Animal Feed Science and Technology140 (2008) 223–232

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Performance and rumen fermentation of dairycalves supplemented with Saccharomyces

cerevisiae1077 or Saccharomyces boulardii1079

J.M. Pinos-Rodrıguez a,b,∗, P.H. Robinson b, M.E. Ortega c,S.L. Berry b, G. Mendoza d, R. Barcena c

a Instituto de Investigacion de Zonas Deserticas, Universidad Autonoma de San Luis Potosı,San Luis Potosı, S.L.P. 78377, Mexico

b Department of Animal Science, University of California, Davis, CA 95616, USAc Instituto de Recursos Geneticos y Productividad, Colegio de Postgraduados,

Montecillo, Edo. de Mexico 56230, Mexicod Departamento de Produccion Agrıcola y Animal, Universidad Autonoma Metropolitana,

Xochimilco, Mexico 04960, D.F., Mexico

Received 6 March 2007; received in revised form 13 June 2007; accepted 2 August 2007

Abstract

To evaluate supplementation with the yeast products Saccharomyces cerevisiae CNCM I-1077 (SC)and Saccharomyces boulardii CNCM I-1079 (SB) on performance of calves, 24 Holstein calves (12males, 12 females) were randomly assigned to each of 3 treatments being: C (control treatment), SC(1 g/d); or SB (1 g/d). Calves were fed whole milk (4.5 l/d) and a starter feed ad libitum from 4 d ofage until weaning. Female calves were weaned at 60 d of age. Neither yeast affected body weight,body weight gain or feed efficiency, although dry matter intake was higher (P<0.01) for SC versuscontrol calves. The incidence of diarrhea and pneumonia was similar between treatments. Ruminal

Abbreviations: ADG, average daily gain; ADF, acid detergent fibre; BW, body weight; CP, crude protein; DM,dry matter; FE, feed efficiency; aNDF, neutral detergent fibre; SC, Saccharomyces cerevisiae; SB, Saccharomycesboulardii; VFA, volatile fatty acid

∗ Corresponding author at: Instituto de Investigacion de Zonas Deserticas, Universidad Autonoma de San LuisPotosı, San Luis Potosı, S.L.P. 78377, Mexico. Tel.: +52 444 842 2359; fax: +52 444 842 2359.

E-mail address: jpinos@uaslp.mx (J.M. Pinos-Rodrıguez).

0377-8401/$ – see front matter © 2007 Elsevier B.V. All rights reserved.doi:10.1016/j.anifeedsci.2007.08.003

224 J.M. Pinos-Rodrıguez et al. / Animal Feed Science and Technology 140 (2008) 223–232

ammonia N, propionate and butyrate increased with SC (P<0.05), but not with SB. Results suggestthat SC modifies ruminal fermentation, but does not impact productive performance of calves.© 2007 Elsevier B.V. All rights reserved.

Keywords: Saccharomyces cerevisiae; Saccharomyces boulardii; Yeast cultures

1. Introduction

Improvements in calf nutrition can decrease morbidity and mortality, as well as increasepost-weaning rate of gain and genetic improvement due to the increased number of animalsavailable for voluntary culling (Baldwin et al., 2004). Cultures of Saccharomyces cerevisiae(SC) are extensively used as feed additives in ruminant rations, principally for dairy cattle,to increase milk yield (Nocek and Kautz, 2006). However, studies on its use in preruminantcalves are limited (e.g., Lesmeister et al., 2004). Saccharomyces boulardii (SB) is a non-pathogenic yeast extensively used in a lyophilized form as a biotherapeutic agent to treat avariety of intestinal diseases in humans and other monogastrics (Buts and De Keyser, 2006).However, studies of its use in preruminant calves are limited (e.g., Galvao et al., 2005).

SB incorporated into milk replacer (Galvao et al., 2005) improved dry matter (DM)intake, while addition of SC to a dairy calf starter (Lesmeister et al., 2004) increasedDM intake and growth, but did not impact rumen development. Oeztuerk et al. (2005)reported that addition of live and autoclaved SB stimulated in vitro ruminal microbialmetabolism, with only small differences between treatments, and concluded that ruminalmicrobes digested SB as a substrate rather than utilizing it as a probiotic. However, effectsof SB might extend beyond the rumen, because a number of yeast cells remain alive duringtransit through the digestive tract (Durand-Chaucheyras et al., 1998).

