      • Ha J.K.
      Direct-fed microbials for ruminant animals.
      ; Ullah Khan et al., 2016). Among the diversity of direct-fed microbials and active dry yeasts, metabolic, productive, and immunological responses to dietary ADY products differ depending on the diet, formulation, and feeding schedule (
      • Elghandour M.M.Y.
      • Salem A.Z.M.
      • Castañeda J.S.M.
      • Camacho L.M.
      • Kholif A.E.
      • Chagoyán J.C.V.
      Direct-fed microbes: A tool for improving the utilization of low quality roughages in ruminants.
      ), and thus results have been inconsistent across studies (
      • Khan R.U.
      • Naz S.
      • Dhama K.
      • Karthik K.
      • Tiwari R.
      • Abdelrahman M.M.
      • Alhidary I.A.
      • Zahoor A.
      Direct-fed microbial: Beneficial applications, modes of action and prospects as a safe tool for enhancing ruminant production and safeguarding health.
      ). A recent meta-analysis (
      • Lopreiato V.
      • Mezzetti M.
      • Cattaneo L.
      • Ferronato G.
      • Minuti A.
      • Trevisi E.
      Role of nutraceuticals during the transition period of dairy cows: A review.
      ) of yeasts and yeast products highlighted mixed results, likely missing strain-specific effects on animal response. To tease apart strain-specific modes of action and animal responses, we opted, in this discussion, to focus primarily on comparing the same strain of ADY among multiple species and physiological states. While commonalities exist among various ADY species and strains in terms of productive responses, immunological responses are considered to be strain-specific (
      • Hill C.
      • Guarner F.
      • Reid G.
      • Gibson G.R.
      • Merenstein D.J.
      • Pot B.
      • Morelli L.
      • Canani R.B.
      • Flint H.J.
      • Salminen S.
      • Calder P.C.
      • Sanders M.E.
      The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic.
      ), hence the primary focus on other research using the same strain.

