MODULE 7 Flashcards
The 21 - day pregnancy rate is the product of
estrus detection/ insemination rate
It is important to emphasize that culling rate must be considered since voluntary culling of
nonpregnant cows could artificially increase pregnancy rate and reduce calving interval
Ideally, the
annual culling rate should not be greater than 25% in dairy herds to maintain the number of milking cows
or even be able to grow or sell heifers.
It is desirable that the interval between
inseminations for more than 60% of detected estrus should be —
between 18 and 24 days.
Shorter intervals suggest inaccurate estrus detection, and longer intervals could indicate
inaccuracy and inefficiency of estrus detection, ovarian abnormalities, or early embryonic mortality.
Will also allow for detection of reproductive
abnormalities such as abnormal vaginal discharge, inadequate uterine involution,
Rectal palpation and/or ultrasonography
fertility increases with DIM and reaches a maximum at approximately 75 days
postpartum. T
In herds with low levels of milk production, the interval from calving to first service could be around 40 – 45 days, and
in herds with high levels of milk production, around 55 – 60 days.
first lactation cows should be allowed an extra 10 – 15 days in the interval from
calving to first service
Considering all these factors, we can conclude that each cow in the herd will have an ideal time
to receive first service, and the more homogeneous the herd, the easier it is to manage the time from calving to first service.
In pasture - based dairy herds with seasonal breeding programs, cows are inseminated during 10 weeks, and
cows that calved the first day of the calving period will be inseminated approximately 85 days postpartum.
At the same time, there will be cows calving during the first 40 days of the breeding season, and some of these cows will not have sufficient time for complete uterine involution and resumption of cyclicity in order to become pregnant during the breeding season.
herds may accomplish 70% insemination rate and 40% conception rate and, by
consequence, a 28% for 21 - day pregnancy rate.
Presynch - Ovsynch protocol includes two doses of prostaglandin F 2 alpha (PGF2α) 14 days
apart, and then 12 days
Ovsynch protocol (gonadotropin - releasing
hormone [GnRH] on Day 0, PGF 2α on Day 7, GnRH 48 – 56 h later, and time insemination 12 – 16 h after GnRH).
- based dairy herds is administration of an intravaginal progesterone device on Day 0 in combination with 2.5 mg of estradiol benzoate, removal of progesterone device on Day 7 with a luteolytic dose of PGF2α, 1.0 mg of estradiol benzoate on Day 8, and timed insemination 24 – 36 h later.
Since high - producing dairy cows have lower levels of circulating estrogen, they have shorter duration of estrus and less number of standing events (6 h with 6 mounts) compared
to low - producing cows (11 h with 9 standing events).
Considering 26 h from LH surge to ovulation, 6 – 12 h for sperm transport, 24 – 32 h of sperm viability, and 8 – 12 h of ovum viability, AI is recommended 12 h after the first standing event (a.m. - p.m. rule)
Treatment with either GnRH or human chorionic gonadotropin to induce accessory corpora lutea
could be considered to increase levels of progesterone during early gestation in cows with very high milk production and losing BCS.
corpora lutea
is the most common method used to breed dairy cows
Artificial insemination
Selection, management, and breeding soundness evaluation of the bulls are crucial to maintain high reproductive performance in herds with natural service
The bull to open cow ratio recommended is approximately from 1:20 to 1:30
Evaluation of the interval from calving to first service, estrus detection and conception rate,
pregnancy losses, and culling due to infertility allow estimating reproductive performance.
Evaluation of the interval from calving to first service, estrus detection and conception rate,
pregnancy losses, and culling due to infertility allow estimating reproductive performance.
