POULTRY NOTES
(Py "Chanticleer.") Egg Formation, ' At the Sow Zealand Utility Club meeting on Tuesday evening, Mr. I. B. ilerrett. gave an address oil the question: "What aro the primary functions of the hen in the fertilisation and production of the ckk?" "This question," 'aid Mr. Merrett, "leads us into the physiology of ecs-Ploduiition, and to undeiotand it ivo must begin with the egg 111 its embryonic state. JThe ovary is attached close to the backoono and contains a cluster of ovulea or minute yolks. These number from 1500 to 3CCO, and from theso como all tho oggs a hen is likely to lay. Wo must realise that in the development of these eggs we Juivo the combined functions of reproduction and food Jecretiou. Then hen. therefore, in every egg she lays practically reproduces herself, because, in the egg, are all tho elements necessary to produce <i chick. Special attention should be given to ovarian development, because liens (litter bo largely iii their auility to develop the ovules. . Some have a natural tendency to convert their food to develop the egg while others divert the food secrctions to produce flesh ti.ud fat in place of eggs. Wo should aim to breed that class of hen with a disposition to lay, and must feed her so sue will function towards the development oi the ovum, the yoke of the egg, secrete the while to nourish tho chick and produce the mineral matter for the bhell which gives protection to' tho chick. The egg yojk attached to tho ovary is enclosed 111 a sac. or follicle, through which it obtains nourishment to develop. As it matures it drops into tho 'funnel-shaped opening of the -oviduct. Scientists arc not agreed <is to whether the vitelline membrane that encloses the yolk ripens and loses adnesivo powers, or whether thu increasing weight juptures the sac and releases it. It :s singular that in every yolk sac there is a suturo line which can bo seen on examination of a dead fowl. This white line splits, and tne yoil: is released and begins its passago along tho oviduct. The yolk sac contracts, and may also be examined in a hen that has laid many eggs. It remains an unabsolved tissue and has nn other function to perform. The empty yolk sacs indicate the number of eggs a hen has laid. The egg at this stage haß neither white nor shell. If the cjg is to be fertilised it is at this juncturo fertilisation must take place before any ■white envelopes the yolk. Experiments show that the shortest time in which Cffgß may become fertile is 42 hours, whilo in the case of old hens it tabes from eight to ten days. Hcneraliy speaking fertility takes place five days after mating. On every yolk ia a germ ceil or blastoderm. It iB a white disc. Ab tho yollt develops the germ cell moves outward, the yellow stratus are added daily, and it is a problem to science how the germ cell moves outward leaving a trail of white yolk behind it across which no yollov,' yolk is deposited. There is also eouie function connected with this germ cell causes it to be uppermost on the yolii, so that it iB nearest to the warmth of the hen's body during incubation. The yolk having been deposited in the oviduct, the fertilisation of the germ cell complete, it is now developed with it layer of albumen that forms the white. Here is now formed the chalazia which are attached to tile yolk and extend towards the ends of the egg. Tluy hold the yolk in place and preserve it from injury. Were it not for' this ingenious provision, the yolk would rise and stick to the shell, making incubation impossible. The yolk is lighter than the whito and has the tendency to rise Tiie chalazae keeps it in position and allows the yolk to revolve so that the germ is always uppermost. Kext to tho Urst layer of albumen is a thicker layer which may be readily distinguished by its jelly-like appearance when an egg is broken. The third layer is thinner and transparent. These three layers ot albumen form the white of the egg. lS'ext come • tho inner and outer membranes, iheso are added m the isthmus of the oviduct. The inner membrane is of n ftii(!r texture than the outer. They protect the egg from evaporation and contamination. If you break a fresh egg you ?° au " CL '" lB lorm ' :l1 between these membranes. The egg now passes on to the uterus, where u receives the iirst of its shell membrane. The glands jn tho uterus are very strong and excrete iiim'ra when stimulated by the appioach of the egg through the oviduct. There are three- layers of calcareous deposit in the shell, and all of which are white, when complete the egg passes on to its final stage in the vagina, when it receives its shell pigment or colouring, and the gelatinous coating we t--i.ll the bloom, the egg is now complete and ready for expulsion through the cloaca tggs vary greatly in shape. Evidently the tension in the oviduct accounts for tnis. In its passage the largo end comos lirst causing the tapering oif in the smaller end. the egg is not always laid laigc end first, bo that evidently the ipomtion changes in the uterus during shell formation. When the egg is hm laid, 110 air'space can be defected. As it cools it contracts. The air space is then usually seen at the large end. Contraction takes place there iirat because of the larger iirea that ia being cooled. The Moom eccreted in the shell can he re-' moved by.-washing jyhile tho pigment or colouring m the shell is only 011 the out* side and can he removed with Band-soup or acids, 'i'lic composition of the ope is as follows:—Water, 70 per ecnt.; fat 9protein, 10; shell and membrane, 9 ' Of tne nine per cent, of fat, none is to bo found in the white. Then hen must therefore be 111 good condition and have a surplus of fat before the yolks will begin to develop.''
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Dominion, Volume 13, Issue 26, 25 October 1919, Page 12
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1,031POULTRY NOTES Dominion, Volume 13, Issue 26, 25 October 1919, Page 12
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