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Genetics and A2 milk: what you need to know

As consumers continuously look for new ways to eat healthy, A2 milk is a trend that emerges on their radar. A2 milk has been a common brand in Australia and New Zealand for several years. It only made its entry to the US marketplace in 2015.

It’s a new concept for many people, so before you join in on the A2 hype, here are a few answers to questions you may have.

What is A2 milk?

A2 milk is produced only from cows having two copies of the A2 gene for beta casein.

To explain further, cows’ milk is about 87 percent water. The remaining 13 percent is a combination of lactose, fat, protein, and minerals that make up the solids in milk.

If we focus on the protein within milk, the major component of that protein is called casein. About 30% of the casein within milk is called beta casein. The two most common variants of the beta casein gene are A1 and A2, so any given bovine will be either A1A1, A1A2 or A2A2 for beta casein.

In the United States nearly 100% of the milk contains a combination of both A1 and A2 beta casein.

What is the benefit of A2 milk?

Researchers believe that A2 is the more natural variant of beta casein, and A1 was the result of a natural genetic mutation that occurred when cattle were first domesticated. With that in mind, studies have been done to see if people digest or react to true A2 milk differently than regular milk.

Some of those studies have found that people drinking milk exclusively from cows producing A2 milk were less susceptible to bloating and indigestion – leading some to conclude that A2 milk is a healthier option than regular milk. The exact science behind the difference in A1 versus A2 milk is complicated, but research has shown that digestive enzymes interact with A1 and A2 beta-casein proteins in different ways. Because of that, A1 and A2 milk are processed differently within the body.

Can you breed for A2 milk?

Yes, in fact the only way to have cows that produce A2 milk is to breed for it.

True A2 milk can only be produced from cattle possessing two copies of the A2 gene in their DNA. Each animal receives one copy of the gene from its sire and one copy from its dam. So for a chance to get an animal with the A2A2 makeup, you must breed a bull with at least one copy of the A2 allele to a cow with at least one copy of the A2 allele.

To ensure with 100% certainty that a female will produce A2 milk once she freshens, she must be the result of mating a cow with two copies of the A2 gene to a sire that also has two copies of the A2 gene.

Does A2 milk only come from colored breeds of dairy cattle?

Traditionally, colored breeds of dairy cattle, such as Jerseys and Guernseys have been the poster children for the A2 gene. Those two breeds still have a higher proportion of A2A2 animals. However, some of the popular Holstein sires of recent years have increased the prevalence of A2A2 sires in the black and white breed as well.

You may be surprised that about 40% of the Holstein sires in active AI lineups, including numerous household names, have two copies of the A2 gene. In addition, over 80% of Holstein sires have at least one copy of the A2 gene.

Is A2 milk the answer for people with lactose intolerance?

A2 milk contains the same amount of lactose as non-A2 milk. So in clinically-diagnosed cases of lactose intolerance, A2 milk will not provide the benefits that lactose-free milk would offer.

Since most cases of lactose intolerance are self-diagnosed, some doctors believe the cause of indigestion in those cases is actually linked to an A1 aversion rather than lactose intolerance. In those cases, drinking A2 milk may help prevent the side-effects otherwise experienced from drinking regular milk.

Should you select for A2 in your breeding program?

With this new information at hand, it may seem compelling to produce only true A2 milk. Many A2A2 sires are available, but you still have an opportunity cost by selecting only A2A2 sires.

When A2A2 is a limiting factor in your genetic selection, you’ll eliminate about half of all bulls available. That means you will likely miss out on pounds of milk, extra health and improved fertility traits.

Regardless of your selection decision around A2 sires, make sure it aligns with the customized genetic plan you put in place on your farm so you can maximize profitability and genetic progress in the direction of your goals.
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Alta Advantage Showcase Tour 2017 – by the numbers

Guests from around the world joined together to share management strategies and insight during the 18th Alta Advantage Showcase Tour held in Michigan June 21-23, 2017.

