Igenity testing

[grassfarmer]

This topic was raised in the Spring but I wonder if anyone has any comments on the tests or where they see their role in purebred cattle breeding. I'm intrigued by the concept but can't get my head around what it's use is.
As I see it one drug corporation (Merial) has patented this test on the assumption that purebred breeders will use it, breed animals with better carcase traits as a result and hope to improve their bull sale prices as a result. This assumes that commercial cow/calf guys will seek out and spend more on bulls with these traits. It looks like technological progress - if it pans out it could be the biggest breakthrough in cattle breeding since Bakewell. But..... what effect will it have on purebred herds if they suddenly select intensively for carcase traits - bearing in mind that the females still have a job to do rearing calves? Will there really be any benefit to cow/calf producers if they don't retain ownership of their cattle through to fat? I'm reminded of the 10:2:1 rule of profitable cow/calf production that I read somewhere which states:
" Fertility traits are 10 times more important than carcase traits and 5 times more important than growth traits."
Any thought on who stands to benefit from this technology?

[jensend]

Any thought on who stands to benefit from this technology?

maybe merial

[15444]

It's a tool and nothing else. Some of the Hereford people have tried to sell their bulls to me with their sole arguement floating around how the animal's Igenity results came back.

Personally, if I had money to burn, I would test every cow and bull in the herd once and then use the info I get back as a tool in culling decisions. Remember, it's a gene thing, so if you used it you could ideally take your herd from producing 50% leptin-gene calves to 80-90% leptin-gene calves in a short time. Of course a few leptin negative cows would stay in the herd or at least I hope nobody would be stupid enough to get rid of good, healthy, young-looking herd builders just because of the results. Only get rid of the cows that just need that little extra to devalue their contribution to the herd.

Don't question the Hereford people about it at the cattle shows though, please, or the next 3 years will circle around Herefords becoming the breed with the highest percentage of leptin positive cattle in Canada....while the truly important traits take a backseat.

[cakadu]

15444, could you please explain a little about what this leptin trait is please?

Thanks.

[15444]

Took bits and pieces from a site independent of Merial as I don't trust Merial's propaganda.

Leptin is a protein hormone with effects in regulating body weight, metabolism and reproductive functions.

As adipocytes (fat cells) increase in size due to accumulation of triglycerides (fats), they synthesize more and more leptin.

Leptin's effects on body weight are mediated through effects on hypothalamic centers that control feeding behavior and hunger, body temperature and energy expenditure.

<u>Interestingly grassfarmer:</u> Leptin concentrations are low in people and animals with low body fat, and <b>leptin appears to be a significant regulator of reproductive function.</b> These effects are probably due in part to the ability of leptin to enhance secretion of gonadotropin-releasing hormone, and thus luteinizing and follicle-stimulating hormones from the anterior pituitary.

This PDF file from Merial probably helps to give you a visual of how leptin works:
http://ca.igenity.com/pdfs/Intro_Leptin3004_Eng_04.pdf

Basically, the prescence of the <b>tt</b> Leptin gene allows the animal to keep eating without any signals of being 'full' , reaching the brain. So the animal keeps on eating and produces more leptin through the deposition of fat into fat cells. So the animal eats increasingly more and more feed and obtains more fat.

The <b>cc</b> Leptin gene does the opposite, meaning the signals of being 'full' reach the animal's brain and then it quits eating until it is hungry again. This means that the animal doesn't consume more feed then neccessary and doesn't gain a large amount of fat cover.

[15444]

I forgot to add that experiments done with mice found that the mice that were homozygous for leptin were obese at a young age, but also reached sexual maturity much earlier then mice that were heterozygous for leptin.

So, upon learning this interesting little tidbit on fertility, leptin might prove to be a bit more important then I originally thought, although it still is only a tool in cattle selection in my mind.

[Cedar]

Grassfarmer:

"what effect will it have on purebred herds if they suddenly select intensively for carcase traits"

Guess that's the unknown part, we get to be the guinea pigs again! Assuming this test proves to be accurate, I could see the end result being that carcass traits become the new "have to have it" fad, just as super growth rates have been in the past. Where did that get us in the end? It never seems to fail that when we select too strongly for any one (or even two) traits, nature dictates that we must give up something in the other traits. Straying too far from the well balanced animal never pays....at least not for the primary producer. But it seems the rest of the industry "links" always have to demand certain characteristics in the animals, and they always get what they want when they decide to pay more for it. Then, once everyone has switched over to supply what they demand, of course supply and demand kicks in and prices...um...adjust!

"Any thought on who stands to benefit from this technology?"

Ultimately....dare I say it??? ... the ....packers!!!! And, of course, once again, it's us who has to pay for it!

Imho, long term survival (and success) depends on keeping a close eye on your bottom line (the net...not the gross), and really watching the traits showing up in various animals and culling accordingly. For example, the highest weaning or yearling weight heifer might not necessarily wind up to be your best cow...in fact, she might be your worst. Sometimes, if you really watch your genetics, you can find those "little wonders" who aren't too big themselves, but will produce a great calf every time....lower feed bill and higher profits....wow, what a combo!

[Cedar]

15444:

Interesting, however I have to wonder....well, we know what obesity does to people, especially at a young age...so, what will the end result of selection for this trait in cattle be? Will our bovines be dropping dead of heart attacks by age 5? Hmmm...especially these days, seems to me longevity is a lot more important than that!

[Cedar]

15444:

So, does this leptin gene have anything to do with the natural ability to produce marbling in the beef (if there is such a thing) or does it simply indicate an animal that doesn't know how to turn off the "hunger button"???? Does eating more actually produce better marbling??? I think I'm confused!

[nerves]

Grassfarmer would add that certain breeds produce more fat than others and they also produce less meat. Then there are breeds that produce red meat but will have less fat. Now if you could find an exotic animal that can produce the meat but can also add marbling then cross them with a british breed type then you should have excellnt carcass animal. You can have animals that are fertile, have feet that do not ever crack or need to be trimmed, are heavy milkers, easy keepers and longevity. We are lucky enough to have one in our herd she is a year Z and is leptin TT the best cow on the place and she is Charolais. We have every daughter she has ever raised and a local rancher buys every bull she has ever raised. We finaly kept a son for ourselves, and we now use three leptin TT bulls of differnt blood lines in our herd. We believe there is merit in it as we finish and sell our yearlings direct to the customer. We also notice less trim on these animals when finished as compared to a staight british bred animal when finished. The butcher charges by the hanging weight so less trim and more meat with marbling is ideal for us. In our opinion it is the future of the livestock industry in North America.

[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.