Performance and Ruminal Function Development of Young Calves Fed Diets with Aspergillus oryzae Fermentation Extract’,* A. A. BEHARKA, T. G. NAGARAJA, and J. L. MORRILL Department of Animal Sciences and Industry Kansas State University Manhattan 6650&1600

tivity than those not fed Amaferm. (Key words: calves, rumen development, Aspergillus oryzae, fermentation extract).

ABSTRACT

Neonatal Holstein heifer (n = 72) and bull (n = 40) calves were used to study the effects of AspergiZZus oryzae fermentation extract (Amaferm) on their performance and on rumen development. The starter diets were formulated to achieve Amaferm consumption of 0, .5, 1, or 3 g per calf daily. Calves were fed milk daily and allowed to consume starter and a mixture of alfalfa and bromegrass hay ad libitum. Weaning was when calves consumed 550 g of starter on 2 consecutive d. Weight gain and feed consumption were recorded weekly. Forty of the heifer calves, 10 from each treatment, were selected randomly to study the effects of Amaferm on ruminal fermentative development. Ruminal fluid samples were collected for pH, ruminal fermentation products, and for bacterial enumerations. Overall, Arnaferm-supplemented calves were weaned 1 wk earlier than unsupplemented calves. They had higher total VFA, propionate, and acetate concentrations in the rumen than unsupplemented calves. Total anaerobic, hemicellulolytic, and pectinolytic bacterial counts were higher; cellulolytic bacterial counts tended to be higher for the Amaferm-supplemented calves than for controls. h general, Amaferm-supplemented calves had greater ruminal microbial ac-

Abbreviation key: F:G = feed:gain ratio. INTRODUCTION

Reports on the use of fungal supplements in calf diets date back to 1924 (4); however, the results of those early studies were inconclusive. In recent years, there has been renewed interest in the use of microbial products as feed additives in ruminant diets, partly because of concerns about antibiotics. Several fungal products currently are available commercially. One of these is Amaferm (BioZyme, Inc., St. Joseph, MO), a fermentation extract of Aspergillus oryzae. The addition of Amaferm, or products containing Amaferm, to adult ruminant diets increases digestion of DM, NDF, ADF, and CP in vivo and in vitro (3, 6, 22, 23). Milk production and milk fat percentage have been increased by Amaferm supplementation, but DMI remained the same; however, this response varied with the forage content of the diet (7, 10, 11). Amaferm supplementation would be beneficial to the neonatal calf if dry feed consumption could be stimulated at an early age. This would result in accelerated ruminal muscle development (8), rumen motility (15), and ruminal microbial activity (2). Additionally, early consumption of dry feed could lead to early weaning, which is beneficial to the producer because of reduced labor and feed costs and because weaned calves have fewer digesReceived November 26, 1990. tive disorders (12, 18). Accepted March 6, 1991. Amaferm stimulates bacterial activity in kontribution W161-J from the Kansas Agriculh~ral Experiment Station. vitro and in vivo (5,23). Bacterial populations 2Reference to a company or a product does not imply are present in calves at very young ages (2). approval or recommendation of the product by Kansas State University to the exclusion of other products that Therefore, Amaferm could stimulate microbial development, resulting in increased ruminal also may be suitable. 1991 J Dairy Sci 7443264336

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ASPERGIUUS ORYZAE EXTRACT IN CALF DIETS

metabolic activity, increased intake of dry feed, and possibly early weaning. Therefore, the purpose of this study was to determine the effects of supplemental Amaferm on calf performance and ruminal microbial and metabolic development.

TABLE 1. Composition and proximate analysis of starter diet.

