Pregnancy detection in cattle Flashcards
What is the Ovsynch method?
The Ovsynch method is a widely used hormonal protocol in cattle reproduction, designed to synchronize ovulation for timed artificial insemination (TAI).
- First GnRH Injection (Day 0) to stimulate the cow’s ovaries to grow and mature follicles. This encourages the selection of a dominant follicle that will later ovulate.
- PGF₂α Injection (Day 7): This injection induces the regression of the corpus luteum (CL) if present, lowering progesterone levels and allowing the cow to resume its estrous cycle.
- Second GnRH Injection (Day 9): Another GnRH injection is administered approximately 48 hours after the PGF₂α injection. This second injection triggers ovulation of the dominant follicle.
- Timed Artificial Insemination (Day 10): Artificial insemination is performed approximately 16–20 hours after the second GnRH injection, ideally when ovulation occurs.
What is the point of the Ovsynch method?
Increase of overall pregnancy rate in the herd without having to detect estruses.
What is the Prid Delta Program?
is a reproductive management tool used in cattle, particularly dairy cows, for synchronizing estrus and improving conception rates.
It involves the use of a device called the PRID Delta (Progesterone-Releasing Intravaginal Device), which slowly releases progesterone to help regulate the cow’s estrous cycle, making timed artificial insemination (TAI) possible.
Prid Delta (Progesterone-Releasing Intravaginal Device) that releases progesterone over a set period.
Progesterone is a hormone that prevents the cow from coming into estrus by mimicking the luteal phase of the estrous cycle (the phase after ovulation). This helps regulate and synchronize the cow’s cycle.
Explain the steps of the Prid Delta Program.
Day 0: Insert the PRID Delta Device and Administer GnRH. The PRID maintains a high level of progesterone, which suppresses estrus. At the same time, a GnRH is administered to promote follicular growth and the selection of a dominant follicle.
Day 7: Remove the PRID Delta Device and Administer PGF₂α. This sudden drop in progesterone levels signals the cow’s body to resume its natural estrous cycle.
Day 8 or 9: Optional Second GnRH Injection.
About 24–36 hours after the PRID Delta device is removed, a second GnRH injection can be administered. This injection helps ensure that the dominant follicle will ovulate, which synchronizes ovulation timing more precisely for TAI.
Day 9 or 10: Timed Artificial Insemination (TAI) approximately 16–24 hours after the second GnRH injection (usually about 56–72 hours after PRID Delta removal).
Rationale for estrus synchronization with progesterone.
With sufficient levels of progesterone in circulation an artificial luteal phase is reached and gonadotrophin secretion is blocked.
Once progesterone effect is withdrawn,
time-synchronized release of gonadotrophin takes place and new follicular phase starts.
Progesterone stimulation helps to induce cyclicity in anestrus cows and advances puberty in beef heifers.
Describe The first cycle following a long term anestrus.
The first spontaneous or GnRH-induced estrus cycle after a period of anestrus (including post partum anestrus) is in a vast majority of animals followed by a luteal phase of shorter duration.
It is believed to be caused by precocious luteolysis.
This negatively affects the fertility results obtained with AI at the first estrus cycle.
What does “Systematic re-breeding programs” refer to?
Following 1st AI, Still 45-55% of the cows open.
Following the pregnancy check after 30-40 days of the first AI, inject open cows with PG. Is Cheap and Works well in farms with good heat detection rates.
Unfortunately a high percentage of cows are not detected and rebred in 3-5 days.
Ov-synch method of ovulation synchronization ensures all cows will be inseminated in the next 10 days.
Start Ov-synch 7 days before the pregnancy check (aggressive re-breeding). Open cows are re-bred 3 days after the pregnancy check.
Regardless of the re-syncronization method chosen, it is extremely important to keep and use accurate records and procedures to ensure pregnant cows are not mistakenly injected with PG and/or re-inseminated, as either will result in abortion.
Animal related Factors influencing the results of oestrus management in dairy herds.
Cyclicity status
Body condition
DIM (days in milk)
Milk production
Uterine health
General heath status:
BVD, IBR status
N. caninum infection
Trichomonas, Campylobacter
Mastitis
Semen quality
Personnel related Factors influencing the results of oestrus management in dairy herds.
