MANIPULATING MILK YIELD AND

COMPOSITION

Leo Timms

Iowa State University

POUNDS

VS.

PERCENTAGES

GENETICS• Milk composition/ yield highly heritable

• Heritability (h2) • milk yield .27

• % fat .58• % protein .49• % lactose .55

• Correlation between % fat and protein: ~.5• Correlation between yield and % fat : ~ -.2

• Correlation between yield and % protein: -.1• Correlation between yield and lbs. fat / prot. ++

GENETICS• Milk composition/ yield highly heritable

• Species and/ or Breed differences• Fat / protein %

• Milk fat globule size• Beta carotene

• Fatty acid profiles• Casein genotypes

PHYSIOLOGICAL FACTORS

• Age• Stage of lactation

- colostrum - rest of lactation• Dry period ( non-lactating)

• Milking fraction (fat, SCC, IG?)• Milking interval

• Reproduction: estrus/ follicular cyst/pregnancy• Temperature

• Factors that affect/ compete for nutrients

PHYSIOLOGICAL FACTORS

• METABOLIC DISEASES• Ketosis (glucose shortage – fat mobilized)

may increase or decrease yield increased fat test ( lipolysis)

increased milk ketones• Milk Fever (Ca drain) decreased production

• MASTITIS ( Future talk)

NUTRITIONAL FACTORS

IF YOU DON’T FEED THEM, THEY WONT MILK! (DMI)

WATER!!!!!

H2O

NUTRITIONAL FACTORS

• Underfeed energy (CHO)

Volume, lactose, protein

• Underfeed protein

Volume, lactose protein

Underfeeding energy: greatest effects!

LACTOSE (VOLUME)• GLUCOSE demands!

• Traditionally hard to change! • Propylene glycol/ glycerol drenches

(bolus effect important!)• Rumensin• Chromium

• Cobalt and Vitamin B12• Niacin and choline (rumen protected)

MILK PROTEINS• Not as easy to change as one thinks!• Worth lots of $ so want to increase!• Dietary protein: minimal effects

• Protected proteins/AA: minimal when protein is sufficient

• Oilseeds: protein%

• Hyperinsulinaemic/ euglycaemic clamp• Increased milk protein 25%

• Same plasma AA: blood flow/AA extraction

VITAMINS• Vitamin A: fresh vs stored feeds

• Increase feed Vit A/E: milk• May be more important for

mastitis and somatic cells

MINERALS

• Very hard to change!!!

IODINE!

MILK LIPIDS• Easiest to change: diet labile

• Change amount and types of FA• Saturated/protected oils: temp • Excessive grain / limited fiber • Rumen buffers: if low, will

• Excess or free oilseeds: • Fiber digestion , CLA isomer

• Feed CLA: CLA ; Fat