Dairy 2

Question 1

describe how ovarian synchronization is used and what it is

Answer 1

• facilitates AI at a fixed time so we don’t need to detect estrus

most common is OvSynch: “0721”

day 0: GnRH, 7 days later: PG, 2 days later: GnRH, 1 day later: AI

Question 2

what is required for a response to GnRH?

Answer 2

a dominant follicle!

Question 3

ideally, when should you start your OviSync?

Answer 3

better results when you start in early estrus compared to late, ideally start it between day 6-7. This is because the 1st wave involved lower P4 levels–>P4 is neccessary for good oocyte quality and therefore the first wave is associated with lower fertility

Question 4

describe why pre-synching is done

Answer 4

if we know the ideal time for starting ovisync is day 6 or 7, then we can pre synch them to make sure they’re all at day 6 or 7 when we start the 0721 protocol!

Question 5

why is there a decrease in fertility from 1955 to 2005? generally speaking?

Answer 5

we have selected cows to produce more milk which requires more energy–>reproduction is a luxury! cows must have adequate nutrition to start cycling again after calving

Question 6

what is ideal BCS at parturition?

Answer 6

3 ish, and after calving most cows will lose 0.5 to 0.75 BCS units

Question 7

cows that keep or gain BCS during transition and or/from calving means…

Answer 7

earlier repro activity and more likely to keep another pregnancy

Question 8

list some problems with bows being too thin and cows being too fat

Answer 8

too thin: more anovular cows, low fertility

too fat: metabolic problems like ketosis

Question 9

when doing preg checks, should you care more about the pregnant ones or the open ones?

Answer 9

the open ones! you’re assuming all your cows will become pregnant

Question 10

list some direct and indirect ways to diagnose pregnancy in dairy cows

Answer 10

direct: palpation and ultrasound

indirect: P4 (2 samples) and pregnancy specific protein B

Question 11

PSPB for detecting pregnancy: how does it work? is this a reliable test?

Answer 11

it is released by embyronic trophoblast cells usually 30 days after breeding. Can get a false positive due to long half life

Question 12

when can you palpate for preg check?

Answer 12

35-40 days post breeding

Question 13

what is the primary sign of pregnancy on palpation? what are some secondary signs

Answer 13

an embryonic vesicle

secondary: membrane slip, placentomes, uterine artery flow (fremitus)

Question 14

when can you identify the fetus sex on ultrasound?

Answer 14

after 55 days (55-70)

Question 15

what are the risks associated with a twin pregnancy?

Answer 15

embyro and fetal loss, abortion, stillbirths, dystocia, neonatal calf mortality and low body weight, free martins possibly

Question 16

what is one possible mechanism of why the amount of twins are increasing over time?

Answer 16

cows with higher milk production means higher dry matter intake, this increases liver blood flow which increases E2 and P4 catabolism. With less estradiol and P4, you can a double ovulation

Question 17

what are some common reproductive parameters (things you can measure) for management?

Answer 17

conception risk: # cows preg/# cows bred (only takes into account AI cows)

pregnancy risk: # cows pregnant/ # cows eligible to be bred (takes all animals into account, standard to evaluate dairy herds repro performance, but doesn’t include how long it took the cows to get pregnant)

calving interval: requires historical data

average days open: interval from calving to next conception