Lactation and Milk Production

Dairy Science: Lactation Cycles, Milking Technology, and Milk Composition

The Lactation Cycle

  • Definition: One lactation cycle is approximately 365365 days (one year).
  • Components:
    • 305305 days of active milk production.
    • 6060 days of a crucial dry period.
  • Dry Period Significance: This 6060-day period is essential for mother cows to recover and prepare for their next lactation cycle.
  • Breeding within the Cycle: Cows are typically re-bred around 6060 to 9090 days into their lactation cycle, usually through artificial insemination.
  • Gestation: Following breeding, the cow enters another gestation period, leading to the birth of a new calf and the initiation of the subsequent lactation cycle, thus maintaining a continuous annual cycle.
  • Lifetime Lactation Cycles: While cows can have more than five lactation cycles, dairy businesses commonly cease inseminating cows after the fifth cycle because milk production efficiency generally declines, making it less profitable.

The Milking Process

  • Hormonal Regulation: The entire milking process and lactation sequence are heavily influenced by hormones.
  • Stimulus for Milk Release:
    • Natural Stimulus: The presence of a young calf attempting to suckle.
    • Dairy Routine: In commercial dairies, an established routine involving specific sounds, smells, and sensations associated with milking serves as the stimulus. Cows often instinctively await milking at regular times.
  • Milking Frequency: Cows are typically milked two to three times per day.
    • Example: Cal Poly Dairy milks cows twice a day, at 4extAM.4 ext{ AM.} and 4extPM.4 ext{ PM.}
  • Milking Duration: The milking process should ideally be completed within 55 to 88 minutes, as the crucial hormone oxytocin begins to decompose after this timeframe.
  • Milking Technologies:
    • Machine Milking (e.g., Cal Poly Dairy System):
    • Design: Involves metal cups connected to a vacuum pump.
    • Mechanism: The vacuum pump generates pulses, creating a vacuum approximately 5050 to 6060 times per minute. This vacuum causes a rubber liner within the metal cup to expand and then contract, mimicking the sucking action of a calf, thereby extracting milk. The milk is then channeled to a storage tank.
    • Robotic Milking (Automated Milking Systems):
    • Philosophy: Systems are designed