Dairy Cattle:reproduction Flashcards
Interval from one heat period to the next
Estrous cycle
Time when female is receptive to male and will allow breeding
Heat or estrus
Is the basic pattern of estrous cycle same or different for all mammals
Same, timing of stages is just different
What controls the estrous cycle
Hormones from the ovary and brain
Around what age does a heifer begin her estrous cycle
4-24 months of age
Avg age is 12 months
What is a yearling
Cattle of either sex 1-2 yrs of age
Once a heifer has her first heat she will repeat it every ____ days
Therefore, the length of the estrous cycle in cattle is ____days
21
21
How long are cattle in estrus (heat) for
Approx. 12-18hrs
Cattle are polyestrus which means
They have many beats per year
Signs of estrus in cattle
Increased activity
Vocalize (bellow)
Interest in other animals (nuzzling, pushing around)
Stand to be mounted “standing heat” most prominent sign
How often cows should be observed for heat
30 mins 2x daily
Heat detection aid example
Mount detectors (crayon on back or vile of dye)
What is ovulation
Time when females egg is released (from ovary and falls into ovaduct) and contraception is most likely to occur
When ovulation happens in relation to estrous cycle
Towards end of estrus period
Define Gestation
Period of carrying a baby
How long cattle gestation is
285 days, aka 9months
How many calves are most cows meant to have per year
1
What are freemartin cattle
When a heifer is born as a twin to a bull. There is a 90% chance she will be sterile (testosterone production from bull flows into females blood vessels)
Is twinning common in cattle
No
Examples of aid to increase reproductive efficiency
Prostaglandin, embryo transfer
What is prostaglandin
Naturally occurring female hormone, can be manufactured synthetically to aid with reproductive problems
What prostaglandin does after injected
Cow comes into heat 2-3 days after injection
When prostaglandin is usually utilized
When cow is hard to catch in heat, farmers want to synchronize cows so they can be bred at same time, shorten estrous cycle
Options for breeding cattle
Natural service (cows bred by bull) or artificial insemination
Pros and cons of natural service breeding
+cheaper and easier
-unsure of genetics and heritable traits, bulls are dangerous, STDs
Pros and cons of artificial insemination
+better genetics available (selection traits), control of STDs, don’t have to keep bull
-homogenous population
How cows are artificially inseminated
Arms inserted into rectum, rod w semen on end inserted into vagina, feel for body of uterus (target of semen placement )
How AI company company selects a bull
Based on pedigree, health and semen evaluation, free of genetic diseases, shape and motility (morphology) of sperm examined
What AI companies do with chosen bulls semen
Semen is mixed w an extender and frozen in individual straws
Bred to limited # of cows, daughter evaluated
What embryo transfer is used for
Increase # of calves from valuable cows
Procedure for embryo transfer
Valuable donor cow goes under hormone regimen to be super ovulated (many eggs develope at once)
AI by valuable sire
Several days later uterus is flushed and embryos collected
Eggs examined to see which are fertilized
Embryos implanted into recipient heifers or frozen in liquid nitrogen and sold
Embryo splitting (breeding advancement)
Fertilized embryo is split producing 2 genetically identical twins (expensive)
Sex control (breeding advancement)
Separating sperm into x& y so animals produce either male or female offspring. (Expensive)
Cloning (breeding advancement )
Several methods available
taking cells from individual and allowing those cells to reproduce another identical individual
