1. FEEDING FOR MILK COMPOSITION
José Eduardo Portela Santos
VMTRC – UC Davis

2. Fat Crude protein Milk Components Content Fatty acid profile
True protein vs NPN
Lactose
Minerals and vitamins

3. 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)

4. 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

5. Ionophores
Fat supplementation
Lack of RDP (fiber digestibility and buffering effect)
Dietary buffers

6. Theories Trans fatty acids 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

11. 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%)

12. 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

13. 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

14. 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

18. Effect of Grain Processing on Plasma Insulin
Data from 832 blood samples from 32 cows (Santos et al., 2000)

21. Diets with more fermentable energy increase milk protein:
Increase flow of microbial protein
increase molar concentration of propionate in the rumen
increase blood insulin

22. 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 (r2=0.35)
The effect of higher CP diet is associated with greater DMI and total energy intake

26. 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

30. Conclusions