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