Lactation AS 1124 Macroscopic Anatomy of the Mammary Gland Species differences in numbers and locations of glands inguinal - caudal to the abdomen, between the hind legs (cow, mare, ewe) abdominal - along the abdomen (pig, dog) pectoral - cranial to the abdomen, between the front legs (primates, elephant) Anatomy Udder is divided into four quarters Fore quarters about 20% smaller than rear quarters Each of the quarters is independent of the other three Milk secretion occurs in the alveoli 1
The Alveoli Alveolus (.1 to.3 mm diameter) lumen hollow cavity epithelial cells inner lining of the alveolus myoepithelial cells outer lining of the alveolus tertiary ducts blood vessels capillaries, arterioles, venules An Alveolus Ducts secondary ducts primary ducts gland cistern holds about 1 kg of milk 2
Teat streak canal opening from the teat cistern to the outside of the teat teat cistern cavity inside the teat Anatomy Support System for the Udder lateral suspensory ligaments median suspensory ligaments 3
Support System for the Udder Arterial Blood Supply (400 lbs of blood for 1 lb milk) Venous Blood Draining the Udder 4
Functions of the Mammary Glands Nutrition Species variations in composition fat content, protein, lactose, etc. glands are separate Immune protection colostrum- first milk provides antibodies until the newborn s immune system can take over Water Milk Fat Protein (casein) Sugar (lactose) Milk Composition Milk Composition - % Species Water Fat Lactose Casein Cow 87.1 3.8 4.8 2.9 Ewe 83.2 6.2 4.3 4.3 Mare 89.3 1.6 6.1 1.6 Sow 82.6 7.0 4.0 3.8 Bitch 79.2 8.5 3.7 3.9 Whale 46.7 44.0 1.8 7.0 Woman 87.4 3.8 7.0 0.9 5
What hormone is involved in milk letdown? Oxytocin Teat Stimulation - Milk Letdown Stress can Inhibit Lactation 6
Hormones Regulating Growth Estrogens ovary cell division of end buds (epithelial cells of the ducts) Induces Progesterone receptors Progesterone ovary growth of lobules and alveoli Mammotrophic Hormones Mammotrophic Hormones Mammotroph = growth & maintenance Placental Lactogen (PL) esp. placenta of ruminants acts like somatotropin and prolactin Prolactin (PRL) from Ant. Pituitary Somatotropin (ST) (GH) from Ant. Pituitary all species, greatest in ruminants Milk Synthesis Lactogenesis = process by which mammary alveolar cells acquire the ability to secrete milk Galactopoiesis = maintenance of actual production/ synthesis of the milk Agalactia = absence of milk production low PRL 7
Milk Ejection Milk removed by : suction myoepithelial cell contraction suckling, hand or machine milking suckling is fastest Neurohormonal reflex acute release of Oxytocin release of Prolactin stimulatory to Somatotropin Effects of Suckling increase in Oxytocin increase Prolactin increase Somatotropin decrease GnRH ( & LH) 8
Milk Fever Milk Fever - parturient paresis low blood Ca and P after parturition generalized paresis, circulatory collapse, death treatment infuse Ca prevention restrict Ca during gestation feed higher Ca at parturition administer vitamin D Ketosis Ketosis (ruminants) imbalance in glucose metabolism elevated ketone bodies, hypoglycemia Mastitis Mastos = breast, itis = inflammation >99% of cases caused by intramammary infections Clinical Mastitis : visible signs of infection are evident Subclinical Mastitis : generally not detected, no obvious signs 9
The Cost of Mastitis Clinical death and premature 14 % culling discarded milk 8 % Treatment 8 % The Cost of Mastitis Clinical death and premature 14 % culling discarded milk 8 % Treatment 8 % Subclinical estimated cost $181 /cow/yr 70 % REDUCED MILK PRODUCTION Causative Organisms Contagious pathogens transmitted from infected glands often subclinical and long duration shed in milk Environmental pathogens manure, bedding, soil confined housing clinical, low incidence 10
Contagious Pathogens Staphylococcus aureus (gram +) colonize teat canal spread by hands, teatcup liners, etc. produces scar tissue difficult to treat - treat during dry period Contagious Pathogens streptococcus agalactiae (gram +) infected udders/glands high SCC surface contact with contaminated milk young females nursing each other treat ASAP- can result in lost quarters Environmental Pathogens streptococcus non-agalactiae species older cows short duration coliforms (e.coli, klebsiella pneumoniae) short duration produce endotoxins clinical, acute, painful 11
Natural Defenses against Mastitis Teat canal sphincter muscle keratin Somatic cells predominant cell - macrophage neutrophils- most active in engulfing bacteria Prevention Antibodies vaccines under development s. aureus vaccine decreased duration not incidence e. coli vaccine decreased incidence Nutrition Vitamin E and Selenium enhance immune response influence muscle tone 12
Detection of Mastitis Clinical easy to detect swelling, red, painful clots in milk or strip cup decreased production Detection of Mastitis Subclinical - no obvious clinical signs increased SCC DHI will measure treatment not based on SCC other reasons for SCC poor response to treatment lag time - SCC increased after microbes decreased economics Detection of Mastitis California mastitis test 13
Prevention Practices Practice milking hygiene teat dipping treatment of all quarters at drying off treatment of clinical cases culling of infected cows 14