LA THERIO - Dairy Cattle

Question 1

What is the main parameter used to measure reproductive efficiency in dairy heifers, and what should be the goal?

Answer 1

1. Age at calving (24 months)
2. Size at first calving (1200 lb)
3. Adequate interval between calving

Question 2

What is the normal estrous cycle length in cattle?

Answer 2

21 days

Question 3

What is the normal duration of estrus in dairy cattle?

Answer 3

7-9 hours
?

Question 4

What is a freemartin heifer, and why are they sterile?

Answer 4

Female born co-twin with a male
Exposed to AMH and testosterone
Causes abnormal development of tubular genetalia
Sterile due to infantile reproductive tract

Question 5

What is the gold standard for diagnosis of freemartinism?

Answer 5

CYTOGENETICS: PCR to detect Y Ag
most are chimera: XX/XY

Question 6

What does “white heifer disease” describe?

Answer 6

recessive sex-linked gene of white hair coat

breeds: belgian blue, shorthorn

segmental aplasia of the paramesonephric ducts

normal ovaries
variable degrees of persistent hymen (shorthorn)
Variable degrees of segmental aplasia of the cervix
mycometra

Question 7

What abnormalities of the reproductive tract are associated with freemartinism?

Answer 7

• abnormal tubular genitalia (paramesonephric duct) and ovaries
• short vagina; uterine horn and cervix are undeveloped
• aplastic ovaries
• male accessory glands may be present (seminal vesicles)
• external genitalia might be normal

Question 8

What abnormalities of the reproductive tracts are associated with white heifer disease?

Answer 8

segmental aplasia of the paramesonephric ducts:
- normal ovaries
- variable degrees of persistent hymen (mostly shorthorn)
- variable degrees of segmental aplasia of the cervix
- mucometra

Question 9

When would a placenta be considered retained in a cow?

Answer 9

> 12 hours postpartum

Question 10

Name some of the most important factors involved in increased incidence of retained placenta.

Answer 10

Abortion
Twinning
C-section

Previous retention
Stillbirth
Veto to my
Age
Dystocia
Selenium/Vitamin E deficiency

Question 11

What treatments are contraindicated or not effective for management of retained placenta?

Answer 11

NO manual removal!!
NO PGF2a - not effective

Abx only when indicated (septic metritis)
Oxytocin used in early pp; not effective for primary RFM

Question 12

List three main risk factors for uterine infection in the dairy cow.

Answer 12

Retained placenta
Stillbirth
Twinning
Dystocia
Primiparous

Question 13

What are the main effects of negative energy balance on reproduction?

Answer 13

happens during transition period: 3 wks before & after parturition

Dystocia
Abortion
Ketosis and fat cow syndrome
Hypocalcemia
Toxic mastitis
Septic metritis
Displaced abomasum
Down cow syndrome

lipid mobilization → increased lvls of NEFAs, ketones: BNB, acetone, etc → decreased immunity: leukopenia, decreased INFy and IgM synthesis → reduced phagocytosis
increased concentrate in the ration → rum acidosis → inflam cytokines + acute phase proteins → increased risk of metritis, mastitis, laminitis, displaced abomasum

Question 14

Define cystic ovarian disease.

Answer 14

follicle is > 25 mm for more than 10 days in absence of CL→ anestrus

Incidence: 10 -30%

50% resolve on their own

Question 15

Describe the types of ovarian cysts in the cow.

Answer 15

Follicular - thin walled
Luteal - thick walled; may produce progesterone

Question 16

How can ovarian follicular cysts be treated?

Answer 16

GnRH or hCG + PGF2a

Question 17

What are the symptoms of pyometra in cattle, and how would you treat?

Answer 17

Pyometra in cattle does not cause systemic effects.
Clinical signs - vaginal discharge, anestrus
Treat with PGF2a to help with uterine contractions so they can deal with it on their own.

Pyometra is characterized by the accumulation of purulent or mucopurulent exudate in the uterus. In cows, it is invariably accompanied by the persistence of an active corpus luteum and interruption of the estrous cycle. In affected mares, the cervix is often fibrotic, inelastic, affected with transluminal adhesions, or otherwise impaired. Mares may continue to cycle regularly, or the cycle may be interrupted. Discharge from the genital tract may be absent or intermittent and corresponding to periods of estrus. In general, affected animals do not exhibit any systemic signs of illness, but affected mares may be in poor condition. In both cows and mares, pyometra must be distinguished carefully from pregnancy before beginning treatment.

TX: In cows, the treatment of choice for pyometra is the administration of PGF2-alpha or its analogs at normal luteolytic doses. Expulsion of exudate and bacterial clearance of the uterus follows in ~80% of treated cases. Although the first-service conception rate after treatment may be low, most cows may be expected to conceive within three or four inseminations. The treatment may need to be repeated in ~20% of cows. No intrauterine treatment is recommended in conjunction with the prostaglandin.

