4IntroductionMilking is the process of persuading the cow to let down its milk and allow dairy farmer to remove it for his or her own consumption or for sale.It is therefore not entirely a natural process.The dairy farmer must manipulate the natural process so that he receives the maximum benefit.It is therefore essential that one understands the natural process in order to manipulate it.
5Mammary glands are the major features that distinguish mammals from other kinds of animals. Cow Goat SheepMammary glands are the organs that, in mammals, produce milk for the sustenance of the young.
6The teats and glands can occur anywhere along the two milk lines, two roughly-parallel lines along the ventral of the body.Pig Cat MouseIn general most mammals develop mammary glands in pairs along these lines, with a number approximating the number of young typically birthed at a time.
7The number and positioning of complex and simple mammary glands varies widely in different mammals. Elephant Human
8The number and position of glands normally found in a range of mammals: SpeciesAnterior (thoracic)Intermediate (abdominal)Posterior (inguinal)TotalGoat, sheep, horse2Cattle4CatDog2-48-10Mouse610Pig16Elephants, primates
12Several examples of species that reflect the range of anatomical location and number of glands or teats.SpeciesLocation (region)Num of glandsNum of teatsCowinguinal (groin)4Ewe, doe2MareSowabdomen10-14CatDogHumanthoracic (pectoral)Elephant
13Anatomy of the udder (cow) Located in the groin (inguinal) areaConsists of four separate glands (quarter), each gland has one teat with one openingRear quarters account for 55-60% of total udder weight and produce 55-60% of milk
14Total weight: 50 lb of empty udder + 60 lb of milk in the gland, or 110 lb suspended from the body prior to milking ----->attachment of udder to the body is critical
15Suspensory SystemSupport system: median and lateral suspensory ligamentsRight and left halves are separated by intermammary groove
16Location of udder, quarters, teats, proportion and attachment
17What are the specific anatomical structures of the udder that are involved in holding the udder onto the body wall?The cow in image A below has an udder that is held firmly to the body wall.In contrast, the cow in image B below has a deep udder that hangs down away from the body.What are the differences in those structures between the cow in A vs B?
18External and internal structure Teat, streak canal and sphincter, teat cisternGland (udder) cisternFatty tissueConnective tissueMilk ductsLobules, lobesAlveoli, secretory (epithelial) cellsLumenMyoepithelial cells, oxytocin hormone, capillary bed
19The inside of the udder has two main type of tissue: Connective (fibrous) tissue or collagenFatty tissue (adipose cells)Secretory (glandular) tissue:Milk ductsLobules, lobesAlveoli, secretory (epithelial) cellsLumenMyoepithelial cells, oxytocin hormone, capillary bed
22Diagram of alveolus showing lumen, epithelial cells Diagram of alveolus showing lumen, epithelial cells. myoepithelial, and capillaries.Form lobe and lobulesLobule: contain 150 to 225 alveoliTissues involved in milk synthesisEpithelial cells: synthesis andsecretion of milk into lumen of alveolic. Tissues involved in milk transport Milk flows from lumen alveoli, ducts, major ducts, gland cistern, teat cistern, teat meatusd. Myoepithelial cells: Covers surface of alveoli and small ducts down within a lobule: contraction for milk ejection
23Internal structure of mammary gland of cow Diagram of the duct system in one quarter of the mammary gland of the cow with a single lobe illustrated.Four quarters are fused into a single gland complex.
24Diagram of the gland complex found in the mare. Diagram of a cross section of the supporting structures of the mammary glands of the cow as viewed from the rear.Lateral suspensory ligaments: not elastic, and sends lamellae into udder, continuous with interstitial framework Median suspensory ligament: elastic, and stretch as udder fills with milk
25Blood vascular systemThe blood supply to the mammary gland is extremely important for mammary function! All of the milk precursors come from blood.On avg units of blood passes through the udder for each unit of milk synthesized by a high producing dairy cow; that is ~280 ml per sec.
26High producing dairy goats have a lower (460:1) ratio of blood flow through the gland:milk produced, compared with low producers (1000:1).This means that the amount of blood flow through the mammary gland may by similar for the high and low producing goats, but the efficiency of extraction of the components from the blood while it passes through the udder is very important. This principle is probably similar for cows.
27Total udder blood volume for lactating cows about 8% of total body blood volume, while for a non-lactating cow it is about 7.4%.There is a 2-6 fold increase in blood flow in the mammary gland starting 2-3 days prepartum.The decrease in production with advancing lactation is not due to decreased blood flow, but it is due to the loss of secretory (epithelial) cells through a process programmed cell death (apoptosis).