The yeast I-1077 is recommended for ruminants while I-1079 is recommended for non-ruminants and young ruminants. For that reason, we speculated the SB could stimulate DMintake, rumen fermentation and growth early in life, while SC would be more efficaciousclose to weaning when the rumen is nearing full development. Therefore, this study wasconducted to determinate effects of feeding SB or SC to preruminant dairy calves on DMintake, average daily gain (ADG) and ruminal fermentation.

2. Materials and methods

This experiment was conducted under the supervision and approval of the AcademicCommittee of the Animal Science Department of Colegio de Posgraduados-MontecilloMexico according to regulations established by the Animal Protection Law enacted bythe Estado de Mexico. The study was completed in the dairy facilities of the UniversidadAutonoma Chapingo in Chapingo, Mexico.

2.1. Animals, housing and diet

Twenty-four Holstein calves (12 males, 12 females) were separated from their dams3 d after birth, randomly assigned within sex to treatment, and placed on experiment on

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Table 1Composition and chemical analysis of the starter feed (n = 8)

g/kg, 105 ◦C

Ingredient compositionSorghum grain, ground 490Alfalfa, hay 100Soybean meal, 480 g CP/kg solvent extracted 210Meat, meal 31Corn grain, ground 109Oil, vegetable 20Molasses, cane liquid 30Mineral/vitamin premixa 10

Chemical composition (g/kg DM)DM (g/kg) 887 ± 11CP 193 ± 12aNDF 329 ± 21ADF 116 ± 12

a Ca 15 g/kg; Co 95 mg/kg; Cu 8 mg/kg; Fe 50 mg/kg; I 250 mg/kg; Mg 90 g/kg; Mn 40 mg/kg; Se 300 mg/kg;Zn 40 g/kg; vitamin A 2 MIU/kg; vitamin D 150 MIU/kg; vitamin E 40 g/kg.

their fourth day of age. Colostrum intake (100 g/kg body weight (BW)) by the calveswas confirmed within 8 h of birth. Calves were housed in a naturally ventilated barn andkept in 1.4 m × 2.6 m individual pens bedded with wood shavings. Female calves wereweaned at 60 d of age. Treatments were: control (C), Levucell (SC) (1 g/(d calf)) or Levucell(SB) (1 g/(d calf)). Levucell® SC, a ruminant specific yeast, contains 2.0 × 1010 CFU/g ofthe Pasteur Institute CNCM I-1077 strain of S. cerevisiae (Lallemand Animal Nutrition,Milwaukee, WI, USA). Levucell® SB, a monogastric or young ruminant specific yeast,contains 2.0 × 1010 CFU/g of the Pasteur Institute CNCM I-1079 strain of S. cerevisiae,spp. Boulardii (Lallemand Animal Nutrition). The SC or SB (1 g/(d calf) containing a totalof 20 billion CFU) was divided into two equal portions and administered orally to each calfwith a 50 ml syringe (1 g of SC or SB diluted in 10 ml sterile water) 10 min before milkfeeding to assure entry to the rumen. An equal volume of water was administered orallywith a syringe to the control calves. Calves were maintained on the study from 4 through60 d of age. All calves received 4.5 kg whole milk (110 g solids/kg, 31 g crude protein/kgand 34 g fat/kg), divided into two equal portions at 07:00 and 16:00 h, and water and starterfeed (Table 1) ad libitum. That every calf drank all of its milk was confirmed daily.

The DM (method 930.15) and N (method 990.03) were determined in the calf starter(AOAC, 1995), as well as aNDF and ADF (Van Soest et al., 1991). The aNDF was analysedwith addition of a heat stable alpha-amylase and without sodium sulphite. The aNDF andADF contents are expressed inclusive of residual ash.

2.2. Experimental measurements, fecal scoring and rumen fluid sampling

Weekly measurements of BW were made and intake of DM from starter and milk wasrecorded daily and averaged weekly. Refusals plus wastage were used to calculate DMintake of starter. Calves were observed daily to detect respiratory problems, and were fecal

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scored for determination of fecal fluidity, consistency, odor and days of diarrhea (Larson etal., 1977).

2.3. Rumen fluid sampling

Rumen fluid was collected by an esophageal tube from nine male calves (i.e., 3/treatment)every 14 d, 4 h after the morning milk feeding without restriction of feeding. Concentrationsof volatile fatty acids (VFA: Erwin et al., 1961), pH (Fisher Accumet, Pittsburgh, PA, USA)and ammonia N (McCullough, 1967) were determined.

