1. MANIPULATING MILK YIELD AND COMPOSITION Leo Timms Iowa State University

2. POUNDS VS. PERCENTAGES

3. GENETICS Milk composition/ yield highly heritable Heritability (h 2 ) 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. ++

4. GENETICS Milk composition/ yield highly heritable Species and/ or Breed differences Fat / protein % Milk fat globule size Beta carotene Fatty acid profiles Casein genotypes

5. 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

6. 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)

7. NUTRITIONAL FACTORS IF YOU DON’T FEED THEM, THEY WONT MILK! (DMI)

8. WATER!!!!! H2O

9. NUTRITIONAL FACTORS Underfeed energy (CHO) Volume, lactose, protein Underfeed protein Volume, lactose protein Underfeeding energy: greatest effects!

10. 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)

11. 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

12. VITAMINS Vitamin A: fresh vs stored feeds Increase feed Vit A/E: milk May be more important for mastitis and somatic cells

13. MINERALS Very hard to change!!! IODINE!

14. 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