Breeding By the Numbers

Author:  Mark V. Baden, ADGA Genetic Advancement Committee Member

“A beautiful oil painting the first time you try” was the claim of the Craft Master paint-kits when first marketed in 1950. Commonly termed, Paint by Number Kits, are boards on which light colored lines indicate areas to paint, each area having a number and a corresponding numbered paint to use. These kits are still in production today in various artistic forms for painting, quilting and needlepoint. Dairy goat breeding is often referred to as an art, so wouldn’t ‘paint by numbers’ type of breeding tool be nice to have to use in your breeding program? Does it exist? Where can you get one? How does it work? The ADGA Genetics Advancement Committee is pleased to say that YES it exists, it’s FREE, and you can paint generations of improved genetics in your herd through its use. What is it called? Predicted Transmitting Abilities (PTAs).

PTAs are the genetic merit that an animal is expected to contribute to its offspring and is based on milk records from the Dairy Herd Improvement program and from linear appraisal data from ADGA.[i] How they are calculated is a complex, statistical process developed by the USDA’s Animal Improvement Programs Laboratory-AIPL, performed by a cooperative agreement between ADGA and the Council on Dairy Cattle Breeding and is released to the public biannually. The calculations account for several impacting factors including; differences in herd management (disease or superior kid raising), herd-sire interaction within the herd (differential use of sires across herds), lactation length, known pedigree data as well as other pertinent items included in the formula. PTAs are calculated for several traits, three that pertain to production; milk, fat, protein, and 13 that correlate to type traits and one for final score.

An evaluation’s (PTAs) accuracy is called reliability (REL). Reliability is based on the amount of information included in the evaluation. All information on the animal, parents and progeny are included. As more daughters are included in a sire’s evaluation, more emphasis is placed on progeny information and less is placed on ancestor information.[ii] The more daughters in more herds increase reliability. An additional daughter in the same herd contributes less than another daughter in a different herd.

The basic purpose of a PTA is to rank sires. If a buck has a PTA of +250 for milk, it does not mean that his daughters will produce 250 pounds more of milk than their herdmates. It does mean that the daughters of this buck have an average milk production 250 pounds higher than the daughters of all bucks used in the genetic base. Sire selection should be based on the PTA value of a buck. A common mistake is to use reliability as the sole criteria. Reliability should be used to determine how heavily to use a particular buck in your breeding program.

So how can you make this work for you in your breeding decisions? Follow along as we demonstrate how iconic movie star, Heidi uses one of the numbered colors of a type evaluation to create her next generational masterpiece.

Using Type PTAs to improve rear udder height.

Dairywoman, Heidi’s herd favorite doe, ADGA’s Not High Enough, is a better than average milker with a first lactation record of 1-08 305 3,200 110F 100P and a linear appraisal score VG89 as a first freshener. Heidi exhibited NOT ENOUGH at the Spindale Goat Festival show where she placed first in her class but was passed over for championship selection because other does in the line-up had much higher rear udders according to the judge. Heidi referred to her appraisal sheet from earlier in the season and noted her doe’s rear udder height (RUH) score of 32 on a linear scale of 50. At the time she thought that was a good score, but now after comparing to the local competition, she wants to concentrate on improving that trait in the next generation of breeding.

In Heidi’s nitrogen tank, she has six proven sires all with evaluations (minimum requirement for an evaluation is 5 daughters on DHI test and 3 linear appraised daughters, sons of a buck are not included in a sire’s evaluation). After consulting www.adgagenetics.org, she has compiled the following data for each buck and how they might assist her goals for improving rear udder height.

SIRE NAME SG Herds Daus Appraisals TraitAve PTA REL
ADGA’s Mr. Reliable SG 49 94 165 35.4 2.1 94
ADGA’s Predicting The Ascent 5 6 11 43.8 4.2 55
ADGA’s Mr. Sky High 1 10 11 45.1 1.5 51
ADGA’s Average Joe GCH 7 8 9 32.8 0 61
ADGA’s Last Year’s News SG 5 6 13 39.9 0.6 57
ADGA’s Currently Trending CH 3 6 8 33.4 -1 47

The method that ADGA derives Rear Udder Height scores is as followed. For Mature does, as ADGA recognizes multiple sized breeds with different body frames, absolute measurement is not the most accurate assessment of the trait…The Rear Udder Height linear trait is scored by the appraiser by visually assessing the halfway spot between the base of the vulva and the point of hock. This point, called the midpoint, is a score of 15 on the linear scale. The appraiser then determines where the milk secretory tissue begins and for each inch above or below the midpoint in the standard breeds equates to +/- 5 points on the linear scale from the midpoint of 15. For miniature breeds the measurement would be ½ so that each inch above or below the midpoint of 15 would equal +/- 10 points on the linear scale.[iii]

Heidi wants to focus on a breeding that will result in an improvement in rear udder height of at least one inch, so she is interested in scores of at least 37 (her doe’s score was a 32 and each inch of height represents 5 additional points). With a base trait score in her mind, she then referred to the ADGA web site’s Performance Programs tab (at the top of the page) and re-read the sire development articles[iv]. Heidi learned that dairy goat type information is not separated by breed unlike the performance records. She also learned that 2/3 of the genetic base falls between -1.0 and +1.0 standard deviations in PTA for a trait, following a traditional bell curve. With this in mind, she has concluded that her best opportunity to improve rear udder height using the data provided is to concentrate on sires with a minimum PTA of +1.1 and a daughter average (D/AV) score of 37 for the trait. Looking at her chart of available sires, she has eliminated the bottom three bucks from contention for this planned breeding because of her PTA criteria. She eliminated the first sire because of the trait score D/AV, leaving her with two good candidates, PREDICTING THE ASCENT and SKY HIGH. The differences in the two buck’s daughter average are only ¼ inch in rear udder height. Heidi has decided to use PREDICTING THE ASCENT because of his impressive PTA value of +4.2, higher reliability and greater use in more herds (5 herds compared to 1), giving her the greatest confidence that her breeding decision will achieve her desired results so that she can present more competitive does in her future show string.

Dairymen and women can use this methodology in each of the 13 primary linear traits scored in the ADGA linear appraisal program to make improvements where they need most. Contact the ADGA office to apply for a 2015 linear appraisal session to have your herd scored and data to use to create your next masterpiece!

[i] Wiggans, Hubbard and Wright. Genetic evaluation of dairy goats for yield and type.

[ii] The Holstein Association USA Sire Summaries.

[iii] ADGA Linear Appraisal Standard Operating Procedures, 2014  12.16 Rear Udder Height

[iv] ABC’s of ETA’s, PTA’s and PTI’s, 2004 Lisa Shepard ADGA Performance Programs Coordinator