Personnel related:
- Correct selection of animals
- Correct execution of the system:
timing of injections
dosing of products
identification of animals
Heat detection
Correct AI process
semen management
service
A target pregnancy rate to a single fixed-time AI is
45-50% should be achievable and improvements can be expected where all management factors are optimal.
Pregnancy detection in the cow. (2)
Anamnesis: About calving dates and insemination dates. Presence or lack of heat after insemination.
Rectal exam: Based on topographic and morphological changes of reproductive organs. May allow detection of infertility causes as well.
Signs what may indicate that animal is pregnant: (7)
Lack of heat after insemination
better appetite and body condition
Loss of milk production and dry off
Change of milk parameters
edema of outer reproductive organs and udder
Increase in udder size
Increase of abdominal area
Normal nonpregnant uterus is located mostly in the
pelvic cavity (heifers), but in multiparous cows most of it is usually located in the abdominal cavity.
In Normal nonpregnant uterus - During palpation we feel (3)
bifurcation clearly
Uterine horns are almost the same size, no fluid inside the uterus.
Multiparous cows usually previously pregnant horn is little bit bigger in lentgh and diameter.
During the palpation we should feel the contractions (tonus). Usually after 2 months of pregnancy contractions are ceased.
PREGNANCY DIAGNOSIS ACCORDING TO MONTHS
Month 1
No clear changes detectable by palpation.
Bifurcation is possible to feel, pregnant horn is about 1,5 times bigger in diameter compared to nonpregnant horn, wall of the uterine horn is somewhat thinner.
Pregnant horn contractility has decreased, or contractility is very weak.
If person palpating is experienced, it is possible to feel some fluctuation inside the horn.
In heifers it might be possible to feel amniotic sac.
CL in ovary.
PREGNANCY DIAGNOSIS ACCORDING TO MONTHS
Month 2
Uterus location usually in abdominal cavity.
Pregnant horn about 6-7 cm wide and approximately two times bigger than non-pregnant horn.
Non-pregnant horn is also usually about 2x bigger than in case of nonpregnant animal.
Bifurcation still detectable.
We should clearly feel that pregnant uterine horn wall is thinner and also fluctuation is clearly detectable.
No uterine contractions.
Fetal fluid amount ca 0.3 – 0.5 l.
PREGNANCY DIAGNOSIS ACCORDING TO MONTHS
Month 3
Uterus down in abdominal cavity and it is hard to palpate whole uterus by hand.
Pregnant horn is 3 – 4x bigger than non-pregnant horn.
Uterine wall is remarkably thinner and due to that we do not feel bifurcation very clearly anymore.
In very seldom cases we can feel the fetus.
PREGNANCY DIAGNOSIS ACCORDING TO MONTHS
Month 4
Uterus location in abdominal cavity and it is not possible to palpate the whole uterus by hand.
Bifurcation hardly palpabale.
During palpation it is possible to feel placentomes (bean size) and fetus.
3 – 4 l of amniotic fluid and the uterine artery on the side of the pregnant horn is palpable.
PREGNANCY DIAGNOSIS ACCORDING TO MONTHS
Month 5
Uterus inside the abdominal cavity, we can palpate only caudal part.
Bifurcation can’t be felt, placentomes Ø ca 4cm diameter.
As the uterus is deep inside the abdominal cavity we can not palpate the fetus.
On the side of pregnant horn the uterine arteria has increased and it is also possible to feel vibration in the arteria which is located in opposite the pregnant horn.
This sign can be mixed up with pyometra.
PREGNANCY DIAGNOSIS ACCORDING TO MONTHS
Month 8
Fetus close to the pelvic cavity or already partly inside the pelvic cavity.
The genital tubercle will become
the penis in the male and the clitoris in the female.
- The GT appears as a bright white bi-lobed structure in both the male and female.
- The GT may appear tri-lobed in older fetuses.
- Scrotum and teats may be visualized, but the genital tubercle is the only “cardinal sign” of fetal sex.
How to find the fetal genital tubercle on U/S?
Start by locating the umbilicus and looking for the male GT directly behind it.
If no male GT is found look for the female GT below the tail.