@)

Item Ingredient1

Com, cracked Soybeans, extruded Soybean hulls oats, ground

MATERIALS AND METHODS Experiments 1 and 2

Seventy-two neonatal Holstein heifer calves (Experiment 1) and 40 neonatal Holstein bull calves (Experiment 2) were separated from their dams within 24 h postpartum and fed colostrum until 3 d of age. Calves were housed in hutches; heifers and bulls were kept in separate locations and were cared for by different people. Calves were assigned to blocks of four according to birth date, and then they were assigned randomly from each block to one of four diets. The control diet contained no Amaferm. Calves assigned to the low, moderate, and high Amaferm diets received Amaferm at .92, 1.83, and 5.5 g/kg of starter until weaning and received .28, .55, and 1.65 g/kg of starter until 11 wk of age, respectively. All calves were fed milk at 8% of birth weight daily, divided into two equal feedings. They were allowed to consume calf starter (Table 1) and water ad libitum and were weaned when they consumed 550 g of starter on 2 consecutive d. The hay consisted of a mixture of 75% bromegrass and 25% alfalfa, The hay mixture was 90% DM, 13% CP, 55% NDF, and 34% ADF. Performance Evaluation. General appearance ratings and observed deviations from normal health were recorded daily. Feces of each calf were evaluated daily using the scale described by Larson et al. (13). Weekly weight gains and feed consumption were recorded, and feed to gain (F:G) ratio was detemined. Experlment 3

Forty heifer calves, 10 from each treatment in Experiment 1, were selected randomly for ruminal metabolic analyses and bacterial enumerations (Experiment 3). Ruminal SampIing and Analytical Procedures. Ruminal fluid samples were collected 3

4321

Molasses, wet Limestone Didcium phosphate Trace-minaalized salt

vitamins2 Amafenn3 chemical aualysis DM

8 NDP ADF

36.0 22.4 19.5 15.0 5.9 .8 .2 .2 40 or

+

89.2 16.6 30.0 12.4

1As-fed basis. *Vitamins: 2200 IU of vitamin A, 330 IU of vitamin D. and 110 IU of vitamin E/kg. 3The low, modexate, and high Amaferm diets had Amaferm at .W, 1.83,and 5.5 g/kg of starter until weaning and .28, 5 5 . and 1.65 g/kg after weaning.

h postfeeding at 2, 4, 6, 8, and 10 wk of age via stomach tube. Sample pH was determined before processing. The sample was blended for 1 min, strained through four layers of cheesecloth under C@ gas, and used for analysis of ammonia N, VFA,and I.-(+)-lactate concentrations and for bacterial enumerations (1, 2). Enumeration of Bacteria. Complete carbohydrate medium was used to enumerate total viable anaerobic bacteria as previously described (2), except that homogenized xylan was added at .30%. Selective carbohydrate media containing .3% soluble starch, homogenized xylan and xylose, or pectin as the single energy source (.3%) were used for the enumeration of amylolytic, hemicellulolytic, and pectinolytic bacteria, respectively. Cellulolytic bacteria were enumerated as previously described (2), except the medium was modified to contain .l% pebblemilled cellulose. Inoculation of media was the same as in Anderson et al. (2). Statistical Analysis. The performance data for each experiment were analyzed individually as a split-plot design using the general linear models procedure of SAS (21). The whole plot was used to test for differences of Journal of Dairy Science Vol. 74, No. 12, 1991

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BEHARKA ET AL.

TABLE 2. Effect of Amaferm on weaning date of control or Amaferm-supplemented calves.

The microbial and metabolic data also were analyzed as a split plot. The whole-plot model was used to test for differences of treatment with treatment and calf as the error term. The Experiment Control Low Moderate High subplot model was used to test for differences (wk) caused by age and treatment x age interaction. Experiment 1 The residual error was the subplot error term. 5.4= 4.6b 4.6b 4.6b heifer calves Least squares means were separated using the Experiment 2 protected least significant differences test when 5.5 4.8 5.1 bull calves 4.7 Experiment 3 significant treatment or treatment x age effects heifer subset 5.7* 4SB 4.IB 4.2B were detected. Significance was declared at P sb9cMeans within a row with different superscripts < .05 unless otherwise noted. differ (P < .OS). L

B

c within ~ ~ a row with different superscripts

.

