FEEDING FOR MILK COMPOSITION

José Eduardo Portela SantosVMTRC – UC Davis

Milk Components

• Fat– Content– Fatty acid profile

• Crude protein– Content– True protein vs NPN

• Lactose

• Minerals and vitamins

• Several nutritional factors affect the composition of milk of dairy cows:

– Energy intake (Mcal of NEL)

– Energy source• CHO• Lipids

– Protein intake– Protein degradability and quality– Interactions between protein and energy– Amino acids– Minerals: Na, K (DCAD)– Feed additives (Niacin, fibrolytic enzymes)

Milk Fat

• Forage:Concentrate ratio

• CHO:

– NDF

– Effective NDF

– Physically effective NDF

– Ruminal digestibility of NDF

– NFC

• Composition of the NFC: sugars, starch and pectin

• Ruminal degradability of starch

• Ionophores

• Fat supplementation

• Lack of RDP (fiber digestibility and

buffering effect)

• Dietary buffers

Theories

• Low fat diets

• Acetate deficiency

• B-OH-butyrate deficiency

• High rumen molar concentration of

propionate: Insulin theory (glucogenic theory)

• Vit. B12 deficiency

• Trans fatty acids

Effect of TFA infusion on milk yield and composition

Gaynor et al. 1994 Romo et al. 1995

Cis Trans Cis Trans

Fat infused, g/d 750.0 750.0 620.0 620.0

TFA infused, g/d 0.0 306.0 0.0 257.0

Milk, kg/d 46.3 47.0 34.5 33.9

Milk Trans-C18:1, % 3.1 8.0 1.7 14.0

Milk composition, %

Fat 3.3 2.6 4.1 3.2

Protein 3.0 3.1 3.2 3.1

Effect of forage level and buffer addition on milk composition

Diet Rumen

pH Duodenal TFA, g/d

Milk TFA, %

Milk TFA, g/d

Milk Fat, %

60% forage, no buffer

6.13 61 3.1 33 4.09

60% forage, buffer

6.15 57 2.9 33 4.22

25% forage, no buffer

5.83 120 5.8 56 3.42

25% forage, buffer

6.02 66 2.9 33 3.91

05

101520253035404550556065707580

g/1

00g

Control4.1%

High Corn2.0%

Control3.3%

High Corn1.8%

Control3.6%

High Corn1.6%

Effect of Forage:Concentrate Ratio on Milk Fat % and Milk Fatty Acid Composition

SCFA, g/100g LCFA, g/100g

Mechanism of Action of Mechanism of Action of Trans FAFA

• Milk fat suppression: reduced SCFA (De Novo

synthesis)

• Trans fatty acids depress milk fat in 48 to 72 hs

• Preliminary data from Maryland (Piperova et al.,

1998):

– Acetil CoA Carboxylase activity decreased (61%)

– Fatty acid synthase activity decreased (54%)

– Acetil CoA Carboxylase mRNA decreased (55%)

Nutritional Causes of Milk Fat Suppression

• Inadequate NDF• Inadequate physically effective NDF (particle

size)• Poor NDF digestibility• Forage source: buffering capacity• Excessive amounts of NFC• Excessive amounts of RDS• High fat diets

• Fat sources with highly unsaturated FA profile– Yellow grease, oils

• Interactions between fat source and forage source (binding sites)– Alfalfa hay vs corn silage

• Protein supplements with high PUFA content– Fish meal, blends of marine by products

• Lack of RDP (fiber digestibility & buffer effect)• Lack of buffers

Milk Protein

• NEL intake

• Forage:Concentrate ratio

• Amount of fermentable CHO (RDS)

• Dietary CP level

• Amino acid profile of the protein flowing to the

duodenum

• Dietary fat

Effect of Varying the Ratio Forage:Concentrate on MilkComposition

Ratio Forage:Concentrate

Item 80:20 65:35 50:50 35:65

Milk, kg 20.80 21.60 22.30 23.40

Composition, %

Protein 3.11 3.12 3.22 3.26

Fat 3.83 3.72 3.68 3.33

Lactose 5.28 5.33 5.33 5.55

Adapted from Macleod et al. (

Effect of Grain Processing on Milk Protein Content

Diet

Cows (Studies) DRS SFS SRC SFC P <

RD Starch, % 52 76 71 81 0.01

92 cows (4) 2.99 3.06 0.11

358 cows (14) 2.95 3.02 0.01

92 cows (4) 2.99 2.92 0.01

Adapted from Theurer et al. (1999) and Santos (2000).