Question 18

How would you calculate a pregnancy rate in the herd?

Answer 18

Preg rate = measurement of repro efficiency = #of pregnant cows / # of all cows that should have gotten pregnant in that time (21 day cycle).

In other words, Conception Rate x Heat Detection Rate

Question 19

How would you terminate pregnancy in a cow between days 30 and 60?

Answer 19

PGF2a or analogues first 150 days of pregnancy – THE GO TO!
Dexamethasone + PGF2a last trimester

Question 20

How does heat stress affect fertility in the dairy cow?

Answer 20

Decreases oocyte quality (possibly early loss) and conception rate

Temp > 26C / 78 -79 F → increased rectal temp and RR →
→ decreased oocyte activity
→ increased granulosa cells degeneration and decreased steroidogenesis
→ decreased progesterone production
→ reduced embryo quality
→ effect can last over several cycles

Question 21

What is the transition period, and what are its implications in dairy cattle reproduction?

Answer 21

3 wks before parturition, 3 wks after : NEGATIVE ENERGY BALANCE + high risk for hypocalcemia

Question 22

How does high milk production affect estrus and pregnancy in the dairy cow?

Answer 22

estrus: increased liver metabolism → increased biodigration of steroids (estrogen) –> poor heat detection

high milk production causes an increase demand for energy which is difficult to achieve with just eating. This will cause a negative energy balance leading to hypoglycemia and lipidosis that will have an affect on the ovaries causing anestrus and cysts

Question 23

What methods can be used for early pregnancy diagnosis in the cow (day 28 to day 30)?

Answer 23

28 days: transrectal US
28 - 30 days: PSPB (pregnancy specific protein B)
32 -35 days: transrectal palpation

Question 24

What is the most common parasitic disease involved in dairy cattle abortions in the western United States?

Etiological agents
Clinical manifestation

Answer 24

Neospora Caninum.
infection: ingestion of oocysts + development of tachyzoites in placenta + amniotic fluid
vertical transmission
bradyzoites in CNS
Cows: no CS, no retained placenta
Placentitis
Fetus: autolyzed w/ no gross lesions (mummified)

Neospora caninum: definitive host is canids, infected by ingestion.
No clinical signs in the cow, but will cause reabsorption or mummification between 4-7 months of pregnancy.
In fetuses look for foci of cellular infiltrates in the brain, non suppurative endocarditis, myocarditis and myositis and portal hepatitis.

Question 25

What are the effects of BVD virus on reproduction and the fetus at different stages of pregnancy?

Answer 25

days 0 - 42: infertility, early embryonic death

days 18 - 125: persistently infected calves, abortions, mummy

congenital defects from 100 days: cerebellar hypoplasia, retina dysplasia, intrauterine growth retardation, mandibular bradygnathism, hydrancephaly, hypomyelinogenesis, partial alopecia.

Days 125-170: abortion possible, fetal abnormalities, calves born w/ congenital defects have precolostral serum virus-neutralizing titers to BVDV

After 170 days: No abortion, birth of normal appearing calves w/ pre-colostral Ab

Question 26

List abortive diseases that can be prevented or controlled by vaccination.

Answer 26

B abortus,
L pomona and L interogans
BVD but no cross protection
IBR/BHV

Question 27

Name two major infectious causes of fetal mummification in cattle.

Answer 27

BVDV, Neosporosis

Question 28

What are the two types of fetal membrane hydrops?

Answer 28

Hydroallantois (hydrops allantois) Hydramnios (Hydrops amnii)

DfDx for both: severe bloat, severe ascites, emphysematous fetus

Question 29

What is the main clinical difference between the two types of fetal membrane hydrops?

Answer 29

Hydrallantois is more common, has rapid development, can’t feel the fetus transrectally, fluid rapidly refills if drained, and will usually kill cow and fetus.

Question 30

What is the prognosis in cases of hydrallantois?

Answer 30

Death

Question 31

What are the options for treatment of mummification?

Answer 31

Death of the fetus without development of infection

Tx: PGE (not FDA approved), Sx removal, PGF2a (if the mummy is Lg, PGF2a is not effective)

VS fetal maceration: fetal death with bacterial contamination (autolysed fetus)

Question 32

What are the direct effects of hypocalcemia on reproduction?

Answer 32

decreased myometrial contractions → dystocia, retained placenta, puerperal metritis → clin metritis →subclin endometritis → low conception rate, early embryo loss→ INCREASED CALVING INTERVAL
ovarian inactivity → anestrous