Repeat breeding & embryonic mortality

Question 1

Reasons for failure of early embryonic development? (3)

Answer 1

poor oocyte quality
delayed ovulation
inadequate pattern of P4 rise

Question 2

Reasons for failure of embryo to prevent luteolysis? (3)

Answer 2

poor embryo quality
“lack of sync between dam and embryo”
infectious factors

Question 3

Reasons for repeat breeding (3)

Answer 3

wrong time of insemination
unpalpable pathological changes of ovarian bursa or oviduct
undiagnosed uterine infections

Question 4

An early repeater is

Answer 4

an animals whose luteal function has been shorter than normal/typical for the physiological estrus cycle in non bred cow.

In these cows the most probable event is either failure of fertilization (delayed ovulation, poor semen quality etc.) or early embryonic death (delayed ovulation, poor embryo quality, unfavorable uterine environment, precocious luteolysis).

The cows will come into heat within 17-24 days after AI (“early”).

Question 5

A late repeater is

Answer 5

a cow that comes into heat later than 25 days after AI.

In these animals the luteal function was maintained for longer than the physiological luteal phase in non bred cows.

Fertilization and initial recognition of pregnancy probably took place but for some reason luteolysis was induced (inadequate luteal function, inadequate embryo signaling, infectious diseases, induced luteolysis) and pregnancy lost.

Good heat detection and records are key to identifying these cows.

Question 6

A repeat breeder is

Answer 6

a cow that is cycling normally, with no clinical abnormalities, but has failed to conceive after at least two consecutive inseminations. “repeated breeding syndrome”

Cow will drop out from normal yearly reproductive cycle. This Problem exists in all intensive milk production farms and countries.

The goal is to keep the repeated breeding rate at normal level (ca 20% from all inseminated cows).

Question 7

Reasons for “repeated breeding syndrome” broadly. (2)

Answer 7

Fertilization failure

Embryonic mortality (fertilization took place, but developing embryo did not survive)

Question 8

Causes of adhesions between ovary and ovarian bursa: (6)

Answer 8

Trauma

Rectal palpation

Cesarean section and post-operative peritonitis

Exogenic infections
(metritis, intrauterine drugs)

Endogenic infections (from peritoneum)

Specific infections (Ureaplasma spp., Mycoplasma spp)

Question 9

What do we need to know for successful impregnation?

Answer 9

When will ovulation likely take place?

How long is an oocyte capable of being fertilized and have normal development potential?

When do sperm arrive to fertilization site?

How long does sperm have fertilization capacity in the cow reproductive tract?

Question 10

Fertilization site in cattle?

Answer 10

bulla of oviducts

Question 11

If you have inadequate heat detection, what should you do

Answer 11

implement estrus synchronization (prostaglandins)

Question 12

Prolonged estrus signs can indicate

Answer 12

delayed ovulation

Question 13

When you have a repeat breeding problem, what 4 things should you check and rule out.

Answer 13

endometritis
errors in heat detection
wrong insemination timing
wrong insemination technique

Question 14

Etiology differences between early repeats (<25d post AI) and late repeats (35-50 post AI).

Answer 14

Question 15

What is Metricure?

Answer 15

An intrauterine suspension of cefapirin for treatment of endometritis in cows. Cefapirin, a first generation cephalosporin, is a broad spectrum antibiotic with bactericidal action against gram-positive and gram-negative bacteria.

15 ml volume

In inseminated animals, Metricure can be used one day following insemination.

Question 16

If insemination time has been correct and insemination procedure is performed correctly, fertilisation failure is not the main cause for repeat breeding, the bigger cause is

Answer 16

EMBRYONIC MORTALITY.

(Prenatal death, embryonic death, hidden (latent) abortion)

Question 17

When the Embryo dies before 42 days of pregnancy (embryonal development stage) its called (3)

Answer 17

Prenatal death, embryonic death, hidden (latent) abortion

(after 42 days we are talking about abortion)

Question 18

Prenatal death, embryonic death, hidden (latent) abortion can be earlier or later. What’s that mean?

Answer 18

Earlier embryonic mortality (about 75% of cases) before day 16 of pregnancy. Interval between heats is normal.
Later embryonic mortality (about 25% of cases) between days 16 – 42 of pregnancy. Interval between heats is more than 24 days.

Prenatal embryonic death in heifers up to 15% & most frequent in repeated breeding cows up to 65%.

Question 19

Subclinical endometritis or bacterial contamination of uterus can result in

Answer 19

Non favorable uterine environment for embryo, and thus implantation failure.

During rectal palpation, uterus is normal, only sign what we can see is the mucus discharge during estrus (cloudy, some pus inside it, viscosity of the mucus is not good (its watery).