RESULTS

differ (P < .01).

Effect of Amaferm on Performance

treatment and block and for interaction of treatment and block; treatment x block was the whole-plot error term. The subplot model was used to test for differences caused by age and interaction of treatment and age. The residual error served as the error term for the subplot.

Experiment 1. Heifer calves receiving s u p plemental Amaferm were weaned almost 1 wk earlier than unsupplemented calves (Table 2); however, level of Amaferm supplementation did not influence weaning date. No differences were found in general health or fecal scores

TABLE 3. Weekly dry feed intake, weight gab, and daily M e n u intake of control or Amafenn-supplemented calves. Amaferm

Ifem ~

~~~~

Control

LOW

Moderate

Hi&

SE

2.4 13.3 7.8

2.9 14.5 8.7

2.5 14.2 8.3

2.8 14.5 8.7

2.4 .1

.2

.4 1.1 .8

1.3 3.1 2.2

.1 .2 .2

.7 .8 .8

1.9

1.2 2.7

~

Experiment 1 heifer calves (n = 72) weekly dry feed intake, kg wk 1-5 wk 6-10 wk 1-10 Daily Amaferm intake, g Wk 1-5 wk 6-10 wk 1-10 Weekly weight g a i ~ kg ~, Wk 1-5 wk 6-10 wk 1-10 Experiment 2 bull calves (n = 40) Weekly dry feed intake. kg Wk 1-5 wk 6-10 Wk 1-10 Daily Amaferm intake, g Wk 1-5 wk 6-10 Wk 1-10 Weekly weight gain, kg Wk 1-5 wk 6-10 wk 1-101

0 0 0

.5

.4

.8

1.9 5.2 3.6

2.2 5.4 3.8

2.1 3.8

2.4 5.8 4.1

2.8 14.3 8.5

2.3 14.7 8.7

2.5 15.0 8.8

14.2 8.0

2 A

.4 1.1 .8

1.o 3.3 2.2

.1 .2 .2

2.6 62 4.4

2.8 5.7 4.3

2.5 5.4 4.0

.9 1.7 1.5

0 0 0 2.6 5.1 3.8

'Treatment x age effect (P < .1). Journal of Dairy Science Vol. 74, No. 12, 1991

.5

5.5

2.5

ASPERGILLUS ORlzAE EXTRACT IN CALF DIETS

4329

TABLE 4. Weekly dry feed intake of control or Amaferm-supplemented heifer calves' (Experiment 3). Merm Age

Control

(wk) .22 '46 1.62

1

2 3 4 5 6 7 8 9 10 SE 1-10

2.%b

4.41' 6.2@ 9.8@ 14.298 14.85' 17.26a .68 7.0b

Moderate

LOW

Weekly dry feed intake (kg) .24 .09 .41 .34 1.86 1.55 3.9Ib 3.71b 7.01b 7.24b 8.Wb 11.03b 11 .WC 12.94b 15.d 14.84' 18.1Sb 16.37" 20.22b 20.33b .76 .74 8.8a 8.8'

High .39

.92 2.19 4.73a 8.11b 10.2Sb 12.49b 15.88b 18.16b 19.Ub .74 9.3a

'Sb*cMeanswithin a row with different superscripts differ (P < .1). 1,

= 40.

among calves in any treatment (data not shown, P = 3). Weekly intake of dry feed (Table 3) of all calves increased with age ( P < .01). Dry feed intake was not affected by Amaferm supplementation for the entire IO-wk trial; however, Amaferm-supplemented heifer calves tended to eat more dry feed during the first 5 wk (P = .11). Weekly weight gain was not affected by Amaferm supplementation. There was no difference in F:G between calves on any treatment (F:G = 2.1; P = A). The heifer calves did not reach the targeted Amaferm levels of .5, 1, and 3 g/d per head until they were 8 wk of age, and the average Amaferm intakes for the experiment were lower than targeted. Experiment 2. Four bull calves were removed from the study for sickness unrelated to the experiment. Weaning date of bull calves tended to be earlier in Amaferm-supplemented calves than in controls. Overall, calves supplemented with Amaferm at the low and moderate levels tended to have higher weekly weight gains and daily feed intakes (Table 3) and tended to be weaned earlier (Table 2) than controls. In contrast, those fed the high Amaferm level tended to have lower dry feed intakes and lower weight gains for the first 5 wk than controls (Table 3). However, weekly weight gains for wk 6 to 10 were slightly higher than those of control animals, causing a treatment x age interaction (P < .1). The F G ratio (2:2) did not differ among treatments (P > .1).

