Synchronization techniques (using hormones to bring animals into heat at specific times) were first in development back in the 1960s, when drug firms like GD Searle [owner of Curtiss Breeding Service] developed “Synchro Mate B” vaginal inserts for sheep and ear implants for beef cattle. “Lutalyse” as developed by Tuco/Upjohn [now part of Pfizer] in injectable form, made it all easier. Lut response was later found to be enhanced by a simultaneous use of “Gnrh” [Gonadatropic release hormone], and most OvSynch protocols today alternate Gnrh and Lutalyse shots to produce stronger heats.
No matter what you hear, however, the following is observationally true: conception rates are much higher when breeding still occurs based upon observed heat signs. In other words, without estrus detection, the best you typically get is 50% conception.
I bring this up, because we hear of instances in which owners of smaller numbers of cows, especially if dependent on an external inseminator, get told by veterinary practitioners that OvSynch is “easy” – and the total detail (what has to happen when, and what results to expect) is not always covered. This is the result of widespread use of OvSynch in Michigan dairy herds (MSU’s Dr Pursley is a leading researcher in synchronized reproduction) where it has proven to maintain reproduction at a utility level, in spite of genetic selection and feed management issues that tend to delay fertility response in many dairy cows.
Veterinarians do not always remember that the cow calf operator, like the grass-based organic dairyman, prefers a tight seasonal calving window—not calvings strung out all year long. AI efficacy in beef has to result in calves with optimal birthdates (to fit marketing windows) and calving dates (to match peak forage production) or the profitability of weight gain can be jeopardized.
Most beef breeds are genetically selected for natural fertility response
With the possible exception of the extreme growth rate and show type bloodlines, where other factors dominate genetic selection, both the major commercial feedlot breeds and the grass-based heritage beef breeds include “fertility response” within maternal trait selection, as well as range sire behavioral trait selection. For the grass-based cow-calf systems, where vegetative grass and sunlight are the nutrient energy sources, breed selection for high rumen feed efficiency and easy conditioning (natural marbling) has assisted in maintaining natural reproductive efficiency that was based in genetic selection.
The reason OvSynch got started in beef cattle was the demand for AI within range-managed cow herds. Exotic genetics (for which service bulls were unavailable) could be introduced easier through AI. But the range cow is not housed in drylots or used to being corral confined in the grazing season (when the AI needs to take place). OvSynch presented the option of corralling the cattle, implanting or injecting them, turn them back out with the calves and the grass; gather them up again a week or two later, run them through an AI chute, breed them, and send them back to the grass. Thus AI became a practical option for the range cattleman, who would get 50% AI calves and 50% cleanup bull calves, enough to provide his next season genetic needs (ie, save his bulls from the AI fraction).
Ov Synch effects on genetic fertility traits
Used in the above way, OvSynch was not a substitute for natural fertility—it was a therapeutic tool to schedule existing fertility convenient to AI use. The more fertile cows conceived to AI, and the bull calves saved from those matings helped maintain fertility in their work as cleanup bulls on cows that did not conceive via AI. Thus the possible longer term genetic consequences were not of great concern.
Is your heat detection up to the job of doing natural heat AI?
This is the first and most important question to ask, prior to entering into the expense of OvSynch. Given we see the highest conception rates from insemination timed from observed natural heats, and the semen many of you are using is rare and expensive, this is a valid question.
The average USA cow calf herd is only 18 cows in size. Even in Texas, the average is only 32! Most of you are breeding from ten to seventy cows per year (a “one man” cow calf operation) and want all the calves born in one season (the rest of you have a second calving season). So your cows are in dry lots or in pasture paddocks of twenty acres or less that lead to your farm buildings.
With a seasonal breeding window, you have perhaps six weeks in which daily heat detection, done three times daily if possible, can optimize your pregnancy rate. Here is a very successful routine: (1) Focus heat detection around the cooler times in the day; (2) Use tighter grazing rotation for the AI window, so the cows are getting fresh grass (stimulant) and you have a smaller paddock to walk through to see them in heat; (3) Breed only those cows you see in heat for 21-24 days. (4) On day 25 synchronize all cows that did not show heat for natural AI; (5) Breed those cows who show heats from a 21-day full synchronization; (6) Turn in cleanup bulls based in numbers on half the synched cows plus all cows not bred on either a natural or synchronized heat.
This approach guarantees that your first calves in the season are from AI selection and a natural service. If you focus on those female calves for replacements you will be selecting for positive natural fertility response as well, but additional heifers can still draw from the synchro calves that come next, as still born within the optimal birthdate window. Late calves by your cleanup bulls may at that point prove to be surplus to your needs, and can be marketed with your steer calves for added income.
Using what Darwin learned to evaluate OvSynch’s impact on cow fertility
The commercial dairy industry is facing higher repro costs and shorter cow herdlife that some feel can be traced back to indiscriminate use of induced reproduction technologies.
80% of the sires in dairy AI result from superovulation [induced fertility] embryo transfer, and over 50% of their parents (sire and dam) are the same. Their progeny are then bred under continuous OvSynch protocols, in which open cows are given continuous injections and timed bred until confirmed pregnant, with many herds now averaging four AI services per pregnancy. This has meant the annual calving interval is nearly impossible to maintain, and numbers of replacement heifers are often short of the herd needs. Thus sexed semen (preferring females) is now selling widely in commercial dairy settings.
The per pregnancy cost of continuous OvSynch reproduction is $200 per dairy cow in many herds. In the beef industry, this would be impractical-- $200 per calf might be our total profit margin many years.
Basically, Darwin’s least controversial research indicates that genes we do not use get lost. “Survival of the fittest” in the natural wild environment is pretty much about being able to outrun predators while seeking out your next source of food. “Survival of the fittest” in domesticated animal production, is more about the gene response to all the ways we interact with (“manage”) animals, and how they adapt to a more limited diet (dictated by the crops we choose to grow and the supplements we buy). Estrus response can change if we no longer value natural fertility and preserve the traits that represent the genes supporting optimal natural fertility—whether the actual insemination is by AI or by a service bull.
HEAT DETECTION AIDS What options work best?
Don’t overlook the eight month old Jersey bull!! He loves to watch for heats—he just is not quite tall enough to do anything about it. Breed the cows he follows around each day. You can always eat him once he gets too big to miss (Jersey beef usually ranks pretty high in blind taste tests).
Then you have the KAMAR heat mount detector—glue over the pelvis, it turns full red after mounting when the cow stands to be ridden. For short haired animals, the Estrus Detect strip is self-adhesive and works similarly—its color is rubbed off by mounting activity. Replace after insemination.
You can take a freemartin heifer, give her hormone shots and a chin ball marker, and she will act as a “gomer” (or you can do the gomer surgery on a bull, it just costs more)—cows in heat will have paint on their backs. Again, you can always eat her too after the season is over.
With any heat detection aid, the trick is to have visible ID on animals, a check list (on which you write down heats observed and breedings made)—and refer to that list each time you look at the animals, so you know what you are seeing has occurred since the last time you checked.
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