NUTRITION PROGRAMS FOR LACTATING DAIRY COWS UNDER HEAT STRESS

J.E.P. Santos and C.R. StaplesDepartment of Animal Sciences

University of Florida

Heat-Stressed Dairy Cow

• Spends less time lying down (9 to 10 h vs. 11 to 13 h)• Spends less time ruminating

• Increases CO2 losses due to hyperventilation

• Increases rumen retention time: greater fermentability of feeds

• Has a deficit of HCO3-, Na, and K

• Has reduced blood flow to the portal-drained viscera (PDV)• Has reduced nutrient uptake by the PDV• Has reduced blood flow to the mammary gland• Has increased energy requirements for maintenance (dissipate heat)

LESS PRODUCTIVE

Consequences for Dairy Cattle

– Reduced dry matter intake

– Reduced yields of milk and milk components

– Decreased fat and protein content in milk

– Reduced growth rates

– Decreased reproductive performance

– Increased incidence of health disorders, particularly retained placenta, metritis, and lameness

The Better-Producing Cows Suffer the Most from Heat Stress

38.9

39.8

38.9

39.1

38.0

38.4

38.8

39.2

39.6

40.0

Bo

dy

Tem

p,

C

283728 37

Milk Production, kg FCM Production, kg

Missouri Israel

n = 170

n = 230

Controlled heat stress in AZ:

- Temperature increased from 80 to 104 ºF- Pair-fed cows under thermoneutral

conditions keep nutrient intake similar

- Duration of 9 days

-Body temperature increased from 101 to 104.5 ºF

- Respiration rate increased from 40 to 70 breaths/min

Heat stress yield ~45%Underfeeding yield by ~19%

feed intake only accounted for 50% of the reduction in milk yield

Heat stress intake by ~ 30%

Rhoads et al. (2009) J. Dairy Sci. 92:1986-1997

Nutritional Management During Heat Stress

• DMI

• Feeding frequency and feed delivery

• Fiber feeding

• Energy sources

• Protein feeding

• Mineral manipulation

Water, the forgotten nutrient……

Cows Drink More Water When Experiencing Ruminal Acidosis

• Subacute ruminal acidosis (SARA) was induced by replacing 25% of the TMR with a 50:50 mix of barley:wheat pellets fed twice daily.

• Cows could choose to drink water containing– No sodium bicarbonate or – 2.5 g of sodium bicarbonate per liter of water

Cottee et al., 2004, JDS 87:2248

Ruminal pH and Water Intake During the 3 Hours of Lowest Ruminal pH

Control SARA

Mean ruminal pH 6.02 5.45*

NaHCO3- water intake, % of

total water intake 39 36

Water intake, L 14.4 18.9*

Cottee et al., 2004, JDS 87:2248

Drinking Water Reduces Ruminal Acidity (Cottee et al., 2004)

5.67

6.045.91

6.19

5.4

5.6

5.8

6.0

6.2

6.4

Control SARA

BeforeAfter

Ru

min

al p

H Drinking Bout0.24

0.15

Cottee et al., 2004, JDS 87:2248

Feeding Frequency and Feed Delivery• Increasing feed frequency increases DMI

– Fresh feed available– Stimulatory effect of feed delivery– Push up feed does not seem to have the same effect

• Feed consumption during heat stress:– Greater after milkings– Greater during the cooler periods of the day ( early in the

morning and during the night)

Frequency of Feed Delivery and Eating Behavior

DeVries et al (2005) J. Dairy Sci. 88: 3553-3562

0

20

40

60

80

100

04:00 07:00 10:00 13:00 16:00 19:00 22:00 01:00 04:00

Milking Milking

── Delivery 2 x daily

── Delivery 4 x daily

% o

f cow

s ea

ting

Hour

── Delivery 1 x daily

── Delivery 2 x daily

0

20

40

60

80

100

04:00 07:00 10:00 13:00 16:00 19:00 22:00 01:00 04:00

Hour

% o

f cow

s ea

ting

Milking Milking

Dietary Fiber

• Cows under heat stress might require a more nutrient dense diet

to compensate for the lower DM intake

• Greater heat production associated with fiber feeding

• Metabolic pathway to synthesize acetate produces CH4 (Loss of

energy)

