Animal Reproduction and Genetics

Terminology Objective: Define terminology related to reproductive management and breeding systems including castration, colustrum, estrus, gestation, lactation and parturition.

Terminology Castration Removing the testicles of the male to prevent breeding Colostrum First milk produced after a mammal gives birth that contains antibodies needed for immunity. Gestation Time an animal is pregnant Puberty Age at which animals reach sexual maturity

Terminology Estrus (Estrus Cycle) When a female is receptive to be bred (also called ‘in heat’) Ovulation Release of an egg from the ovary Lactation Period of time that milk is secreted by the mammary glands Parturition The act of giving birth

Breeding Systems Objective Discuss crossbreeding, grading-up, inbreeding, linebreeding, and purebreeding

Breeding Systems X Pure Breeding Registered male and female animals Angus X Angus X

Breeding Systems X Cross Breeding Mating a male and female of different breeds Angus X Charolais = Crossbreed X

Breeding Systems Inbreeding Mating closely related animals Brother X Sister Son X Mother Father X Daughter

Breeding Systems Linebreeding Breeding more distant relatives than inbreeding Cousin X Cousin

Breeding Systems Grading-Up Mating purebred male (sires) to unregistered or crossbred females (dams) Yorkshire bore X Yorkshire/Hampshire sow Hybrid Vigor Superior traits from crossbreeding Offspring are better than parents

The Female Reproductive System Objective: Identify the parts of the female reproductive system of livestock

Reproductive Traits Species Age Range at Puberty Average Length of Estrus Cycle Average Length of Estrus Average Length of Gestation Cow 6-8 months 21 days 16-18 hours 283 days Swine 4-7 months 3 days 114 days Sheep 4-8 months 22 days 30 hours 148 days Goat 1st autumn 2.5 days 151 days Horse 12-15 months 3-7 days 345 days

Female Tract

Female Reproductive System Ovary Function  Produce ova called eggs. Description  Two oval shaped organs located near the end of the reproductive tract inside the body cavity. the ovary is comparable to the male testicle and is the site of gamete production.

Female Reproductive System 3 Major Functions of Ovaries Gamete Production Estrogen Secretion Corpus Luteum Formation Estrogen Hormone absence of muscle development development of mammary glands development of reproductive systems and external genitalia fat deposition on hips and stomach (source of energy) triggering of heat

Female Reproductive System Infundibulum Function  Picks up eggs at ovulation and directs eggs to oviduct Description  - the funnel shaped portion of the fallopian tube near the ovary Oviducts Function  Carry the eggs from the ovary to the uterus. Also called fallopian tubes. Description  Small tubes that are near but not attached to ovaries and have a funnel-shaped end near the ovary.

Female Reproductive System Uterus - Muscular sac connecting fallopian tubes and cervix 1. Sustains the sperm and aids in its transport 2. Supports embryo and fetus during gestation 3. Expels fetus at parturition

Female Reproductive System Cervix - Area between the uterus and vagina Normally closed Opens at estrus and parturition Shape will match penis of male Vagina – the female organ of copulation 1. Admits penis 2. Receives semen 3. Passageway for fetus at parturition Vulva - external genitalia opening for both urinary and genital tracts

Reproductive Functions (Female) Steps in the female reproductive process: 1. Ovulation Produce gamete (ova or ovum) Release of egg(s) Infundibulum pushes the ovum into the fallopian tube Estrus (heat, estrous period) Gestation Fertilization to parturition Embryo developing in uterus Parturition Expel fetus/give birth Lactation Milk production

Ovulation Rates by Species Cow- 1 egg per estrus Ewe- 1 to 3 eggs per estrus Sow- 10 to 20 eggs per estrus Mare- 1 egg per estrus Hen- Approx. 28 eggs per month

Gestation and Lactation Periods: Species Gestation Period Lactation(Milking) Cow 275 - 285 days beef 180 - 270 days dairy 305 - 365 days Ewe 115 - 142 days 60 - 90 - 120 days Sow 112 - 115 days 21 - 42 days Mare 330 - 345 days 90 - 150 days Woman 270 days ? years

The Male Reproductive Tract Objective: Identify the parts of the male reproductive system of livestock and poultry

Male Reproductive Tract

Male Reproductive Tract Scrotum Holds and protects the testicles keeps sperm 4-5oF cooler than the body temperature Testicles the primary male organs of reproduction inside scrotum produces sperm secretes testosterone Epididymis Long coiled tube that is a path for sperm out of seminiferous tubules Storage for sperm while they mature Fluid secretion to nourish sperm

Male Reproductive Tract Vas Deferens slender tube from epididymis to urethra moves sperm to the urethra Urethra long tube from bladder to penis passageway for urine and sperm out of the body Penis male organ of copulation deposits semen into female (same as papilla in poultry) Shape will match cervix of female Sheath - Skin that covers and protects penis from injury

Accessory Glands Seminal Vesicles add fructose and citric acid to nourishes, protects and transports sperm Prostate Gland located at the neck of the bladder produces fluid that is mixed with seminal fluid, the medium for sperm transport Cowper’s Gland Also called Bulbourethral gland Paired organs Cleans and neutralizes the urethra prior to semen passage

Male Reproductive Tract

Objective: Specify how the reproductive system for poultry functions Poultry Reproduction Objective: Specify how the reproductive system for poultry functions

Reproduction in Poultry The poultry oviduct has five parts: 1) Vagina Holds the egg until laid 2) Uterus Secretes the shell 3) Isthmus Adds the two shell membranes 4) Magnum Secretes the albumen 5) Infundibulum Where fertilization takes place

Reproduction in Poultry Major difference: Embryo of livestock develop inside the female’s body Embryo of poultry develops inside the egg. Poultry only have the left ovary and oviduct The yolk is the ovum Chicken Incubation 21 days

Parturition of Animals Objective: Understand animal reproduction and parturition.

