Tom Jenkins Professor Emeritus Animal & Veterinary Sciences

Milk Fat Depression: How Important is Rumen pH?

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5 5.2 5.4 5.6 5.8 6 6.2 6.4 6.6 6.8 7

%, r

elat

ive

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H 6

.78

pH

Lipolysis

C18:2 BH

Van Nevel and Demeyer. 1996. Reprod Nutr. Dev 36:53.

Milk Fat Depression: How Important is Rumen pH? Influence of pH on Lipolysis and Biohydrogenation In Vitro

Milk Fat Depression: How Important is Rumen pH? CLA Shift vs. pH

Shift in biohydrogenation intermediates!

MFD

t10c12 CLA Trans-10 (18:1)

Linoleic (18:2) Stearic (18:0)

c9t11 CLA trans-11 (18:1)

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Milk Fat Depression: How Important is Rumen pH? CLA Shift vs. pH

Continuous culture data taken from Fuentes et al, 2009.

Linoleic (18:2)

t10c12 CLA t10

Stearic 18:0

Milk Fat Depression: How Important is Rumen pH? Bottleneck vs. pH

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Milk Fat Depression: How Important is Rumen pH? Bottleneck vs. pH

Continuous culture data taken from Fuentes et al, 2009.

55%

62%

How Much Does pH Need to Change?

Milk Fat Depression: How Important is Rumen pH? Dr. Tom Jenkins, Clemson University

Milk Fat Depression: How Important is Rumen pH? pH Dynamics and Bacterial Community Composition in the Rumen of Lactating Dairy Cows A. Palmonari ,* D. M. Stevenson ,† D. R. Mertens ,† C. W. Cruywagen ,‡ and P. J. Weimer †§2

The data indicate that cows with widely differing pH profiles can have similar ruminal bacterial community compositions, and that milk fat depression can occur at intermediate ruminal pH.

J. Dairy Sci. 2010. 93:279.

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Milk Fat Depression: How Important is Rumen pH? pH & Corn Oil Interactions

Sun et al. 2014. J. Dairy Sci. 97 (E-Suppl. 1): 319. Slide courtesy of Dr. Adam Lock

t10c

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Milk Fat Depression: How Important is Rumen pH? pH & Corn Oil Interactions

Sun et al. 2014. J. Dairy Sci. 97 (E-Suppl. 1): 319. Slide courtesy of Dr. Adam Lock

t10c

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OIL concentration

Milk Fat Depression: How Important is Rumen pH? Rumen pH vs. Milk Fat

Zebell et al. 2010. Livestock Science 127:1-10.

Starch

Milk Fat Depression: How Important is Rumen pH? Does pH Explain Other Nutritional Effects on Milk Fat Depression?

Potassium Carbonate

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Milk Fat Depression: How Important is Rumen pH? High Forage vs. High Grain Effects in Continuous Cultures

Gudla et al. 2012. AFST 171:108-116.

High Starch • Shifts rumen microbial population

• Shifts BH pathways to yield more t10c12

• Increases risk of MFD Is this because of low pH?

a% of total CLA 20 min incubations rumen in vitro 2 (starch levels) x 2 (pH) but hay LpH not shown 3g meadow hay or 1.5g corn starch plus 200mg grapeseed oil Calculated from Anim. Physiol Anim. Nutr. 2014. 98:704–713

Milk Fat Depression: How Important is Rumen pH? Starch x pH Interactions

Hay–HpH Starch–LpH Starch–HpH

Initial pH 6.75 6.25 6.78

Final pH 6.71 5.82 6.56

c9, t11 CLA, %a 94.3 68.4 83.2

t10, c12 CLA, %a 3.6 24.6 9.2

Milk Fat Depression: How Important is Rumen pH? K Carbonate1 Effects on Milk Fat

Milk Fat, % △ TMR K -K +K P< Reference

1.2 to 2.0% 4.01 4.38 0.05 Harrison et al. 2012

1.2 to 2.2% (LF) 2.74 2.99 0.05 Kamar and Weiss, 2013

1.2 to 2.2% (HF) 2.39 2.64 0.05 Kamar and Weiss, 2013

1.8 to 2.3% 4.06 4.28 0.05 Ma et al., 2013

1Added as K carbonate sesquihydrate (DCAD Plus, C&D, Inc.)

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ab K means with the same letter are significantly different (P ≤ 0.05).

Jenkins et al., 2014

Milk Fat Depression: How Important is Rumen pH? K Effect on trans-10 cis-12

§ Effective fiber § Particle Length (Cornell Epi)

§ Bottom Pan of Penn State Shaker Box <54% § > 49% on middle screen § Top screen didn’t matter

§ Grain – amount and source § Buffers § Management

§ TMR mixing § Feeding frequency § Crowding

Milk Fat Depression: How Important is Rumen pH? Resolve MFD – Manage Rumen pH

§ Low rumen pH § Causes a microbial shift that affects biohydrogenation § Leads to a t10c12 CLA shift and bottleneck that allows it to

accumulate § Dramatic changes in rumen pH are not needed § Low pH might explain much of the MFD risk of high starch § Manage rumen pH by following good feed and cow

management practices

Milk Fat Depression: How Important is Rumen pH? SUMMARY

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