Sheep Estimated Breeding Values

In the past, farmers had to base their ram choice entirely on what the animal looks like – conformation, length, flesh cover, muscularity etc, with the hope that a good-looking ram will pass these traits to his off-spring. However, we know these traits can be easily masked or enhanced by environmental factors – for example high levels of feeding. The ram’s true value lies in his genetics, or more specifically, the genetics that are expressed by his off-spring. Performance recording schemes, such as Signet, have been developed to make it easier to identify the superior genetics and see past the influence of non-genetic factors. It also allows assessment of maternal traits, such as maternal ability and prolificacy, which cannot be assessed visually.

What is an Estimated Breeding Value?

Recorded rams have a series of Estimated Breeding Values (EBVs) assigned to them, which indicate their breeding potential for various traits. They take into account the performance data of known relatives and the degree to which each trait is passed down the generations. EBVs are expressed in the same units as the recorded trait (for example, the EBV for Eight Week Weight is measured in kg) and relate to a common baseline of zero. The value “zero” is considered to be average for the breed, so a positive EBV indicates a better-than-average trait, and a negative EBV indicates a worse-than-average trait. So, for example, a ram with an EBV for Eight Week Weight of 3kg is estimated to be 3kg heavier at 8 weeks old, than a ram with an EBV of 0kg. 

There have been significant advancements in the development of EBVs for rams, with new data from the AHDB’s RamCompare project now available for breeders to use. This information bolsters performance-recording data that has been collected over the last 50 years. 

With profit margins as tight as ever, maximising efficiency in production is vital to future-proof your flock. There is only so much advantage to be gained from improvements in diet, pasture rotation and (dare I say it) disease prevention. The really significant gains are to be made in genetic improvement – hence the industry interest and funding being poured into these projects!

1. Set breeding objectives:

What traits do you want to see introduced to your flock? Consider the intended future for the lambs you are producing – are these rams going to sire meat lambs, or will they be your future breeding stock? This influences whether you focus mainly on the terminal traits or maternal traits. 

What issues currently limit your flock productivity? Do you struggle with low scanning percentages, or maybe your ewes are rubbish mothers? Do your lambs seem to grow OK but you just can’t seem to get the flesh on them? Decide on just one or two traits you would like to see improvement in the most. 

2. Select your EBV priorities:

The following EBVs are readily available for Signet recorded rams:

Maternal traits:

·Litter size – prolificacy
·Maternal ability (kg) – ewe milk production
·Eight Week Weight (kg) – growth rate to eight weeks of age (relates to maternal ability)
·Mature size (kg) – ewe weight at first mating (relates to ewe efficiency)

Terminal traits:

·Scan weight (kg) – growth rate up to 21 weeks, at which point they are scanned by a Signet technician for carcass traits
·Muscle depth (mm) – carcass muscling
·Fat depth (mm) – leanness

Other EBVs are becoming available, for example birth weight, lambing ease, thoracic and lumbar spine lengths, days to slaughter and parasite burdens.

3) Consider the breeds:

Estimated Breeding Values compare rams to others of their own breed. They do not allow comparison of animals of two different breeds. It is important to factor this in when you are making your breeding decisions, rather than focusing on EBVs alone. As an obvious example, a Texel with a relatively poor score for muscle depth will probably still have more muscle than a Romney. Often the most innovative farmers will experiment with different breed crosses until they produce the kind of replacement thaves they are looking for – and this will be different for every farm. A completely different breed of ram might then be used to produce meatier finishing lambs. 

RamCompare has published productivity data on 468 rams across 17 different breeds. All these rams under test had EBVs in the top 20% of their breed. The growth rates and carcass traits of their progeny (over 44,000 lambs!) have been monitored and recorded, giving us a strong data base to work from. Data is published on individual rams, rather than averages across the breeds, allowing farmers to source specific bloodlines based on the results. 

4) Go shopping!

Once you have an idea of the breeds you are interested in, take a look at the “Sheep Search” section of the Signet Breeding Services website. Here you can search for registered flocks by breed and postcode, or find rams based on their EBVs. You can also find the latest breed information for terminal, maternal and hill breeds, including up-to-date EBV benchmarks for 2024 progeny, compared to the original benchmarks set in 2010. Under the “Search sheep for sale” section, you will find rams currently listed for sale, with all their EBVs listed, their location and contact details of the breeder.

Another good place to look is the breed society website. As well as information about breeders and breed standards, you will find details of upcoming shows, sales and links to breed-specific listings on Sell My Livestock. Always go to see the animal in person before you part with any cash, so you can check his ear tags, body condition, teeth and feet. Rams should be fertility tested, with certificates available to see at the time of purchase.

It goes without saying that recorded animals are likely to sold at a premium, so it is important to know if your investment is going to pay off. Trials have shown that the difference between a ram with average EBVs compared to one with high EBVs could be worth up to £600 in his lifetime.  The difference between the lowest and highest performing rams could enhance flock profitability by £1200–1500/ram over their working lifetime. The most important thing is to choose carefully, selecting for the traits that will have the biggest impact on your flock productivity.