Bovine Breeding Management

Question 1

what is the length of gestation in cows

Answer 1

280 days

Question 2

what is the period of involution in cows

Answer 2

50 days

Question 3

what is the natural length of the cycle in cows

Answer 3

21 days

Question 4

how many heat cycles do producers have to get cows pregnant and meet their economic target of 1 calf/cow/13 months

Answer 4

3

Question 5

The duration of estrus and # of events during estrus in heifers is higher/lower than in cows

Answer 5

higher

Question 6

The duration and signs associated with estrus are higher/lower in high vs low producing cows

Answer 6

lower

Question 7

overall, the duration of standing estrus over the entire estrus period in cows is under

Answer 7

30 seconds!

Question 8

on average, estrus in cows lasts

Answer 8

12-18 hours

Question 9

what is Heat Detection Rate (HDR)

Answer 9

proportion of cows detected in estrus

Question 10

what is Insemination Risk

Answer 10

cows submitted for AI that are in estrus (proportion of AI eligible cows detected in heat)

Question 11

what is Conception Risk

Answer 11

probability that AI results in pregnancy (proportion of breedings that result in pregnancy)

Question 12

what is the 21-day pregnancy risk roughly equal to

Answer 12

HDRxCR

Question 13

what is 21-day pregnancy risk

Answer 13

proportion of open cows that become pregnant every cycle

Question 14

how many days after ovulation does the CL become mature/responsive

Answer 14

7

Question 15

how quickly does PGF2α cause luteolysis in a mature CL in cows

Answer 15

1 day

Question 16

PGF half life is (seconds/minutes/hours/days)

Answer 16

minutes

Question 17

GnRH is a chain of amino acids. What does this mean

Answer 17

if you ingest it, it is digested

Question 18

What hormone, when given exogenously, causes blood/milk levels LOWER than the endogenous hormone

Answer 18

progesterone (P4)

Question 19

what is the BIGGEST challenge for bovine producers in getting cows pregnant

Answer 19

DETECTION of HEAT

Question 20

what are factors that can confound heat detection in cows (5)

Answer 20

confinement, lameness, flooring, comfort, negative energy balance

Question 21

ovulation occurs in cows how many hours after standing heat

Answer 21

27h later

Question 22

after ovulation, the ovum lifespan in cows is

Answer 22

6-8h

Question 23

capacitation of sperm occurs how many hours after ejaculation

Answer 23

10

Question 24

what is the basis of activity monitors for heat detection

Answer 24

there is a huge spike in activity the day a cow comes into heat

Question 25

what are the limitations to PGF2α for estrus synchronization in cows (3)

Answer 25

1) not all will respond (66% apparent response) 2) need to be able to detect a mature CL 3) variable time to ovulation depending on the phase of the wave in individual cows

Question 26

T/F PGF2α allows for timed AI

Answer 26

F (it does not control follicles so it cannot)

Question 27

the average interval from PGF2α to estrus detection is

Answer 27

3 days

Question 28

describe OvSynch

Answer 28

1) give GnRH on day 1 to stim follicular growth 2) give shot of PGF2α to lyse any CL on day 7 3) give GnRH again 2- 2.5 days later 4) timed AI within the next day

Question 29

T/F OvSynch allows for timed AI

Answer 29

T

Question 30

what is a key step to improve fertility during OvSynch

Answer 30

ovulating after the first shot of GnRH so that there is a CL producing progesterone during the follicular growth before the dose of PGF2α

Question 31

we want to inseminate ~ how many hours after giving the second dose of GnRH in an OvSynch program

Answer 31

16

Question 32

what is the effect on OvSynch if we start 1-4 days after the last heat

Answer 32

failure to synchronize new follicular wave

Question 33

what is the effect on OvSynch if we start 13-17 days after the last heat

Answer 33

spontaneous luteolysis and ovulation before timed AI

Question 34

what is the effect on OvSynch if we start 18-21 days after the last heat

Answer 34

unresponsive CL when we give PGF

Question 35

how many days after the last ovulation is ideal to start OvSynch

Answer 35

5-12 (but goal of presynching is to get them at 6-7 days)

Question 36

what are the two methods of pre-synchronizing the estrus cycle before starting OvSynch

Answer 36

1) Pre-Synch: 2 PGF, 2 weeks apart, 2 weeks before OVS 2) Double OvSynch: Ovsynch -> no AI -> 7d -> OvSynch -> timed AI

Question 37

what is the goal of pre-synchronization

Answer 37

start OvSynch when the cows are 6-7 days after the last ovulation

Question 38

what can be used to stimulate ovulation in anestrus cows

Answer 38

CIDRs (intravaginal progesterone)

Question 39

what 2 uses can CIDRs be used for

Answer 39

1) bring cow out of anestrus 2) stimulate turnover in cystic cows

Question 40

what is a potential side-effect of using CIDRs in cows

Answer 40

if used for longer than 14 days, it produces a persistent dominant follicle (cyst) -> reduced fertility