Animal Reproduction

Animal Science II

Estrus Cycle

• Time of day when a female will accept a male for breeding

• Length– 21 day cycle

• Cow- 16-18 hours• Sow- 2 days

• Best indicator is when the animal stand to be mounted

Ovulation

• Release of the egg from the ovary• Number of young born is an

indicator of eggs released– Sows: 10 to 15– Cow: One

• Split eggs produce identical twins, triplets, etc.

Methods of Reproduction

• Natural• Artificial Insemination (AI)• Embryo Transfer• Cloning using Nuclear Transfer

Artificial Insemination

• Steps– Insert hand into the rectum and grasp

cervix– Insert insemination rod– Deposit bull semen from the middle of

the cervix to just into the uterus

Artificial Insemination

Bovine Reproductive Tract Diagram

Artificial Insemination

Sow Reproductive Tract Diagram

Artificial Insemination

Artificial Insemination

Artificial Insemination

Artificial Insemination

• Advantages– Wider variety of superior bulls used– Increase number of cows that can be

bread to a superior bull– Reduces disease– Don’t have to keep a bull on the farm

Artificial Insemination

Artificial Insemination

• Disadvantages– Requires a trained inseminator– Requires more time and herd

supervision

Embryo Transfer

• Procedures– Superovulate donor– AI– Flush embryos (catheter)– Isolate and classify embryos– Store in liquid nitrogen– Transfer to recipient– Diagnose pregnancy 1 to 3 months later

Embryo Transfer

• Advantage– Genes of the female (dam) can be

passed on faster than natural breeding

Cloning

• Using Nuclear Transfer• Procedures

– Flush (same as embryo transfer)– Filter– Remove genetic materials from

recipient oocytes– Nuclei is removed through

microsurgery

Cloning

• Procedures (continued)– The nuclei are separated and each

one is transferred to an unfertilized egg cell that has had its nucleus removed

– Plugs are placed in sheep for 5 to 6 days (develops to the 32 to 64 cell stage)

– Embryos are placed in surrogate, frozen or used to clone more animals

Cloning

• Advantages– Increase herd uniformity– Increase herd quality– Produce genetically identical animals

Parturition Process

• Increased estrogen causes uterus muscles to contract

• Water bag appears and breaks• The second water bag appears

with the fetus

Parturition Process

• Normal Presentation• Front feet first• Nose• Head and shoulders• Hips• Rear legs• Rear feet last

• Any presentation not in order could cause death of the baby and/or mother

Parturition Process

• Several hours later the placenta and other membranes (afterbirth) are expelled– A retained placenta is deadly