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The New Zealand Shorthorn Association Genetic Evaluation Sire And Dam Summary

by Steven Skinner BREEDPLAN, ABRI

The information contained in this Report was compiled by the Agricultural Business Research Institute (ABRI) from data input to the pedigree and performance database of the Shorthorn Society of Australia, the Beef Shorthorn Society of Australia Inc. and the New Zealand Shorthorn Association. The Estimated Breeding Values (EBVs) have been calculated from the raw data as supplied by members. Neither the Societies nor the ABRI oversee or audit the collection of this data.

Introduction

This report contains a summary of the Group Breedplan Estimated Breeding Values (EBVs) as calculated in the Shorthorn Group analysis. This analysis combined the intergrated pedigree and performance databases of the Shorthorn breed in Australia and New Zealand. This report presents Shorthorn breeders with a listing of genetic merit (or EBVs) for Shorthorn sires and dams.

Group Breedplan estimates the breeding values for individual animals using all available information on the animal as well as its progeny and close relatives. The calculation of EBVs takes into account the influence of management, environmental effects and the non-genetic effects. Group Breedplan provides the best possible estimate of an animal's breeding value, that is, the animal's EBV.

Group Breedplan EBVs for up to 16 economically important traits are included in this report. This does not constitute an exhaustive list of the traits that must be considered during the selection of functional cattle. However, Group EBVs are the best figures available on the relative performance of animals for these important traits. Group EBVs used in conjunction with assessment for structural soundness, fertility, mature size and muscling will help take a lot of the guess-work out of cattle breeding.

The Analysis

The EBVs published in this Genetic Evaluation Report were produced using the latest version (4.3) of Group Breedplan software. This model is an advanced implementation of the Best Linear Unbiased Prediction (BLUP) technology for across-herd genetic evaluation of beef cattle and was developed at the Animal Genetics and Breeding Unit (AGBU) at the University of New England. Version 4.3 of Breedplan software includes a number of enhancements, such as:

  • An enhanced procedure for including American EPD data supplied by the American Shorthorn Association.
  • Improved contemporary grouping strategy for Mature Cow Weights, such that cows are now only included if they have a calf weighed at weaning.
  • Revised carcase parameters - reflecting the latest research from the Beef CRC.
  • Revised adjustment factor files
  • Increasing the maximum age for submission of scrotal measurements to 700 days of age.
  • Reducing the minimum carcase weight from 200kg to 150kg.

This version of Group Breedplan software also includes:

  • allowance for re-ranking of sires when used in different herds
  • allowance for differences in the variation of performance between herds
  • an enhanced estimation procedure for generating EBVs for groups of base animals

This evaluation is based on a wide range of information including the performance of the individual and its relatives for a number of traits, the genetic relationships between the traits and the pedigree links between animals and between herds. EBVs are reported relative to a base of zero set for each trait using historic performance records for the breed.

The Report

The Main Sire listing reports GROUP EBVs for 300 sires for up to 16 traits. To be eligible for reporting in this listing a sire must have performance recorded progeny born in the last five years and must have an accuracy of at least 70% for one of the growth traits (ie 200-Day Growth, 400-Day Weight or 600-Day Weight).

Sire trait leaders are highlighted in the sire list by boxing the EBVs for which the animal is a trait leader. To qualify as a trait leader the sire must have at least 75% accuracy for that trait (only 65% accuracy for eye muscle area, retail beef yield percent and intra muscular fat percent) Having met this criterion, sires are reported as trait leaders if their EBV for the trait is within the top 10% of the breed (top 5% of the breed for the 200, 400 and 600-Day weights). The sire trait leaders for Birth Weight also must have a positive post-birth growth traits (measured at 200, 400 & 600 days). No trait leaders are reported for Calving Ease, Mature Weight, Rib Fat or Rump Fat.

The Junior Sire listing is similar to the sires listing but includes only bulls born in 2003 who have at least two post-birth performance observations (one of which is a weaning weight). Having met this criteria, young sires are reported if ther EBVs for 200-day growth, 400-day weight and 600-day weight are among the to 10% for the year drop.

