How is goat milk produced ?

1. How isgoatmilkproduced? Alveoli are the milkproducing structures of the mammary gland. Eachalveoli has a richsupply of bloodthatbrings the components to producemilk to the cells. Alveoli are linkedwithCapillariesthatbring the components and Venuolesthatremoveexcessfluids. About 500 volumes of blood must passthrough the udder to maque 1 volume of milk. The lining of eachalveolusiscomposed of cells (Epithelialcells) thatsurround a cavitycalled the lumen.

2. The Epithelialcells The Epithelialcellsactlikefactories, let’s explore it’sfunctions in milk production As all cells, epithelialcellsneedenergy to work. One of the products by microbian fermentation in the rumen ispropionicacid. It isabsorbedinto the blood and transported to the liverwhereitisconverted to glucose. More thanhalf of the glucose thatwillget to the alveoluswillbeused as a source of energy for the cells ( the otherhalfwillbeused to crate lactose). CH3CH2COOH  C6H12O6

3. The epithelialcellsneed to synthetise components of milkthat are not present in bloodsuch as lipids (fats), someproteins and lactose (milk’ssugar). The cells control by the way the amount of each component in the milk. A fattyacidis a moleculethat has a long or short of carbonatomswhitthis structure at the end. Where C=Carbon, O=Oxygen and H=Hydrogen(here an examplewith an aceticacid). Lipogenesisis the processwheresyntesis of milk fats isdone. This fats are manufacturedfromprecursorsbrought to the cells by blood. Aceticacid (C2H4O2) and β –hydroxybutyric (C4H8O3) are alsoproducts of the rumen fermentation and are the main precursors of milkfattyacidssynthesisin the mammary gland. In a complicatedseries of steps, the acids are combined to crate a long chain of fattyacidcalledpalmiticacid. Palmiticacid has a 16 carbonatoms in it’schain. Palmiticacidcanbeused to synthetise fat or itcanbebroken down into a shorterchainfattyacidsuch as carpicacid. Wichispresent in a bigamount in goatmilk Carpicacid has 10 carbonatoms in it’schain.

4. The percentage of fats in milkisinfluenced by nutrition and environment. A fat iscretedwhen 3 fattyacidsattach to a glycerolmolecule. The resultiscalled a triglyceride, the most commun kind of fat in milk. This is a long chaintriglyceride fat. Fattyacids Glycerol

5. Proteins are made fromaminoacids. The genes in the nucleus of the cell direct the types of proteinscreated. There are 20 differentaminoacidswhich are the end product of intestinal digestion of proteins. The aminoacids are absorbedthrough the intestinal walland transported by the blood to the liverwhich directs them to the body tissues as needed. In the nucleus, a template of the DNA iscreated, the Messanger RNA. This copy of DNA willget out of the nucleus and counter the differentaminoacids. EachMessanger RNA sequence has a different code, the aminoacidswillbefixed in differentways and orders to formchains, the proteins.

6. Let’stry to understandwhatreallyhappenswithproteins. Most of the protein in milkiscasein. There are four kinds of caseinprotein: -Two types of alpha casein (α1 & α2) -a beta casein (β) -a kappa casein (κ) The four caseinformsagregate Kappa caseinisdifferent. It prevents Alpha and Beta caseinproteinsfromcombiningwithadditional calcium. That’swhyindividual micelles repeleachother. In fluidmilk, caseinproteinsformsmallspherescalled micelles Alpha and Beta proteins are connected to eachother by phosphate and calcium. But the Chymosinenzime, thatwefind in rennet, has the capability to change the kappa caseinprotein. Weobtain para-kappa-caseinwhichis no longer able to prevent calcium and phosphate frombinding to the caseinproteins. Micelles clumpthustogethercausing the milk to coagulate. An important stem in cheese production.

7. β-lactoglobulin and α–lactalbuminproteins are alsosynthesizedonly in the mammary gland. Otherproteins and the immune globulins are sinthesizedelsewhere in the body. Galactose isverysimilar to glucose except for the orientation of thesemolecules. Lactose is the sugar of milk. It iscreatedonly in the alveolarcells of the udder by combining glucose and galactose. Glucose isabsorbedfromblood. Inside the cellsome glucose isconvertedinto galactose. In a few more steps, Galactose and Glucose are combined to form Lactose

8. The alveolarcells have to regulate the amount of components that come directlyfrom the blood but are not changed in the cell, such as water, vitamins and minerals. • Vitamins are synthesized in the goat’s body or come directlyfromfeed sources. • Vitamine A: Vitamine A precursorcomesfrom plant diet and isconvertedinto vitamine A in the wall of small intestine. • Vitamine D: comesfromexposure to the sun and fromsome plants. • Vitamine E: comesfrom green feed • Vitamine K: issynthesized by bacteria in rumenand intestines. Both K and D are present in smallquantities in milk. • B vitamine: issynthetized by rumen bacteria. The bacteriaisbroken down whenitgoesthrough the intestine and the vitamine canbeused. • Vitamine C: isnaturallysynthesizedby the goat. Water flowsthrough and betweencells by diffusion. • The amount of mineralsincluded in the milkisalsoregulated by alveolarcells. • Major minerals: • Calcium • Phosphorus • Chlorine • Magnesium • Sodium • Trace minerals (oligo-éléments): • - Iron • - Manganese • - Copper • - Zinc

9. The milkcontainsnow all it’selements and isready to beexpulsedfrom the alveolus. It has the following composition:

10. During the manufacturing of milk, lumen fillswithmilk. Eachalveolusissurrounded by cellscalled basket cellswhichactlike muscles. Whenactivated by the oxytocin hormone the basket cellscontractpushing the milk out of the alveoliinto the collectingducts.