Amaferm intake up to wk 7 was less than the expected consumption rate of 3, 1, and .5 g/d per head; however, the Amaferm intake was higher than targeted after wk 8 because of the increased dry feed consumption. By wk 10, the calves receiving the high Amaferm supplement were eating over 135% of the targeted level. Experiment 3. Amaferm-supplemented heifer calves were weaned earlier than controls (P c .Ol) (Table 2). Weekly dry feed intake and weight gain showed a treatment x age interaction (P < .1). Amaferm-supplemented calves had higher dry feed intakes than those not receiving Amaferm; however, the differences were not significant until wk 4 for the high and wk 5 for the moderate and low levels of Amaferm, respectively (Table 4). Calves supplemented with Amaferm had higher weekly weight gains than controls (Table 5), but the diffemnce was significant only at 5 wk of age for all levels of Amaferm (P < .l) and at week 10 (P c .l) for calves on the low Amaferm supplementation. An analysis of total weight gain for the entire trial (wk 1 to 10) showed that the calves fed the low and high Amaferm supplement gained more than controls. There were no differences (P = .38) in F G between supplemented and unsupplemented calves. The average daily Amaferm intakes for the heifer subset (Experiment 3) were not different from those for the heifer group as a whole (Experiment 1) (Table 2); treatment averages were .38, .7, and 2.3 g/d per head for the low, J o d of Dairy Science Vol. 74, No. 12, 1991

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BEHARKA ET AL.

TABLE 5. Weekly weight gain of control or Amafem-supplemented heifer calves’ (Experiment 3).

Amaferm Age

Control

Hiah

Moderate

LOW

Weekly weight gain (kg)

(wk) I

.98 .5 3 1.78 3.37 1.ab 3.56 4.43 6.06 5.91 5.87b 3.4= .73

2

3 4 5

6 7 8

9 10 1-10

SE

3.38 2.93 3.54’ 4.09 4.04 6.31 7.22 7.83’ 4.e

-.23 1.05 1.18 4.14 3.41’ 4.05 5.14 5.14 4.82 6.82b 3.5k

.77 .55 3.14 4.05 3.458 4.59 4.68 7.23 7.18 6.27b 4.2a

.84

.80

.80

.61

.so

“bMeuleans within a row without common superscripts differ (P < .1). 1,

= 40.

moderate, and high Amaferm treatments, respectively. Ruminal Fermentation Products. Rumen pH declined with age (P < .01) (Table 6). but supplemented and unsupplemented calves had similar rumen pH. Lactate concentrations decreased with age but was not affected by Amaferm supplementation. Ammonia concentrations in the rumen showed a treatment x calf age interaction (Figure 1). Calves fed the moderate level of Amaferm had higher ammonia

concentrations during wk 2 and 4 (P< .l), and the low Amaferm group had a higher ammonia concentration for wk 4.Total VFA concentrations increased with calf (P < .01). Calves supplemented with moderate or high levels of Amaferm had or tended to have higher total VFA concentrations after wk 4 than those of controls (Figure 1). After wk 2, Amaferm calves supplemented at the high or moderate levels had or tended to have higher acetate (P < .lo) and propionate concentrations than con-

TABLE 6. Ruminal fermetation characteristics in control or Amafem-supplemented heifer calves’ eperiment 3).

Weeks of ape Item Control PH Lactate, mM Ace.tate:propionate Low m e r m PH Lactate, mM Acetate:propionate Moderate Amaferm PH Lactate, mM Acetate:propionate High Amaferm PH Lactate, mM Acetate:propionate