• Efficiency of metabolizable energy utilization increases with low

forage diets (Tyrrel et al., 1979)

• At the same ME diet, high forage diets increases portal blood flow

and O2 utilization by the PDV (Reynolds et al., 1991)

Fiber Level and Heat Stress (West et al, 1999)

DMI, % BW

3.00

3.25

3.50

3.75

4.00

4.25

4.50

4.75

5.00

30.2 33.8 37.7 42

% B

W

Cool Hot

DMI

15

16

17

18

19

20

21

22

23

24

30.2 33.8 37.7 42

kg/d

Cool Hot

Fiber Level and Heat Stress (West et al, 1999)

Milk

20

22

24

26

28

30

32

34

30.2 33.8 37.7 42

kg

/d

Cool Hot

3.5% FCM

20

22

24

26

28

30

32

34

30.2 33.8 37.7 42

kg

/d

Cool Hot

Effect of Heat Stress on Ruminal pH of Holstein Cows (JAS 30:1023)

6.5

6.1 6.1

5.5

5

5.3

5.6

5.9

6.2

6.5

6.8

High Forage Diet High Concentrate Diet

COOL

COOL

HOT

HOT

Ru

min

al p

H

Diet by Environment Interaction, P < 0.01

Effect of Heat Stress on Ruminal Activity

Environ. Rectal RuminalReference Temp,°F Temp,°F ContractionsFlorida Shade 38.7a 2.4/mina

JDS 64:844 No shade 39.6b 1.7/minb

Missouri 18°C 38.4a 2.2/minJAS 29:734 38°C 40.9b 1.7/min Remastication ratesMaryland 20°C 39.2a 90/mina

JAS 17:326 35°C 40.3b 80/minb

Cows Under Heat Stress Are at Greater Risk for Rumen Acidosis

Month of Diagnosis of 1st Lameness CaseAugust to November

December to April

May to July

Dietary Fat

• Fat contains 2.5 to 3 x more calories than CHO

• Fat is a source of non-fermentable energy

• Fatty acids: DE content = ME content (no gas or urinary losses)

• Fat may alleviate heat production during periods of thermal stress

Effect of Fat and Heat Stress on Performance of Dairy Cows

Treatment

Cool Hot P <

Control HF Control HF Fat F x E

DMI, kg/d 20.2 19.9 14.2 14.9 NS NS

FCM, kg/d 32.3 35.0 26.1 27.9 0.05 NS

Milk

Fat, % 3.16 3.42 3.15 3.51 0.05 NS

Protein, % 2.82 2.84 2.62 2.56 NS NS

Adapted from Knapp and Grummer (1991)

Effect of Supplemental Fat on NEL Intake and Milk Yield During Moderate and Hot Weather

38

39

40

41

42

43

44

45

46

Moderate Heat Stress

Mc

al/

d

Control PFA

Huber et al. (1994) J. Dairy Sci.

28

29

30

31

32

33

34

35

Moderate Heat Stressk

g/d

Control PFA

Dietary Protein• Diets with a high CP content usually are detrimental to

cows under heat stress

• Protein degradability and quality affects performance of heat-stressed dairy cows

• Balance diets for metabolizable protein and limiting essential amino acids that allows to reduce the total dietary CP – Corn/corn silage and alfalfa based diets – methionine and lysine– Grass silage/barley-oat based diets - histidine

Effect of Decreasing RDP on Milk Yield

Location% RDP as a %

of CPMilk yield increase

Arizona JDS 72:2554

65% 60% 3.3 kg/d

Arizona JDS 74:243

61% 47% 6.0 kg/d

Greece WRAP 30:21 69% 61% 2.4 kg/d

Arizona JDS 76:819

58% 58% lysine 3.1 kg/d

Mineral Nutrition• Heat stress: metabolic alkalosis due to hyperventilation

• Blood pH increases, but total HCO3- drops

• Ruminant sweat is high in K

• Thermal stress reduces DM intake, milk yield and milk fat content

• Altering the concentration of some macro minerals in the diet influences:– rumen metabolism– blood buffering– yields of milk and milk fat

