CIC 2020: Precision Breeding and You Don't Need a GPS

Darrh Bullock
University of Kentucky

Precision agriculture has come to various industries. Luckily, there are already tools to do precision breeding in beef cattle.

Let's talk about farm/ranch goals.
For example, our goals may be to

• Support two families
• Keep workers safe
• Effectively use the resources we have

Breeding objectives are genetically influenced objectives to help achieve farm and ranch goals. In Darrh's opinion, breeding objectives should impact the quality of life of the farm and ranch owners and workers. These objectives should improve economic, social, welfare and convenience factors of a farm. Certain traits in our breeding objective will allow us to be more efficient and have a smaller environmental impact. Other traits will be in our breeding objective simply because they make our life more convenient.

Darrh pointed out that production efficiency is the key. The beef industry needs to reduce the amount of mature size and milk so that cows are more efficient. This will mean that we won't have the heaviest calves at weaning. But, it will mean that we are more efficient and more profitable. Bragging about weaning weights should not be our goal.

Genetics in the beef industry is simple. It requires crossbreeding and selection for improvement.

Crossbreeding allows us to have heterosis, also called hybrid vigor. This means that offspring outperform the average of the parents. This does not mean that the offspring outperform the best parent. But, we can match the weaknesses of one breed with the strengths of a different breed for several traits. This leads to a better overall calf.
Breed complimentary is also an important part of crossbreeding. Traditionally, we talked about this as maternal breeds and terminal breeds. Breed complimentary allows us to match the crossbreeding system to our environment and management. We match the breed of the cows to the environment and management, and get additional growth, performance, and carcass from the breed of the bulls.

Let's talk about the economics of heterosis.
Assume a 100 head cow herd, 525 lbs weaning weights, $1.50 per lbs at weaning.
In this setting, straight breeding, has no economic advantage in terms of heterosis. In a 2-breed composite, there is 50% retained heterosis with a $7,363 annual value of heterosis. In a 2-breed rotation there is 67% retained heterosis with an economic value of about $9,000. A 4-breed rotation had the largest economic value.

Now, let's talk about genetic change. Genetic change is explained by a simple equation, consisting of intensity, accuracy, genetic variation in breed, and the generation interval.

What is intensity of selection? Intensity of selection is where is the bell shaped curve are you drawing the line between animals you keep (or purchase) and animals you don't use (cull). More intensity is further into the tail of the bell curve, the further into the tail, the faster genetic change is.

What is accuracy of selection? Accuracy of selection has new opportunities to increase our accuracy.
If we had 100% accuracy, we would know the genetic merit of all of the available animals. In this case, our selection decisions would be perfect. If we have 50% accuracy, we unluckily choose some of the wrong animals. Some of the animals we selected have a true genetic merit that does not meet our criteria. EPDs are not perfect. EPDs are a risk management tool. Increased accuracy improves our decisions. Increased accuracy improves the rate of genetic change.

So, how do we get more accuracy?
More data, in terms of phenotypic records
Contemporary grouping strategies can improve accuracy, but this can be pretty minimum.
The big improvement comes from genomic testing. Genomic testing improves the pedigree and provides information that is equivalent to additional progeny.

Genomic testing allows us to identify mistakes in the pedigree and correct them. When the pedigree is corrected, the EPDs are much more accurate. The genomic data also allows us to measure the real genetic similarity rather than the expected genetic similarity. Consider six full siblings. The expected relationship is 0.50. If we account for inbreeding, the expected relationship is 0.59. The actual relationship varied from 0.49 to 0.65 between pairs of full siblings.

The DNA testing provides the same amount of information as 8 to 24 offspring in the AGI analysis and 3 to 25 progeny in the IGS analysis.

Generation interval is the time required to replace one generation with the next. Generation interval is affected by culling rate and selection intensity. If herd size remains constant, the selection intensity on the heifers determines the selection intensity of culling cows.

There is a difference between generation interval in seedstock and commercial herds. Seedstock herds seek to shorten the generation interval. Commercial producers should want to use the added maternal performance of older cows and shortening the generation interval is much less important.

Darrh emphasized that we should not focus on single trait selection. This leads to problems. We should select multiple traits. The traits we select for should be determined by our environment and management and our marketing strategies.

One of the big factors in our breeding objective (and which traits we are emphasizing) is determined by whether or not you are keeping heifers (or buying replacement females).

We need to make sure that the performance we are putting in our cattle matches the environment and management that we are putting them in. If their genetic potential is higher than supported by your management, this will lead to inefficiencies.

Whether a trait is an indicator trait or an economically relevant trait may depend on your operation.

So, what are some economically relevant traits in a maternal setting?

• Calving ease (birth weight is an indicator of calving ease)
• Calving ease maternal
• weaning weight
• milking ability
• Reproduction
• Maintenance

Reproduction is one of the most neglected traits. Darrh hopes that genomics will allow us to create better reproduction genetic predictions.

How do we do multiple trait selection?
Tandem- select for one trait the the next. This is a very inefficient strategy.
Independent culling levels- set individual criteria for each trait. This tends to really limit our selection candidates. And, this leads to us lowering our criteria.
Selection indices are the best way to make multiple trait selection progress.

A wild ass guess is how most of us create a selection index. This selection index changes because we are trying to formulate the index in our head. This allows us to justify our selection decisions, but it probably isn't very good decision making progress. An economic index has the data lead us to the answer.