Repeat breeding & embryonic mortality Flashcards
Reasons for failure of early embryonic development? (3)
poor oocyte quality
delayed ovulation
inadequate pattern of P4 rise
Reasons for failure of embryo to prevent luteolysis? (3)
poor embryo quality
“lack of sync between dam and embryo”
infectious factors
Reasons for repeat breeding (3)
wrong time of insemination
unpalpable pathological changes of ovarian bursa or oviduct
undiagnosed uterine infections
An early repeater is
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”).
A late repeater is
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.
A repeat breeder is
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).
Reasons for “repeated breeding syndrome” broadly. (2)
Fertilization failure
Embryonic mortality (fertilization took place, but developing embryo did not survive)
Causes of adhesions between ovary and ovarian bursa: (6)
Trauma
Rectal palpation
Cesarean section and post-operative peritonitis
Exogenic infections
(metritis, intrauterine drugs)
Endogenic infections (from peritoneum)
Specific infections (Ureaplasma spp., Mycoplasma spp)
What do we need to know for successful impregnation?
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?
Fertilization site in cattle?
bulla of oviducts
If you have inadequate heat detection, what should you do
implement estrus synchronization (prostaglandins)
Prolonged estrus signs can indicate
delayed ovulation
When you have a repeat breeding problem, what 4 things should you check and rule out.
endometritis
errors in heat detection
wrong insemination timing
wrong insemination technique
Etiology differences between early repeats (<25d post AI) and late repeats (35-50 post AI).
What is Metricure?
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.
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
EMBRYONIC MORTALITY.
(Prenatal death, embryonic death, hidden (latent) abortion)
When the Embryo dies before 42 days of pregnancy (embryonal development stage) its called (3)
Prenatal death, embryonic death, hidden (latent) abortion
(after 42 days we are talking about abortion)
Prenatal death, embryonic death, hidden (latent) abortion can be earlier or later. What’s that mean?
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%.
Subclinical endometritis or bacterial contamination of uterus can result in
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).
Hidden (subclinical) infection in cervix, uterus and oviducts can cause:
Closure of oviducts: outcome of inflammation (salpingitis), rarely independent illness, possible when hydro – or pyosalpinx has been present (flucuating structures).
Uterine atonia is when
there is no uterine motility (contractions), traffic of sperm into oviducts is limited in this case.
Hormonal factors which lead to disturbances in endometrium:
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
What factors increases progesterone concentrations?
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).
Progesterone deficiency can be caused by (2)
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).