The Dam trait leader lists include the top 30 dams for each of the traits Birth Weight, 200-day milk, 200-day growth, 400-day weight, and 600-day weight. To be included in a particular trait leader list a dam must have had at least one calf in the past two years, at least 3 natural calves recorded and an EBV accuracy of at least 60% for that trait. For inclusion in the birth weight trait leader list a dam must have a low birth weight EBV with positive EBVs for post-birth growth traits (measured at 200, 400 & 600 days).

The trait leader flags are a useful guide to the top performance animals in the breed for the nominated traits. However, the trait leader flags DO NOT attempt to identify the best animals for use in YOUR breeding program. You must determine the best possible combination of EBVs an animal should have to fit into your selection criteria. To select an animal for your breeding program you should consider the animal's performance overall. Take all its EBVs into consideration and use these figures to predict how that animal will improve your herd. Genetic progress in a herd depends on the breeders ability to select the best animals that genetically suit the breeders own breeding objectives.

Accuracy of EBVs

By definition EBVs are estimated breeding values. They are estimated because it is impossible to predict with 100% certainty the genetic merit of an animal and therefore the genetic merit of the progeny of a particular mating.

The accuracy of an EBV depends on two major factors:

  1. The heritability of the trait. That is the proportion of an animals superiority that is passed on to its progeny; and
  2. The amount of performance information available on an animal and its relatives.

As more performance information on an animal and its relatives becomes available, the accuracy of an EBV increases. The following examples indicate how accuracy is related to progeny numbers and relatives. If the only information available is a bull's own performance for one trait with a heritability of 30%, the accuracy will be 55% (provided the bull is in an effective contemporary group). Animals with parents of high accuracy could have higher accuracy than those shown in Table 1.

Table 1: Accuracy of EBVs for a trait with heritability of 30% (400-Day Weight)

 

Information Available Accuracy
Individual 55%
Individual + 10 PHS* + 2 MHS** 61%
Individual + 20 PHS* + 4 MHS** 64%
10 Progeny 67%
Individual + 10 PHS* + 2 MHS** + 10 Progeny 77%

* PHS = Effective paternal half sibs (ie same sire).
** MHS = Effective maternal half sibs (ie same dam).

Highly accurate EBVs are very reliable; there is little risk that the progeny performance of an individual with high accuracy EBVs will, on average, be much different than the EBVs indicate. Alternatively, the average progeny performance of an individual with low accuracy values may be quite different from what his EBVs indicate.

Accuracy for a particular trait and heritability for that trait can be used to calculate confidence intervals for EBVs. Table 2 shows the possible changes in EBVs (known as standard errors) for various accuracy levels.

Statistically, there is a 67% chance that an animal's true breeding value will be within plus or minus 1 standard error of the EBV, and a 96% chance that it will be within 2 standard errors.

For example, for a 600-Day Weight EBV that is reported with 99% accuracy, there is a 67% chance that the true breeding value is within plus or minus 2.8 kg. Further, there is a 96% chance that that the true breeding value is within plus or minus 5.6 kg (ie 2 x 2.8 kg). This means that as further information is added for this animals (eg from progeny), the EBV would be expected to fall within the range of ± 2.8 kg 67% of the time and within ± 5.6 kg 96% of the time.

 

Table 2: Standard errors of EBVs at different levels of accuracy

 

EBV trait Accuracy (%)
60% 70% 80% 90% 99%
Gestation Length 1.9 1.7 1.4 1.0 0.3
Birth Weight 1.7 1.5 1.3 0.9 0.3
200-Day Milk 6.7 6.0 5.0 3.6 1.2
200-Day Growth 9.7 8.7 7.3 5.3 1.7
400-Day Weight 12.7 11.3 9.5 6.9 2.2
600-Day Weight 16.1 14.4 12.1 8.8 2.8
Mature Weight 27.7 24.7 20.8 15.1 4.9
Scrotal Size 1.0 0.9 0.8 0.5 0.2
Carcase Weight 12.8 11.4 9.6 7.0 2.3
Rib Fat 1.2 1.0 0.9 0.6 0.2
Rump Fat 1.6 1.4 1.2 0.9 0.3
Eye Muscle Area 2.0 1.7 1.5 1.1 0.3
Retail Yield % 1.2 1.1 0.9 0.7 0.2
IMF % 0.8 0.7 0.6 0.4 0.1

GROUP EBVs - Traits Reported

Calving Ease EBVs: are based on calving ease (CE) scores, birth weights and gestation length information. More positive EBVs are favourable and indicate easier calving.

