Midterm 3 - Lecture 25

Question 1

Why is it important to determine pregnancy status as early and accurately as possible?

Answer 1

• to minimize economic losses and rebreed or cull non-pregnant animals ASAP

Question 2

What are the different pregnancy detection methods?

Answer 2

1. Absence of estrus
   - inexpensive, early indicator of pregnancy
2. Clinical detection
   - rectal exam
   - ultrasonography
3. Laboratory detection
   - detection of pregnancy associated substances
   - vaginal biopsy

Question 3

Why is ‘absence of estrus’ not always a dependable pregnancy diagnosis method?

Answer 3

1. silent heats
2. retained corpus lutea
3. early abortion

Question 4

Rectal examination

Answer 4

• mainly used for large domestic species (cows and mares)
• somewhat invasive
• requires training/expertise

Question 5

Ultrasonography

Answer 5

• non-invasive
• requires special equipment
• requires training/expertise required

Question 6

2 methods of ultrasonography pregnancy diagnostics

Answer 6

1. Doppler method
   - sounds
2. Real time ultrasound
   - images

Question 7

Doppler Method (ultrasonography)

Answer 7

• Doppler are particularly suitable for use in pigs, dogs, sheep and goats
• allows for detection of a number of different indicators of pregnancy (sounds):
  1. increased blood flow in 1 or more uterine arteries
  2. fetal heartbeats
  3. umbilical artery pulsations
  4. fetal movement

Question 8

How does an ultrasound work?

Answer 8

• propagation and interaction of sound waves through body tissue
• image based on the intensity of the reflected echos
• no echo: liquid = dark
• low-intensity echo: low-density tissues (muscle) = grey
• high-intensity echo: high-density tissues (bones) = bright

Question 9

Real time ultrasound - pigs

Answer 9

• allows for non-invasive detection of pregnancy
• generally done in animals you can’t do a rectal exam in (ex. pigs)
• requires training, expertise, and equipment ($)

Question 10

Real time ultrasound - cow or mare

Answer 10

• conformation of estrous cycle/pregnancy
• ovarian structures
• embryonic membranes
• fetus(es)
• sex
• go into rectum and probe is placed inside, right over top of the repro tract

Question 11

Using ultrasound pregnancy diagnostics, what is the earliest you can detect pregnancy after mating/insemination of: cattle, horse, pig, sheep, goat

Answer 11

Cattle: day 25
Horse: day 18
Pig: day 21
Sheep: day 30
Goat: day 30

Question 12

Can substances related to pregnancy be detected in serum or milk? How?

Answer 12

Yes! By using assays or tests
- reliable
- relatively inexpensive
- non-invasive
- requires purchase of on-farm assays or access to diagnostic services

Question 13

What assays are capable of accurately measuring several different hormones associated with pregnancy?

Answer 13

1. Sensitive radio immunoassays (RIA)
2. Enzyme-linked immunosorbant assay (ELISA)

Question 14

What hormone is most commonly associated with pregnancy?

Answer 14

P4
- commercial on-farm milk tests for cattle are common

Question 15

Other than P4, what are some hormone indicators of pregnancy?

Answer 15

1. Estrone sulphate
   - compound produced by the fetus and measurable in maternal plasma, milk, urine or fecal matter
2. Gonadotropins
   - eCG: appears in the blood of pregnant mares as early as day 40 and is also measurable in urine
   - hCG: appears in the blood and urine of pregnant women

Question 16

Prior to the commercial availability of assays, what was used to detect pregnancy on-farm? How?

Answer 16

• Vaginal biopsies; vaginal epithelium changes w/ pregnancy (cell layers reduced)
• vaginal tissue is biopsied, fixed, stained & examined microscopically
• requires access to a diagnostic lab