anne laarman, m.sc. ph.d. student university of guelph alaarman@uoguelph.ca

EFFECTS OF SOLID FEED ON RUMEN pH AND MOLECULAR

ADAPTATIONS IN DAIRY CALVES

Anne Laarman, M.Sc.Ph.D. Student

University of Guelphalaarman@uoguelph.ca

VFAs(incl. butyrate)

Rumen Development

Starter

Acidotic pressure

Protein

Epithelium

Rumen Development

With low pH, fermentation bacteria start to die off

Starter VFAs

(incl. butyrate)

Acidotic pressure

Protein

Epithelium

Calf Starter Study

MilkHay

MilkHay

Starter

Weaning

Weaning

• Experiment set-up for investigating the role of calf starter in rumen pH and metabolic adaptations

Small Ruminant pH Logger System

Dosing Small Ruminant pH Logger System

Sample pH Results

6:00

7:59

9:59

11:5

9

13:5

9

15:5

9

17:5

9

19:5

9

21:5

9

23:5

91:

593:

595:

594.5

5.0

5.5

6.0

6.5

7.0

7.5

Duration of Acidosis (pH < 5.8)

Area under the curve (pH < 5.8)

Time of Day

pH

Hay DMI and Average Rumen pH

Calves that consume more hay have a higher rumen pH

Laarman et al., 2012. In press

0 0.1 0.2 0.3 0.4 0.5 0.64.8

5

5.2

5.4

5.6

5.8

6

6.2

6.4

Hay DMI

Avera

ge p

H

Hay intake and Severity of Rumen Acidosis

Calves that consume very little hay are at greater risk of more rumen acidosis (pH < 5.8)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.70

50

100

150

200

250

Hay DMI, kg/d

Are

a u

nd

er

the

Cu

rve,

pH

*min

/d

Laarman and Oba, 2011

Rumen pH profile  Milk & Hay Milk & Hay &

StarterAverage pH 6.42 ± 0.10 6.27 ± 0.12

Duration Rumen Acidosis, min/d

101 ± 100 237 ± 126

Area under the Curve, pH*min/d

49.3 ± 36.5 64.2 ± 47.4

Total VFA, mM 64.6 ± 8.6  99.1 ± 8.1*

Butyrate, % Total 7.9 ± 1.9 15.6 ± 1.7*

Hay DMI, kg/d 0.23 ± 0.07 0.34 ± 0.8

Starter DMI, kg/d N/A 0.76 ± 0.04• Hay consumption appears unrelated

to calf starter intakeLaarman and Oba, 2011

Forage Consumption

Hay intake increases with age Doesn’t appear directly related to feeding

program

De Passillé et al., 2011

Rumen pH profile  Milk & Hay Milk & Hay &

StarterAverage pH 6.42 ± 0.10 6.27 ± 0.12

Duration Rumen Acidosis, min/d

101 ± 100 237 ± 126

Area under the Curve, pH*min/d

49.3 ± 36.5 64.2 ± 47.4

Total VFA, mM 64.6 ± 8.6  99.1 ± 8.1*

Butyrate, % Total 7.9 ± 1.9 15.6 ± 1.7*

Hay DMI, kg/d 0.23 ± 0.07 0.34 ± 0.8

Starter DMI, kg/d N/A 0.76 ± 0.04• Despite higher VFA concentrations, calves fed calf starter did not have lower rumen pH

Laarman and Oba, 2011

Adaptations in the Rumen Epithelium

• Changes in gene expression suggest epithelium is adapting on a metabolic level

Milk & Hay

Milk & Hay & Starte

r

NHE-3 0.82 ± 0.12

0.37 ± 0.12*

NHE-2 0.84 ± 0.16

0.86 ± 0.17

MCT-1 0.53 ± 0.23

1.45 ± 0.22*

Laarman et al., 2012

Adaptations don’t just happen in the rumen

epithelium, but also in the liver

Urea Cycle - Liver  Milk & Hay

Milk & Hay & Starter

Carbamoyl phosphate synthetase

8.67 ± 1.10 9.90 ± 1.10

Ornithine transcarbamoylase

1.34 ± 0.11 1.64 ± 0.11*

Arginosuccinate synthetase

1.56 ± 0.29 2.67 ± 0.29*

Arginosuccinate lyase

0.99 ± 0.10 1.44 ± 0.10*

Arginase 1.74 ± 0.32 3.21 ± 0.32*Laarman et al., 2012. In press

• Calf starter increases gene expression of 4 out of 5 urea cycle genes

Conclusion

Feeding solid feed can affect gene expression in rumen epithelium and liver pH regulation in epithelium Urea cycle in liver

Roughage can help manage rumen pH

Developing rumen adapts to increased acidotic pressure from calf starter fermentation

Acknowledgements

Dr. Tom Wright, University of Guelph Dr. Brian McBride, University of Guelph Dr. Masahito Oba, University of Alberta

OMAFRA HQP Program Japanese Federation of Dairy Co-Ops Agriculture and AgriFood Canada