Estimated Breeding Value 

EBVs predict the superiority (or inferiority) of the genes that an animal possesses for each measured trait. They are expressed in the same units as the recorded traits (e.g. kg for liveweight) and expressed relative to a common baseline for all animals in the same evaluation.

EBVs predict the breeding potential of the recorded animal. On average each animal only passes half of its genes to the next generation. Consequently their EBVs must be halved in order to estimate how much of its genetic superiority (or inferiority) will be passed on.

EBVs can be calculated on an across-flock basis, enabling animals in the same breed to be directly compared, provided that strong genetic linkage exists between flocks. EBVs can not be compared across different breeds.

8-Week weight EBV

This is a measure of the animal's genetic potential for growth from birth to weaning at 8 weeks.

A ram with an EBV of +3 for 8-week weight is expected to produce lambs which, on average, are 1.5 kg heavier at weaning compared to lambs sired by a ram with an EBV of 0.

Scan weight EBV

This is a measure of the animal's genetic potential for growth from birth to 21 weeks of age (age at scanning). Selection for high scan weights results in animals that will have heavier carcases at a constant fat class or leaner carcasses at a constant age.

A ram with an EBV of +4 for scan weight is expected to produce, on average, lambs 2 kg heavier at 21 weeks than lambs sired by a ram with an EBV for this trait of 0.

Muscle depth EBV

This is a assessment of loin muscle depth and therefore likely lean meat yield.

A ram with an EBV of +1 for muscle depth is expected to produce, on average, lambs with 0.5 mm greater eye muscle depth at 21 weeks compared to lambs sired by a ram with an EBV of 0.

Fat depth EBV

Negative values indicate animals with lower fat levels, which will produce leaner carcases or which can be taken to heavier weights without becoming over-fat.

A ram with an EBV of -1.0 for fat depth is expected to produce, on average, lambs at 21 weeks with a subcutaneous fat thickness 0.5 mm less than lambs sired by a ram with an EBV of 0.

Mature size EBV

Positive figures identify breeding lines that will be bigger at maturity. In certain hill breeds, even though it is advantageous to enhance lamb growth rates, it may be desirable to restrict increases in the mature size of the ewe.

A ram with a litter size EBV of +0.3 is expected to produce ewe lambs that will have, on average, 0.15 more lambs than ewes from a ram with an EBV of 0.

Maternal Traits

Many traits are expressed by both sexes (e.g. growth rate and muscling), but maternal traits (e.g. litter size and maternal ability) are only expressed by females.

A ram's maternal EBVs, when halved, provide an indication as to how his female offspring will perform when they become mothers.

Litter size born EBV

A ram with a litter size EBV of +0.3 is expected to produce ewe lambs that will have, on average, 0.15 more lambs than ewes from a ram with an EBV of 0.

Maternal ability EBV

This is the maternal component of the 8-week weight measurement. It gives an indication of how well a ram's ewe lambs will perform as mothers. A ewe's EBV for maternal ability estimates how much of its lambs' performance up to eight weeks of age is due to maternal characteristics such as milkiness and maternal care of the lamb.

A ram with a maternal ability EBV of +0.5 is expected to produce ewe lambs that will have above average maternal characteristics leading to their lambs being 0.25 kg heavier at 8 weeks than lambs from ewes sired by a ram with an EBV of 0.

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