      Saccharomyces cerevisiae boulardii and Productivity

      The current study investigated SCB supplementation. The ADY supplementation improved milk yield and also decreased BW loss in the first 7 wk of lactation without changes to DMI; this explains the tendency for feed efficiency to increase with SCB supplementation. In addition, energy status metabolites were unaffected by ADY supplementation. Other types of yeast products have also shown increased feed efficiency in lactating dairy cows (
      • Casper D.P.
      Effects of Saccharomyces cerevisiae fermentation products on the lactational performance of mid-lactation dairy cows. Factors affecting feed efficiency of dairy cows.
      ;
      • Moallem U.
      • Lehrer H.
      • Livshitz L.
      • Zachut M.
      • Yakoby S.
      The effects of live yeast supplementation to dairy cows during the hot season on production, feed efficiency, and digestibility.
      ;
      • Dias J.D.L.
      • Silva R.B.
      • Fernandes T.
      • Barbosa E.F.
      • Graças L.E.C.
      • Araujo R.C.
      • Pereira R.A.N.
      • Pereira M.N.
      Yeast culture increased plasma niacin concentration, evaporative heat loss, and feed efficiency of dairy cows in a hot environment.
      ). During postpartum, when high producing cows are in negative energy balance, an increase in feed efficiency would be beneficial. Cows with higher BW loss during the transition period are more likely to have reproductive challenges (
      • Poncheki J.K.
      • Canha M.L.S.
      • Viechnieski S.L.
      • de Almeida R.
      Analysis of daily body weight of dairy cows in early lactation and associations with productive and reproductive performance.
      ), so the higher BW in the ADY groups suggest SCB is beneficial for dairy cows during the lactation transition.
      Several possible modes of action for SCB supplementation exist, all of which center around protection of the postruminal, lower gastrointestinal tract. Low abomasal pH is not a barrier for SCB (CNCM I-1079), which survives low pH of 2.5 for several hours (
      • Czerucka D.
      • Piche T.
      • Rampal P.
      Review article: Yeast as probiotics—Saccharomyces boulardii.
      ;
      • Edwards-Ingram L.
      • Gitsham P.
      • Burton N.
      • Warhurst G.
      • Clarke I.
      • Hoyle D.
      • Oliver S.G.
      • Stateva L.
      Genotypic and physiological characterization of Saccharomyces boulardii, the probiotic strain of Saccharomyces cerevisiae.
      ;
      • Ma T.
      • Renaud D.
      • Skidmore A.
      • Aguilar A.
      • Chevaux E.
      • Guan L.
      • Steele M.
      Alteration of fecal bacterial composition in pre-weaned veal calves by supplementation of Saccharomyces cerevisiae boulardii in milk replacer.
      ), allowing it to also impact the lower gut. In the lower gut of Holstein calves, SCB supplementation in milk replacer increases crypt depth (
      • Fomenky B.E.
      • Chiquette J.
      • Bissonnette N.
      • Talbot G.
      • Chouinard P.Y.
      • Ibeagha-Awemu E.M.
      Impact of Saccharomyces cerevisiae boulardii CNCMI-1079 and Lactobacillus acidophilus BT1386 on total lactobacilli population in the gastrointestinal tract and colon histomorphology of Holstein dairy calves.
      ), tight junction structure (
      • Mumy K.L.
      • Chen X.
      • Kelly C.P.
      • McCormick B.A.
      Saccharomyces boulardii interferes with Shigella pathogenesis by postinvasion signaling events.
      ), and mucin production (
      • Fomenky B.E.
      • Chiquette J.
      • Bissonnette N.
      • Talbot G.
      • Chouinard P.Y.
      • Ibeagha-Awemu E.M.
