Dairy 4

Question 1

Importance of reproduction

Answer 1

-calving required for lactation. Also for replacement heifers, breeding bulls
-get cows pregnant quicker= genetic improvement through shorter generation intervals
-consistent calving distribution for constant milk supply, and more animals close to peak

Question 2

Ideal cow stats

Answer 2

-1 calf/year
-negative energy balance: days 0-60 of lactation so never try to get them pregnant then
-305 days left
-280 day gestation

**25 days left to get them pregnant

Question 3

Holstein pregnancy rates

Answer 3

-Much lower than beef cattle
-Preg rate is incorporated into genetic index
-has increased over the last 20years

Question 4

Assessing readiness for breeding

Answer 4

-post partum exams
*often not worth it in terms of cost-benefit

Question 5

When to breed cows?

Answer 5

-Heat detection + technology

-Timed artificial insemination (AI) protocols
*manage CL function, follicle development, ovulation

Then can breed cow by AI or bull breeding

Question 6

Ideal timing of breeding

Answer 6

-breeding should take place 12 hrs following observed standing estrus
*aim for more than 50% heat detection rate

-should spend 2-4hrs a day detecting heat but doesnt really happen

Question 7

Aids for heat detection

Answer 7

-pedometers
-k-mar detectors
-teaser bulls

Question 8

Why do some dairy herds use estrus synchronization?

Answer 8

-modern dairy cows are bad at showing estrus behaviour
-leads to timed AI and estrus synchronization

*This is all due to increased milk production. 21 dairy cycle was common years ago, but now estrus cycle varies

Question 9

Principles of timed AI protocols

Answer 9

-control CL function
-control follicle development
-control ovulation

Question 10

What rates are used to determine effectiveness of timed AI?

Answer 10

1. Insemination rate: % cows inseminated of those eligible to be inseminated during single estrus cycle
2. conception rate: %inseminated cows that become pregnant during a single estrus cycle
3. Pregnancy rate: % of all cows that become pregnant during a single estrus cycle

Question 11

Benchmark rates for timed AI

Answer 11

Insemination rate= 44%
Conception rate= 42%
Pregnancy rate= 17%

Question 12

Insemination risk is not equal to heat detection rate

Answer 12

Cow eligible for insemination= insemination= preg check

BUT if a cow is seen in standing heat 21 days after insemination, producer will rebreed
So if cow gets pregnant= 2 inseminations, 1 pregnancy, insemination risk=50% but heat detection rate= 100%

Question 13

Bull breeding

Answer 13

-no need for estrus detection
-no breeding date available
-disease spread
-need increased housing and facility= expensive
-risk to humans and cows
-may need separate bull pens when AI is not permitted

Question 14

Artificial insemination

Answer 14

-max genetic improvement potential
-need to detect estrus
-skilled staff needed
-genetic concentration in a herd meaning that the effective population size ~50, very interbred

-sexed semen >90% accuracy
-animals with most genetic merit can produce heifers

Question 15

Strategy: AI first then bull breeding

Answer 15

-allows for genetic improvement
-animals not responding to AI may respond to bull

Question 16

Issues with doing AI and then bull breeding

Answer 16

-need a big enough herd for 2 groups (more than 350 cows)
-increased housing and facility expense
-danger of the bull loose in pen

Question 17

Embryo transfer

Answer 17

-high genetic merit cow undergoes superovulation and AI

-multiple embryos recovered by uterine lavage 6-8days after insemination

-implanted in recipient cows

Question 18

Genomics of bovine

Answer 18

-54,000 relevant single nucleotide polymorphisms in bovine genome

-most commercial tests look at most important 6000 single nucleotide polymorphisms

-ID genetic merit in all ages

Question 19

Pregnancy diagnosis

Answer 19

-ID open animals so they can return to breeding program

*errors are rare but they do happen

Question 20

When to preg check?

Answer 20

30-32 days following insemination
*using palpation and ultrasound

Question 21

Technology used for pregnancy diagnosis

Answer 21

-blood assays
-milk assays

*can test at 23 days following insemination

Question 22

What do you do when cows open and an error is made?

Answer 22

Think non pregnant, so give prostaglandin
-will cause fetus to come out end and farmer will be mad

Question 23

Dairy producers give own medication

Answer 23

-dairy producers buy their own ultrasound machines
-medication can be given by owner in vet act