Animal Reproduction

I.	Why Sex?

	1.	Genetic recombination
	2.	Improve production traits
		A.	Milk
		B.	Meat
		C.	Wool
		D.	Eggs
		E.	Speed

II.	Reproductive Efficiency

	1.	Great Economic Importance to Animal Producers
	2.	Measures
		A.	Litter size
		B.	Number of offspring per 100 females per year
		C.	Calving Interval
		D.	Farrowings per year
		E.	Conception Rate
	3.	A basic understanding of the physiology of reproduction 
		is needed to reach a high rate of reproductive efficiency

III.	Female Reproductive Organs

	1.	Ovary
		A.	Produce the Ovum
			a.	Follicle
				--Rupture Ovulation
		B.	Produce Female Sex Hormones
			a.	Follicular cells
				i.	Estrogens
				ii.	Progesterone
		C.	Maintain Pregnancy
			a.	Corpus Luteum
				i.	Progesterone
		D.	Ovary (and Testis) under the control of endocrine 
			glands in the brain
			a.	Hypothalamus
				i.	Gonadotropin Releasing Hormone 
					(GnRH)
					--Causes release of Gonadotropins 
						from Pituitary
					--Controlled by Female Sex Steroids (Feedback)
			b.	Pituitary
				i.	Follicle Stimulating Hormone (FSH)
					--Stimulates Follicle Development 
						and Growth
				ii.	Luteinizing Hormone (LH)
					--Required for Ovulation
					--Corpus Luteum Formation
	2.	Oviduct
		A.	Site of Fertilization
			a.	Haploid sperm and egg fuse Diploid zygote
	3.	Uterus
		A.	Site of Embryo and Fetal Development
		B.	Produces Prostaglandin if not Pregnant
			a.	Causes Luteolysis
	4.	Cervix
		A.	Barrier
			a.	Selectively lets sperm in uterus and oviducts
			b.	Closed or sealed during pregnancy
		B.	Expulsion of Fetus
	5.	Vagina
		A.	Female Copulatory Organ
		B.	Birth Canal
	6.	Vulva
		A.	Opening to female reproductive tract

IV.	Male Reproductive Organs

	1.	Testis
		A.	Produce Spermatozoa
		B.	Produce Male Sex Hormones
			a.	Androgens
	2.	Scrotum
		A.	Temperature Regulation
	3.	Epididymis
		A.	Sperm Maturation
		B.	Sperm Storage
	4.	Vas Deferens
		A.	Sperm Transport
		B.	Some Storage
	5.	Accessory Sex Glands
		A.	Seminal Vesicles, Prostate, Bulbourethral glands
		B.	Functions:
			a.	Add Fluid (Seminal Plasma) to Semen
			b.	Provide Nutrition to Sperm
			c.	Lubricant
	6.	Urethra
		A.	Sperm Transporter
	7.	Penis
		A.	Copulatory Organ
		B.	Must be rigid and erect to penetrate female

V.	Reproductive Cycles

	1.	Puberty
		A.	Sexual Maturity
		B.	Ability to Mate and Produce Offspring
		C.	Age of Puberty
			a.	Cattle = 12 months
			b.	Swine = 6-7 months
			c.	Sheep = 6-7 months
			d.	Horses = 15-18 months
		D.	Maximum Sexual Maturity happens later
	2.	Estrous Cycle
		A.	Regular Periods of Sexual Receptivity (Estrus)
		B.	Stages
			a.	Estrus (or Heat)
				i.	Sexual Receptivity
					--Caused by Estrogens
				ii.	Ovulation
					--Caused by LH spike
			b.	Luteal Phase
				i.	Corpus Luteum on Ovary
				ii.	Progesterone concentrations rise
			c.	Follicular Phase
				iI.	Corpus Luteum Regresses
					--Prostaglandin F2 
				ii.	Follicles Develop
				iii.	Estrogen concentrations rise
			d.	Estrus
		C.	Duration and Frequency of Heat and Time of Ovulation

Farm		Length of	Duration of 	Time of 
Species		Estrous Cycle	Estrus		Ovulation

Cattle		21 days		12 hours	30 hrs after start of estrus
Pigs		21 days		44 hours	34 hrs after start of estrus
Sheep		17 days		30 hours	26 hrs after start of estrus
Horses		21 days		6 days		1 day before end of estrus
	
		D.	Seasonal Breeders
			a.	Horses and Sheep
			b.	Have estrous cycles only certain periods of 
				the year
			c.	Pineal Gland
				i.	Secretes Melatonin
				ii.	Effects Hypothalamus
			d.	Sheep
				i.	Breeding season in Fall 
					(Shorter Days)
				ii	Anestrus Spring and Summer
			e.	Horses
				i.	Breeding season in Spring 
					(Longer Days)
				ii.	Anestrus Fall and Winter
	3.	Pregnancy
		A.	Fertilization
			a.	Sperm must undergo Capacitation
				i.	Maturation to ready for penetration of egg
			b.	Occurs in Oviduct
		B.	Period of the Embryo
			a.	Migration to Uterus (3-4 days)
			b.	Stages
				a.	One Cell Zygote
				b.	Cleavage
					--Division without an increase in 
						size
				c.	Morula
					--Last Cleavage Stage
				d.	Blastocyst
					i.	Fluid filled cavity 
						(Blastocoel)
					ii.	Trophoblast
						--Become Placental Membranes
					iii.	Inner Cell Mass
						--Becomes Embryo Proper
				e.	Gastrulation
					i.	First stage of organogenesis
					ii.	Division into three germ 
						layers
						--endoderm, mesoderm, 
						ectoderm
			C.	Maternal Recognition of Pregnancy
				a.	Occurs day 12 to 21 after 
					fertilization depending on species
				b.	Factors produced by embryo inhibit 
					Prostaglandin production by uterus
			D.	Implantation
				a.	Embryo attaches to Uterine Lining
			E.	Period of the Fetus
				a.	Much of Organogenesis has occurred
				b.	Conceptus looks like species
				c.	Growth Stage
			E.	Parturition
				a.	Process of Birth
				b.	Signaled by Fetus
				c.	Stages
					i.	Dilation of cervix
					ii.	Expulsion of Fetus
					iii.	Expulsion of Placenta
				d.	Difficult Birth = Dystocia
			F.	Gestation Lengths and Usual Number 
				of Offspring

	Farm Species		Length		Number of Offspring

	Cattle			285 days	1 calf (1-3.5% Twins)
	Swine			114 days	6-14 piglets
	Sheep			147 days	1-3 lambs
	Horses		        336 days	1 foal (1-2% Twins)