1. Maintenance
1.1. maintenance occurs primarily through hormonal influences
1.1.1. Prolactin
1.1.2. thyroid hormones
1.1.3. adrenal hormones
1.1.4. growth hormones
1.2. milk production increases the first 4 to 6 weeks into lactation
1.2.1. decreases over the weeks
1.3. PERSISTENCY IS IMPORTANT
1.3.1. Milk production of current month as a percentage of milk production of previous month
1.3.2. lactation curves
1.3.3. typical dairy cows lactates for 305 days
1.4. Decreased milk production occurs as active alveoli and secretory tissue decreases
1.4.1. this is usually caused from hormonal influences
1.5. When milking and suckling stop, this tells the mammary gland to stop producing milk
1.5.1. Short-term: alveoli are distended and capillaries are filled with blood
1.5.2. After a few days: secretory tissue becomes involuted and leaves ducts and connective tissue
1.5.3. Cow is now “dry” which lasts approximately 60 d in dairy animals
1.5.3.1. This gives her time to recover and prepare for parturition
2. Factors Affecting Milk Production
2.1. Genetics
2.1.1. Inheritance determines the potential for milk production
2.1.1.1. dairy cow genetics make her have a greater potential for milk production than a beef cow
2.2. Proper Nutrients and Managment
2.2.1. must be provided in order for her to reach genetic potential
2.3. Overall Health
2.3.1. Mastitis: inflammation of the udder, can decrease production by 30%+
2.4. Demands
2.4.1. production changes to match demands
2.4.1.1. sex, multiples, etc.
3. Milk Composition
3.1. Milk Composition has multiple variations across species
3.1.1. Mares
3.1.1.1. only 1.2% fat and 2.3% protein
3.1.2. Cows
3.1.2.1. about 4% fat and 3.3% protein
3.1.2.2. In dairy cows, % fat is related to roughages fed
3.1.3. Very little variation in percent protein or lactose with changes in the diet
3.2. Total solids = fat + protein + lactose + minerals
4. Summary
4.1. Lactation:
4.1.1. the production of milk from the mammary gland
4.2. Milk from mammals
4.2.1. provides nutrients and passive immunity to the young and is a nutrient source for humans
4.3. Colostrum
4.3.1. the first milk produced after the young are born
4.3.2. the source of immunoglobulins that provide early immunity to the offspring
4.4. The mammary gland
4.4.1. an exocrine gland that produces an external secretion (milk) from structures called alveoli
4.5. Several hormones: estrogen, progesterone, thyroid hormone, growth hormone, adrenal hormone, and prolactin
4.5.1. affect mammary gland development, milk secretion, and the maintenance of lactation
4.6. Lactation curves
4.6.1. for most farm animals peak a few weeks after lactation is initiated, then decrease throughout the lactation period
4.7. Milk Composition
4.7.1. composed primarily of water with lesser amounts of protein, fat, lactose, and minerals
5. Mammary Glands
5.1. Functions:
5.1.1. 1. It provides nutrition to animal offspring
5.1.2. 2. It is a source of passive immunity to the offspring
5.2. Structure:
5.2.1. Exocrine gland: produces milk that is externally secreted through a series of ducts
5.2.2. Udder is supported both horizontally and laterally by suspensory ligaments
5.2.3. Alveoli: millions of grapelike structures which are the secretory tissues
5.2.3.1. Each alveolus has its own separate blood supply to provide milk constitents
5.2.3.2. Milk collects in the alveolus lumen
5.2.3.3. During milk letdown, it travels through ducts to gland cistern
5.2.3.4. Its then forced into the teat cistern and through the streak canal to the outside
5.2.4. Different Animal Structures
5.2.4.1. Cow
5.2.4.1.1. 4 mammary glands that terminate into 4 teats
5.2.4.2. Sheep/Goats
5.2.4.2.1. 2 glands and 2 teats
5.2.4.3. Mare
5.2.4.3.1. 4 glands and 2 teats
5.2.4.4. Sows
5.2.4.4.1. 6 to 20 glands located in 2 rows
5.3. Development
5.3.1. occurs rapidly as female reaches puberty
5.3.1.1. Estrogen causes duct and cistern growth
5.3.1.2. Progesterone causes growth of alveoli
5.3.1.3. Growth hormone and placental lactogen are also important
5.4. Milk Secretion
5.4.1. Growth hormone, adrenal corticoids, and prolactin initiate lactation
5.4.2. They take over as estrogen and progesterone decrease around parturition
5.4.3. • Oxytocin causes “milk letdown” by making myoepithelial cells contract
5.4.3.1. Suckling reflex, nudging, sounds/smells, washing teats all stimulate oxytocin
5.4.3.2. Stress, loud noises, pain can all inhibit release of oxytocin
6. Lactation Curve
7. Colostrum
7.1. this is the first secretion from the mammary glands after giving birth, rich in antibodies.
7.2. During gestation, fetus is developing in a sterile environment
7.3. Its immune system must become functional or it will die after birth
7.4. Immunoglobulins are involved in the passive immunity transfer from dam to offspring
7.4.1. These can be passed via blood stream in some animals (depends on type of placenta)
7.4.2. These antibodies provide protection from microorganisms
7.4.2.1. Antibodies are absorbed through intestinal wall during first 24 hrs of birth
7.4.3. This is why its “passive”…have to be in colostrum and offspring needs to get them in first few hours of life