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The majority of mammals ovulate and become sexually-receptive (express estrus) spontaneously at defined intervals.
The female of most species will only allow the male to mate during a restricted time that coincides with ovulation.
Some species in which estrous cycles only take place for short periods during the year, such as dogs, may have prolonged periods of estrus (receptivity).
This way, females have more time to find a mate, and more opportunities to mate, before the ovulatory cycle ends.
Estrous Name used for the ovulatory cycle (initiation of oocyte maturation through to release and potential fertilization and uterine implantation) in vertebrates, particularly mammals.
Anestrus “Not” estrus. Temporary or permanent cessation of ovulatory cycles. Can be caused by pregnancy, nursing, season of year (in some species), very poor nutrition, or pathological condition.
Estrus Time period around ovulation (release of eggs), in many species, when female is sexually receptive. Commonly called “heat.”
Seasonal Breeder Species which has one or more estrous cycles that only occur during certain times of year (typically spring-only [long-day] or fall-only [short-day])
Polyestrous Estrous cycles repeat throughout the year (cattle, swine, humans, etc.). In livestock, it is suspected the fully polyestrous physiology is largely produced by domesticated conditions (continual food supply, selective breeding).
Seasonally Polyestrous Species that have multiple estrous cycles, but only during certain times of year.
- Short-Day Breeders Estrous occurs when days are getting shorter (fall), and Anestrous when days are getting longer (spring/summer). True of sheep, goats, deer and elk.
- Long-Day Breeders Estrous occurs when days are getting longer (spring), and Anestrus when days are growing shorter (fall). True of horses and hamsters.
Monestrous Species that have one estrous cycle per year, True of canids* and ursids (dogs, wolves, foxes, and bears). Estrus periods are longer in these species, which increases the probability of mating and pregnancy from the single estrous event.
Oocyte An immature egg cell.
Ovulation The release of mature eggs (ova) from ovarian follicles.
Placenta The structure through which nourishment for the fetus is received from, and wastes of the fetus are eliminated into, the circulatory system of the mother.
Photoperiod Scientific term used for “daylength”. Photoperiod is an important calibration and time-keeping system in living organisms of all types, but especially plants and animals.
Photoperiod 2 Living organisms generally recognize changes in daylength through photoreceptors in animal eyes and plant leaves. These trigger biochemical actions as changes in one direction or the other reach certain levels of magnitude.
Artificial Insemination The practice of collecting semen from a male and transferring it to a female (into the cervix or uterus) at the time of ovulation.
Estrus Synchronization Causing a group to begin ovulating at the same time.done by grouping them in common facilities, exposing them to males at the sametime, causing them to simultaneous stress, or dosing them with hormones that initiate oocyte development at the same time.
Superovulation Development of bullet-proof egg cells. Causing the ovary to develop and release a greater number of ova than would normally occur in a single ovulation.
In-vitro Fertilization Performing the fertilization of egg cells by sperm outside the body (in a lab petri dish). Used for many purposes, not least of which is embryo transfer.
Embryo Transfer The implantation of a fertilized egg into the uterus of a female other than the one who produced the ovum.
Pre-Selection of Embryos The selection of one or more fertilized embryos out of a larger group of fertilized embryos for implantation and development.
Cloning Creation of a replica of another animal. Can be accomplished by duplicating fertilized eggs (similar to natural ‘twin’ formation), or by inserting genetic material from a developed animal into an egg cell.
Transgenic Animal An animal into which DNA from another organism has been inserted into its genome, for purposes of allowing its cells to produce structures and compounds that it could not beforehand.
Diffuse Almost the entire surface is involved in formation of the placenta. Seen in horses and pigs.
 Cotyledonary Uses multiple, discrete areas of attachment. The fetal connectors are called “cotyledons.” The maternal contacts are called “caruncles.”) This type of placentation is found in ruminants.
 Zonary The placenta takes the form of a complete or incomplete band of tissue surrounding the fetus. Seen in carnivores like dogs and cats, seals, and bears, but also in elephants.
 Discoid A single placenta is formed and is discoid in shape. Found in primates and rodents.
Created by: 629943656



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