Relationship Between DCAD and DM Intake in Lactating Dairy Cows (69 diets)

Hu and Murphy, 2004 JDS 87:2222

Recommended DCAD: +30 to +40 mEq/ 100 g DM

Relationship Between DCAD and Milk Yield in Lactating Dairy Cows (69 diets)

Hu and Murphy, 2004 JDS 87:2222

Recommended DCAD: +30 to +40 mEq/100 g DM

Yeasts and Fungal Cultures• Yeasts (Saccharomyces cerevisiae either as live yeast or yeast

culture) and fungal cultures (Aspergillus oryzae) act as rumen microbial modifiers:– Stimulate fiber digestion

– Reduce lactic acid accumulation in the rumen fluid

– Typically improve efficiency of feed conversion into milk or 3.5% FCM

http://www.chemistrydaily.com/chemistry/upload/0/09/Saccharomyces_cerevisiae.jpg

Summary of Responses of Lactating Dairy Cows Fed 3 g/day of Aspergillus oryzae

02468

10121416

DM intake Milk yield Rectal temp

Nu

mb

er o

f ex

per

imen

ts

No change Significant improvement

Huber et al. (1994) J. Dairy Sci.

6 4

88

Effect of Feeding Yeast Culture (YC)1 on Lactating Dairy Cow Performance in Summer

Site Diets DMI, kg/day Milk kg/day Efficiency

CA, 2010 Cont 26.0 42.2a 1.62

YC 25.8 43.4b 1.68GA, 2007 Cont 26.2 39.2a 1.50a

YC 25.6 41.0b 1.60b

SD, 2004 Cont 23.1 34.9 1.49a

YC 22.1 35.3 1.59b

IL, 2000 Cont 15.2 25.9 1.70

Jerseys YC 16.5 27.2 1.65

a, b P ≤ 0.101Diamond V Mills ‘XP’ or Vi-Cor AMAX-Xtra

Effect of feeding increasing amounts of live yeast to cows under heat stress on rumen fluid composition

Live yeast1, g/d P

0 0.5 1 Linear

Rumen pH 5.99 ± 0.11 6.03 ± 0.11 6.30 ± 0.11 0.04

Rumen pH < 5.8, % (n/n) 45.0 (9/20) 36.8 (7/19) 10.5 (2/19) 0.02

Lactate 4.9 ± 1.8 4.5 ± 1.8 1.3 ± 1.9 0.18

Detectable lactate, % (n/n)

70.0 (14/20) 57.9 (11/19) 57.9 (11/19) 0.58

Lactate > 1 mM, % (n/n) 35.0 (7/20) 21.1 (4/19) 5.3 (4/19) 0.04

VFA, mM 123.4 ± 5.8 124.7 ± 5.9 125.3 ± 6.1 0.82

Marsola et al. (2009) J. Dairy Sci.1 Levucell SC (Lallemand Animal Nutrition)

Recommendations

• Feed cows more frequently during periods of heat stress

• Cows under heat stress should be fed the highest quality forage available - Minimizes the need for high-starch feeds

• In my opinion, NDF should be increased from the traditional 28-30 to 31-33%

– When forage quality is a problem, then replace part of the starch with a highly digestible NDF source

• Formulate diets with moderate concentration of CP

– Review the metabolizable protein needs of the cows and formulate based on MP and essential amino acids.

– Keep rumen-degradable protein at ~ 10% of the diet DM

Recommendations• Feed moderate to high (up to 5% of the diet DM) fat diets, but avoid

excessive amounts of unsaturated fatty acids

• Increase Na and K – Add 1 to 1.2% of the total ration as sodium bicarbonate to increase the

total Na up to 0.4 to 0.5%– Increase the K content up to 1.6 to 1.8% with potassium carbonate– DCAD of the ration should be between 300 and 400 mEq/kg of DM

• Dietary Mg should be at 0.35 to 0.4% in high K diets

• Incorporate a live yeast or yeast culture to the ration– Improve production of fat-corrected milk– Improves feed efficiency– Reduces the risk of rumen acidosis

Got questions?

This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2010-85122-20623 from the USDA National Institute of Food and Agriculture.