Reproductive Management of Dairy Cows

Question 1

Name a grain we commonly use to feed dairy cows?

Answer 1

barley or corn

Question 2

fibre in the ration supports milk fat production or glucose precursors?

Answer 2

glucose precursors

Question 3

What is the importance of reproductive management?

Answer 3

• calving is required for lactation
• impact on genetic improvement through shorter generation intervals

Question 4

What is important about a consistent calving distribution in dairy herds?

Answer 4

• required for constant supply of milk (quota)
• more animals close to peak milk production

Question 5

What do calves provide in dairy herds?

Answer 5

• replacement heifers
• breeding bulls

Question 6

What stats do you need to get a dairy cow pregnant?

Answer 6

• ideally 1 calf/yr
• negative energy balance in days 0-60 of lactation (dont even try to get them pregnant then)
• 305 days left
• ~280 day gestation
• ~ 25 days left to get them pregnant (just over 1 cycle - 21 days)

Question 7

How do we assess readiness for breeding in a dairy cow?

Answer 7

• post-partum exam
• cost-benefit analysis
• heat detection +/- technology

Question 8

What do timed artificial insemination (AI) protocols do in dairy herds?

Answer 8

manage CL function, follicle development, ovulation

Question 9

how do we breed dairy cows?

Answer 9

• AI
• bull breeding

Question 10

What is ideal heat detection in dairy herds? How long to spend detecting heat?

Answer 10

• breeding should take place 12 h following observed standing estrus
• aim for > 50% HEAT DETECTION RATE

Question 11

What kind of aids are their for heat detection in dairy herds?

Answer 11

• pedometers
• K-mar detectors/ Estrotect patches
• (teaser bulls)

Question 12

Why do some dairy herds use estrus synchronization?

Answer 12

modern dairy cows are really bad at showing estrus behaviour & this is why we have started switching to timed AI

Question 13

What are the principles of timed AI protocols?

Answer 13

• control CL function
• control follicle development
• control ovulation

Question 14

What is the insemination rate in dairy cows?

Answer 14

% cows inseminated of those eligible to be inseminated during a single estrus cycle

Question 15

What is the conception rate in dairy cows?

Answer 15

% of inseminated cows that become pregnant during a single estrus cycle

Question 16

What is the pregnancy rate in dairy cows?

Answer 16

% of all cows that become pregnant during a single estrus cycle

Question 17

What is the benchmark for insemination rate in dairy cows?

Answer 17

~44%

Question 18

What is the benchmark for conception rate in dairy cows?

Answer 18

~42%

Question 19

What is the benchmark for pregnancy rate in dairy cows?

Answer 19

~17%

Question 20

Why does insemination rate not equal heat detection rate?

Answer 20

• cow eligible for insemination -> insemination -> preg check
• cow seen in standing estrus 21 days after insemination, producer will rebreed
• if cow gets pregnant after 2 inseminations, insemination rate is 50%, but heat detection rate was 100%

Question 21

What are the pros & cons of bull breeding in dairy herds?

Answer 21

• no need for estrus detection
• no breeding date available
• disease spread
• increased housing & facility expense
• risk to humans & other cows
• potentially separate bull pens

only done if AI not permitted (Hutterite colonies)

Question 22

What are the pros & cons of AI in dairy herds?

Answer 22

• maximize genetic improvement potential
• need to detect estrus
• skilled staff needed
• genetic concentration in a herd
• sexed semen (animals w/ most genetic merit can produce heifers

Question 23

What are other strategies than bull breeding or AI in dairy herds?

Answer 23

• AI first then bull breeding
• embryo transfer
• genomics

Question 24

What is important about AI first then bull breeding in dairy cows?

Answer 24

• allows for genetic improvement
• animals not responding to AI may respond to bull
• require big enough herd for 2 groups (>350 cows)
• increased housing & facility expense
• danger of the bull loose in a pen

Question 25

What is important about embryo transfer in dairy cows?

Answer 25

• high genetic merit cow undergoes superovulation & AI
• multiple embryos are recovered by uterine lavage 6-8 days after insemination
• implanted in recipient cow

Question 26

What is important about genomics in dairy cows?

Answer 26

• 54,000 relevant single nucleotide polymorphisms (SNPs) in bovine genome
• most commercial tests look @ most important 6,000 SNPs
• identify genetic merit in all ages

Question 27

Why is identification of pregnant (open) animals most important in pregnancy diagnosis?

Answer 27

to return them to the breeding program ASAP

Question 28

pregnancy diagnosis in dairy cows?

Answer 28

• EARLY & ACCURATE
• palpation/ultrasound at 30-32 days following insemination
• errors rare but they do happen

Question 29

what technology is used for pregnancy diagnosis in dairy cows?

Answer 29

• blood assays
• milk assays
• sensitivity & specificity is 0.98 23 days following insemination

Question 30

What happens when there is an error and pregnancy is not diagnosed?

Answer 30

open animals will be given prostaglandin which causes pregnant cows to abort

Question 31

why are herd health skills becoming more & more important in dairy med?

Answer 31

• vets have used their pregnancy diagnosis skills to get onto dairy farms
• as tech gets better & dairy producers are buying their own U/S units & learning, this is how we might get onto farms in the future