UNIVERSITY OF MISSOURI COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BULLETIN 344
The Structure of the Cow's Udder
C. w. TURNER
COLUMBIA, MISSOURI JANUARY, 1935 UNIVERSITY OF MISSOURI COLLEGE OF AGRICULTURE Agricultural Experiment Station EXECUTIVE BOARD OF CURATORS.-MERCER ARNOLD, Joplin; H.J. BLANTON. Pari1; GEORGE C. WILLSON, St. Loui1
STATION STAFF, JANUARY, 1935 WALTER WILLIAMS, L.L. D., President FREDERICK A. MIDDLEBUSH, Ph.D., Acting President F B. MUMFORD, M S~ D. Agr., Director S. B. SHIRKY, A. M., ABBt. to Director MISS ELLA PAHMEIER, Secretary
AGRICULTURAL CHEMISTRY E. MARION BROWN, A.M.* A.G. HOGAN, Ph.D. MISS CLARA FUHR, M.S.* L. D. HAIGH, Ph.D. E. W. CowAN, A.M. HOME ECO NOMI CS LUTHl!ll R. RICHARDSON, Ph.D. U. S. AsHwOJ.TH. Ph.D MABEL CAMPBELL, A.M. A.M. ]ESSIE ALICE CLINE, A.M. s. R. JOHNSON, ADELLA EPPEL GINTER, M.S. HELEN BERESFORD, B.S. AGRICULTURAL ECONOMICS BERTHA BISBEY, Ph.D. 0. R. JOHNSON, A.M JESSIE V. COLES, Ph.D. BEN H. FRAME, A.M. BERTHA K. WHIPPLE, M.S F. L. THOMSEN, Ph.D C. H. HAMMAR, Ph.D. HORTICULTURE AGRICULTURAL ENGINEERING T. J. TALBERT, A.M. J.C. WOOLEY, M.S. A. E. MuRNEEI<, Ph.D. MAcJC M. JoNEs. M.S. H. G. SWARTWOUT, A.M. G. W. GILES, B.S. in A.E. GEO. CARL VINSON, Ph.D. FR.ANE Ho1tSFALL, J:a..., A.M. ANIMAL HUSBANDRY R. A. SCHROEDER, B.s. in Agr. GEORGE E. SMITH, B S. in Agr. E. A. TROWBRIDGE, B.S. in Agr. L.A. WEAvER,....B.S. in Agr. A. G. HoGAN, rh.D. POULTRY HUSBANDRY F. B. MUMFORD, M.S., D. Agr. H. L. KEMPSTER, M.S. F. F. McKENZIE, Ph.D.• E. M. FuNJC, A.M. J.E. COMFORT, A.M." li. C. MOFFETT, A.M. RURAL SOCIOLOGY A. T. DYn, B.S in Agr E. L. MORGAN, Ph.D. s. R. JOHNSON, A.M. L. G. BROWN, Ph.D. C. E. TERRILL, B.S. SOILS BOTANY AND PHYSIOLOGY M. F. MILLER, M.S.A. w. ]. ROBBINS, Ph.D. tH. H. KRUSEIDAIRY HUSBANDRY t. D. BAVER, Ph.D. A. C. RAGSDALE, M.S. H. F. WINTERI, B.J , Ass't. Agr. Editor C. A. HELM, A.M.* J. F. BARHAM, Photographer L. J. STADLER, Ph.D.* LEON WAUGHTAL, A11istant Photographer B. M. KING, A.M.* TANE FRODSHAY, Librarian
*In cooperative service with the U. S. tOn leave of absence. Department of Agriculture. The Structure of the Cow's Udder
C. v\'. 'f u RNE R
The mammary g lands of the cow are grouped together in a struc ture called the udde r. There are two no rm a l g lands ( the fore and rear quarters) in ea ch ha lf, and in addition there ma y be one ro two super numerary teats associated with small glands. The ri ght and left halves of the udder are separated by a well detined lo ngitudinal groove which extends upward as the median connec tive ti ssue septum. Vi ewed fro m the s id e, the udder presents a more o r less rounded sacc ul ar appear ance with attachments usua ll y extending hi gh b ehind and well fo rward. The several dairy cattle breed rs' a ssoc iations have prepared pictures and models of cows s howing ideal udders (Fig. 1). While there are some differences in these pictures, the read er will note· that they are all characterized by good size, well bl ended attachment o f the
GUERNSEY HOLSTEIN - FRIESIAN
Fi g, 1.- The model udder, of the doi ry breed,. 4 11l1ss11uRr AGRl CLT LTU iiAL Exl'ERI~tEl';T STATION
fu re quarters, levelness of the fl oor, well placed teats of good size, and with rear attachments wide and carried high behind. The Internal Structure of the Udder llpon dissection of the udder, it will be ohserv ecl that each half is encloscd in a strong fibrous sa c. O n the inner si de where the halves join, the tibers in termingle and ex tend upward to the abdomen wh ere an attachment is made. This stru cture is known as the med ian suspensory li ga ment. On either side are the lateral suspensory li gaments, which in conjunction with the skin, serve as the chief support of the udder (f.'ig. 2). The indi vidual glands (the quarters) in each half of the udder are not as distinctly separated as are the halves. For this reason the earli er anatomists were of the o pinion that the ciuarters were connected.