On-farm stations were set up to provide insight on all areas of dairy herd management. Some of the topics covered included:

  • Reproduction
  • milk quality and parlor management
  • transition cow management
  • feed and nutrition
  • colostrum management and calf raising
  • heifer raising
  • labor organization
  • genetic planning
  • dairy technology
  • Performance Pens featuring some of the newest Alta sires to have milking daughters
  • and more!
Here’s a look at the 2017 Alta Advantage Showcase Tour, by the numbers:
360guests
26countries represented
18Alta Advantage Showcase Tours now complete
35on-farm stations that guests experienced throughout the tour
6charter buses required to transport guests
19,000cows milked among all pre-tour and Showcase host farms
9outstanding host dairies that graciously opened their farm for our guests to visit
Pre-tour host: Rich-Ro South Dairy | St. Johns, MI
Pre-tour host: Berlyn Acres | Fowler, MI
Walnutdale Farms | Wayland, MI
Prairie View Dairy | Delton, MI
Schaendorf Farms | Allegan, MI
Tubergen Dairy | Ionia, MI
Simon Farms | Westphalia, MI
Steenblik Dairy | Pewamo, MI
Double Eagle Dairy | Middleton, MI

These numbers sum up to ONE tremendous tour!

Guests enjoyed the friendly camaraderie and the ability to learn from both our host farm owners and others on the tour. These experiences left everyone with a lasting impression of Alta’s progressive approach to create value, build trust and deliver results to clients around the world.

 

Click HERE to view the collection of photos and videos from the tour!

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Genetic thresholds versus genetic plans

“Give me a bull that’s over 1,000 pounds of milk and positive for DPR.”

Does this sound like you describing sire selection criteria for your dairy? If so, you are among the many other dairy producers who are leaving extra pounds of milk and additional pregnancies on the table.

The traditional threshold method can be a risky approach to selecting bulls when you are aiming to maximize genetic progress.  Setting a minimum level for any given trait and completely eliminating sires that fall short of those minimums means you could be missing out on a number of bulls that could actually help propel your genetic level to new heights.

A genetic threshold versus a genetic plan

Take for example, the old-fashioned threshold method for choosing the bulls you pick. If you direct your AI rep to drop off five bulls that are over 1000 pounds of milk and over 0.0 for DPR, he may leave you with a group of sires like those in Table 1 below.

Since your AI rep did his/her job and followed your wishes, you can see the averages for milk and DPR are pretty good – even above your set thresholds. But is that really the best group of bulls you can get?

If you reset your thought process for sire selection, you can choose to set a genetic plan that aligns with your goals. The previously mentioned thresholds would equate to a genetic plan with about 50% emphasis on production traits, 50% emphasis on health traits, and 0% emphasis on conformation or type traits.

By using this 50-50-0 genetic plan for selecting your bulls rather than limiting yourself by thresholds, you could end up with a genetic package like the five bulls shown in Table 2.

Table 1. SirePTA MilkDPR
Al11810.6
Bob11430.1
Carl11400.6
Doug10270.1
Ed10230.1
Average11030.3
Table 2. SirePTA MilkDPR
George2207-0.1
Henry2171-0.1
Ivan1986-0.1
Jack9725.2
Kurt9004.6
Average16471.9

Not even one of the five bulls selected based on the genetic plan fit both the criteria of being over 1,000 pounds of milk and being positive for DPR, but you can see they just barely miss the mark on one trait or the other.

Looking at Jack, you can notice that by sacrificing a few pounds of milk below your 1000 pound threshold, you gain an extra 5.2 points for DPR. And even though George and Henry both fall 0.1 short on their DPR values, they provide well over double the pounds of milk that your thresholds would have dictated.

So if you look at the average genetics of this group, they are above and beyond what you achieve with the group of sires that meets both criteria. In this case, by setting a genetic plan to select your bulls, you will gain almost 550 additional pounds of milk and see nearly a two percent higher pregnancy rate than by stating clear-cut threshold limits.

The tables above illustrate that setting a genetic plan to put emphasis on the traits that matter to you can boost your genetic levels well beyond what you achieve with restrictive thresholds.

Genetic plans – not just for sire selection

When setting a genetic plan, the most common focus is on sire selection. However, with genomic testing and various reproductive technologies readily available, many dairy farmers also rank females to determine which cows or heifers should receive sexed semen versus convention semen, or to know which animals are the best candidates to flush, versus which should serve as recipients.

If you rank your heifers and cows, it is important to remember to use the same genetic plan on the female side as you use for selecting your sires. Otherwise you will lose the full effect of the genetic progress you could make with the sires you select.

If you select your sires based on a genetic plan of 50% production, 50% health and 0% type, but then you rank females by TPI, NM$, or a completely different index your overall genetic progress toward your goals will suffer. A mixed approach will slow your progress and lessen your results.

In a nutshell

Maximize genetic progress in your herd by setting your own customized genetic plan to emphasize the traits that matter to you, rather than limiting your options with strict trait thresholds. To drive your genetic progress even further, make sure the genetic plan you put in place for sire selection matches the one you also use to rank your females.

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