Livestock Reproduction

Livestock Reproduction

• Vitally important for livestock producers

• Low fertility causes loss of revenue for farmers

• Many recent technological advances

Male Reproductive Tract

• Testes

• Scrotum

• Seminal Vesicles

• Sigmoid Flexure

• Retractor Muscle

• Glans Penis

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Female Reproductive Tract

• Ovaries

• Oviduct

• Uterus

• Cervix

• Vagina

• Vulva

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Differences with Humans

• Females have an Estrus Cycle

• Animals can only become pregnant when in “Heat”

• Timing depends on light & temperature– Keep sheep in dark barns to synchronize

estrus

METHODS OF INSEMINATING LIVESTOCK

• NATURAL INSEMINATINATION - Involves using animals to mate in pastures or pen breeding.

• ARTIFICIAL INSEMINATION - Involves collecting semen from a male and depositing it in the reproductive tract of the female.

Artificial Insemination

• Dairy Cattle used exclusively• Frequently used for purebred operations in

beef cattle, horses, sheep & pigs• Thoroughbreds may not be bred by AI

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ADVANTAGES OF USING AI

• AI allows the use of semen from superior males that are owned by another party.

• AI makes it possible for a male to breed many more females than could be done naturally.

• Semen can be stored for a week at 41F or for several months frozen at -320F (liquid nitrogen).

Limitations of AI

• Physiological Principles: timing of heat

• Requires skilled technicians

• Costly to start

• Can accentuate damage of poor sires

• May restrict sire market (avg or poor bulls)

• May increase spread of disease (none to date, but is possible)

• Abuse: mislabeled semen

IMPORTANT INFORMATION IN BREEDING ANIMALS

• SPECIES AGE/BREED GESTATION

• COW 14 MONTHS 283 DAYS

• SOW 12 MONTHS 114 DAYS

• EWE 17 MONTHS 148 DAYS

• DOE 18 MONTHS 151 DAYS

• MARE 2-3 YEARS 336 DAYS

ESTRUS SYNCHRONIZATION

• Involves using hormones to get several females to come in heat at the same time.

• Used when using advanced breeding procedures such as superovulation (getting the female to produce a number of eggs at one time) and embryo transfer.

Embryo Transfer

Synchronize Heat Cycles of donor & recipients

Inject drug to superovulateBreed donor (natural or AI)Collect eggsExamine eggs (if fertilized)Synchronize recipients ovulationtransfer eggs

When to Breed• Female is only fertile when an egg is

present which can be fertilized

• Eggs short lived

• Inseminate before egg is shed

• Cow doesn’t shed egg until 10 hours after standing heat, lives 6-10 hours

• Cows in standing heat in morning are bred in afternoon or evening

Manipulating Estrous

• Artificial Lighting: ewes, mares, fowl

• Lengthen days, then shorten to simulate natural breeding season

• Hormones:

• Progestagens: mimics pregnancy, feed, inject, implant, for 14-20 days, when removed, cows cycle 2-8 days later

• Prostaglandins: single dose injection, 90 hours later = estrous

Induced Calving

• Artificially shortening gestation

• Lower birth weight, less calving difficulty

• Predict calving dates

• Longer period from calving to breeding

• After 269 days, cows injected with adrenal steroid

• Calve 5-8 days earlier, 6-8 lb lighter calf

• Higher rate of retained placentas, lower milk production

GIVING BIRTH

• Most animals give birth without assistance.

• Calves should be born within one hour after labor begins.

• Calves are normally delivered with the head between the two front legs.

• Cow may need assistance if calf is in a different position.

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