2

4

6

8

10

SE

6.4 4.5 2.9

5.7 3.5 1.8

5.6 .8 1.9

5.7 .5 1.5

5.8 5

.2

1.3

.4 .3

6.7 4.3 2.8

6.0 3.5 1.9

5.6 .9 1.3

5.8 .5 1.3

5.8 .6 1.3

.4 .3

6.4 4.4 3.9

5.5 3.2 1.8

5.7 1.o 12

5.4 .6 1.1

6.0 .6 1.2

6.3 4.6 3.4

5.8 3.1 1.6

5.9

5.8 .7 12

6.0 5 1.2

‘n = 40.

J o d of Dairy Science Vol. 74, No. 12, 1991

.8 1.6

2

2 5 .3

.1 .5

.3

ASPERGILLUS ORYZAE

30

r

433 1

EXTRACT IN CALF DIETS

. . . I

Control

Low Amaf erm

@BlModerate

High Ama f erm

Amaferm

12

6

0

W

2

4

6

8

10

WEEKS OF AGE Figure 1. Ruminal VFA (treatment, P < .OS; treatment x age effect, P < .15) and ammonia N concentration (treatment x age effect, P < .01) in Amaferm-supplanented or unsupplementai calves. Dierent from control (+P < .IO,*P < .OS, and ++P < .01, respectively). Staudard error is 6.8 for VPA and 1.3 for ammonia N (n = 40).

Jonmal of Dairy Science Vol. 74, No. 12, 1991

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BEHARKA ET AL.

trols (Table 8). The acetate:propionate ratio was not affected by treatment (Table 6). Also, Amaferm supplementation had no effect on butyrate concentration. Isovalerate showed a treatment x age interaction (P e .01). Overall, the concentration of isovalerate was higher for controls than for Amaferm-supplemented calves at 2 and 4 wk of age (P < .l) but was similar for the remaining weeks (Table 7). Similarly, isobutyrate concentrations tended to be higher (P = .13) for the control calves during wk 2 and 4. Ruminal Bacterial Counts. Counts of total viable anaerobic bacteria were affected by treatment and age of calves (P < .Ol) (Figure 2). The high Amaferm-supplemented group had higher counts than controls at 4 and 10 wk of age, and all Amaferm-supplemented calves tended to have higher bacterial counts than controls. Amaferm-supplemented calves tended to have higher amylolytic bacterial counts than controls, but the differences were not significant. Amaferm-supplemented calves also had higher pectinolytic (Figure 3) and hemicellulolytic counts (P < .lo) and tended to have higher cellulolytic counts (P = .19). DISCUSSION

The results of supplemental Amaferm on ruminant performance have been variable. Amaferm supplementation has increased daily weight gains of beef cows and calves on poor quality pasture and has increased milk production in lactating dairy cows (10, 11). In other studies, performance was similar for Amafermsupplemented and unsupplemented market lambs and lactating dahy cows (7, 9). In our experiments, Amaferm-supplemented and control calves had similar dry feed intakes and weight gains with the exception of the subset of 40 heifer calves used for microbial and metabolic enumerations (Experiment 3). Even though this subset was selected randomly, less animal variation was noted. The calves in Experiment 3 fed the high A m a f m supplement tended to have higher intakes from wk 1; however, significant differences in feed intakes did not occur until wk 4 with the high Amaferm levels and until wk 5 for the low and moderate Amafenn levels. This increase in dry feed intake corresponded to calf weaning date; all heifer @xperiments 2 and 3) calves suppleJournal of Dairy Science Vol. 74, No. 12, 1991

