Justine的異想世界

讓工作效率UP起來

效率明快把工作變輕鬆－事務處理力

文/蕭志強

Avian Incubation and Hatching for the Practitioner

Many avian veterinarians quake at the thought of advising or helping an aviculturist with issues related to incubation and hatching. Once you learn the principles of artificial incubation and hatching, you should be able to offer competent assistance. If you are serious about becoming a good avian veterinarian, however, please consider purchasing an inexpensive incubator (or borrow one from a client or friend) and try to incubator-hatch a few eggs yourself. Cockatiels are a good bird to begin with. Do not attempt this with quaker parakeets, as incubator hatching them is quite difficult. You will learn more by hatching some birds yourself than from sitting in ten lectures on the subject!

The process of incubation is a wondrous process, and nature has provided the perfect incubator, the bird. However, for many reasons, aviculturists may choose to artificially incubate eggs. There are many different types of incubators, but the success of artificial incubation depends more on the knowledge and skills of the person using the equipment than of the sophistication of the incubation equipment.

It is important to have a basic understanding of the egg to successfully artificially incubate eggs. The egg must contain all of the nutrients necessary to sustain a growing embryo until hatching. The shell contains pores that allow respiration of moisture and gasses through the egg. These pores can also allow bacteria and other pathogens into the egg under certain conditions. The shell contains three layers: the cuticle, the testa and the mammillary layer. Eggs have two shell membranes, the inner and outer shell membranes. At the area of the air cell, these two membranes are separated. If the egg is opened during an assisted hatch over the air cell, the inner shell membrane will be visible covering the chick. The egg white, albumen, consists of three proteins. Thick and thin albumen and the chalazae, which are two strands of thick albumen, connect to the shell membranes. These act to keep the yolk in the center of the egg.

The yolk provides the main source of nutrition for the growing embryo. The yolk has four membranes and blood vessels develop around the membranes to carry nutrients to the embryo. At hatch, the twitching of the muscles of the embryo help pull the remaining yolk into the coelom, where it is utilized during the first few days of life. The germinal disc is the nucleus of the female egg. If the egg is fertile, it is the blastoderm, and if infertile, the blastodisc. In most psittacines, the reproductive tract of the hen includes only the left ovary and left oviduct. The parts of the oviduct include the infundibulum, magnum, isthmus, uterus and vagina.

The embryo actually begins to develop before oviposition. The egg may be candled to assess fertility after is it laid, and in some cases, it may show development within a few days of being laid. Fertility is ascertained by the development of blood vessels within the egg. The developing embryo is subject to damage by chilling or jarring (addling.) For best hatchability, it is best to leave eggs under the hen for at least 14 days, to ensure the health of the developing chick, but this is not always possible or economically advisable. By pulling eggs for artificial incubation, many birds can be induced to lay more eggs than would normally occur, this increasing productivity. Optimum temperatures that simulate those of the natural parents will produce the healthiest chicks.