Animal Reproduction Animal Science II Unit 10

Objectives Identify and describe the male and female reproductive organs Describe the function of the endocrine glands and hormones in reproduction Describe the reproductive failures that may occur Define: fertilization, gestation, parturition and estrus cycle

Reproduction When organisms multiply or produce offspring Sexual Asexual

Sexual Reproduction Union of male and female gametes or copulation Fertilization occurs when the sperm penetrates the egg cell Embryo or new animal begins to grow It is fed and protected in the female reproductive tract until birth Parturition is the act of giving birth and the final step in reproduction

Asexual Reproduction Does not involve the gametes Simple cell division in bacteria is an example

Male Reproductive Organs

Male Poultry Reproductive Organs

Female Reproductive Tract

Female Poultry Reproductive Organs Fig 10-5 page 215

Ovulation Cycle Before ovulation begins the egg cell is contained in the follicle Follicle breaks open, releasing the egg. Egg moves into one of the oviducts. If live sperm are present, it may be fertilized. If the egg is fertilized Corpus luteum forms on the ovary If the egg is not fertilized the corpus luteum does not grow.

Estrus Cycle Period of time in which the female will accept the male for breeding Begins when the animal reaches breeding age (see Table 10-1 p. 217) Cycle begins when a follicle on the ovary begins to develop Estrogen is produced and cause the animal to show the signs of estrus

Signs of Estrus See p. 216

Ovulation Cycle Egg cell is contained in follicle Follicle breaks open, releasing the egg Egg moves into one of the oviducts Fertilization occurs if live sperm are present Corpus luteum forms on the ovary shortly after ovulation. It releases the hormone progesterone If the egg is not fertilized the corpus luteum does not grow, it waste away allowing another follicle to grow

Progesterone Causes four things to happen – The fertilized egg (embryo) is implanted in the uterus – Other eggs are stopped from forming – The pregnant condition is maintained – The mammary glands begin to develop.

Several Offspring Fraternally Related – Animals that have several young at one birth – They each come from a different egg cell Identical – Offspring that result from 1 egg splitting to form two animals

Fertilization Union of the sperm and the egg cell Only 1 sperm fertilizes the egg cell Sperm do not live very long in the female reproductive tract – In cattle sperm live only about hours Egg cells do not live very long either, only about 12 hours if not fertilized Pregnancy will only occur if the sperm and egg cell are present and alive at the same time

Gestation Period The time during which the animal is pregnant Fetus is surrounded by a watery enclosed in membranes Blood vessels in the umbilical cord supply nutrients and oxygen and carry off waste – Umbilical cord connects from the navel of the fetus to placenta The placenta lies along the wall of the uterus-food, oxygen and waste are exchanged with the mother through a process called diffusion Fetus grows slowly—most growth occurs in the last 1/3 of the gestation period – Early growth-head, nervous system, blood vessels – Later-bones and limbs

Parturition The process of giving birth Corpus luteum reduces production of progesterone Increase in the amount of estrogen produced Uterine muscle contractions begin The birthing process begins 1 st Water bag appears, gets larger and breaks Second water bag appears, this contains the fetus Presentation of the fetus begins Normal presentation will vary with species

Birth Umbilical cord is broken, this causes the animal to breathe Progesterone has stimulated the mammary glands, so the mother will have milk for the young animal to nurse The first milk, called colostrum is very important because it is rich in antibodies, vitamin and minerals needed by the young animal – It is important the young animal receive colostrum milk during the 1 st hours of life

After Birth Afterbirth is expelled from the uterus several hours after the birth – Afterbirth consist of placenta and other membranes that were not expelled when the fetus was born If not expelled it will decay inside the uterus causing infection Care must be taken to prevent infection when removing the afterbirth from the uterus—if not the animal may become sterile.

Reproduction in Poultry Read p

Reproductive Failures Physical Condition Nutrition Exercise Disease/Infection Hormone levels/balances Cysts – A swelling containing fluid or semisolid substance. – May occur in the reproductive organs Other Unknown reasons

Summary Mating of male and female animals begins the process of reproduction Female gamete is called an ovum or egg Male gamete is called the sperm Sperm are deposited in the female reproductive tract where they move to the oviduct and fertilize the egg cell Females have an estrus or heat cycle during which she will accept a male for mating An egg cell is released during the heat period, if fertilized it moves to the uterus where it grows into a fetus Hormones control the release of egg cells and maintain pregnancy in the animal When the fetus reaches the right time for birth, the uterine muscles contract, forcing the fetus through the birth canal Reproduction in poultry is similar to mammals—the main difference is that they embryo develops in the eggshell outside the mothers body Eggs must be kept the proper temperature and humidity to hatch—this is usually done with an incubator