Wednesday, April 30, 2014

Green Pastures, Genetics, and Environment

Yesterday my cows got turned out on grass. Despite it being a cloudy day, I think they were pretty happy!

Let me tell you the story of these three cows. Last August my mother brought three of her two-year-old cows to Missouri. In New Mexico they have been struggling with drought, so the cows would benefit from some extra feed. And they did. In the first three months their body condition score increased by one (almost two) units. But, then my pastures ran out of grass, so I started feeding hay, and I started to observe big differences between the cows. I started to notice their feet were sore, and I soon realized I was dealing with fescue toxicosis. Two of the three responded rapidly to 20% protein cube supplementation, but the third one never did. So, I have made a selection decision, and this fall after she weans her calf, the fescue sensitive cow will be culled from my herd.

In a previous post, one commenter mentioned gene-by-environment interactions. In my case, my cow likely has a genetic predisposition to fescue toxicosis sensitivity and then she was placed in an environment containing fescue with a high level of endophytes. Thus, an example where genes and environment interact. This highlights that EPDs are one of many tools that we use when making selection decisions. EPDs only account for additive genetics, and do not consider gene-by-gene or gene-by-environment interactions (additive genetic variation is inherited in a predictable manner, thus the reason we use additive genetic variation to predict EPDs).  In the beef industry we still lack genetic evaluations for many economically important traits such as structure and locomotion, feed efficiency, disease susceptibility, and fertility. Currently, we still have to rely on phenotypic selection (using our eyes) to make selection decisions for these traits.

Graybull quoted Johann Zietsman who stated EPDs for traits like fertility with strong gene-by-environment could not be calculated. Zietsman broke fertility into hormonal balance and body condition. He left out an important player, embryonic lethal variants. These are variants which "break" genes, causing the protein coded by the gene not to function properly. When an embryo inherits two copies of an embryonic lethal variant, the fetus is aborted sometime during the pregnancy, perhaps as early as the first 45 days. In the next four years we will produce a fertility EPD, which will be incorporated into economic selection indexes, that will account for the embryonic lethal load an animal carries. We will deliver a genomic EPD which directly tests the number of variants (alleles) which decrease fertility, and this test will be directly comparable across environments.

Furthermore, 10% of the variation in fertility is due to additive genetics, which excludes gene-by-environment effects. Keep in mind that in EPD calculations, animals are compared to their contemporary groups which are all managed in the same environment. By selecting for fertility EPDs, such as heifer pregnancy, we can improve the 10% of fertility that is due to genetic merit (in other words additive genetics estimated by EPDs). To further improve fertility, we need to take a systematic approach and use best practices to properly manage the fertility in our herds and use phenotypic selection to identify any gene-by-environment interactions.

Friday, April 11, 2014

Technology Lag: We Don't Have Time

From Shauna Hermel's Twitter feed, I came across this article about David Buchanan's talk at the 2013 BIF Research Symposium and Convention. Buchanan said,
There is a sizable investment being made in agricultural research, which should result in new technologies, but it takes time for development and adoption, and then for the benefits to be realized. Historically, it takes about 30 years. We don’t have 30 years.
I also see technology adoption as a major shortcoming of the beef industry. This will be a continued theme of this blog and my extension program.

But, in this post I want to discuss the unresolved concern raised in Troy Smith's article. He quotes Buchanan as saying, "“We’ve done pretty well, but we could do better. But better selection tools just get us into trouble faster if we aren’t selecting for the right things.”

Yet, the article does not suggest what are the "right things". In your experience and based on scientific information, what are the right things?

Please leave your thoughts in the comment section below.
(I have turned off word verification, so it should be easier to comment on the blog. If spam gets out of control, I'll have to turn word verification back on.)

After you have left a comment, click on the button below to see my thoughts.



Tuesday, April 8, 2014

Use Genomics to Maximize Dairy-Beef Crossbreeding

In the March-April 2014 issue of Best of the West, there is an article about producing beef cattle by breeding dairy cows to beef bulls. At the Midwest American Society of Animal Science meetings in Des Moines, Iowa, Kent Anderson of Zoetis discussed this practice and how genomics plays a part in selecting the animals used in these crosses. A dairy producer can use a genomic prediction test, such as Zoetis' CLARIFIDE®, to rank the cows in their herd. The producer can breed the top portion of their cows to dairy sires to produce replacement heifers. The use of sexed semen increases the efficiency of this strategy, as ~90% of these matings result in heifer pregnancies. Then the producer can breed the bottom portion of the cows to a beef sire to produce calves that will be marketed as beef feeder cattle. It is important to select beef bulls that excel at rib eye area and yield grade, as these are the main weaknesses of dairy steers. Research is underway to develop genomic EPDs for feed efficiency, another weakness of dairy steers, so that beef bulls with superior feed efficiency can be used in dairy-beef crosses.

Dairy cattle make up 20% of the beef production in the United States. By using available technologies, dairy producers can increase their income and provide the type of cattle feedlots and packers need to market.