Lecture 6

Question 1

What is the typical gestation length in cattle?

Answer 1

283 days; range from 270 to 333

Question 2

What are the factors that influence gestation length?

Answer 2

-breed
-age of mother
-season
-nutrition
-sex of fetus
-sire of fetus
-twins

Question 3

What are the different stages of the pregnancy?

Answer 3

-zygote; fertilization to syngamy
-first period of embryo; days 0 to 15
-second period of embryo; days 15 to 42
-period of fetus; days 42 to term

Question 4

What are the characteristics of the first period of the embryo?

Answer 4

-days 0 to 15
-embryo enters uterus around day 5
-nourishment comes from uterine milk produced by uterine glands
-embryonic loss is common; most common time frame
-losses prior to day 15 will allow cow to go back into estrus as if never pregnant
-maternal recognition of pregnancy occurs here

Question 5

What are the characteristics of IFN-t?

Answer 5

-blocks oxytocin-r
-blocks PGF2a release
-responsible for maternal recognition of pregnancy

Question 6

What are the characteristics of the second period of the embryo?

Answer 6

-days 15 to 42
-organogenesis occurs
-fetal membranes develop
-embryonic loss may be common
-most teratological defects occur here
-placentation occurs

Question 7

What are the characteristics of the period of the fetus?

Answer 7

-days 42 to term
-post-attachment phase
-maturation of nervous system
-most fetal growth occurs in last two months of gestation

Question 8

What are the characteristics of multiple pregnancies in cattle?

Answer 8

-about 30% of twin pregnancies are not carried to term
-dizygotic heterzygous twins can cause freemartinism in the female
-twins occur in 1.5 to 9% of dairy cows older than 5
-triplets are rare
-multiple pregnancies in beef cattle are rare

Question 9

What are the characteristics of progesterone in pregnancy?

Answer 9

-the CL of pregnancy is the source of P4 for the first 3 to 4 months of pregnancy and the last month of gestation
-placenta is the primary source of P4 for the remaining time of the pregnancy
-progesterone concentration drops just before parturition

Question 10

What are the characteristics of early embryonic loss?

Answer 10

-fertilization occurs in around 90% of cows with adequate heat detection and fertile semen
-pregnancy rates after mating range from 30 to 85%
-most pregnancy failures are early embryonic loss
-most early embryonic losses occur around 5 to 8 days
-losses on day 14 or earlier do not affect cycle length

Question 11

What are the characteristics of repeat breeders?

Answer 11

-cows bred 3+ times and not pregnant
-half of the cows are normal
-the other half have abnormalities such as anatomical defects, infections, vitamin A or E deficiencies, or selenium or phosphorus deficiencies

Question 12

What are the characteristics of Tritrichomonas foetus?

Answer 12

-causes bovine trichomoniasis
-has 3 anterior and 1 posterior flagella
-has undulating membrane
-around the size of a sperm head

Question 13

What are the clinical signs of bovine trichomoniasis?

Answer 13

-slow increase in infertility; scattered calf crop, increase in interestrus intervals
-early embryonic death and abortions up to 7 months; typically 50 to 70 days
-postcoital pyometra *(important for NAVLE)
-unacceptable number of open cows at preg. check
-bull in poor BCS/tired

Question 14

What is the pathogenesis of bovine trichomoniasis?

Answer 14

-organism is introduced by new cow or bull
-spread from cow to cow by the bull while bull remains asymptomatic
-recovery in cows typically occurs after 3 estrous cycles; some maintain chronic vaginal infections

Question 15

Which samples can be collected for bovine trichomoniasis testing?

Answer 15

-preputial smegma from bull
-vaginal mucus from recently bred cows
-pyometra fluid
*use modified diamonds media or InPouch TF

Question 16

What are the characteristics of bovine trichomoniasis lab testing?

Answer 16

-must have 3 negative cultures or PCRs to be declared negative
-a single positive PCR or culture sample is diagnostic
-samples must be stored at room temperature and tested within 24 to 48 hours of collection

Question 17

What is the treatment/control for bovine trichomoniasis?

Answer 17

-imidazole derivatives (not in US)
-ID and cull infected bulls
-sexual rest for cows; breeding with uninfected bulls after rest
-quarantine or divide herd
-antibiotics
-use of culture negative bulls
-tight breeding season
-vaccination

Question 18

Why is there a low prevalence of bovine trichomoniasis in TN?

Answer 18

-most herds are small, single sire herds
-provides a natural buffer to bovine trichomoniasis

Question 19

What are the characteristics of Campylobacteriosis?

Answer 19

-caused by C. fetus subspecies venerealis
-not zoonotic
-gram-neg., comma shaped rod
-motile and microaerophilic
-obligate parasite of bovine genitalia
-venereal transmission
-causes infertility, death of late embryo/early fetus, and sporadic abortion

Question 20

What is the pathogenesis of campylobacteriosis?

