Igenity testing

[15444]

Cedar: As far as the heart attacks, I guess that would depend how heavily guys feed their cattle.

Secondly, as far as I know, the trait doesn't have anything to do with marbling, only feed consumption. So basically, your relying on the animal to consume more feed then it needs and storing the rest as fat in its tissues, hoping most of it settles in between the muscle layers as marbling.
So in the end, your breeding for an animal that fattens easier, not greater marbling grades.

[nerves]

15444 we also combine ultrasound data on our animals before we test for the leptin gene it saves alot of money on the procedure. We are looking for low backfat and AAA marbling in the meat. In our minds this tells us it is genetic not just fed in. We have had 4 year old bulls tested by ultasound and have seen them make the AAA grade with low backfat. Then they were test for leptin gene and came back with TT results. ( bulls are not supposed to grade well period).

[smcgrath76]

Thought I'd leap in here uninvited.
Leptin regulates fat deposition. It does not specifically segregate marbling vs. backfat.
A couple of things to remember about gene markers...
There are more gene markers than just leptin (Merial is actually releasing several more in the coming weeks).
There are roughly 30,000 genes controlling the bovine genome (give or take). Some of these genes have a significant impact on traits that are important to us, such as reproduction, production and product. Some genes don't.
In the example of marbling there may be 15 to 20 genes that impact the process. Leptin is one, Thyroglobulin (genestar) is another.
There are also some new markers for tenderness (Calpain/calpastatin genes).
Recently the bovine genome has been included in a major mapping effort which means we could see upwards of 1000 markers or more in the near future.
I would suggest that this is probably more confusing than the 15 or so EPD we have at the moment.
What is happening/will happen is that gene marker results will find their way into genetic evaluation to improve the accuracy of prediction. What this basically means is that we could have highly accurate EPD on a yearling bull for traits he has been marker tested for. Currently the SM breed is using calpain results (Merial is releasing this in Canada shortly) and warner-bratzler shear test values to conduct a genetic evaluation for tenderness (basically a tenderness EPD).
Where it really helps is with hard to measure traits such as feed conversion, and carcass traits. Potentially we could take a young bull with an ultrasound record and some gene test results and get a very accurate prediction of the carcass genetics he is carrying.

I agree 100% with the argument about chasing carcass, or worse yet a specific gene. Different breeds/breeding programs need to target different things but we all need to remember reproduction, production, product (probably in that order).

That's my 25 cents worth.

[ValueChainFX]

Cut and paste for you

Effects based on Leptin Genotypes
Canada grades beef primarily on the amount of marbling present within the steak. Ranchers try to breed for cattle of AAA or premium grade because they receive a payment bonus for delivering beef of such quality. Feeding is also important, of course, so that cattle are finished properly before slaughter. Marbling affects the flavor of the meat. It also adds juiciness, even when steaks are cooked well.Marbling is fat within the muscle but there are two other major fat depots: subcutaneous fat, called back fat in cattle parlance and fat which surrounds the inner organs, called kidney fat in the U.S. and body cavity fat in Canada. Marbling is the last type of fat to be laid down during the finishing period. Therefore marbled cattle typically also have high backfat levels (>10 mm) and also considerable body cavity fat.
Leptin is a hormone in the fat metabolism pathway that has been shown to affect the amount of fat deposition in beef. A DNA variant alters a critical amino acid which affects the folding of this hormone. The leaner cattle have a "C" and the more marbled cattle a "T" in the critical position. Therefore cattle are CC, CT or TT. For more details about why this mutation has "causative" effects, see another webpage.

Leptin research began some years ago in our lab. Several cattle trials involving both purebred and crossbred cattle in several feeding situations have been conducted. Although the results vary in terms of the proportion that grade AAA or higher, the trend has always been the same: TT cattle have a much higher chance of AAA, or in the U.S. system "choice".
Because this T variant is inherited, a beef producer can try to purchase bulls that are TT and then know that every calf sired by such a bull will receive a T from him. The other allele of each calf obviously comes from its dam and so depending on the genotypes of the dams in the herd, calves could be TC or TT. Nevertheless the TT bull would ensure that all have a better chance of achieving a higher grade.
All of the cattle breeds that we have studied have both CC and TT animals. The proportion of these alleles does vary among breeds. The table below shows proportion of T in breeds where we have tested a sufficient number of purebreds to estimate this.

Breed Frequency T variant Proportion TT
Angus 58% 30%
Hereford 55% 32%
Charolais 34% 10%
Simmental 32% 10%

[Cedar]

"Marbling is the last type of fat to be laid down during the finishing period. Therefore marbled cattle typically also have high backfat levels (>10 mm) and also considerable body cavity fat."

Just to throw a "monkey wrench" into all this, check out the November issue of Cattlemen, page 20, "Marbling starts early". The more I read about this stuff, the more it seems nobody really knows anything for sure! But, everybody knows everything, especially when there are possible financial gains, eh?!?! (Ooops, sorry for the cynicism, don't mean to be that way, but something seems to be making me more that way lately!.... ouch, not good!)

In any case, I have to wonder if anyone has ever followed through on these leptin tests with a taste-test. That would be interesting, to see if the beef actually measures up on the plate.

[Cedar]

All great conversation, however, has anyone ever bothered to ask the consumer? I guess that is supposed to be Cargil/Tyson's job, or maybe Safeway.
I cannot personally understand why triple A carcasses are seen as such a superior product. Other than the fact that Cargil/Tyson have created a neat little market where they pay a little bit more to the producer and get a whole lot more wholesale or retail.

The demand from our Calgary customers through our two meat shops, and numerous restaurants is more for cut size than marbling. A nice double A with a size to allow thickness in a New York Strip is far more important. Of course some of the specialty restaurants demand triple A, but once again try to convince those Chef's to make a 1/2 cut medalion out of naturally shaped piece of meat.

There is room for every breed of cattle in this industry, and we need not fear not having a Leptin gene to succeed.

Practical thinking, raising beef cattle, not Oxen, and looking at eliminating growth hormones (no hormones means earlier marbling) makes far more sense than worring about a gene marker which I agree with smcgrath76 is only the tip of research in this area.

[nerves]

I wonder all this discussion on testing how many people out there use ultrasound on thier cattle? Seems to me that there is alot of purebred cattle breeders use this site. Does anyone ultrasound thier replacement hiefers and yearling hiefers both? Some people do yearling bulls just to have more information for thier bull customers. Seems to me that we have all this access to technolgy it may explain why that favorite old cow that never misses is your favorite. EPDs are one thing that I have never made work very well some of the best EPD cows produce scrubs while some of the moderate EPD cows produce at the top end. They don"t say that little 1300 pound cow produced a 750 pound calf while that 1800 pound cow did the same. Yet go to a bull sale and people buy and choose on EPD traits. We use ultrasound and have had some interesting results on our cow familys. The leptin test help prove to me what was going on so in my mind I can feel more confident in what we are raising. people talk about branded beef products is that not in essence what these technolgys lead up to.

[nerves]

That should read replacement hiefers and yearling bulls both.