Animal Reproduction and Genetics

Estrus Cycle  Time during which the female will accept the male for breeding  Length of estrus cycle in both cattle and swine is about 21 days  The actual time a cow is in heat is about hours, sow about 2 days

Estrus Cycle w.hyperi onfarm.c om/Estro us.htm

Estrus Cycle  There are several signs of heat including swelling of the vulva, frequent urination, nervousness or restlessness, mounting other animals and letting other animals mount.

Estrus Cycle  Best indication that a cow is ready to breed is when she stands when mounted by another cow

Ovulation  Number of young that animals gives birth to at one time is indication of number of eggs released or ovulated  Sows: 1-15  Cows generally 1

Ovulation-Fertilization m/baby/stage1.html

Ovulation  At ovulation, fertilization will take place and the animal will become pregnant if the animal is bred so that the egg cell and live sperm are present at the same time

Fertilization

Artificial Insemination  Placing sperm in the female reproductive tract using other than natural processes

Artificial Insemination  Cow: person’s hand is inserted into the cow’s rectum to grasp the cervix, and then then inseminating tube or rod is used to deposit the bull semen from the middle of the cervix to just into the body of the uterus when the cow is in heat

AI- transfer gun ?action=showThumb&start=1&DeptCode=38

Artificial Insemination  Advantages  Wider variety of superior bulls  Increases number of cows bred to superior bulls  Reduces the spread of diseases  Don’t have to keep bulls on the farm

Artificial Insemination  Disadvantages:  Requires a trained inseminator  Requires more time and herd supervision

Embryo Transfer  Superovulation of donor with hormones  Artificial insemination  Flush embryos and remove with catheter  Isolate and classify embryos

Embryo Transfer  Store embryos in liquid nitrogen  Transfer embryos to recipient cows  Diagnose pregnancy 1 to 3 months later  Birth 9 months after transfer of embryos

Embryo Transfer  Advantage:  Genes of the female (dam) can be passed to more offspring faster than natural breeding

Embryo Transfer

Cloning Cattle Using Nuclear Transfer  Process:  Flush and remove embryos with catheter same as regular ET  Filter the flushed liquid to remove embryos  Remove genetic material from recipient oocytes

Cloning Cattle Using Nuclear Transfer  The nuclei are removed through microsurgery  The nuclei are separated and each one is transferred to an unfertilized egg cell that has had its nucleus removed (thus the term nuclear transfer)

Nuclear transfer

Cloning Cattle Using Nuclear Transfer  Plugs with 3 or 4 embryos are placed in oviducts for 5 to 6 days to develop to the 32 to 64 cell stage  Embryos are removed and placed into surrogate mothers, frozen for long term storage or used to produce another generation of cloned embryos

Stages of Nuclear transfer ac.uk/library/

Cloning Cattle Using Nuclear Transfer  Advantages:  Increased herd uniformity  Increase herd quality  Produce genetically identical animals

Parturition Process  Begins when increased estrogen causes the uterus muscles to contract  First water bag appears, enlarges and breaks open

Parturition Process- water bag breaking

Parturition Process  Soon afterwards, the second water bag containing the fetus breaks open and the presentation of the animal begins

Parturition process- amnion sac

Parturition Process  Normal position of the fetus at birth is front feet first, followed by the nose, then the head, shoulders, middle, hips, rear legs, and feet

Parturition process- foaling

Parturition Process  Several hours later, the placenta and other membranes (afterbirth) are expelled.  Afterbirth must be expelled or the animal will become sick

Parturition process- placenta

Parturition Process  Any presentation that does not have the order as previously stated is abnormal and could cause problems such as death of the young or the mother

Body Conditioning  Important because it affects conception in cows, and the goal is to have each cow give birth and wean a calf every year  Underconditioned or thin cows are the major cause of all reproductive problems

Timing  Size is the most important consideration when breeding heifers that are sexually mature ( pounds)  Age is second (2 years calve)  Calving in the herd should occur during a 40 to 60 day period

Synchronization of Estrus  Use of hormones to cause all the female sin a herd to come into heat in a short period of time  Shorter breeding and calving seasons are advantages

Multiple farrowing  Arranging the breeding program so that groups of sows farrow at regular intervals throughout the year  The number in the group should match facilities

Advantages  Higher average prices for hogs sold because sales are spread throughout the year  Spreading income throughout the year  More efficient use of facilities

Disadvantages  Requires better management  Requires a year-round labor supply

Other considerations  Because the producer needs to make maximum use of farrowing facility capacity, it is very important that conception rates and litter sizes be the best possible

Other considerations  Disease prevention and control, proper boar to sow ratio and breeding each sow at least twice during each heat period (multiple breeding) increase conception rates

Reproduction Practices in Poultry  AI is used for large, heavy breeds of turkeys because of low fertility rates and eh large size of males (toms) used for natural breeding

Reproduction Practices in Poultry  Since chickens and turkeys come from fertile eggs, reproduction efficiency involves the eggs being fertile, the incubation process and control of diseases

Reproduction Practices in Poultry  In breeding flocks, eggs are gathered several times each day and packed with the large end up to protect the air cell  Hatching eggs are fumigated with chemicals to help prevent the spread of egg-borne diseases

Palpation  The process of diagnosing pregnancy by feeling the reproductive tract of a cow  Experience is necessary for accuracy because the person doing the diagnosis compares the feel and size of different parts of the tract to determine the stage of pregnancy

Palpation  Good website otocols/palpation.manual.htm /ansc3023/ai/sld011.htm

Palpation  Must use plastic sleeves and lubricant to palpate in the rectum  Breeding records are used to indicate when the cow was bred and when to check for pregnancy

Genotype  Kinds of gene pairs the animal has

Genes  Dominant: hides or dominates the effect of the other gene in the pair and is indicated by upper case letters  Recessive: is hidden or covered by the gene in the pair and is indicated by lower-case letters

Gene pairs  Homozygous carries two genes for the same trait (uppercase letter or lowercase letter)  Heterozygous carries two different genes for the same trait (uppercase letter and lowercase letter)

Gene pairs  See Gillespie p  IMS p 8406 p 8834-A, B

Sex determination  After meiosis, one half the sperm carries an X chromosome and one half carries a Y  All ova carry an X chromosome  In mammals XX females, XY male

Sex determination in poultry  Males carry ZZ  Females carry ZW  Sex is determined by females

Sex Linked Characteristics  Some traits are carried on X some on Y –Those on Y are only transmitted from fathers to sons –Certain genes are expressed only in one sex even if carried on both chromosomes (lactation, egg laying, rooster tail feathers, etc.)

Terms  Sex linked are often recessive and covered by dominant genes  Incomplete Dominance: takes place when one gene does not completely hide or dominate another gene, mixture of two genes (example roan: combo of red/white)

Terms  Linkage: tendency for certain traits to appear in groups in the offspring because the genes for those traits are located near each other on the chromosome and stay together to pass traits in groups

Terms  Crossover: when chromosomes cross over one another and split to form new chromosomes with different combinations of genes  Mutation: when a new trait appears which did NOT exist in the genetics of either parent

Punnett Square  See Gillespie p  THE END!!!!!