Introduction + Milk Basics

Milk Basics

• Developmental differences between mammals and other species

• High digestibility

• High bioavailability

• High quality protein

• Composition matches developmental needs of the offspring (species specific)

Species Variability

Days to birth weight example

• Amount of protein (g) in milk compared to days to reach double birth weight

• Rabbits have 10g protein/100g of milk and only take 10 days to get to 2x bw

• humans have ~2g/100g of milk and take 200 days to get to 2x bw

Mammary Anatomy: Udder

• Most ungulates

• Much more connective tissue internally than adipose tissue

• Fad pad sits above the mammary gland

Mammary Anatomy: Breast

• Humans, elephants, other primates, etc

• More adipose tissue internally than connective tissue

Teat

• Differences in gland/teat number between species

• Typically 1 teat per functional mammary gland unit

• Majority of species have 1-2 openings per teat

Common Structure (Mammals)

• Lobuloalveolar unit and mammary alveolar cell (epithelial cells)

• Ductal networks: individual ducts that branch off and terminate in lobes

Isometric Growth Period

• Part of mammary gland development

• Embryonic development to the beginning of puberty

Allometric Growth

• Part of mammary gland development

• In females only

• Puberty to maturity

Quiescent State

• Part of mammary gland development

• Predominance of tissue and the ductal system

• Few alveolar cells at this point

Fastest Allometric Growth

• Pregnancy to parturition

• Alveolar cells and secretory tissue proliferates at the end of each duct during gestation

Lactation

• Parturition through lactation: small decrease in cell number over time

• End of lactation: involution

  • Complete regression of the gland back to quiescent state

Aftershock 3918

• Cow with record lactation

• 35,531 kg milk/one year (one lactation

• Nearly 10,000 gallons (23 gal/day)

  • 1406 kg fat

  • 1087 kg protein

• US average: 11,617kg

Black Bear (Ursus americanus)

• 200 kg sow with approx. 3 pups/year

• 300 day lactation

• Denning for 4-5 months

  • No food/water/urine/feces

  • Last 6-8 weeks of gestation

  • First 10-12 weeks of lactation

  • Milk yield during denning: 1/3 total BW

  • Able to nourish their offspring with adequate amount of milk without eating/drinking/etc. during denning

Northern Elephant Seal (Mirounga angustirostris)

• 500 kg female with one pup/year

  • 25 kg BW; 3-4 kg gained per day

• Fast lactation: 30 days

  • No food/water

  • Loses nearly 42% BW in lactation

Blue Whale (Balaenoptera musculus)

• 120,000 kg (30m long)

• One calf/year

  • 2500 kg BW; 100 kg gained per day

• 210 day lactation

  • Lactate while migrating

  • Little/no food

  • 400L/d milk production

  • Gains 50-70% BW in preparation