FEEDING FOR MILK COMPOSITION

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FEEDING FOR MILK COMPOSITION

• José Eduardo Portela Santos
• VMTRC UC Davis

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Milk Components

• Fat
• Content
• Fatty acid profile
• Crude protein
• Content
• True protein vs NPN
• Lactose
• Minerals and vitamins

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• 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)

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Milk Fat

• ForageConcentrate 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

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

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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

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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)

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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

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• 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

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Milk Protein

• NEL intake
• ForageConcentrate ratio
• Amount of fermentable CHO (RDS)
• Dietary CP level
• Amino acid profile of the protein flowing to the
  duodenum
• Dietary fat

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Effect of Grain Processing on Plasma Insulin
P lt 0.05

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

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

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Dietary Protein and Milk Protein

• Low efficiency of N utilization for milk protein
  synthesis (lt 30)
• Sp?rndly (1986) No relationship between dietary
  CP content and milk protein concentration
• Emery (1978) correlation between dietary CP and
  milk protein content (r20.35)
• The effect of higher CP diet is associated with
  greater DMI and total energy intake

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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

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Conclusions
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