Lactation

The Udder

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.

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

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 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

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

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.

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

Why 3 rd 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

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

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.