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FEEDING FOR MILK COMPOSITION
José Eduardo Portela Santos
VMTRC – 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 NE L ) 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 buffering effect)
•
Dietary buffers (fiber digestibility and
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 Fat infused, g/d TFA infused, g/d Milk, kg/d Milk Trans-C18:1, % Milk composition, % Fat Protein Gaynor et al. 1994
Cis Trans
750.0
0.0
46.3
3.1
750.0
306.0
47.0
8.0
3.3
3.0
2.6
3.1
Romo et al. 1995
Cis
620.0
0.0
34.5
1.7
4.1
3.2
Trans
620.0
257.0
33.9
14.0
3.2
3.1
Effect of forage level and buffer addition on milk composition Diet 60% forage, no buffer 60% forage, buffer 25% forage, no buffer 25% forage, buffer Rumen pH Duodenal TFA, g/d Milk TFA, % Milk TFA, g/d Milk Fat, % 6.13 61 3.1 33 4.09 6.15 5.83 6.02 57 120 66 2.9 5.8 2.9 33 56 33 4.22 3.42 3.91
Effect of Forage:Concentrate Ratio on Milk Fat % and Milk Fatty Acid Composition 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 Control 4.1% High Corn 2.0% Control 3.3% SCFA, g/100g High Corn 1.8% Control 3.6% LCFA, g/100g High Corn 1.6%
Mechanism of Action of Trans FA
• • •
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
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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
• • • • •
NE L 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 Milk Composition Ratio Forage:Concentrate Item Milk, kg Composition, % Protein Fat Lactose Adapted from Macleod et al. ( 80:20 20.80
3.11
3.83
5.28
65:35 21.60
3.12
3.72
5.33
50:50 22.30
3.22
3.68
5.33
35:65 23.40
3.26
3.33
5.55
Effect of Grain Processing on Milk Protein Content Cows (Studies) DRS SFS Diet SRC RD Starch, % 92 cows (4) 358 cows (14) 52 76 71 2.99
2.95
3.02
92 cows (4) 2.99
2.92
Adapted from Theurer et al. (1999) and Santos (2000).
SFC 81 3.06
P <
0.01
0.11
0.01
0.01
Effect of Isocaloric Infusions of Propionate or Acetate in the Duodenum, or Glucose in the Rumen on Milk Protein Content Milk Protein, % Treatment DRS + DP DRS + RG 2.99
3.18
SEM 0.01
P < 0.03
Reference 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
14 13 12 11 10 9 8 7 6 Effect of Grain Processing on Plasma Insulin 12.66
P < 0.05
10.38
•
Data from 832 blood samples from 32 cows (Santos et al., 2000) Insulin SFS SRC
Effect of Duodenal Infusion of Amino Acids and Insulin Treatment on Milk Protein Synthesis of Dairy Cows Treatment Item DMI, kg/d Milk, kg/d Water 26.2
26.5
b BC 27.6
27.5
b Water+I 25.1
28.3
ab BC+I 25.2
29.8
a Insulin
P <
0.08
0.05
Protein, % Protein, g/d 3.29
b 867 b Adapted from Mackle et al. (1998).
3.31
b 895 b 3.52
995 a a 3.66
1080 a a 0.01
0.001
250 200 150 100 50 0 Lys + Met Casein bST Insulin
•
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%) Sp
rndly (1986): No relationship between dietary CP content and milk protein concentration Emery (1978): correlation between dietary CP and milk protein content (r 2 =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 Ft. Meal C.G. Meal DDG + Solubles Brewers Grains Alfalfa Meal M&B Meal Meat Meal SB Meal F. Meal B. Meal Microbes 11 67 74 56 69 64 67 89 77 100 90 59 100 84 100 100 64 65 100 69 100 97 66 100 72 83 55 46 46 56 58 93 54 59 60 63 65 80 59 59 74 68 86 100
Met Lys 23 100 81 78 60 49 49 56 100 45 97 13 18 24 34 46 55 58 70 80 91 100
Arg 32 36 42 53 50 76 76 89 59 33 79 Val 38 48 53 65 66 48 51 60 59 70 66 Ile 32 40 38 74 51 36 36 55 47 10 61 Trp 29 30 45 87 100 32 39 75 71 76 99
Comparison of Nitrogen Flow to the Duodenum of Cows Fed SBM or a High RUP Supplement (14 Studies with 27 comparisons) Item N intake, g/d Flow to duodenum, g/d Microbial N NANMN NAN EAA Lys Met Treatment SBM RUP 469.1
463.6
275.6
201.1
474.3
1,102 230.5
45.11
240.2
248.9
486.7
1,159 138.7
46.54
Difference g/d - 6.5
- 35.4
47.8
12.4
57.0
- 91.8
1.43
% - 1.4
- 12.85
23.77
2.61
5.17
- 39.83
3.17
P <
0.67
0.001
0.002
0.31
0.11
0.14
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 Mammary blood flow L/h L/kg milk Cant et al. (1993) RC-LF Treatment AC-LF RC-HF AC-HF 937.8
912.8
911.6
854.5
860.5
756.9
854.1
724.6
Fat
P <
0.65
0.07