      Impact of Saccharomyces cerevisiae boulardii CNCMI-1079 and Lactobacillus acidophilus BT1386 on total lactobacilli population in the gastrointestinal tract and colon histomorphology of Holstein dairy calves.
      ). Further, SCB supplementation decreases pathogen load (
      • Ma T.
      • Renaud D.
      • Skidmore A.
      • Aguilar A.
      • Chevaux E.
      • Guan L.
      • Steele M.
      Alteration of fecal bacterial composition in pre-weaned veal calves by supplementation of Saccharomyces cerevisiae boulardii in milk replacer.
      ;
      • Lee J.S.
      • Kacem N.
      • Kim W.S.
      • Peng D.Q.
      • Kim Y.J.
      • Joung Y.G.
      • Lee C.
      • Lee H.G.
      Effect of Saccharomyces boulardii supplementation on performance and physiological traits of Holstein calves under heat stress conditions.
      ) as well as days and severity of diarrhea (
      • Villot C.
      • Ma T.
      • Renaud D.L.
      • Ghaffari M.H.
      • Gibson D.J.
      • Skidmore A.
      • Chevaux E.
      • Guan L.L.
      • Steele M.A.
      Saccharomyces cerevisiae boulardii CNCM I-1079 affects health, growth, and fecal microbiota in milk-fed veal calves.
      ). The changes in lower gut morphology, namely crypt depth and tight junction improvements, in turn affect pathogen load, secretory IgA secretion (
      • Buts J.P.
      • Bernasconi P.
      • Vaerman J.P.
      • Dive C.
      Stimulation of secretory IgA and secretory component of immunoglobulins in small intestine of rats treated with Saccharomyces boulardii.
      ), and can increase the innate immune response (
      • Kayser W.C.
      • Carstens G.E.
      • Washburn K.E.
      • Welsh Jr., T.H.
      • Lawhon S.D.
      • Reddy S.M.
      • Pinchak W.E.
      • Chevaux E.
      • Skidmore A.L.
      Effects of combined viral-bacterial challenge with or without supplementation of Saccharomyces cerevisiae boulardii strain CNCM I-1079 on immune upregulation and DMI in beef heifers.
      ).
      It is possible that supplementation with SCB improved overall nutrient digestibility in the dairy cow. Increases in nutrient digestibility, as determined by the indigestible marker chromium oxide, were seen in both piglets fed probiotics including SCB (
      • Giang H.H.
      • Viet T.Q.
      • Ogle B.
      • Lindberg J.E.
      Growth performance, digestibility, gut environment and health status in weaned piglets fed a diet supplemented with potentially probiotic complexes of lactic acid bacteria.
      ) and in grower pigs fed grape pomace fermented with SCB (
      • Yan L.
      • Kim I.H.
      Effect of dietary grape pomace fermented by Saccharomyces boulardii on the growth performance, nutrient digestibility and meat quality in finishing pigs.
      ). Total-tract digestibility has been measured for dairy cattle supplemented with other yeast products (
      • Bitencourt L.L.
      • Silva J.R.M.
      • de Oliveira B.M.L.
      • Dias Jr., G.S.
      • Lopes F.
      • Siécola Jr., S.
      • de Fátima Zacaroni O.
      • Pereira M.N.
      Diet digestibility and performance of dairy cows supplemented with live yeast.
      ;
      • Ferraretto L.F.
      • Shaver R.D.
      • Bertics S.J.
      Effect of dietary supplementation with live-cell yeast at two dosages on lactation performance, ruminal fermentation, and total-tract nutrient digestibility in dairy cows.
      ;
      • Ferreira G.
      • Richardson E.S.
      • Teets C.L.
      • Akay V.
      Production performance and nutrient digestibility of lactating dairy cows fed low-forage diets with and without the addition of a live-yeast supplement.
      ) but not for the specific strain used in the current study.