Question 20

Hidden (subclinical) infection in cervix, uterus and oviducts can cause:

Answer 20

Closure of oviducts: outcome of inflammation (salpingitis), rarely independent illness, possible when hydro – or pyosalpinx has been present (flucuating structures).

Question 21

Uterine atonia is when

Answer 21

there is no uterine motility (contractions), traffic of sperm into oviducts is limited in this case.

Question 22

Hormonal factors which lead to disturbances in endometrium:

Answer 22

Mostly, low progesterone

• Progesterone level >3 ng/ml pregnancy rate 55%.
• Progesterone level <3 ng/ml pregnancy rate less thana 10%.

Less progesterone = less pregnancy

Question 23

What factors increases progesterone concentrations?

Answer 23

increased number of lactations so the older the cow the more progesterone it produces

cows whose progesterone levels are <3 ng/ml 5 days post-insemination will increase after each lactation
1. lactation 10%
2. lactation 20%
from 3rd lactation 30%

Some studies claim P4 can be increased by feeding more fatty acids too (e.g. sunflower cakes).

Question 24

Progesterone deficiency can be caused by (2)

Answer 24

Low production of the hormone (due to too little cholesterol or due to urea and mycotoxins).

or

Too high a metabolism (high-producing cows lose P4 to milk).

Question 25

Non-protein nitrogen is converted to what in the rumen?

And protein-nitrogen?

Answer 25

Non-protein nitrogen: converted to ammonia.

Protein nitrogen: will be converted to peptides, amino acids, but also to ammonia.

Ammonia will also be produced during glucose synthesis from amino acids.

Question 26

In the rumen, Ammonia will be converted to

Answer 26

microbial protein.

In turn, the amount of microbial protein produced will depend on how much the ammonia will be diluted in liquid, on pH and on the amount of fermented carbohydrates available.

Question 27

Those Ammonia left overs that will not be converted to microbial proteins will be

Answer 27

absorbed through the rumen wall and will be converted to urea in the cow liver (additional energy waste).

Blood ammonia content will increase when the liver’s capacity to produce the urea is exhausted.

Question 28

If we increase raw protein in the ration, we get higher production.

But if we overfeed protein, we get lowered fertility.

Why?

Answer 28

When the ration reducible protein exceeds the ruminal requirements for reducible protein, the blood ammonia content will increase.

Ammonia will be converted to urea in the liver, and urea content will increase in plasma, milk and urine, cervical mucus and uterine mucus.

High urea levels will decrease the pregnancy rate by disturbing fertilization and through early embryonic death (urea level in vaginal discharge over 100mg/100ml).

Question 29

Changes in certain hormonal levels will stimulate milk production, but they may be potentially damaging to other physiological processes like reproduction. What’s an example of this?

Answer 29

Higher production will increase somatotropin and prolactin levels in blood (lactation stimulators), but at the same time decreases insulin levels (lactation antagonist).

Insulin is important for normal follicle development.

Question 30

Influence of environment on reproduction rates.
What’s the main environmental factor to contribute?

Answer 30

Climate (heat stress), Critical level +25 - 27° C.

Heifers are less influenced

Decreased duration of estrus (t° >27°C)
Ovulation without estrous signs

Embryonic death
Negative influence on retained fetal membranes more prominent

Lower birth weight in calves and lower milk production in dams when heat stress occurs in last trimester of pregnancy.

Question 31

Effect of temp on the endocrine system (and in turn, reproduction). (2)

Answer 31

Effect on hypothalamo–hypophyseal axis not fully clear yet.

FSH production:
- Is not disturbed in case of high temperature

LH production:
- Clear decrease in LH pulse frequency
1. dominant follicle will develop in LH deficiency
2. Low estrogen production
3. weak estrous signs and low general fertility

P4 production decreased

Question 32

Decrease in LH pulse frequency and low LH level will lead to: (4)

Answer 32

1. prolonged development process of dominant follicle
2. Delayed ovulation (= aged oocyte will be ovulated)
3. Presence of persistent dominant follicle
4. Decreased quality of oocyte and low pregnancy rate

Question 33

Progesterone and heat stress

Answer 33

Period of heat stress will decrease the progesterone level (up to 25%), low luteinization rate of theca cells.

Poor CL development.

Question 34

In heat stress, the Uterine endometrium starts to produce

Answer 34

Uterine endometrium starts to produce heat-shock proteins and decreases the production on interferon-τ by the embryo.

Question 35

Temperature and its effects on nutrition and energy balance and in turn, reproduction.

Answer 35

Heat stress decreases dry matter intake.

Prolongation of negative energy balance stage.

Will negatively influence blood plasma insulin, IGF-1 and glucose levels with the following outcome:
- Disturbances in follicular development
- Decreased estrus signs
- Low quality oocytes