2.4. Experimental design and statistical analyses

The growth and ruminal experiment was a randomized complete block (sex) design.Data for initial and final BW, and BW gain, were analyzed as a randomized completedesign. Continuous data collected over time (i.e., BW, DM intake, ADG, feed efficiency(FE), ruminal pH, ammonia N, VFA) were analyzed for repeated measures by the ‘MIXED’procedure of SAS (1999). Calf nested within treatment was a random effect in the model.The covariance structure for the data was tested and the structure that best fitted the datawas chosen (Littell et al., 1998). The statistical model utilized was

y = μ + treatmenti + d of agej + (treatment × d of age)ij + εijk

where y is the dependent variable; μ the average experimental value; treatmenti is thefixed effect of yeast culture (Control, SB or SC); d of agej is the effect of period (4–60 d);(treatment × d of age)ij is the effect of interaction between treatment and d of age; �ijk is anerror term; and k is 1, . . ., 24.

Four-day-old BW was used as a covariate and ‘sex’ was included in the model but theywere not significant (i.e., P≥0.05). Treatment differences with P≤0.05 were consideredas statistically significant. When a treatment effect occurred, individual comparisons usedthe PDIFF adjusted = Tukey statement of SAS (1999). Diarrhea and pneumonia data wereanalyzed with χ2 using CATMODE of SAS (1999).

3. Results

3.1. BW gain, intake and health

Initial BW was similar among treatments (Table 2), and neither SC or SB affectedBW, total BW gain, ADG, FE or frequency of diarrheas and pneumonias. However, SCsupplemented calves had a higher overall total, and starter, DM intake during the periodfrom 4 to 60 d of age, versus control calves (Table 2), with SB calves intermediate. TheBW, total DM intake and ADG increased (P<0.0001) with calf age (Figs. 1–3).

There were no differences among groups of calves in the occurrence of diarrhea orpneumonia, but less calves receiving SC had these diseases (diarrheas = 3; pneumonias = 1)or SB (diarrheas = 3; pneumonias = 1) than control calves (diarrheas = 6; pneumonias = 5).

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Table 2Initial and final BW, BW gain and digestibility in calves supplemented with SC or SB yeast culture strainsa

C SC SB S.E.M.

Initial BW (kg) 41.8 41.2 42.3 1.27Final BW (kg) 59.1 59.8 61.3 2.21BW gain (kg) 17.3 18.6 19.0 1.40Starter DM intake (g/d) 842 b 911 a 857 ab 16.4FE (DM intake/ADG) 3.46 3.51 3.23 0.259

Means in the same row with different letters differ (P≤0.05).a Treatments were—C: control; SC: Saccharomyces cerevisiae1077; SB: Saccharomyces boulardii1079.

3.2. Ruminal parameter values

The pH, total VFA, acetate:propionate ratio (Table 3) acetate, propionate and butyrate(Fig. 4) differed among treatments with age, but ruminal pH and total VFA were notaffected by SC or SB. Calves fed SC had a higher ammonia N concentration versus con-

Fig. 1. BW of calves not supplemented (control) or supplemented with Sacharomyces cerevisiae (SC) orSacharmyces boulardii (SB) (yeast: NS; age: P<0.0001; interaction yeast × age: NS; S.E.M. = 1.68).

Fig. 2. Total and starter DM intake in calves not supplemented (control) or supplemented with S. cerevisiae (SC)or S. boulardii (SB) (yeast: P<0.05; age: P<0.0001; interaction yeast × age: NS; S.E.M. = 32.97).

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Fig. 3. ADG in calves not supplemented (control) or supplemented with S. cerevisiae (SC) or S. boulardii (SB)(yeast: NS; age: P<0.0001; interaction yeast × age: NS; S.E.M. = 49.23).

