How to use EBVs for Selection

How to use EBVs for Selection

By Quentin de Bruyn

When selecting animals to buy or retain in your herd its physical appraisal or how it “looks” will always be important. Stockmanship, or the art of being able to judge how an animal will breed on its “looks” is an art that takes years of experience, working with cattle, attending breeders courses and learning from experienced stockmen. Nothing can replace this skill. 

However, good stockmen also know that the best “looking” cow is often the poorest producer – these cows either don’t have enough milk to raise a decent calf or they are not good mothers and lose their calves through neglect. “Looks” are also not a reliable indicator of other important traits such as milk, how easily she calves or her ability to raise a healthy calf. The best mothers give everything to their calves, which can leave them looking in poor condition. Therefore, relying on “looks” alone can be problematic. 

Using Estimated Breeding Values (EBVs) from performance tested herds is a critical tool to identify animals that not only look good, but are also good breeders. However, EBVs are only as good as the numbers behind them. They are only useful if they are accurate and they are only accurate if proper performance testing and data collection is done on an ongoing basis across the whole herd. It is very important to understand that inaccurate EBVs could be more misleading than helpful and should not be relied upon to make decisions. 

The following are some broad principles to use EBVs correctly for selection: 

  • EBVs tend to work against each other i.e. high scores in some areas will lead to low scores in others. For example, a cow with a high calving ease index (small calves) will tend to have a lower growth index. Similarly, a high “milk” index often contributes to a lower “fertility”, because cows that give everything to their calf can lose too much condition and struggle to fall pregnant again. The aim is therefore not to “maximise” EBVs but to be aware of the interplay between them and to understand what they say about the animals production potential. 
  • To use EBVs most successfully you need to have a very clear idea of your own breeding objectives and the needs of your particular farming environment. When you know what you want to achieve, accurate EBVs can help you select animals that fit into your environment and help you achieve your breeding objectives by addressing short-comings in your herd like growth or milk. 
  • Ideally, one should strive for balance across performance indicators rather than chasing outliers. 

Interpreting EBVs

Eve VST 14-59

In an auction catalogue, the Breeding Values for each animal are shown in a table at the bottom of each animals Lot card. (See example of Eve VST 14-59). There are four values in each Breeding Value column. The first value given, labelled “BV” on the left is the actual breeding value of that specific trait, the second line “Acc” indicates the accuracy in %,  while the third line expresses the actual breeding value as an INDEX against the breed average. The fourth line is a compilation of the relevant breeding value indexes into a single broader breeding value, such as fertility being based on both AFC and ICP. 

The EBV accuracy will give you an indication of the reliability of the figures. In general, anything less than 50% tells you that the actual recorded data underlying the figures is weak and unreliable. The more data that is collected through performance testing on an ongoing basis over generations within family lines the more value the EBVs have as a selection tool.

Breeding Values and the Breeding Value Indexes

  1. Calving Ease (CE)– The “Calving Ease” Index is compiled from the “Birth direct” and a “Birth Maternal” breeding value. An index of above 100 indicates that the animal will deliver below average size calves and therefore should reduce the chance of calving difficulties due to big calves. 
  2. Growth – The “Growth” Index is compiled from weaning weights and the 12 to 18 month growth performance as well as other data collected in the phase-C and phase-D tests. An index of above 100 indicates better growth than the breed average. This is particularly important for weaner production and an indication of their performance in a feedlot environment. 
  3. Milk – The “Milk” Index is made up of information from pre-weaning weights and weaning weights. An index of above 100 here indicates above breed average milk production which leads to higher calf survival rates and heavier weaners.
  4. Fertility – The “Fertility” Index is made up of Age at First Calving (AFC) and Inter Calf Period (ICP) and I think longevity also plays a role here. An animal with a fertility index of above 100 will give birth for the first time sooner and more frequently thereafter and for longer than the breed average in these traits.
  5. Maintenance – The “Maintenance” Index is based on the size and weight of an animal. The bigger the animal the higher the Direct Breeding Value (2nd to last line) will be, but the poorer the Maintenance Index will be. This is because bigger animals require more food and more hectares. A index of above 100 in maintenance indicates a smaller than breed average animal and will allow higher stocking rates.
  6. Cow Value – The “Cow Value” index is a tool rather than an EBV in itself. The Boran technical committee tries to determine what the ideal Boran animal should look like and how it should breed. This is expressed by giving a weight/importance to each individual breeding value. In the Boran breed the following weights have been determined – calving ease (9%), growth (25%), milk (18%), maintenance (12%) and fertility (36%). The “Cow Value” is a weighted composite of an animal’s individual EBVs and is meant to indicate how the animal is expected to perform against what the breed deems to be the perfect animal. The higher the Index the better the animal is expected to perform against the ideal breed standard.
  7. n my opinion, the individual EBVs are more useful than the “Cow Value” for selecting animals which help to fix a short-coming in your herd or which would be more suited to your own specific environment. Personally, I tend to discount calving ease because I think we are fortunate to have a breed with low birth weights and little calving issues. I also prefer to choose animals that are slightly above breed average in size because the Boran breed is a smaller breed and most South African farmers are weaner producers and want bigger weaners with good growth to get better per kg prices from the feedlots.
  8. Bull Value – The “Bull Value” index is generated from measurements in Phase-D and Phase-C performance tests of the testicles circumference of peer groups. An index above 100 will indicate that the animal will have above breed average testes in the male offspring. Testicle circumference is directly linked to fertility in cows and the quality and quantity of semen produced by bulls, which affects their ability to get many cows pregnant in the shortest time possible.

