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FEEDING FOR MILK COMPOSITION

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:

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FEEDING FOR MILK COMPOSITION

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

  2. Milk Components • Fat • Content • Fatty acid profile • Crude protein • Content • 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 • 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

  7. 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%)

  8. 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

  9. 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

  10. 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

  11. Effect of Grain Processing on Plasma Insulin P < 0.05 • Data from 832 blood samples from 32 cows (Santos et al., 2000)

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

  13. 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

  14. 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

  15. Conclusions

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