Bill Bowman and Sally Northcutt
Method Genetics LLC
Bowman and Northcutt discussed several new EPDs either in development or released by AHA, including:
- Dry Matter Intake
- Sustained Cow Fertility
- Heifer Calving Rate
- Udder Quality (Teat Size and Udder Suspension)
Heifer Calving Rate,
Sustained Cow Fertility, and
Dry Matter Intake are currently released as prototype evaluations and can be accessed as a downloadable Excel file.
"One of the things you all have going for you is the foresight to begin a
TPR program," said Bowman.
Heifer Calving Rate
Heifer Calving Rate (HCR) is a categorical trait, they either calved or they didn't. Method Genetics reports a heritability of 15% for Heifer Calving Rate. They analyzed 98,000 records, of which 73% had calved by 800 days of age, 27% had not calved. Contemporary grouping for heifers is based upon their herd, yearling weigh date, calf birth year and season.
"This EPD goes beyond a traditional heifer pregnancy EPD." said Northcutt.
Bowman added, "This follows through to calving, which is really what we want."
The higher value is more favorable for the Heifer Calving Rate EPD. If Sire A has a HCR EPD of 8% and Sire B has a HCR EPD of 2%, we would expect 6% more of Sire A's heifers to calve.
The benefits of this EPD include improvement for a lowly heritable trait, provides an opportunity for selection pressure to improve calving, and can now directly include fertility (Heifer Calving Rate) into AHA indexes in the future.
Sustained Cow Fertility
Whole Herd TPR allows a spring board for Heifer Calving Rate, which acts as a first step in looking at Sustained Cow Fertility. Sustained Cow Fertility is a survival analysis that is different from a typical longevity EPD. It uses the Heifer Calving Rate evaluation as the starting point. After this point contemporary groups become
dynamic; after calving as a heifer females exposed together make up a contemporary group. Calving intervals and age at calving are calculated. The model accounts for milk and total maternal calving ease EPDs.
A cow is "Successful" until she fails to have a calf. But, some records are "Censored", i.e. the data is handled carefully for exceptions like a cow being sold as a breeding female (registration transferred) or becoming a donor dam. Sustained Cow Fertility has a heritability of 20%.
A higher value is more desirable for sustained cow fertility.
Dry Matter Intake (DMI)
This EPD starts with a multi-trait animal model including:
- Individual feed intake (standardized)
- National Cattle Evaluation weaning and yearling weights
- Four-generation pedigree
Feed intake has a heritability of 40%.
Weaning records are included for contemporaries of calves with an individual intake record to account for selection bias (sending the best calves to feeding test to measure feed intake).
In Dry Matter Intake (DMI) lower values are predictive of less intake. When you begin looking at feed intake, cattle that gain well tend to be more efficient, but they tend to eat more. We want to find outliers who eat less feed but gain more weight. Downloadable Excel spreadsheets contain both DMI EPDs and Yearling Weight EPDs to allow breeders to look at this. Single trait selection should be avoided. Incorporation of Dry Matter Intake genetic values into the AHA indexes will be the greatest benefit.
As
we have discussed in the past, depending on how you slice it, feed efficiency rankings can be different and the most effective strategy is an economic index.
Think about the entire system, not a single trait!
Challenging traits are now more accessible from a genetic standpoint. Reproductive traits with lower heritability are addressed. A foundation is established for genomic-enhanced EPDs in these traits.
Udder Quality
In the current udder quality evaluation, it is a standalone evaluation, meaning no other traits are fit in the model, only Udder and Teat scores. Currently there is no genomic component. Since 2008 the genetic trend for udder and teat scores have increased dramatically.
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| Genetic Trends for breed averages in udder suspension and teat size EPDs. Data from Fall 2015 AHA Sire Summary. |
The genetic correlation between Udder and Teat EPDs is about 0.8. But, this does not mean the udder score should always equal the teat score; in fact we should see many instances where this is not the case.
Higher scores are more favorable for both Udder Suspension and Teat Size EPDs.
This is an example of publish it and they will come; from the Spring 2015 and Fall 2015 evaluations 25,000 records were added to the Hereford udder and teat data set.
Repeated measures on females are included in this analysis. Scoring system is designed for characterizing udder quality - not milk production levels.
[My question, is there an optimal level for udder suspension? If the udder is too tight, will milk production suffer?]
The contemporary group records account for subtle differences between how different farmers and ranchers score the udders and teats.
The purpose of scoring udders is to provide commercial producers with problem-free genetics. Producers are encourages to score udders when taking calf's birth weights.
When scoring, 9 is favorable and 1 is unfavorable. Be consistent in scoring within your cow group and herd. In scoring, suspension is always the first number and teat score is the second number.
Udder scores should be collected within 24 hours of calving. Udders should be scored annually. Contemporary groups account for herd, year, and season difference in scoring.
Keep scoring independent of milk production levels.
See the
Udder Scoring Fact Sheet for more information.
Northcutt encouraged Hereford breeders, saying "You have some exciting new traits."
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