      Saccharomyces cerevisiae boulardii and Immunological Impacts

      Feeding ADY products can stimulate intestinal epithelial innate immunity, leading to reduced inflammation in the intestine through increases in secretory IgA production (
      • Buts J.P.
      • Bernasconi P.
      • Vaerman J.P.
      • Dive C.
      Stimulation of secretory IgA and secretory component of immunoglobulins in small intestine of rats treated with Saccharomyces boulardii.
      ), leading to an immune-protective effect. In calves, SCB supplementation improved innate immune response by increasing oxidative bursts and phagocytosis (
      • Fomenky B.E.
      • Chiquette J.
      • Bissonnette N.
      • Talbot G.
      • Chouinard P.Y.
      • Ibeagha-Awemu E.M.
      Impact of Saccharomyces cerevisiae boulardii CNCMI-1079 and Lactobacillus acidophilus BT1386 on total lactobacilli population in the gastrointestinal tract and colon histomorphology of Holstein dairy calves.
      ). SCB has been shown to decrease levels of circulating cytokines such as IL-6 and TNF-α, though these studies have been performed in pigs (
      • Collier C.T.
      • Carroll J.A.
      • Ballou M.A.
      • Starkey J.D.
      • Sparks J.C.
      Oral administration of Saccharomyces cerevisiae boulardii reduces mortality associated with immune and cortisol responses to Escherichia coli endotoxin in pigs.
      ), cell lines (
      • Dahan S.
      • Dalmasso G.
      • Imbert V.
      • Peyron J.F.
      • Rampal P.
      • Czerucka D.
      Saccharomyces boulardii interferes with enterohemorrhagic Escherichia coli-induced signaling pathways in T84 cells.
      ), or mice (
      • Martins F.S.
      • Dalmasso G.
      • Arantes R.M.E.
      • Doye A.
      • Lemichez E.
      • Lagadec P.
      • Imbert V.
      • Peyron J.F.
      • Rampal P.
      • Nicoli J.R.
      • Czerucka D.
      Interaction of Saccharomyces boulardii with Salmonella enterica serovar Typhimurium protects mice and modifies T84 cell response to the infection.
      ) and have not been repeated in adult ruminants. In the current study, SCB supplementation increased TNF-α and tended to increase serum amyloid A, with only a tendency for changes in inflammatory cytokine IL-6 and no changes seen in IL-18 or haptoglobin. Taken together, these results suggest SCB may cause an acute immune response, but this response is inconsistent and does not affect all proinflammatory pathways.
      In canonical inflammatory pathways, TNF-α will stimulate the production of IL-6, which in turn stimulates the release of haptoglobin. Interleukin-6 increases acute phase proteins in several inflammatory diseases but has shown lower circulating levels postpartum in dairy cattle (
      • Ishikawa Y.
      • Nakada K.
      • Hagiwara K.
      • Kirisawa R.
      • Iwai H.
      • Moriyoshi M.
      • Sawamukai Y.
      Changes in interleukin-6 concentration in peripheral blood of pre- and post-partum dairy cattle and its relationship to postpartum reproductive diseases.
      ). In this study, TNF-α spiked at wk 1 postpartum in primiparous cows, likely because damaged cells in the uterus caused a chain reaction for the release of haptoglobin and the recruitment of neutrophils. An increase in circulating TNF-α levels has been previously reported in dairy cattle supplemented with yeast products (
      • Spaniol J.S.
      • Oltramari C.E.
      • Locatelli M.
      • Volpato A.
      • Campigotto G.
      • Stefani L.M.
      • Da Silva A.S.
      Influence of probiotic on somatic cell count in milk and immune system of dairy cows.
      ). It is not clear if an increase in circulating cytokines constitutes an improvement in the functioning of the immune system. Previous work saw a 16% increase in neutrophils with SCB supplementation in beef heifers (
      • Kayser W.C.
      • Carstens G.E.
      • Washburn K.E.
      • Welsh Jr., T.H.
      • Lawhon S.D.
      • Reddy S.M.
      • Pinchak W.E.
      • Chevaux E.
      • Skidmore A.L.
      Effects of combined viral-bacterial challenge with or without supplementation of Saccharomyces cerevisiae boulardii strain CNCM I-1079 on immune upregulation and DMI in beef heifers.
      ). In this study, we did not observe any effect of treatment or time on IL-18 and only saw a tendency for the interaction of treatment × parity to affect IL-6, contrary to a study in feedlot steers where ADY supplementation decreased cytokine production following an LPS challenge (
      • Buntyn J.
      • Carroll J.A.
      • Chevaux E.
      • Barling K.
      • Sieren S.E.
      • Schmidt T.B.
      Modulation of the acute phase and metabolic response in feedlot steers supplemented with Saccharomyces cerevisiae subspecies boulardii CNCM I-1079.
      ). The TNF-α stimulation of acute phase proteins appears to be species-specific (
      • Nakagawa-Tosa N.
      • Morimatsu M.
      • Kawasaki M.
      • Nakatsuji H.
      • Syuto B.
      • Saito M.
      Stimulation of haptoglobin synthesis by interleukin-6 and tumor necrosis factor, but not by interleukin-1, in bovine primary cultured hepatocytes.
      ), and thus, it is unclear if the tendency for serum amyloid A increase was due to TNF-α stimulation or some other mechanism. Interleukin-18 has also been cited for its immune-enhancing effects (
      • Shi X.J.
      • Wang B.
      • Wang M.
      Immune enhancing effects of recombinant bovine IL-18 on foot-and-mouth disease vaccination in mice model.
      ) and tends to increase around parturition (