mented with Amaferm were weaned at least 1 wk earlier than controls. Additionally, the increase in dry feed consumption was due to increased consumption of calf starteq there were no treatment differences for hay consumption. Animal responses resulting from Amafenn appeared to vary with diet composition; the effects were more pronounced for diets containing higher concentrate levels (6, 10.11). In this trial, Amaferm supplementation had no effect on feed efficiency. However, Amafenn has been shown to increase both ruminal and total digestive tract DM, ADF, and NDF digestibilities (6, 22, 23). Amaferm-supplemented calves had higher total VFA, acetate, and propionate Concentrations than controls. Amaferm has been shown to stimulate VFA production in vitro (3) and in vivo (23). Using the rumen simulation technique Rusitec, reductions in methane production have been reported when diets were s u p plemented with Amaferm (5), suggesting that fungal cultures may divert ruminal hydrogen flow away from methane into propionate and butyrate. This could explain the increased propionate concentration observed in our study and in the in vitro study of Martin and Nisbet (14). However, Arambel et al. (3) and Frumholz (5) have reported increased butyrate but decreased propionate concentrations. We observed no increase in the ruminal butyrate concentration. Because of the shift in calves’ diet from milk to dry feed, the acetate:propionate ratio declined with age in all the calves (1, 17). Amaferm supplementation had no effect on the acetate:propionate in this study, which agrees with previous research (6, 23). However, Martin and Nisbet (14) reported a decrease in acetate:propionate ratio with the addition of Amaferm to an in vitro, soluble starch fermentation. Despite higher VFA concentrations, the xumen pH of Amaferm-supplemented calves was not significantly lower than that of controls, which agrees with the results of GomesAlarcon (6). This may have been partly due to increased salivary production and the buffering effect associated with increased dry feed consumption in the Amaferm-supplemented calves. Experiments using Rusitec showed that Amafenn had no effect on the prefeeding pH, but it abolished the postfeeding decline in pH (5). This buffering capacity may be associated

4333

ASPERGILLUS ORYZAE EXTRACT IN CALF DIETS

TABLE 7. ~uminalconcentrations of WA in control or Amafem-supplemented heifer calves CEXperiment 31.l

weeks of age2 Item

2

4

6

8

10

SE

Control Acetate3 propionate4 Isobutyrate Butyrate ~sova~erate~ Valerate

16.4 5.8 .6 1.6 .7 .6

27.1 18.7 .7 3A .7 1.6

372 25.4 .4 5.9

50.6 33.9 .4 9.2

5

5

3.3 3.5 .1 1.1 .1

2.5

2.2

53.8 41 .O .6 7.6 .6 3.2

9.2 2.6 .3

30.7

44.7 34.6t .4 6.5 .5 3.0

48.0

16.8 .4 4.8 .6 1.9

53.0 41 A .7 9.1 .6 3.2

3.3 34 .1 1.o .1 .5

33.2 20.2 .2 4.3 .3* 1.6

482 41.1** .3 6.2 .4 3.0

57.0 53.0.3 9.0 .4 3.1

61.4 51.1* .4 7.6

3.3 3.4 .1 1.1 .1 .5

39.4* 27.0t .3 7.9 .4t 3.0

53.3** 37.5* .3 6.5 .4 2.8

53.2 44.6* .3 9.9 .5 3.6

.5

Low Amafem

Acetate Propionate Isobutyrate Butyrate Isovalerate Valerate Moderate Amaferm Acetate Propionate Isobutyrate Butyrate Isovalerate Valerate High Amaferm Acetate Propionate Isobutyrate Butyrate Isovalerate Valerate

.5

.3* .1

14.9 42 .4

.9 .6 .2 12.5 5.0 .1

.7 .2** .3

37.4 .3 8.5

.4 2.5

.S

3.1

66.v 56P* .6 10.5 1.6** 4.8

3.3 3.4 .I 1.1 .1 .5

'n = 40. 2Within each week. means differ from control: tP < .lo, *P < .05. **P < .01. 3 T r e a ~ e n effect t (P < .lo). dI'reatment effect (P < .05). 'Treatment x age effect (P

2

a

h

m

\

1

. I -

o

Y

4 oc w I-

o

s

0 m

2W

a Z a -1

2

2 2

4

6

8

10