Table 3Ruminal pH, total VFA and acetate propionate ratio in calves supplemented with SB or SC yeast culture strainsa

Yeast Age (d) Significance

C SC SB 18 32 46 60 S.E.M. Y A Y × A

pH 5.6 5.4 5.3 5.8 5.5 5.3 5.4 0.11 NS *** NSTotal VFA (mmol/l) 81.5 112.6 103.7 69.3 101.5 115.5 110.8 18.82 NS ** NSAcetate:propionate 1.4 b 1.7 a 1.6 ab 1.8 1.7 1.3 1.4 0.12 * *** NS

Means in the same row with different letters differ (P≤0.05). NS: not significant. *P≤0.05; **P≤0.01; ***P≤0.001.a Treatments were—C: control; SC: S. cerevisiae1077; SB: S. boulardii1079; Y: yeast; A: age; Y × A = interaction.

trol calves during the 18 and 60 d growth period (Fig. 5). The acetate concentration incontrol calves (54.2 mol/100 mol) was lower (P<0.05) than in calves supplemented withSB (57.0 mol/100 mol), but similar to those fed SC (54.3 mol/100 mol). Propionate con-centration was lower at 32 d of age with SC (P<0.05), but not with SB. Rumen butyrateconcentration in calves supplemented with SC at 18 (P<0.05) was higher than control,but similar to those with SB, while at 32 d of age the SC calves had higher concentra-tions than control or SB calves (P<0.001). Ruminal acetate:propionate ratio was lower inunsupplemented calves than SC, but both were similar to SB (Table 3).

Fig. 4. Ruminal acetate (S.E.M. = 1.57), propionate (S.E.M. = 1.70) and butyrate (S.E.M. = 0.98) of calves notsupplemented (control) or supplemented with S. cerevisiae (SC) or S. boulardii (SB). Acetate (yeast: P<0.05;age: P<0.001; interaction yeast × age: NS); propionate and butyrate (yeast: P<0.01; age: P<0.01; interactionyeast × age: P<0.05).

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Fig. 5. Ruminal ammonia N in calves not supplemented (Control) or supplemented with S. cerevisiae (SC) or S.boulardii (SB) (yeast: P<0.01; age: NS; interaction yeast × age: P<0.05; S.E.M. = 1.83).

4. Discussion

4.1. BW gain and DM intake

Differences in DM intake of starter suggest that SC may aid adaptation to dry feeds(Seymour et al., 1995), and are consistent with Lesmeister et al. (2004) findings in preweaneddairy calves. However, in spite of increased DM intake with SC, there was no change in ADGor FE. Results of S. cerevisiae feeding on calf performance have been variable. For example,it increased ADG in feeder calves (Phillips and Von Tungel, 1985), while performance hasbeen similar (Seymour et al., 1995; Wagner et al., 1990) in other studies with calves.Effects of supplemental S. boulardii in calves were evaluated by Galvao et al. (2005), whoreported that BW, intake of grain DM and FE prior to weaning was higher for SC1077, butnot for SB1079 versus the control diet. Calf responses from yeast supplementation appearto vary with diet composition (Wagner et al., 1990), level of yeast feeding (Lesmeisteret al., 2004), as well as yeast strain and supplementation method (Galvao et al., 2005. S.cerevisiae cultures may increase DM intake by improving ruminal conditions that stimulateto cellulolysis (Williams et al., 1991).

4.2. Ruminal fermentation

In other studies in which S. cerevisiae has been fed to calves, there were no differencesin pH or total VFA concentrations (Dawson et al., 1990), which could be due to the lowerruminal pH in young ruminants versus adults (Kumar et al., 1994). Some studies suggested(Beauchemin et al., 2003) that ruminal conditions, such as pH, should be sub-optimal foryeast growth and expression of benefical effects. However, stimulatory effects of most yeastson ruminal microbial growth is probably not be due to their growth in the rumen (Oeztuerket al., 2005).

SC could potentially minimize fluctuations in rumen pH, and reduce risk of acidosis,because it reduces availability of glucose for lactate synthesis by S. bovis, and enhancesutilization of l-lactate by M. elsdenii (Chaucheyras et al., 1996). However, in our studyruminal pH did not differ among treatments, but acetate propionate, butyrate (Fig. 4) and

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acetate propionate ratio were impacted by yeast feeding. Results have been variable forrumen ammonia N concentrations when S. cerevisiae has been supplemented by others, withno differences (Mutsvangwa et al., 1992) or an increment (Newbold et al., 1995), which mayhave been due to a response of rumen microorganisms to substrate supply rather than a shiftin fermentation (Newbold et al., 1995). Yeast cell walls contain glucans, mannoproteins andchitin (Klis, 1994; Moukadiri et al., 1997) which are appropriate substrates for microbialfermentation in the rumen regardless of whether the yeast are viable or dead. SB can increaseammonia N and total short-chain fatty acid production, principally acetate and butyrate(Oeztuerk et al., 2005). Positive effects of feeding yeast on ruminal fermentation may berelated to DM intake since S. cerevisiae influences microbial colonization in the rumen,which could influence fermentation (Chaucheyras-Durant and Fonty, 2001), principally ofcarbohydrates, which would stimulate DM intake (Galvao et al., 2005).

