This article by Dr. Marj Faust is the first in a series of regular columns on breeding and genetics she’ll be preparing for DairyBusiness Digital magazine.
She was an R&D executive at ABS Global and Genus plc, served on the faculty at Iowa State University, and provided consulting services in regulatory sciences to Novartis/Syngenta Seeds and FASS.
Throughout her career, Faust has served in leadership roles in national and international dairy industry organizations including American Dairy Science Association, National Assn. of Animal Breeders, CDCB, Interbull, and Dairy Calf and Heifer Association. She has spoken to dairy producers, scientists, consumers, and livestock, dairy, poultry, and food industry groups. She has an undergraduate degree from Penn State and earned M.S. and Ph.D. degrees from North Carolina State University. She grew up on a diversified farm in eastern Pennsylvania.
Readers may contact her with questions or suggestions at [email protected]
With the Council on Dairy Cattle Breeding’s (CDCB) release for Holsteins of official genomic evaluations for six Health Traits, dairy breeders and managers have reliable tools for creating long-term permanent genetic improvements in disease resistance. Health Trait Evaluations for the Protein Breeds will be added in the near future. The six CDCB Health Traits are:
- Milk Fever
- Displaced Abomasum
- Retained Placenta
Deriving profit in today’s economic environment requires that dairies leave no money on the table. Subpar dairy cow health can be a bit like an iceberg with a significant portion of the costs remaining out of sight. Unseen costs due to disease can include factors such as labor, lost production, discard milk, lost beef value, and reduced feed efficiency. Overall herd costs and direct treatment related costs for six important disorders are in Table 1.
Well managed dairies control factors both large and small that affect profit. Even the best managed dairies can expect to treat cows for disorders including milk fever, displaced abomasum (DA), ketosis, mastitis , metritis, and retained placenta.
|Table 1. Costs for six important dairy cow health disorders.|
|Health Event||Costs for an average 1,000 cow herd*||Direct cost, per case**|
|Milk Fever||$ 30,000||$ 34|
|Displaced abomasum||$ 197|
|Mastitis||$ 57,000||$ 75|
|Metritis||$ 14,000||$ 112|
|Retained placenta||$ 20,000||$ 68|
|*Derived based on published results from various peer-reviewed scientific articles.
**from Liang and co-workers, 2017; Donnelly and co-workers, 2016.
- What are the benefits of these CDCB genetic evaluations for health traits?
- Incorporate data from a very large number of cows and records. Each trait includes more than 1.0 million records in the calculations.
- Herds are located across the U.S. and represent a variety of management systems and climates.
- Profit-focused herds like yours – not a selected group of dairies.
- As we have seen with many other traits – this combination of benefits is expected to deliver robust genetics that work across a range of systems in the U.S. as well as around the world.
- I’ve always heard that it isn’t worthwhile to use genetics for traits such as health because such traits have low heritability – is this true?
It certainly is true that the heritabilities of Health Traits are low, but despite this real genetic progress can be achieved as we have learned from successes with other low heritability traits such as Daughter Pregnancy Rate (DPR).
- We already use traits like Productive Life (PL) and Somatic Cell Score (SCS), do these new health traits add anything in addition to what we know/use today?
Research results from the CDCB and USDA demonstrate that the genetic information provided by these new traits is quite unique and adds a great deal to our knowledge about the robustness and disease resistance of future parents. The genetic correlations between traits generally are lower than expected for disease resistant traits and respective counterpart management traits. This means that the new Health Traits do not substitute for existing management traits, and instead complement traits such as Productive Life (PL), Livability (LIV), Somatic Cell Score (SCS), Daughter Pregnancy Rate(DPR), Cow Conception Rate (CCR), Heifer Conception Rate (HCR). For example, to maximize selection information for udder health and disease resistance, Udder conformation traits, SCS, and the new Health Trait Mastitis should be used.
- What do the gPTAs for these Health Traits mean?
Positive PTAs are desirable and indicate greater resistance to the respective diseases for animals and their progeny. Table 2 includes key PTA values for Genomic Sires and the associated disease risks for daughter groups.
|Table 2. PTA values for Genomic Sires and associated disease risks for daughter groups.|
|PTAs for Genomic Sires|
|Health Trait||Bottom 16%||Average||Sire PTAs and influence on disease cases in daughter groups|
|Milk Fever||-0.3 and lower||+0.1||50% more risk for -0.05 sires than for +0.40 sires|
|Displaced Abomasum||-0.7 and lower||+0.3||50% more risk for +0.45 sires than for +1.0 sires|
|Ketosis||-0.5 and lower||+0.4||50% more risk for -0.45 sires than for +0.90 sires|
|Mastitis||-0.7 and lower||+0.9||50% more risk for -2.7 sires than for +1.6 sires|
|Metritis||-0.3 and lower||+0.6||50% more risk for -1.75 sires than for +0.90 sires|
|Retained Placenta||-0.6 and lower||+0.2||50% more risk for -0.60 sires than for +0.80 sires|
- Where can we find Health Trait PTAs for sires?
Data on PTAs for Milk Fever, Displaced Abomasum, Ketosis, Mastitis, Metritis, and Retained Placenta are available via the CDCB website. Access data for individual sires using the query function (https://queries.uscdcb.com/login/). Given the large number of new health traits, it will take some time to incorporate these data into individual company databases and materials.
- How do we incorporate CDCB Health Trait Genetic Evaluation information in our sire selection and breeding program?
Today the recommendation is to avoid using animals as parents for replacements when they have undesirable PTAs for the Health Traits (see Table 2), unless the low disease resistance animals excel and are elite for other more economically important traits.
- Select a group of sires that meet your selection targets for one of the economic selection indexes such as Lifetime Net Merit $ (NM$), Cheese Merit $ (CM$), and Fluid Merit $ (FM$).
- Eliminate sires which have undesirable PTAs for one or more individual Health Traits, i.e. large negative values (see Table 2).
In the very near future, these traits – Milk Fever, Displaced Abomasum, Ketosis, Mastitis, Metritis, Retained Placenta – will be incorporated into economic selection indexes.
- How can we ensure that our herd’s dairy cow health data are included in future CDCB Health Trait Genetic Evaluations?
Speak to your local DHI field service organization representative about whether your herd health data qualify currently, and what if any adjustments can ensure inclusion going forward.
Using the CDCB’s official genomic evaluations for six economically important health traits, breeding a more profitable dairy herd just got easier and more reliable.