Effect of Isocaloric Infusions of Propionate or Acetate in the Duodenum, orGlucose in the Rumen on Milk Protein Content

Treatment

DRS + DP DRS + RG SEM P < Reference

Milk Protein, % 2.99 3.18 0.01 0.03 Aquino-Ramos,1996

DRS + DA SFS + H2O

Milk Protein, % 2.85 2.91 0.04 0.50 Aquino-Ramos,1996

DRS + DP DRS + RG

Milk Protein, % 2.72 2.88 0.03 0.08 Wu et al., 1994

Effect of Grain Processing on Plasma Insulin

12.66

10.38

6

7

8

9

10

11

12

13

14

uIU

/ml

Insulin

SFS SRC

• Data from 832 blood samples from 32 cows (Santos et al., 2000)

P < 0.05

Effect of Duodenal Infusion of Amino Acids and InsulinTreatment on Milk Protein Synthesis of Dairy Cows

Treatment

Item Water BC Water+I BC+I Insulin

P <

DMI, kg/d 26.2 27.6 25.1 25.2 0.08

Milk, kg/d 26.5b 27.5b 28.3ab 29.8a 0.05

Protein, % 3.29b 3.31b 3.52a 3.66a 0.01

Protein, g/d 867b 895b 995a 1080a 0.001

Adapted from Mackle et al. (1998).

0

50

100

150

200

250

Lys + Met Casein bST Insulin

Ext

ra m

ilk p

rote

in (

g/d

)

• Diets with more fermentable energy increase milk protein:– Increase flow of microbial protein

– increase molar concentration of propionate

in the rumen

– increase blood insulin

Dietary Protein and Milk Protein

• Low efficiency of N utilization for milk protein

synthesis (< 30%)

• Sprndly (1986): No relationship between dietary

CP content and milk protein concentration

• Emery (1978): correlation between dietary CP and

milk protein content (r2=0.35)

– The effect of higher CP diet is associated with

greater DMI and total energy intake

Chemical Scores of Protein Sources in Relationship to Milk Protein (Chandler, 1989).

Protein Source His Phe Leu Thr Met Lys Arg Val Ile Trp

Ft. Meal 11 59 66 59 23 13 32 38 32 29

C.G. Meal 67 100 100 60 100 18 36 48 40 30

DDG + Solubles 74 84 72 63 81 24 42 53 38 45

Brewers Grains 56 100 83 65 78 34 53 65 74 87

Alfalfa Meal 69 100 55 80 60 46 50 66 51 100

M&B Meal 64 64 46 59 49 55 76 48 36 32

Meat Meal 67 65 46 59 49 58 76 51 36 39

SB Meal 89 100 56 74 56 70 89 60 55 75

F. Meal 77 69 58 68 100 80 59 59 47 71

B. Meal 100 100 93 86 45 91 33 70 10 76

Microbes 90 97 54 100 97 100 79 66 61 99

Comparison of Nitrogen Flow to the Duodenum of Cows Fed SBM ora High RUP Supplement (14 Studies with 27 comparisons)

Treatment Difference

Item SBM RUP g/d % P <

N intake, g/d 469.1 463.6 - 6.5 - 1.4 0.67

Flow to duodenum, g/dMicrobial N 275.6 240.2 - 35.4 - 12.85 0.001

NANMN 201.1 248.9 47.8 23.77 0.002

NAN 474.3 486.7 12.4 2.61 0.31

EAA 1,102 1,159 57.0 5.17 0.11

Lys 230.5 138.7 - 91.8 - 39.83 0.14

Met 45.11 46.54 1.43 3.17 0.42

Summary of Studies Comparing SBM with all RUP Sources

Milk FCM Fat % Protein %

- 0 + - 0 + - 0 + - 0 +

TOTAL 8 103 25 4 94 11 21 99 9 28 95 6

Santos et al. (1998)

Dietary Fat and Milk Protein

• Negative relationship between dietary fat and

milk protein concentration

• Independent of fat source

• Increased efficiency of amino acid extraction

• Supplying more fermentable CHO or high quality

RUP partially overcomes milk protein depression

Effect of Dietary Fat on Mammary Blood Flow

Treatment

Mammaryblood flow

RC-LF AC-LF RC-HF AC-HF Fat

P <

L/h 937.8 911.6 860.5 854.1 0.65

L/kg milk 912.8 854.5 756.9 724.6 0.07

Cant et al. (1993)

Conclusions