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