HORMONES

Dominion, Volume 7, Issue 1996, 2 March 1914, Page 10

HORMONES

STIMULATING MILK SECRETION. Several years, ago the Missouri Experiment Station fed a "cow, freshly calved,"only enough food for maintenance,' giving ; no food for- the production of. milk. In spite of this handicap tho 'cow continued' to product* and"at. the end of thirty days was giving within two potinds /of tho milk '< sho gave at tho beginning. During this period slie •est, over 120 pounds in/weight, showing that she sacrificed her body to produce the milk. Until very recently this action)has r betfn' difficult to'explain. Now through the discovery-of a body which is commonly termed, a "hormone" the explanation is rendered comparatively siniple.

A hormone may be. defined as a stimulant secreted in one part of'the' body which passes in the blood stream to affect the action of a second part. It exerts a; stimulating effect upon the glands and increases ; their activity. The hormones affecting, milk secretion may be 1 produced in one of several bodies but it is now thought that the hormones of the' most importance in milk protection como: from - the pituitary body, a small grayish gland situated .in tho cavity; just beneath the_ cere-belliim or rear'pbrtidh of the. brain: . Stimulative action has also been secured from the injection of extracts of functional udder glands, and other extracts of various organs related to;sex. ".

It lias been observed that heifers may secrete - milk previous to calving. It may ( bo caused from sucking by: another calf, but occasionally-it is stimulated without such mechanical cause. Investigations into; tho value V hormones in stimulating milk, secretion have' been numerous on lxJth eides of the Atlantic. Lederer. and Prizibram. found in goats that' the' injection of extracts of. i'resh tissues froia-tho after-birth greatly,stim-. ulatea the action of the mamary glands' and increased the milk flow.. The powerful effect of these -hormones on tlio milk 1 flow; can be more fully appreciated when ,it is known that extracts of these various tissues when injected into, females not:)giving /milk cause,a secretion,of amorous fluid closely, resembling milk.- This effect was secured by,' Dr. MacKenzie of-tho University of Edinburgh.' " ■ ■ \ - Tho, action of hormones is 'almo'st- immediate. Hammond, of Cambridge'Uiuj versityj.England, secured - some very in-' teresting data with goats. Ho milked tho goat at 10.40 and then, injected' an extract of tho pituitary, body. He followed this; with a sefcond injection at 11.50 with'the appended results:—. |°- Timeof C; C. milk - Timoof-O. O. milk milking, .-secured, .milking, secured.', ,;10;42 130.0, 11.55 22.0 i'i' : 10/67 3.012.10. 4.3 I 1.5/ 12.27 '. 1.9 <11.33- ' ::9 - ' 12.'41 1.9 •11.50 ' ' .9

Tho effect of hormones'upon the composition of .milk has .befenxatefully studied.,- .Usually. the;percentage-of ■fab' is increased, although' it is . not always true. There is, however, usually a .drop ill the/'percentago ,of fat ; below normal after, tlfo ..stimulating .effect, has,,' been lost, This decrease is ' usually not-, aspreat as the increase sucured by the mjectitiiii "Hence, thefe is an increase for:tho , 'entirei i 'j)eriod. : . "'i 1 ' A >i tafher peculiar-action of hormones is on the relative ..'composition of first niilk and tlio stripping!. Uridbr-'iiormal conditions tto. fit.pQ'.qpptage is larger in " tlio' jTirst-_-iiiilfc-; t : han 'in ,the .-later;-.-but wlien horaoiiM'''aro injected the perthroughout. The,,'.percentage;,of .solids,.-.that .aro, iu tlio fat- remains i unchanged. 'fhe hormones probably ''stimulate■ the 'secreted cells: of : the;- milk'/glands, so that'milk is giffin'*ffhi(ili' : otherwis6! , w6utd. ri'ot ; bV -secreted-until a-subsequent-milking. If tliis' is the action of tho extract' then tiie increase of. niilk. followed by a slight drop below normal is explained." There is u-direct relation between tho amount of a-result of tlio inaction aha. the timo in the period of lactation.' • This'fact to snow-that tho secreting'action is directly upon the cells of the gland and not upon the miisculpr.abtion.,,'Suddenly altered cbnditions'in' tliese cells probably .cau'se'the fat. globules which have accumulated in the ends of the cells to be discharged immediately, thus explaining the increased percentage of fat in the early pari of the milking. It is obviously important from'the commercial point of view; to determine whether tho amount of milk por ,day and its quality can be influenced sufficiently .to pay for tho commercial.use of tissue -injections. W. Gavin, of England, conducted experiments with milk cows in which he emphasised the.: commercial viewpoint. The cows wore fed as-usual and niilked twjco a day. - Hi> draws tho following conclusions: "Under ooiitlitions, of ordinary farm practice no comjnSrcial benefit arises from the administration of these glandular extracts, no matter how given. Injections of pituitary extract into tlie blood iiiay be t ?!|?^ d ±I b y a" inpreasea "collection of milk in, the reservoirs of the-udder, but in spito of. this, .no alteration.-in the quantity of milk per day or in the quality occurs. -.This - result . shows that' .there is no commercial valuo to tho Knowledge of hormones at" the present time., Nevertheless, their influence on milk secretion cannot .be questioned in esplaiiiing many of the peculiarities of dairy farm practice."