4.3. S. cerevisiae vs. S. boulardii

Comparisons of yeast strains have shown variability in their ability to alter ruminalfermentation (Newbold et al., 1995; Arcos-Garcia et al., 2000). Butyrate and, to a lesserextent, propionate are used as energy sources by rumen epithelium and, subsequently, havethe biggest influence on epithelial development (Tamate et al., 1962). However, it is possiblethat the lower ruminal butyrate concentrations in SB versus SC calves was the result ofincreased uptake of ruminal butyrate by ruminal epithelium (Lesmeister and Heinrichs,2004), which could accelerate functionality, or improve stability, of the rumen ecosystemin young ruminants (Chaucheyras-Durant and Fonty, 2002).

5. Conclusion

Feeding SC or SB yeast cultures to preruminant calves did not improve their productiveperformance or health despite an increase in DM intake, and improved ruminal fermentation,with SC feeding.

Acknowledgements

The first author thanks the UCMEXUS-CONACYT Faculty Fellowship program forsupport in writing the manuscript, and to the Universidad Autonoma Chapingo in Mexicofor the facilities, especially to Dr. Jose Ayala.

References

AOAC (Association of Official Analytical Chemists), 1995. Official Methods of Analysis, 16th ed. AOAC,Arlington, VA, USA.

Arcos-Garcia, J.L., Castrejon, F., Mendoza, G.D., Perez, E.P., 2000. Effect of two commercial yeast cultures withSaccharomyces cerevisiae on ruminal fermentation and digestion in sheep fed sugar cane tops. Livest. Prod.Sci. 63, 153–157.

J.M. Pinos-Rodrıguez et al. / Animal Feed Science and Technology 140 (2008) 223–232 231

Baldwin, R.L., McLeod, K.R., Klotz, J.L., Heitmann, R.N., 2004. Rumen development, intestinal growth andhepatic metabolism in the pre- and postweaning ruminant. J. Dairy Sci. 87 (E. Suppl.), E55–E65.

Beauchemin, K.A., Yang, W.Z., Morgavi, D.P., Ghorbani, G.R., Kautz, W., Leedle, J.A.Z., 2003. Effects of bacterialdirect fed microbials and yeast on site and extent of digestion, blood chemistry, and subclinical ruminal acidosisin feedlot cattle. J. Anim. Sci. 81, 1628–1640.

Buts, J.P., De Keyser, N., 2006. Effects of Saccharomyces boulardii on intestinal mucosa. Dig. Dis. Sci. 51,1485–1492.

Chaucheyras, F., Fonty, G., Bertin, G., Salmon, J.M., Gouet, P., 1996. Effect of a strain of Saccharomyces cerevisiae(Levucell SC-I), a microbial additive for ruminants, on lactate metabolism in vitro. Can. J. Microbiol. 42,927–933.

Chaucheyras-Durant, F., Fonty, G., 2001. Establishment of cellulolytic bacteria and development of fermenta-tive activities in the rumen of gnotobiotically reared lambs receiving the microbial additive Saccharomycescerevisiae CNM I-1077. Reprod. Nutr. Dev. 41, 57–68.

Chaucheyras-Durant, F., Fonty, G., 2002. Influence of a probiotic yeast (Saccharomyces cerevisiae CNM I-1077)on microbial colonization and fermentation in the rumen of newborn lamb. Microb. Ecol. Health Dis. 14,30–36.

Dawson, K.A., Newman, K.E., Boling, J.A., 1990. Effects of microbial supplements containing yeast and lacto-bacilli on roughage-fed ruminal activities. J. Anim. Sci. 68, 3392–3398.

Durand-Chaucheyras, F., Fonty, G., Bertin, G., Theveniot, M., Gouet, P., 1998. Fate of Levucell SC I-1077 yeastadditive during digestive transit in lambs. Reprod. Nutr. Dev. 38, 275–280.

Erwin, E.S., Marco, G.J., Emery, E., 1961. Volatile fatty acid analysis of blood and rumen fluid by gas chromatog-raphy. J. Dairy Sci. 44, 1768–1771.

Galvao, K.N., Santos, J.E., Cosconi, A., Villasenor, M., Sischo, W.M., Berge, A.C., 2005. Effect if feeding liveyeast products to calves with failure of passive transfer on performance and patterns of antibiotic resistance infecal Escherichia coli. Reprod. Nutr. Dev. 45, 427–440.