First Steps of Development After fertilization, the embryo begins to develop After a period of embryological development, the developing animal is referred to as a fetus. During gestation, the fetus develops in the uterus. At the end of the gestation period, parturition begins.

Fetus Position at Birth Normal Position: Front feet first with legs slightly offset from each other to allow for shoulders to pass through birth canal. Nose tucked between front legs. Shoulders. Body or middle of animal. Hips. Back legs and feet. Any else is abnormal and could cause problems as severe as death of the newborn animal and/or the mother.

Parturition Process Increased estrogen causes the uterus muscles to contract. Water bag appears, enlarges and breaks open. Second water bag containing the fetus breaks open and the presentation of the fetus begins. Several hours later, the placenta and other membranes (afterbirth) are expelled. If afterbirth is not expelled, the animal will become sick (Retained placenta or Septicemia)  

Parturition in Action Mare Foaling Cow Calving Birth Process of Pigs

Animal Reproduction and Genetics Objective: Describe the cell and process involved in cell division including how genes affect the transmission of characteristics

Animal Cell The body is made up of millions of tiny cells Most of the cell is made up of protoplasm Cell parts: Nucleus Cytoplasm Cell membrane

Animal Cell Nucleus/Nucleolus - gives cell ability to grow, to digest food and to divide, contains chromosomes composed of genes Cytoplasm - gives the cell shape and contains components necessary for cell functions Cell Membrane – outside of cell; allows passage of some materials Centrosome - The centrosome divides during mitosis Nuclear Membrane – membrane that surrounds nucleus Ribosome – site of protein synthesis Endoplasmic Reticulum – transports material throughout the cell Golgi Body – produces membrane that surrounds lysosome Lysosome - round shaped organelles that contain digestive enzymes that allow for digestion of cell nutrients Mitochondria - rod-shaped organelles that convert the energy stored in glucose into ATP (adenosine triphosphate)

Cell Division Mitosis Meiosis Increases total number of cells Results in animal growth Chromosomes pairs are duplicated Meiosis Produces gametes Sperm/Eggs Only have one-half the chromosomes of normal cells

Fertilization When the sperm from a male reaches the egg from a female Two cells join to form a complete cell Pairs of chromosomes are formed again Many different combinations of traits are formed

Chromosomes Rod shaped bodies Made of protein Found in the cell nucleus Exist in pairs except for gamete cells The number of chromosome pairs differ for various animals Cattle 30 Swine 19 Horses 32 Chickens 39 Humans 23

Genes Located on chromosomes Thousands found in each animal Control inherited characteristics Carcass traits Growth rate Feed efficiency Two types of inherited traits Dominant Recessive

Genes Dominant gene Hides the effect of another gene Polled condition in cattle is dominant The gene is represented by a capital letter Recessive Gene that is hidden by another The gene is represented by a lower case letter

Genes Example: The dominant gene is written- P The recessive gene is written-p P= Polled p= horned

Homozygous and Heterozygous Homozygous gene pair Carries two genes for a trait Polled cow might carry the gene PP Heterozygous Carries two different genes that affect a trait Polled cows might carry a recessive gene with the dominant Pp

Predicting Genotype Genotype-kind of gene pairs possessed Phenotype- the physical appearance of an animal Punnett squares are used to predict genotypes and phenotypes of animals

Genotypes Three class genotypes Homozygous Dominant = PP Homozygous Recessive = pp Heterozygous = Pp P = Polled & p = horned Six possible crosses: PP x PP, PP x Pp, PP x pp, Pp x Pp, Pp x pp, pp x pp

Punnett Square P= Polled p= horned P Example: Polled Dam P= Polled p= horned Example: Two polled cattle that are homozygous for the polled trait Genotypic Ratio: 4PP : 0 Phenotypic Ratio:4 polled animals Polled Sire Polled Dam P PP Polled Sire

Punnett Square N= Normal size n= Dwarfism Example: Normal Dam N= Normal size n= Dwarfism Example: Normal size in cattle is dominant to dwarfism Genotypic Ratio: Phenotypic Ratio: Sire Carrier Normal Dam N NN n Nn Sire Carrier

Punnett Square N= Normal size n= Dwarfism Example: Normal Dam N= Normal size n= Dwarfism Example: What if both parents are carriers for a trait or disorder? Genotype: Phenotype: Sire Carrier Normal Dam N n NN Nn nn Sire Carrier

Assignment Complete a Punnett Square for two animals that are heterozygous for two traits: Polled=P Black= B (Alternatives are horned and red) Dam Sire

Answer A Punnett Square for two animals that are heterozygous for two traits: Polled=P Black= B (Alternatives are horned and red) Dam PB Pb pB pb PPBB PPBb PpBB PpBb PPbb Ppbb ppBB ppBb ppbb Sire

Heritability Objective: Discuss hertability estimates for beef and swine

Heritability Estimated the likelihood of a trait being passes on from the parent to the offspring Low heritability slow herd improvement High heritability faster improvement

Heritability Swine rates are usually lower than cattle Heritiability for carcass traits are higher than reproductive traits Estimates vary from 0 to 70%

Heritability Estimates Birth weight 40% Weaning Weight 25-30% Yearling Weight 60% Fertility 10% Tenderness 60%

Heritability Review Herd improvement slow for low heritability faster for high heritability Estimates are higher for: beef compared to swine carcass traits compared to repro