      • Muneta Y.
      • Yoshihara K.
      • Minagawa Y.
      • Nagata R.
      • Mori Y.
      • Yamaguchi T.
      • Takehara K.
      Bovine IL-18 ELISA: Detection of IL-18 in sera of pregnant cow and newborn calf, and in colostrum.
      ); however, there was no effect of parturition or treatment on IL-18 concentrations. Further research is required to better understand how inflammatory pathways are affected by SCB supplementation.
      While the proinflammatory response was somewhat inconsistent, the acute phase response was consistent with previous studies (
      • Alsemgeest S.P.
      • Taverne M.A.
      • Boosman R.
      • van der Weyden B.C.
      • Gruys E.
      Peripartum acute-phase protein serum amyloid-A concentration in plasma of cows and fetuses.
      ;
      • Humblet M.F.
      • Guyot H.
      • Boudry B.
      • Mbayahi F.
      • Hanzen C.
      • Rollin F.
      • Godeau J.M.
      Relationship between haptoglobin, serum amyloid A, and clinical status in a survey of dairy herds during a 6-month period.
      ). Both serum amyloid A (SAA) and haptoglobin are markers of acute inflammation (
      • Humblet M.F.
      • Guyot H.
      • Boudry B.
      • Mbayahi F.
      • Hanzen C.
      • Rollin F.
      • Godeau J.M.
      Relationship between haptoglobin, serum amyloid A, and clinical status in a survey of dairy herds during a 6-month period.
      ), but interpreting results in the week after calving can be difficult due to the natural rise in SAA and Hp concentrations that occur with parturition (
      • Alsemgeest S.P.
      • Taverne M.A.
      • Boosman R.
      • van der Weyden B.C.
      • Gruys E.
      Peripartum acute-phase protein serum amyloid-A concentration in plasma of cows and fetuses.
      ;
      • Humblet M.F.
      • Guyot H.
      • Boudry B.
      • Mbayahi F.
      • Hanzen C.
      • Rollin F.
      • Godeau J.M.
      Relationship between haptoglobin, serum amyloid A, and clinical status in a survey of dairy herds during a 6-month period.
      ). From our results, it is difficult to tell if the tendency for increased SAA is due to the calving event itself or recruitment due to injury and infection postcalving, as they often occur together. Previously, it was demonstrated that SAA responds to infection (
      • Heegaard P.M.H.
      • Godson D.L.
      • Toussaint M.J.M.
      • Tjørnehøj K.
      • Larsen L.E.
      • Viuff B.
      • Rønsholt L.
      The acute phase response of haptoglobin and serum amyloid A (SAA) in cattle undergoing experimental infection with bovine respiratory syncytial virus.
      ) and also increases with physical stress (
      • Alsemgeest S.P.
      • Lambooy I.E.
      • Wierenga H.K.
      • Dieleman S.J.
      • Meerkerk B.
      • van Ederen A.M.
      • Niewold T.A.
      Influence of physical stress on the plasma concentration of serum amyloid-A (SAA) and haptoglobin (Hp) in calves.
      ) that occurs with parturition. Since SAA responds to both infection and physical stress, determining if 1 or both are the cause is difficult. In this study, SAA levels were low on the day of parturition but steadily increased through wk 4 after parturition. This is consistent with the inflammatory pathway and healing of the uterus postcalving. There was also a tendency for SAA to increase due to ADY treatment; it is unclear if this is due to an enhanced immune response to the stressors of parturition, or increased inflammation due to supplementation.
      Altered immunological activity may contribute to energetic savings resulting in improved milk production seen in this study. An immune response increases energy demand up to 55% (
      • Burdick Sanchez N.C.
      • Broadway P.R.
      • Carroll J.A.
      Influence of yeast products on modulating metabolism and immunity in cattle and swine.
      ), or the equivalent of 1 kg of glucose utilized in a 12 h period (
      • Kvidera S.K.
      • Horst E.A.
      • Abuajamieh M.
      • Mayorga E.J.
      • Fernandez M.V.S.
      • Baumgard L.H.
      Glucose requirements of an activated immune system in lactating Holstein cows.
      ), so alterations in immune response may conserve energy without affecting DMI. In this study, the altered immune response may have resulted in energetic savings that improved milk production without affecting DMI, though this was not directly measured. Further research could lead to better quantification of the benefits of immunomodulation of dairy cattle during the calving transition period. Future research should also focus on measuring and quantifying the energetic use of transition dairy cows fed SCB.

      CONCLUSIONS

      During the parturition transition, SCB supplementation increased milk production without an increase in DMI. Also, SCB appears to improve feed efficiency while maintaining body fat mobilization. This increase in efficiency suggests energetic savings in metabolic processes in the body. More research is needed to fully understand the mechanisms of energy metabolism with SCB supplementation.

      ACKNOWLEDGMENTS

      The authors thank technical support from work studies and technicians in the Laarman and Rezamand laboratories and the staff and management of the University of Idaho Dairy Center. This study was funded by Lallemand Animal Nutrition (Milwaukee, WI) and the College of Agricultural and Life Sciences at the University of Idaho (Moscow). The authors have not stated any conflicts of interest.

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