DIR direct CE indicates how this animal influences the birth of its progeny.

DTRS is daughter's calving ease and indicates how well the animal produces daughters that have easier calving.

Gestation Length EBV: indicates lighter birth weights, easier calving and increased growth after birth.

Birth Weight EBV: indicates the genetic potential for birth weight. The lower the birth weight EBV of a sire the lighter is the birth weight potential of his progeny.

Milk EBV: reflects extra calf weight which is due to the genetic influence a sire has on his daughters' milking and mothering ability. Bulls with above average Milk EBVs are expected to sire daughters with above average milking potential. To improve milk in your female herd, select bulls with well above the current breed average EBV and with high accuracy. An animal's Milk EBV is usually less accurate than its growth EBVs because of the lower heritability of the trait and the time lag before the performance of the daughter's calves becomes available.

200-Day Growth EBV: is an estimate of an animal's genetic potential for growth to weaning. This trait should be emphasised if you are selecting cattle to finish for the lightweight domestic trade. It is also important to consider the maturity patterns required for this trade.

400-Day Wt EBV: is an estimate of an animal's genetic potential for yearling weight. This trait should be emphasised where you are targeting the domestic and/or yearling trade, or where you require increased weights of your vealers.

600-Day Wt EBV: is an estimate of an animal's potential for growth to maturity. This trait should be emphasised if you breed for the heavyweight export markets or if you wish to extend the growth potential of your progeny.

Scrotal Size EBV: is an indicator of fertility in males, which passes on in part to female relatives. Increased scrotal size is associated with increased fertility in male progeny and with earlier age at puberty of male and female progeny.

Days to Calving: is an indicator of female fertility based on the time between the cows first exposure to a bull and when she subsequently calves. Cows that calve late in the season or fail to calve are penalised. This is more useful as a sire trait. Lower (negative) EBVs are preferred indicating shorter days to calving for the sire's daughters.

Carcase Weight EBV: is an indicator of the genetic difference in carcase weight at a standard age of 650 days. Sires with relatively higher Carcase Weight EBVs are expected to produce progeny with heavier carcases at 650 days of age.

Eye Muscle Area EBV: indicates an animal's genetic potential for eye muscle area on a standard 300 kg carcase. Sires with relatively higher EMA EBVs are expected to produce better muscled and higher percentage yielding progeny at the same carcase weight than will sires with lower EMA EBVs.

Rib and Rump Fat EBVs: are indicators of an animal's genetic potential for subcutaneous fat depth on a standard 300 kg carcase. Sires with low, or negative, fat depth EBVs are expected to produce leaner progeny at any particular carcase weight than will sires with higher EBVs. Differences between Rib Fat and Rump Fat EBVs may indicate differences in fat distribution.

Retail Beef Yield Percent EBV: indicates genetic differences between animals for retail yield percentage in a standard 300 kg carcase. Sires with larger EBVs are expected to produce progeny with higher yielding carcases.

Intra Muscular Fat Percent EBV: indicates genetic differences between animals for intra muscular fat percentage (marbling) in a standard 300 kg carcase. Sires with positive EBVs are expected to produce progeny with higher average marble scores.

Comparing Animals Using EBVs

EBVs are a tool that will help you to make more "educated" decisions when you are choosing breeding stock. In this Report you have access to EBVs for 16 important traits. Always remember to consider the many other important traits such as structural soundness.

To compare animals it is necessary to have a base for comparison. The current genetic level for the breed is the average GROUP EBVs for that yearsanalysed in the Shorthorn Group Breedplan. This is the latest year where progeny will have later weights measured.