Two genetic indexes are available on a large proportion of pedigree rams. These indexes allow farmers to rank animals based on their genetic potential across a range of terminal and replacement traits writesNoirin McHugh, Research Officer - Beef and Sheep Geneticist, Teagasc.
- Terminal index - ranks animals based on their ability to produce live, fast-growing terminal progeny with little lambing difficulty. This takes into account the progeny’s growth rate, carcass characteristics, days to slaughter and also lamb survival and lambing difficulty.
- Replacement index - ranks animals on the expected maternal performance such as milk yield, lamb survival and the ease of lambing, however, it also includes some terminal traits to account for the efficiency at which animal’s progeny are finished.
Before selecting a breeding ram, each farmer should focus on a couple of key aspects of the €uro-star indexes of each ram;
- Index of choice – farmer should pay particular attention to the index of choice. For example, if farmers are interested in finishing all their lambs then they should focus on the terminal index. On the other hand, if a farmer is looking to retain replacements from a ram then they should focus on the replacement index.
- €uro-star value - from 2019, onwards the €uro-value also with each ram is now presented across all breeds, which allows any two breeds to be compared to each other. For example, a ram with a €uro value of €1.15 is expected, on average, to produce progeny that will generate €1.15 more profit compared to their average contemporaries. Assuming that a ram produces 100 progeny per year and survives within a flock for 4 mating seasons this ram is expected to generate €460 more profit across his lifetime compared to the average ram.
- Star rating – within each index animals are ranked on a scale of 1 to 5 stars within breed; a 1-star indicates that the animal lies within the bottom 20% of ranked animals for the given trait and a 5 star corresponds to the top 20% of animals
- Accuracy - irrespective of the type of animal that is needed, careful attention should be placed on the accuracy associated with the index or trait of interest. The higher the accuracy the more information that is known about the animal and the greater the confidence we have that their index value will reflect their true performance potential. For ram lambs, farmers should aim to select animals with an accuracy value of at least 30% or greater.
- DQI – the Data Quality Index (DQI) index rates flocks based on the quality and quantity of the data recorded on the flock over the previous year. This index can be used to help pedigree farmers identify the areas where their data recording needs the most attention in the year ahead. When selecting rams from pedigree flocks, farmers should aim to purchase rams from flocks with a high DQI (i.e. 65% or greater).
€uro-star Indexes – do they work?
The Sheep Ireland €uro-star indexes have been available on a large selection of pedigree rams over the last number of years, however, the question remains are high star rated rams outperforming lower star rated rams?
To assess the relevance and accuracy of the sheep €uro-star indexes for improving lamb performance, the star ratings of rams were compared to the subsequent performance of their progeny on commercial sheep farms over a four-year period.
The commercial data was collected across 7 commercial flocks with records available on over 10,000 progeny from the rams.
Information was available on a number of key parameters including live-weights of ewes and lambs, lambing and reproduction data. The performance of the progeny from the 1 and 5-star rams is highlighted in Table 1 and the results clearly show that lambs from rams with five-star ratings had greater performance compared to lambs from one-star rams.
The key differences between progeny born to five and one-star rams were:
- More lambs –ewes from five-star replacement index, rams had a higher number of lambs born and also had less dead lambs at lambing.
- More efficient ewes – ewes from five-star replacement index rams, on average, had a lighter mature weigh relative to 1-star ewes. At the same levels of output, this would allow farmers to increase the number of ewes in the flock.
- Less labour at lambing – on average lambs born to 5-star terminal index rams experienced less lambing difficulty relative to rams of lower star ratings.
- Greater growth rates – lambs form 5 star index rams were on average 2.13 kg heavier than one-star lambs at 7 weeks of age, this resulted in heavier lambs at weaning relative to 1-star lambs.
Table 1. Mean on-farm performance of offspring of sires differing in star ratings for key performance traits.
|Index||Trait||1 Star||5 Star|
|Replacement Index||Number of Lambs Born||1.92||1.97|
|Lamb mortality (%)||10.65%||9.45%|
|Ewe Mature Weight (kg)||78.78||76.88|
|Terminal Index||Lambing Difficulty (%)||23.06%||18.17%|
|40 Day Weight (kg)||18.09||20.22|
|Weaning Weight (kg)||31.94||34.94|
These results show the benefit of selecting a high star rated ram based on either the replacement or terminal index, depending on the most suitable ram from their production system.
The greater on-farm performance of progeny sired by high star rated rams also increases the profitability at farm level, in economic terms the benefit of selecting high star rated rams can increase the profit on a per ewe basis by as much as €5/year.
Where to find €uro-star rams?Farmers can now find €uro-star rams at most pedigree society sales throughout the year.
They can also search for rams on Ramsearch.ie where you can apply filters for breed, location and Star rating.
There is a list of performance-recording breeders on the Sheep Ireland website where breeders can find breeders in their area.
By Noirin McHugh, Research Officer - Beef and Sheep Geneticist, Teagasc.