MEDIAN SUSPENSOR'\' LI GAMENT
Fi K, 2.-Crou Rt!cti on of the re ar quart~r& of a cow's udder. Buu .ETJN 344 5
Several lines o f evidence suppo rt the present view that each quarter is quite separate and distinct. In s tudies of the e arl y development of the teat and gland the separation i s d istin ctly shown (see J\1issouri Agri cultural Experiment Station Research Bulletin 160). Bitting a nd many others since have injected varied colored dyes into fore and rear quarters (Fig. 31 . The line o f division thus shown appears to be a ve ry thin connective tissue septum, irregular in outline but permitting no mingling of the secretion of the two glands.
Fi ,i::. 3.-Section o f lh c fro n l. and renr qunr1e r1 ol a co w's udrler. The ci tcn L ,,( th e t.1u:1r 1cra i1 ehow n by Lh e in1cctio 11 of vnric cl colo red 10\u1i na. The cl arkc 1 sec ti o n ie the fore <:llarl er .
In a recent study of 74 lactation records,- the writer fo und that on t he average the two fro nt quarters each produced sli ghtl y more tha n 20 per cent of the total milk yield, wh ereas the two rear quarters each p roduced sli ght ly less t ha n 30 per cent. Conside red t ogether t he fro nt q u arters produced 41. 90 p er cent and t he rear quarters 58.10 per cent f t he total milk. The mi .lk production fro m t he ri ght a nd left ha lves was practicall y uniform, 49.93 per cent and 50.07 per cent, respectively . H owever, in a total of 16 lactation records, the largest quarter productio n oc-urred in one o f the fo re quarters. ·
At the e ntrance to th e teat t here is a duct called the streak canal or ductus papillaris. It is usually from ¼ to ;),13 inches long a nd is held :\f 1,;,;1,1 1111 J\c1nct1LTUHAL Ex1·EH1 :11 EXT ST.-\T111 ~
closed by the aid of a circular sphincter muscle. The streak canal is designed to retain the milk in the udder against the pressure developed in the storage s1·stem during the interval between milkings. It also makes difficult the entrance of foreign matter and bacteria. At times the canal is so small that there is diAiculty in milking (the so-called "hard milker"). This condition may frequently he remedied by surgical treatment. Above the streak canal the cavity of the teat widens out gradually until a space of considerable..: siz e is formed. This is called the cistern of the teat. The 1q,pe 1· end of the cistern uf the teat opens into the cistern of the gland ahove. Fre quently the teat cistern is sharply distinguished from the gland cistern Liy a constriction in the form of a circular fold which has a central or somewhat excentric opening. It has been suggested that when the opening is very narrow, there is considerahle hindrance to the out- 2 flow of milk. In a few cases a horizontal membrane of connective J tissue may form which completely separates the two parts of the cis- F ig. ·!.-Cross Semon o r th e udde r s ho win g· tern at this point, resulting in a ( I ) 111cd i ,,1 1 suspe nso r y li ;.