WEEKS OF AGE Figure 2. Semilog plot of total anaerobic (treatment effect, P < -1) and amylolytic ) a d d (colony-formingunits per gram) in Amaferm-supplementedor unsr~pplcmentedcalves. Different from control ( P < .05). Staudard error is 5.8 x

109 (n = 40).

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ASPERGILLUS O R W

4335

EXTRACT IN CALF DIETS

10.

10'

10 .

10.

109

10.

10'

10

10

10

2

4

0

6

WEDCS

10

OF AGE

Rgure 3. Semilog plot of hemicellnlolytic (treatment effect, P < .I), pectinolytic (treatment effect, P < .l), and celldolytic bacteria (treatment effect, P > .lo) (colony-forming units per gram io Amafm-supplementd or unsupplemented calves. Different from control (*P < 05). Standard error is 5.0 X l& 4.9 X 108, and 8.0 X 10s. respectively.

Journal of Dairy Science Vol. 74, No. 12, 1991

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BEHARKA ET AL.

controls. This agrees with previous reports of increased total anaerobic and cellulolytic bacterial numbers with Amaferm supplementation in vitro and in vivo (5, 23). Although Amafern supplementation has been shown to increase hemicellulose digestibility (23), this is the first report of increased numbers of hemicellulolytic and pectinolytic bacteria The stabilization of m e n pH may partially explain the increased bacterial numbers, because lowering pH has been shown to decrease growth of ruminal bacteria in pure culture (19, 20). Cellulolytic bacteria are especially sensitive to changes in pH (19). In conclusion, Amaferm-supplemented calves were weaned earlier than controls and had increased numbers of ruminal bacteria and greater ruminal fermentative activity. REFERENCES 1 Anderson, K. L., T. G. Nagaraja, and J. L. M o d . 1987. Ruminal metabolic development in calves weaned conventionallyor early. J. Dahy Sci. 701000. ZAnderson, K.L., T. G. Nagaraja, J. L. Morrill, T. G. Avery, S. J. Galihu, and J. E.Boyer. 1987. Ruminal microbial development in conventionally or early weaned calves. J. Anim. Sci. 64:1215. 3 Arambel, M.I., R. D. Weidmeier, and J. L. Walters. 1987. Influence of donor animal adaptation to added yeast culture and/or Aspergillus oryzae fermentation extract on in vitro rumen fermentation. Nutr. Rep. Iut. 35:433. 4Bkles. C. H., V. M. Williams,and J. W. Wilber. 1924. Yeast as a supplementary feed for calves. J. Dairy Sci. 7421. 5 Frumholtz, P. P., C. J. Newbold, and R J. Wallace. 1989. Influence of Aspergillus oryzae fermentation extract on the fermentation of a basal ration in the rumen simulation technique (Rusitec). J. Agric. Sci. (Camb.) 113:169. 6Gomez-Alarcon, R. A,, C. Dudas, and J. T. Hnber. 1990. Influence of cultures of Aspergillus oryzue on rumen and total tract digestibility of dietary components. J. Dairy Sci. 73:703. 7 Harris, B., Jr., H. H. Van Horn, K. E. Manooldan, S. P. Marshall, M. J. Taylor, and C. J. Wilcox. 1983. Sugarcane silage, sodium hydroxide- and stuun pressure-treated sugarcane bagasse, corn silage, cottonseed hulls, sodium bicarbonate, and Aspergillis o r y m product in complete rations for lactating cows. J. Dairy Sci. 66:1474. 8 Harrison, H. N.,R G. Warner, E.G. Sander, and J. K. Loosli. 1960. Changes in the t i m e and volume of the stomachs of calves following the nmwal of dry feed or consumption of inat balk. J. Dairy Sci. 43:1301. 9Herring. M. A., and D. M. W o r d . 1990. Gmwth and CharactCriStiCS and ~ a a mgr~wlhhor-

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