Farminlund":1t3ul0ul said:
The sperm requires ~5 hrs to be able to fertilize the egg (looked for the article but could not find it). The sperm lives for ~24 hrs in the cow. The egg once released, lives to be fertilized for 8-12 hrs. The egg is release ~ 28 hrs after the onset of standing heat. Thus breeding 9-18 hrs post standing heat gives a high potential of sucess.
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Farminlund,
Here's the article I was referring to;
Heat Detection vs. Ovulation Prediction
by Mel DeJarnette,
Select Sires Reproduction Specialist
I recently had the opportunity to spend a week riding with several Select Sires technicians across central Wisconsin. It was an eye-opening experience for me in more ways than one. It was a pleasure to spend some time with these dedicated employees and to see first hand some of the problems they deal with on a day-to-day basis. One area that surprised (and troubled) me was the number of cows being bred based on some secondary sign of heat followed by the farmer telling the technician to "Palpate her and see what you think."
When a technician or veterinarian palpates an animal for signs of estrus, he is basically feeling for tone in the uterus in response to rising estrogen levels in the circulatory system. Any mucous that can be discharged and ovarian status (presence of follicle and/or CL) are additional clues to estrous diagnosis. However, these symptoms (along with a red swollen vulva, mounting cows not in heat, excessive bellowing, nervous or restless behavior, and many others) are all secondary signs of estrus and are less reliable as predictors for proper timing of insemination compared to the primary sign "standing to be mounted."
OVULATION PREDICTION PROGRAMS
Perhaps the wrong term was coined when breeding programs for cattle were first developed many years ago. Instead of calling them "Heat Detection Programs," we should have called them "Ovulation Prediction Programs." In order to achieve maximum fertilization rates, cows must be inseminated at such a time that ovulation (release of the egg from the ovary) occurs when viable sperm cells are present in the oviduct. Thus, in order to properly time inseminations, we must have a reasonably accurate prediction of when ovulation will occur.
The term "heat detection" implies that a herdsman must watch for signs of estrus. Signs of estrus, however, are of limited value if the herdsman does not consciously attempt to predict time of ovulation and then inseminate animals based on that prediction.
Figure 1 below displays a time scale scenario of the physiological events occurring proximal to estrus and ovulation in the cow. As estrogen levels rise in the circulatory system, animals will begin to show many of the secondary signs of estrus. Eventually estrogen reaches a threshold level and triggers two events simultaneously; 1) standing heat and 2) ovulation.
Figure 1. Time scale synopsis of physiological events occuring proximal to estrus, ovulation and proper insemination timing.
Standing heat varies in length and intensity from cow to cow but on the average last about 10-12 hours.
Although ovulation is triggered by the same hormonal mechanism that causes the cow to enter standing heat, it does not actually occur for another 25-30 hours.
Secondary signs of estrus, including uterine tone, are stimulated by small increases in estrogen levels. In some cases, secondary signs may often be observed as much as 48 hours prior to standing heat. However, in others, they may occur only a few hours prior to standing heat. Absence of secondary signs of estrus are a good indication that animals should not be bred. However, since they may occur two days before, the day of and a day or two after standing heat, presence of secondary signs (again including uterine tone) are indicators that an animal is under the influence of estrogen but does not yield any reliable prediction of ovulation.
Accurate timing of insemination is only accomplished by knowing initial time of "standing heat." Inseminating animals 10-12 hours after first observing standing heat will allow the viable life span of spermatozoa (20-24 hours) to overlap with ovulation and the viable life to the egg (6-8 hours). Inseminating cows based on secondary signs of heat will often result in many animals being inseminated too early and the sperm life is depleted prior to ovulation.
I realize that in many instances animals must be bred strictly on secondary signs of estrus. This is particularly true during the winter months in many northern states when cows are kept in stanchions or tie stalls because there is a "Nor'Easter" bearing down on the farm. However, whenever possible and practical, cows should be allowed every opportunity to display mounting behavior.
Breeding cows based on secondary signs, including "palpate her and see what you think," is the exception and not the rule in herds with high levels of reproductive efficiency."
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PS. I can't get the graphs/stats to transfer...don't know why. The stats/graphs can be seen at;
http://www.selectsires.com/heatdet.html