Klis, F.M., 1994. Review: cell wall assembly in yeast. Yeast 10, 851–869.Kumar, U., Sareen, V.K., Singh, S., 1994. Effect of Saccharomyces cerevisiae yeast culture supplement on ruminal

metabolism in buffalo calves given a high concentrated diet. Anim. Prod. 59, 209–215.Larson, L.L., Owen, F.G., Albright, J.L., Appleman, R.D., Lamb, R.C., Muller, L.D., 1977. Guidelines toward

more uniformity in measuring and reporting calf experimental data. J. Anim. Sci. 60, 989–991.Lesmeister, K.E., Heinrichs, A.J., 2004. Effects of corn processing on growth characteristics, rumen development,

and rumen parameters in neonatal dairy calves. J. Dairy Sci. 87, 3439–3450.Lesmeister, K.E., Heinrichs, A.J., Gabler, M.T., 2004. Effects of supplemental yeast (Saccharomyces cerevisiae)

culture on rumen development rumen development, growth characteristics, and blood parameters in neonataldairy calves. J. Dairy Sci. 87, 3439–3450.

Littell, R.C., Henry, P.R., Ammerman, C.B., 1998. Statistical analysis of repeated measures data using SASprocedures. J. Anim. Sci. 76, 1216–1231.

McCullough, H., 1967. The determination of ammonia in whole blood by direct colorimetric method. Clin. Chem.Acta 17, 297–304.

Moukadiri, I., Armero, J., Abad, A., Sentandreu, R., Zueco, J., 1997. Identification of a mannoprotein present inthe inner layer of the cell wall of Saccharomyces cerevisiae. J. Bacteriol. 179, 2154–2162.

Mutsvangwa, T., Edwards, I.E., Topps, J.H., Paterson, G.F.M., 1992. The effect of dietary inclusion of yeast culture(Yea-Sacc) on patterns of rumen fermentation, food intake and growth of intensively fed bulls. Anim. Prod.55, 35–40.

Newbold, C.J., Wallace, R.J., Chen, X.B., McIntosh, F.M., 1995. Different strains of Saccharomyces cerevisiaediffer in their effect on ruminal bacterial numbers in vitro in sheep. J. Anim. Sci. 73, 1811–1818.

Nocek, J.E., Kautz, W.O., 2006. Direct-fed microbial supplementation on ruminal digestion, health and perfor-mance of pre- and postpartum dairy cattle. J. Dairy Sci. 89, 260–266.

Oeztuerk, H., Schroeder, B., Beyerbach, M., Breves, G., 2005. Influence of living and autoclaved yeast ofSaccharomyces boulardii on in vitro ruminal microbial metabolism. J. Dairy Sci. 88, 2594–2600.

Phillips, W.A., Von Tungel, D.L., 1985. The effect of yeast culture on the poststrees performance of feeder calves.Nutr. Rep. Int. 322, 287–295.

SAS, 1999. User’s Guide: Statistics. SAS Institute, Cary, NC, USA.

232 J.M. Pinos-Rodrıguez et al. / Animal Feed Science and Technology 140 (2008) 223–232

Seymour, W.M., Nocek, J.E., Siciliano-Jones, J., 1995. Effects of a colostrum substitute and of a dietary brewer’syeast on the health and performance of dairy calves. J. Dairy Sci. 78, 412–420.

Tamate, H., McGillard, A.D., Jacobson, N.L., Getty, R., 1962. Effect of various dietaries on the anatomicaldevelopment of the stomach in the calf. J. Dairy Sci. 45, 408–420.

Van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Symposium: carbohydrate methodology, metabolism, andnutritional implications in dairy cattle. J. Dairy Sci. 74, 3583–3597.

Wagner, D.G., Quinonez, J., Bush, J., 1990. The effect of corn or wheat based diets and yeast culture on perfor-mance, ruminal pH and volatile fatty acids in dairy cattle. Agric. Pract. 11, 7–12.

Williams, P.E.W., Tait, C.A.G., Innes, G.M., Newbold, C.J., 1991. Effects of the inclusion of yeast culture (Sac-charomyces cerevisiae plus growth medium) in the diet of dairy cows on milk yield and forage degradationand fermentation patterns in the rumen of steers. J. Anim. Sci. 69, 3016–3026.