ASBVs are calculated using data on any known relatives as well as trait measurements collected on individual animals. Pedigree is crucial for genetic analysis, as we expect that an animal will receive half of their genetics from their sire and dam. When trait measurements are supplied for an animal, their performance for key traits contributes to ASBVs. Through use of 16-digit IDs, Sheep Genetics tracks relationships with other animals in the database, so that their parents, progeny, and siblings all provide information to make the animal’s ASBVs more accurate. Sheep Genetics uses all available pedigree for an animal when calculating ASBVs and indexes.
Pedigree can be recorded using different methods. The chosen method will depend on labour, cost and practical considerations.
Methods of recording pedigree
Tagging at birth
Tagging at birth is considered the gold standard for recording pedigree, birth traits and associated fixed effects. It involves tagging the lamb(s) at the birth site (or within 24 hours of birth), which enables recording of the dam, as well as exact birth date, birth weight, maternal behaviour score, and lambing ease. Important fixed effects that are also captured include dam age and accurate birth type. These are important in accounting for any non-genetic factors which impact the lamb’s performance (e.g., dam age, single vs multiple, born early or late, etc.) when calculating ASBVs. Sire pedigree can only be obtained from tagging at birth when mate method was AI or ewes were joined in single sire groups.
Mothering up (after birth)
Mothering up after birth refers to allocating dam pedigree to each lamb after observing the ewes and lambs interact, often in the yards. Mothering up often fits in with other operations and the only cost involved is the labour, although this can be time consuming. The accuracy of mothering up declines as the lambs age and are less dependent on their dams. Similar to tagging at birth, sire pedigree can only be recorded for mothering up if single sire joining or ewes were AI-ed. Accurate fixed effects are not able to be recorded, such as the lamb’s birth and rear type. Also, there is a risk of misallocation of birth mother to lamb due to lamb pirating, resulting in incorrect pedigree.
DNA parentage
DNA parentage may be recorded at any stage of an animal’s life and generally involves collecting a DNA sample using a tissue sampling unit (TSU). To receive DNA parentage, the lamb and potential parents must be tested. DNA parentage enables the identification of sire pedigree where syndicate mating occurs and the only labour involved is taking the samples. However, DNA parentage has a cost involved and does not capture fixed effects recorded at the birth site (for example date of birth or real birth type).
Proximity technology
Use of proximity technology, such as collars or recording devices that recognise interactions between dams and lambs, is another method of recording dam pedigree. Where more interactions are recorded between a certain ewe and lamb, the technology determines the ewe as the dam of that lamb. Pedigree MatchMaker and SmartShepherd are both examples of proximity technology. Proximity technology is relatively cheap and simple to use, and does not require needing to be at the birth site to record the pedigree. There are short periods of labour required in attaching the collars, or they may not always be an option – for example, Pedigree MatchMaker may not suit where there are multiple water points in a paddock allowing the sheep to avoid the reader. Also, proximity technology does not capture fixed effects recorded at the birth site (for example date of birth or real birth type) and there is a risk of misallocation of birth mother to lamb due to lamb pirating, resulting in incorrect of pedigree.
| Pros | Cons | |
| Tagging at birth |
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| Mothering up |
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| DNA parentage |
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| Proximity technology |
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