What is an EBV and what is it not

The question

Two ewe lambs weigh the same at 100 days. One was a single raised on good pasture in a mild month; the other was a triplet born in the dry season. Which one carries better genes for growth? The scale cannot tell you. An EBV can.

The concept

An EBV (estimated breeding value) is a prediction of the genetic merit an animal transmits to its offspring for one trait, expressed in the unit of that trait: kilograms for weights, days for lambing interval, lambs for litter size. It is estimated from the animal's own records, its relatives' records and the pedigree that links them, after correcting for the environment the records were taken in: contemporary group, age, sex, birth type and rearing. BreedIQ applies a standard, published methodology (a BLUP animal model with parameters from the literature), the same for every farm.

Half of an EBV is what one parent actually passes on. That half is the EPD (expected progeny difference), and it is the number BreedIQ uses when it combines traits into an index.

Why it matters

Selecting on raw weights rewards the lambs that had the easiest life. Selecting on EBVs rewards the lambs whose genes made the difference. Over several lambings that difference compounds: the flock's genetic base moves, and the next generation starts higher.

The data behind it

An EBV is only as good as the records that feed it. BreedIQ reports an accuracy next to each estimate and says what it rests on: own performance, progeny, or mostly pedigree. A lamb with one weight and no progeny has a low accuracy; a proven sire with 30 offspring has a high one. When a trait has no information at all, the profile says so ("No EBV for…") instead of inventing a value, and indices computed on incomplete traits are flagged partial.

How to read it in BreedIQ

In the animal profile, the Pedigree & genetics block shows the three indices (Growth, Flock, Prolific Flock) with their percentile, the standardized rating, the inbreeding coefficient and the accuracy of each component. The Weights tab lists every EBV in its own unit, for example "Gain 50–100 (direct) +1.21 kg" or "Lambing interval +2.11 days". Zero is the farm's genetic base; positive is above it, negative below.

Decisions it supports

Rank candidates by the trait that matters to you, compare two rams head to head, and keep the replacements whose merit, not whose luck, is above the base. The evaluation is recomputed when you run it from Settings › Genetics after loading new weights, lambings or pedigree.

Limitations

An EBV is an estimate with an error margin, and a low-accuracy EBV can move a lot once progeny data arrives. It compares animals within the same evaluation; an imported EBV from another program sits on its own scale (shown in blue, while BreedIQ's are green). And it says nothing about traits you never recorded. BreedIQ detects; the producer decides.