Intro To Breeding Programs Flashcards
Length of estrus and when ovulation occurs in relation to it for MARES
4-7 days
24-48hr BEFORE end
Length of estrus and when ovulation occurs in relation to it for COWS
12-18 hours
4-16 hours AFTER end
Length of estrus and when ovulation occurs in relation to it for EWES/DOES
36 +/- 12 hours
during last half
Length of estrus and when ovulation occurs in relation to it for SOWS
2-3 days
24-40 hours after onset
Length of estrus and when ovulation occurs in relation to it for BITCHES
5-10 days
6 days before 1st day of diestrus
Length of estrus and when ovulation occurs in relation to it for QUEENS
3-6 days
25-50 hours after breeding
When is the best to get sperm into a cow?
-BEFORE ovulation or within 6 hours after because of how short it is
-Best to inseminate in the last half of standing hear
What is the AM/PM rule for AI in cows?
If cow is seen in estrus this morning, AI in the evening and again the next morning
What are some issues with estrus detection in cows? (4)
-Staffing is very costly
-Short estrus duration
-70% of activity happens overnight
-~25% of heats are low intensity
What % of cows are detected in heat on average?
30-40%, very poor average detection
When should you breed a mare with AI?
Best to get sperm in BEFORE ovulation, once she has been in estrus for about 2 days
What happens if you breed a mare on the first day of estrus?
If you breed/inseminate on the first day, the sperm must live 4-6 days before ovulation happens which is too long
What happens if you breed a mare on the last day of estrus?
If you breed on the last day it might be after ovulation and too late
When to breed a mare when using natural cover?
breed every other day when she will stand for the stallion
When to breed a mare when using frozen semen?
as close to ovulation as possible
What are some challenges in equine breeding? (4)
-Most farms dont have a stallion
-Many owners arent knowledgable about signs of estrus
-Many mares dont show strong signs
-Vets use results of repro exams to time breeding
What are some advantages of using estrous synchronization programs? (4)
-Use multiple sires
-Shorten the breeding season = shorter calving season
-Produce uniform groups of calves/lambs/kids
-In horses; it results in better planning for the stallion especially early in the year
What are some reasons to manipulate the cycle? (6)
- Assist producers in achieving their goals!
- Manipulate to allow out of season breeding (mares, ewe)
- Induce estrus (alone or in groups of females)
~Planned breeding
~Shorter breeding/calving season
~Uniform groups of calves/kids/lambs - Timed breeding
- Synchronize cycles (embryo transfer)
- Keep out of estrus (performance mares)
What are some disadvantages of breeding programs? (4)
-Not all animals will respond to the program
~Genetics, BCS, nutrition, management factors
-In some programs the expressed estrus is weak, low intensity
-Cost of drugs and manpower for giving injections or oral medications
-Stress to animals if handling multiple times
What are four approaches to controlling the estrus cycle?
- Management techniques
- Control the luteal phase
- Control of the follicular phase
- Combination programs (both phases)
2-4 are hormonal manipulation
Four management techniques for estrous cycle control
A) Manipulate daylength by controlling environmental lighting
B) Male Effect
C) Short Term Weaning
D) Increasing Plane of Nutrition
What is the effect of melatonin and GnRH for mares when days are short?
short days = increased melatonin = SUPPRESSES GnRH
What is the effect of melatonin and GnRH for sheep when days are short?
shortening days = increased melatonin = STIMULATES GnRH
How do you fool mares into thinking its spring?
Expose them to artificially long days starting in the Fall
How do you fool small ruminants into thinking its fall?
Expose them to increasing darkness beginning in late summer
What does male exposure do?
will induce release of GnRH and LH, stimulating cyclicity and ovulation in virtually all spaces
How long must males be out of sight, sound, and smell before reintroduction to induce cycling?
More than 30 days.
How does daily exposure to a boar affect gilts?
It induces estrus in gilts within 10-20 days.
