Lactation

1. Lactation

2. The Udder

3. Milk Production • After birth, milk production peaks and then gradually decreases. Birth of a calf stimulates hormone production which causes milk letdown • After approximately 305 days, the cow should “go dry”, or stop producing milk. • If the cow is not re-bred, she will not produce any more milk. • An approximate 60-day drying off period is vital to milk production because it allows time for the udder to heal.

4. Milk Production • If the cow is not milked during her 305-day lactation period, she will also “go dry”. • Milking, either by hand or mechanically, stimulates milk production over the lactation period

5. Colostrum • Colostrum is the first milk to come from a cow after birth and contains a high concentration of antibodies. • The calf’s intestines at birth are very porous, which allows it to absorb the antibodies from the milk. • The intestines begin to “close up” from 24-48 hours after birth, so it is imperative that the calf suckles within the first 24 hours of life. • The calf must ingest the colostrum in the first 24 hours because colostrum gives the calf immunity against disease

6. Hormones • Prolactin is involved in the development and differentiation of mammary gland • Oxytocin causes the muscles to contract and squeeze the milk into the milk ducts and toward the teat • Epinephrine signals the let down and stopping of milk flow

7. How does milk travel from udder to milker? • Prolactin stimulates the alveoli cells to produce milk. • The milk drains into the lumen of the alveoli. • The clusters of alveoli, called lobules, contain ducts that drain into larger ducts. These larger ducts drain into the gland cistern. • The milk is stored in the gland cistern. • The sphincter muscle prevents the milk from leaking into the teat.

8. Trends in dairy production • In nature, animals only produce enough milk for their offspring. Over time, we have selected high producing animals that have come to produce excess amounts of milk • Changes have come about due to improvements in genetics, feeding, and environmental conditions • We now have fewer cows with more production, fewer farms with more cows, and more Grade A milk

9. Why 3rd world countries don’t have dairy cows • They are not adapted to the hotter, drier conditions • They require more maintenance than may be available • They might not survive limited grazing/feeds that may be available • The countries have few to no transportation systems. • Households will generally have one or two hardy animals to produce milk for the family • Goats

10. Other dairy animals • Goats • Sheep • Goats and sheep can survive on less feed than cows. • They can also utilize browse better than cattle. • A ewe’s milk has twice the fat and 40% more protein than cow’s milk. • Camels • Horses

11. Let down • The hormone oxytocin is released by the pituitary gland into the bloodstream when the udder is stimulated. • Oxytocin causes the alveoli to “squeeze” and release the milk. • Oxytocin release can be caused by: washing the udder prior to milking, suckling of the calf, or other pleasant stimuli. • If an animal becomes frightened or upset, a hormone called epinephrine is released that inhibits milk letdown.