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Sheep Matters_Aug-Sept 17 (redesigned)

Sample copy of new publication aimed at the progressive farmer and professional in the UK sheep industry. For further information and to register your interest go to www.sheepmatters.co.uk

Understanding EBVs for

Understanding EBVs for better performance Genetics and productivity Building a flock that requires fewer inputs but gives increased outputs will lead to improved profitability. Selective breeding provides farmers with the tools to produce lambs that better meet customer requirements. It is achieved by using high performance rams to improve the long-term genetic make-up of a flock. Recorded information about the genetic potential of a ram allows producers to make informed choices about which ram will best serve their productivity goals. Using a high-performance ram can lead to increased lamb growth rates and improved carcass conformation. This will result in shorter finishing times, lower feed and labour costs and higher prices. Ewe fertility and mothering ability can also be enhanced because maternal traits are passed via the ram to his female offspring. ‘Can you afford not to know the genetic potential of your rams?’ Gains in lamb growth rates and carcass indicators have improved at a greater rate in recorded flocks that use selective breeding compared to producers who rely on more traditional approaches. Breeding gains for the UK sheep sector have been estimated at an annualised value of £10.7M (1). And this pattern applies across the major sheep producing countries in the world. Trials in the UK suggest that an additional £2-£3 per lamb can be achieved by using high performance recorded rams (2,3). What are EBVs and Genetic Indexes? Estimated Breeding Values (EBVs) have been used in the sheep industry for 25 years. They predict the merit of the genes that a breeding stock animal has 10 AUGUST & SEPTEMBER 2017 “Photograph courtesy of Rob Kemp/Shutterstock.com”

for a variety of traits. Data are recorded by breeders at premating, lambing, 8-weeks post lambing and 21 weeks postlambing. Modern methods also use CT scanning to generate data. EBVs are calculated from these performance data along with information about known relatives, where the effects of environment (e.g. nutrition, management) are removed. This analysis uses a procedure called BLUP (Best Linear Unbiased Predictor). An EBV gives an independent assessment of an individual ram’s genetic potential relative to a common baseline. EBVs have been developed for a range of traits. A Breeding Index may also be generated that combines a number of EBV traits. This aids decisionmaking around a set of objectives that require the improvement of several traits at once. Economic weightings are applied to the individual traits that make up the breeding index to reflect current market conditions. Commonly used Indexes include the Terminal Sire Index (combining growth and carcass traits to select superior terminal sires); the Maternal Index (focusing on early lamb growth rate, maternal ability and prolificacy. These indexes are useful for self-replacing flocks), and the Hill 2 Index (improves the overall productivity of hill ewes). Information about the use of Breeding Indexes is available from Signet Breeding Services (5). ‘EBVs are easy to interpret’ • ●EBVs are expressed in the same units as the recorded trait (e.g. kilograms for the 8-week weight). EBV of zero the greater the genetic potential of the ram. For example, a ram with an EBV of +3 kg for 8-week weight is estimated to produce lambs that are 1.5 kg heavier at eight weeks compared to the baseline EBV of zero. The baseline represents the average eight-week weight of the animals from the same flock in the year when the EBV was first produced. EBVs are published for each trait that is recorded. This allows a producer to focus on EBVs that are pertinent to specific breeding goals. Further detail on interpreting EBVs can be found via the Levy Boards (2,3,6). Genes Pay On an average Non-SDA farm with a breeding flock of 688 and a replacement rate of 22.9% this could potentially lead to an additional return of £2211 to the business each year. The potential additional return increases to £2520 for an average SDA farm with a breeding flock of 814 and a replacement rate of 26.3%. Based on average ewe to ram ratios this means that knowing the genetic potential of your rams could increase your returns by between £769 and £942 per ram over four breeding years. Calculations based on data from Stocktake Report 2016 (4). • ●Because a lamb only inherits half its genes from the ram the EBV must be halved. • ●Depending on the trait an EBV may be expressed as a negative or a positive value. • ●The further away from the average Q 2017 AUGUST & SEPTEMBER 11

Sheep Matters - August/ September 2017