What effect does the sight, smell, and suckling of a calf have on LH levels postpartum?
It decreases LH levels, inhibiting cycling and ovulation (lactational anestrus).
What is a recommended practice for weaning calves to enhance reproductive cycling?
Wean calves for 48 hours at the beginning of the breeding season
What effect does weaning calves have on LH levels and estrus onset?
It increases LH levels and leads to the onset of estrus
How does improving nutrition affect cycling rates in cattle after weaning?
It increases the cycling rate from 40% to over 75%
What is the combined effect of weaning sows and boar exposure?
Approximately 90% of sows will be in estrus within 10 days after weaning
What is flushing?
When you increase level of prebreeding nutrition
When does flushing work best?
Start 2-3 weeks ahead of breeding season
Works better in thin compared to fat ewes/cows
Why is the luteal phase P4 dominant?
due to the CL
What happens when estrus ends in the cow? (Overview of the rest of the cycle)
-When estrus ends and the cow ovulates, she forms a CL that produces P4 through the luteal phase of the cycle.
-When she isnt pregnant, the endometrium releases prostaglanin which will lyse the CL, P4 levels will drop and she will come into estrus
-Estradiol and LH levels increase when shes in estrus and developing follicles and ovaries (follicular phase)
How do you shorten the luteal phase and what point does it mimic?
shorten by inducing luteolysis by giving a prostaglandin shot
mimics what happens naturally at day 16-17 of eyes
what are some disadvantages of prostaglandins
-only works on a mature CL
-not all animals will response
-some dise effects like sweating, diarrhea, colic, crampiness
Can you use lower than label doses of prostaglandins to try and avoid side effects?
Yes, results are just as effective
Why doesnt prostaglandin injections work in anestrus animals?
because it only works if you give it to animals with a mature CL (>6 days post ovulation)
Do prostaglandin injections synchronize ovulation
Nope. just induces estrus. range of 2-5 days after injection that animal will come into estrus
How can you prolong the luteal phase?
administer progesterone or synthetic progestagens
What happens when you provide an exogenous P4?
It mimics CL presence = suppresses LH release during treatment which suppresses estrus and ovulation = LH builds up in the pituitary gland and when the P4 source is taken away = surge of LH = estrus = ovulation
What are some available forms of progesterone? (5)
-Intravaginal devices
-Oral preparations (MGA or altrenogest)
-Daily injections of P4
-Long acting injections of altenogest or P4
-Ear implants
What are some hormones that we can use to control the follicular phase? (6)
-PMSG (eCG)
-HCG
-GnRH (or synthetic deslorelin)
-estrogens
-FSH
-LH
What happens when you use GnRH to control the follicular phase?
It stimulates LH and FSH. Mostly its used for its LH activity to induce ovulation though
Wha are some examples of GnRH products and what it does in MARES
deslorelin to induce ovulation in mares
Wha are some examples of GnRH products and what it does in CATTLE
cystorelin, fertiline
depending on when its given, GnRH will induce ovulation OR emergence of a new follicular wave in cows
What does hCG do in mares?
Acts like LH. Used to induce ovulation in mares
What do estrogens do in cattle?
Its used to induce estrus, ovulation or emergence of new follicular wave. Banned from food producing animals in USA and Europe
How can you increase the number of follicles? when is it normally used
Give folltropin; FSH which stimulates follicular growth and development
often used for superovulation im embryo transfer programs
where is PMSG produced naturally in the mare?
produced by the endometrial cups from day 35-120 of pregnancy in the mare
What is the difference in the effect of PMSG is mares vs ruminants
Mares = mostly LH activity during pregnancy
Ruminants = acts like FSH which stimulates follicular development
what is PMSG used for in sheep
out of season breeding
what is PMSG used for in cows and sheep
superovulation
What is a combination program? example in mares
use of multiple hormones for specfic reasons. programs are species specific
P4 and estradiol in mares
What does control of follicular waves allow for?
More precision for timed AI
