Week 3 and 4: Move Over Dolly Parton!

I suddenly realized last Tuesday that my chickens turned 5 weeks old! So, I've slacked a little on my blogging process - no biggie. But, I'll tell you who hasn't been slacking these past couple of weeks - my chickens. They are huge - literally! I would say that by the end of last week they were at least three pounds and counting. Needless to say they've grown a tremendous amount in just a short period of time, which I attribute to two things: feed and genetics, with the later being the focus of my blog this week.

Compared to the broiler of yesteryear that our great grandparents raised in their backyards, the modern chickens in my own yard are much more efficient. Within today’s poultry industry, growers have the ability to produce birds that weigh about 3 pounds more than those that were produced 30 years ago, and they’re able to do that about one week sooner than they could have back then.

Now, 3 pounds may not sound like a lot to you, so let’s put that into perspective. In the 1930s, broilers were harvested at about 100 days of age, weighing only about 2 ½ pounds. In the 1950s, broilers were harvested after about 75 days of age, weighing only about 3 pounds. Today, we have the ability to harvest broilers that weigh over 6 ½ pounds and they’re only about 6 weeks old! Although there are many factors that can be attributed to this marked increase in efficiency, genetic selection is the primary reason.

In just about every basic biology course offered across the country, students learn about a guy named Gregor Mendel. His work on pea breeding in the 1800s gave rise to what we now refer to as Mendelian genetics. So, you may be asking, “What does pea breeding have to do with the price of tea in China?” or better yet, the ability of the modern chicken to grow so big so fast? Well, everything! You see, over the course of 50 plus years, broiler breeders have used the principles behind Mendelian genetics to breed and select for faster growing, more efficient birds. As a result, the chicken you buy at the grocery store today is both cheaper and meatier than the chicken your mom bought back in, say, 1980.

When producers design their breeding programs around the principles of Mendelian genetics, what they are really doing is selecting for only one or two traits. When breeders place their selection emphasis on just a few rather than a dozen traits, genetic progress can be made very rapidly. Just look at breast size as an example. Since consumers today primarily consume breast meat when they eat chicken, breast size has been a focal point for genetic improvement in recent years. In 1980, breast weight accounted for about 10% of the bird’s total harvested weight. Today, in 2010, breast weight accounts for more than 25% of the total carcass! Just check out the breasts on some of my gals to see what I mean – can someone say move over Dolly Parton???

Seriously though, because broiler breeders narrow in on just a few economically significant traits, like breast size, our poultry industry has made tremendous strides in making our chickens more efficient. As a consumer, what this means is that you can guarantee that whenever you walk into a grocery store there will be lots of chicken available for purchase, and that it will almost always be the cheapest source of protein available in the retail meat case.

But, as beneficial as Mendelian genetics can be, I’d be amiss to not mention that there are some pitfalls. You see when you chase after just one or two traits and place your selection emphasis on those traits alone, you can bring about some unintentional consequences and reduce performance in other traits. So what are those consequences? Well, I’m sure you’ve probably heard about them if you’ve ever listened to a PETA representative or watched the documentary Food Inc. Although the broilers of today are extremely growthy, if you spend any time at all around them during the grow-out period, you’ll quickly realize that they are balancing right on the edge of their physiological limits. Since these broilers have been selected to reach their full genetic potential for growth and muscle development, and not for other traits like feather, organ or structural development, their bodies sometimes lack the ability to keep up with their rapid growth. As birds reach the end of their grow-out period, they spend less time walking around since their feet and legs can’t hold them up for great lengths of time. Additionally, you’ll notice that they don’t really obtain a full set of feathers – both because feather development takes longer than it does to grow-out a bird and because they spend so much time lying down. In worst case scenarios, you’ll actually lose birds either because their organs (especially they heart) can’t keep up with their rapid growth or because they become completely immobile. As bad as this all sounds, it is a fact of life – one that must be taken into consideration when you contemplate how our industry has to keep up with the current and future demands for protein, like chicken.

As a result, broiler producers employ management strategies that slow down growth and reduce the negative impact Mendelian genetics have on broiler health and welfare. Producers can slow growth down primarily by restricting feed intake or by adjusting the dietary nutrient density of the broiler’s diet (mostly through decreased protein intake). One of the first things the Simmons told us when we began was to pull the feed out around dusk. They told us that they would perform better if they were restricted a bit in their feed intake, which makes perfect sense knowing now what I do about broiler selection and growth. As a whole, the industry would be at a benefit to do the same, which is why growers have begun to take similar measures. Remember, food animal producers know the value of keeping their animals healthy and happy – both from an economic standpoint as well as from a consumer perception standpoint.