Answer 20

-infection establishes in vagina and cervix
-progresses to uterus and uterine tubes
-causes endometritis and salpingitis
-causes early embryonic death prior to maternal recognition of pregnancy

Question 21

How is campylobacteriosis diagnosed?

Answer 21

-history of poor fertility +/- irregular inter-estrous interval
-culture of preputial smegma, semen, fetal fluid, placenta, or vaginal discharge on Clark’s media

Question 22

What is the treatment and control for campylobacteriosis?

Answer 22

-use negative bulls and antibiotics in semen for AI
-vaccinate cows 2 weeks before breeding season with oil-adjuvanted vx
-use multiple vx doses for bulls
-use younger, virgin bulls
-exclusively do AI breeding
-test and cull/sexually rest
-keep herd as closed as possible

Question 23

What are the characteristics of abortion?

Answer 23

-loss of fetus from 42 to 260 days gestation
-2 to 5% of normal pregnancies are lost
-many abortions are not noticed

Question 24

What are the characteristics of stillbirth?

Answer 24

-death from 260 days gestation to 24 hours after birth
-due to fetal asphyxia or birth injury
-can occur with inadequate protein or energy in late pregnancy

Question 25

What are the possible fates of a fetus after death?

Answer 25

-maceration: fetus becomes soft and liquifies -mummification: desiccated; intact skin and skeleton; lack of bacterial infection -emphysema: gas distention of fetal tissue by gas-forming bacteria; associated with dystocia -stillbirth: full term fetuses -abortion: premature birth; most common fate

Question 26

What are the potential routes of fetal infections?

Answer 26

-hematogenous: viral and protozoal -aspiration/ingestion: bacterial and fungal

Question 27

What are the characteristics of brucellosis?

Answer 27

-reportable disease -zoonotic -causes abortions between 7 and 9 months -oral transmission; sheds in uterine discharge from 2-3 weeks before to 2-3 weeks after abortion -intercotyledonary areas are thickened -causes fetal pneumonia

Question 28

How is brucellosis diagnosed?

Answer 28

-isolation of organism from blood, semen, or other tissues -serology; agglutination test and ELISA -fluorescent antibody on placenta or fetus

Question 29

What is the prevention and control for brucellosis?

Answer 29

-immunize heifers between 4 and 12 months in areas of high prevalence -identify vaccinated animals -screen and cull infected cattle

Question 30

What are the characteristics of leptospirosis?

Answer 30

-single species with many serovars -hardjo-bovis and hardjo-prajitno are host-adapted and cause persistent infections in cattle -sporadic/incidental infections with other strains (esp. pomona) can cause abortions

Question 31

What are the charactersitics of lepto-induced abortion?

Answer 31

-fetal death occurs 24 hours prior to abortion -fetus is markedly autolyzed with no specific lesions -placental cotyledons are uniformly light tan to yellow

Question 32

How do host-adapted lepto strains differ from non-host adapted strains?

Answer 32

HOST-ADAPTED: -low pathogenicity -causes abortion, stillbirth, infertility -abortion at all stages; usually last trimester -abortion rate <10% -early embryonic death -autolyzed fetus -no other clinical signs NON-ADAPTED: -sporadic disease/disease outbreaks -abortions in last trimester only -abortion rate 50% -causes hepatorenal dz, photosensitization, and hemolytic anemia

Question 33

How is lepto diagnosed?

Answer 33

-fluorescent antibody test -PCR*

Question 34

What is the available prevention for lepto?

Answer 34

-multi-strain vx: does not protect against host adapted strains -mono-strain vx: prevents renal infection

Question 35

What are the characteristics of neospora dz?

Answer 35

-in cattle and sheep -multiple white foci on cotyledons -fetal encephalitis and systemic lesions -abortions from 3 to 6 months -fetuses may die in utero, be reabsorbed, mummify, autolyze, be stillborn, die after birth, or live but be chronically infected

Question 36

What are the characteristics of the neospora parasite?

Answer 36

-N. caninum sporozoites cause cell change -tachyzoites divide rapidly and cause tissue damage -tachyzoites transform into bradyzoites that are found in tissue cysts

Question 37

How is neospora transmitted?

Answer 37

-oral transmission; cattle infected by oocysts shed by dogs -vertical transmission; dams pass infection on to offspring (81-95%)

Question 38

How is neospora diagnosed?

Answer 38

-clinical history and epidemiology -presence of dogs with access to cattle feed -IFAT or ELISA on serum and milk -PCR of blood, semen, or tissues

Question 39

What are the diagnostic challenges with neospora?

Answer 39

-non-pregnant cattle are asymptomatic -diagnostic techniques for aborted fetuses

Question 40

How is neospora prevented?

Answer 40

-identify route of transmission -perform serology on purchased cattle -use pre-suckle antibodies to prevent congenital infection -reduce dog contact with cattle and feed -vaccine available; not super effective