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An animal’s breeding value is its genetic merit, half of which will be passed on to its progeny. While we will never know the exact breeding value, for performance traits it is possible to make good estimates. These estimates are called Estimated Breeding Values (EBVs).

EBVs are expressed in the units of measurement for each particular trait. They are shown as + ive or – ive differences between an individual animal’s genetics difference and the genetic base to which the animal is compared. For example, a bull with an EBV of +50kg for 600-day weight is estimated to have genetic merit 50kg above the breed base of 0kg. Since the breed base is set to an historical benchmark, the average EBVs of animals in each year drop has changed over time as a result of genetic progress within the breed.

The absolute value of any EBV is not critical, but rather the differences in EBVs between animals. Particular animals should be viewed as being “above or below breed average” for a particular trait.

While EBVs provide the best basis for comparing the genetic merit of animals reared in different environments and management conditions, they can only be used to compare animals analysed within the same analysis.

Simmental NZ animals EBVs can be compared to any other animals within the IGS evaluation, this included other breeds.

MATERNAL EBVs

CALVING EASE DIRECT (CE-D)

Reported as the percentage of extra unassisted births in first calving heifers, relative to the average. CE-D is relative to the direct Calving Ease of the animal. Higher values are more favourable.

CALVING EASE MATERNAL (CE-M)

Reported as the percentage of extra unassisted births in first calving heifers, relative to the average. CE-M is relative to the Calving Ease of the daughters of the animal. Higher values are more favourable.

MILK

Reported as kilograms of weaning weight of progeny from the animals daughters, relative to the average. Predicts the difference in maternal production of daughters relative to milk production and mothering. Values are relative to the environment of the production system. Low input environments should be very conscious of introducing too much milk due to the increased nutrient requirements that it can place on cows.

MATERNAL WEANING WEIGHT

Reported as kilograms of weaning weight of progeny from the animals daughters, relative to the average. This is a measure of weaning weight differences relative to the combined effects of growth and milk. Breeders who are not looking to change milk production should consider Total Maternal as the most relevant EBV for maternal weaning weights. Higher values are more favourable.

STAYABILITY (STAY)

Reported as the differences in percentage of a sire’s offspring that are predicted to still be in the herd at 6 years of age, given that they calved at 2, relative to the average. Stayability is a measure of reproductive longevity. Higher values are more favourable.

DOCILITY

Reported as the percentage of progeny, relative to the average, that will record a score of docile. Higher values are more favourable.

 

GROWTH EBVs

BIRTH WEIGHT

Reported in kilograms of weaning weight of direct progeny, relative to the average. Higher values are usually more favourable dependant on its relationship with birthweight.

WEANING WEIGHT – ADJUSTED TO 205 DAYS

Reported in kilograms of weaning weight of direct progeny, relative to the average. Higher values are usually more favourable dependant on its relationship with birthweight.

YEARLING WEIGHT – ADJUSTED TO 365 DAYS

Reported in kilograms of yearling weight of direct progeny, relative to the average. Higher values are usually more favourable dependant on its relationship with birthweight.

 

CARCASE EBVs – ADJUSTED TO 475 DAYS OF AGE.

CARCASE WEIGHT

Reported as kilograms of Carcase Weight relative to the average. Higher values are usually more favourable, however this is relevant to each producers target market.

RIB EYE AREA

Reported as square centimetres relative to the average. Higher values are usually more favourable.

FAT

Reported as millimetres of back fat relative to the average. Higher values are usually more favourable, however this is requires a balance between adequate doing ability in daughters and carcase fat thresholds for target markets.

MARBLE SCORE

Reported as the differences in actual carcase marble scores relative to the average.This is different to IMF% which is used as an indicator trait in Marble Score. Higher values are more favourable.

PURPOSE $INDEX (API)

Though EBVs allow for the comparison of genetic levels for many economically important traits, they only provide a piece of the economic puzzle. That’s where $ Indexes come in. Through well conceived, rigorous mathematical computation, $ Indexes blend EBV’s and economics to estimate an animal’s overall impact on your bottom line. The All Purpose $Index (API) evaluates sires for use on the entire cow herd, bred to both first-calf heifers and mature cows, with the portion of their daughters required to maintain herd size retained and the remaining heifers and steers put onto feed and marketed for both quality grade and yield.

TERMINAL INDEX (TI)

Evaluates sire for use on mature cows with all offspring put on feed and sold grade and yield.

Both heifer and steer progeny are pasture grown and finished and are slaughtered to produce a 300kg carcass at 15 months. All progeny are slaughtered. More information is available on the EBV weightings and profit drivers for the Terminal Index.

Note that $Index Values for individual animals are sensitive to the assumptions used in the BreedObject analysis to calculate the relevant selection index.

UNDERSTANDING ACCURACIES

BOLT EBV accuracies have experienced the most change, usually lowering numerically and especially for non-parent animals, however the reported accuracy will be more accurate. Accuracy refers to the amount a reported EBV can possibly change as more data is added. EBV values with higher accuracy result in less possible change for the value over time. More accurate accuracies better represent the amount of possible change for each EBV.

Accuracy range	Interpretation
less than 50%	Low accuracy. EBVs are preliminary and could change substantially as more performance information becomes available.
50-74%	Medium accuracy, usually based on the animal’s own records and pedigree.
75-90%	Medium-high accuracy. Some progeny information included. EBVs may change with addition of more progeny data.
more than 90%	High accuracy estimate of the animal’s true breeding value.

As a rule, animals should be compared on EBVs regardless of accuracy. However, where two animals have similar EBVs the one with higher accuracy could be the safer choice, assuming other factors are equal.

For more information contact the New Zealand Simmental Association.

Birth weight: Must be between 14 to 73 kg.

Calving Ease: 1 = Unassisted – 6 = Stillborn/early term abortion

Weaning weight: Recommendations for weaning weight is 160 to 250 days of age. Animals must weigh between 91 to 545kg and be between 100 and 310 days.

Dolicity: 1 = Docile – 6 = Very Aggressive

Yearling weight: Recommendation for yearling weight is 320 to 410 days of age. Animals must weigh between 159 to 909 kg and be between 270 and 500 days of age. Note: Must have at least 60 days between weaning and yearling

Carcass records: Slaughter age between 270 to 900 days of age and carcass weight between 136 to 773 kgs

Marbling between 100 to 1090

Rib eye area between <6.00 or >21.00 square inches (38.7 to 135.5 square centimeters)

Ultrasound scan age must be between 270 to 900 days

For more information check out PBB NZ IGS