2021 Vastrap Auction

The importance of accurate EBVs in animal selection

In this blog I would like to focus on Estimated Breeding Values (EBV’s) and why are they so important. In particular, how can EBVs be used to help pick which animals to buy in order to build or improve one’s herd. The main point I would like to make is that EBVs supply crucial decision-making information to a buyer, but they are only as useful as the data used to calculate them. It is important to bear in mind that the EBVs published in an auction catalogue do not indicate whether the breeder participates in the National Beef recording and Improvement scheme or how accurate the particular set of EBVs are (i.e. what data on the individual animal has actually been captured rather than inferred). As you will see below, we are doing everything we can at Vastrap to make sure the EBVs in our sale catalogue are meaningful and can be used as an extra tool to select the right animal for your herd.

Unpacking EBVs

Basically, when one buys a stud animal, there are three ways in which to judge the potential value of that animal to your stud. Firstly, one can look at the parentage or genotype (hence the importance of doing proper DNA parentage verification see The importance of  parentage verification through DNA testing), secondly one can look at build or phenotype and lastly one can use EBVs. In rare cases one is able to look at progeny when buying older animals. While parentage and sound functional physical attributes like muscling, leg structure, udder conformation and teat quality will always play a very important role, EBV’s can be used to complement visual screening to select animals. There are several individual EBV’s that allow a breeder to come to an informed decision about what the animal in question can offer the breeder beyond good looks.

All EBV’s are expressed as an index where 100 is the average. Where an animal’s index is below 100, then it has faired poorer than the breed average, while an index above 100 means it has faired better.

I will briefly discuss the individual EBVs below.

  1. Birth EBV – One wants animals that have smaller or lighter calves. This EBV serves as an indication of whether this animal will produce smaller/lighter or bigger/heavier calves. An index of over 100 will mean better than average and equate to a better chance of below average birth weight. This EBV is broken into two categories: the animal’s own birth weight EBV (Direct) and the maternal EBV.  The data that feeds into these EBVs are recorded birth weights of calves born. If one has a calving problem in your herd, one would look to buy a bull with a high calving ease EBV index (i.e. low birth weights)
  2. Calf Growth and Milk EBVs – These values are calculated using the data gathered from wean weights, the mother’s weight at weaning, 12 month weights and 18 month weights as well as the phase-D growth performance testing of bulls which is more accurate than just 12 and 18 month weights and also includes other important data points. Generally a growth and milk index above 100 is very desirable, though like all things in life some balance must be kept. Milk and fertility generally have an inverse relationship and so does growth and calving ease. If one were predominantly a weaner producer, then one would want higher milk and higher growth.
  3. Fertility EBV – The fertility EBV is made of two sub components namely the age at first calf (AFC) and inter-calf period (ICP). Obviously, one wants an animal that has the ability to calve first amongst her peer group and that calves regularly, preferably once a year. An index above 100 is an indication that the animal is more fertile than the breed average and this is based on the past performance of the family members of the animal in question. Milk and fertility often are inversely correlated (the more cow gives to a calf the less likely she is to fall pregnant again), so while one wants the most fertile herd possible, one should avoid negatively influencing the herd milk values in this pursuit.
  4. Cow Weight EBV – The cow weight EBV is made up of the 18 month EBV and adult weight EBV. A heavier animal at 18 months and as an adult has an index of above 100, while smaller animals have indexes low 100. The combined indexes are then used to derive a cow maintenance index, which is inversely proportional to the cow weight indexes, since a smaller cow is deemed to have a lower maintenance value. In harsher environments one would want smaller cows to reduce the maintenance factor.
  5. Cow Value EBV – This is an accumulation of the individual EBV indexes and uses a formula using different weights of importance for the individual EBVs to give an indication of the value of the cow. Personally, I am of the opinion that individual breeders have different needs and therefore place different emphasis on individual EBVs. A breeder should rather look at the individual EBVs to see what is needed in their herd than to rely on a set formula that does not take into account different environments and individual preferences.

EBVs and data collection

Our main purpose in writing this blog is to underline the importance of thorough record keeping and the supply of accurate performance data to the National Beef recording and Improvement scheme. The EBVs supply crucial decision-making information to a buyer, but they are only as useful as the data used to calculate them. It is important to bear in mind that the EBVs published in an auction catalogue do not indicate whether the breeder participates in the beef improvement scheme or how accurate the particular set of EBVs are. One can only judge this by looking at the production data on Logix (Live Stock Information and Genetic Information Exchange) to see whether any weights have been captured.

In the Boran industry, the number of breeders participating in the National Beef recording and Improvement Scheme and performance testing is still low. I am often disappointed to see that animals in which I have a strong interest at auctions do not have a single measured data point – no birth weight, no wean weight, no mother weight at weaning and certainly no 12 or 18 month weight. Without this data, no meaningful insight can be drawn about the potential future performance of the animal and one only has genetics and physical attributes on which to make a decision.

Since buying the Mollshoop Boran stud in 2011, our policy at Vastrap Boran has been to collect as accurate data as possible on every single animal, including birth weight, wean weight and the mother’s weight at weaning. We also collect 12 month and 18 month weights. In addition, since 2011 Vastrap has put 95% of its bull calves through the Studbook administered phase-D veld performance test, which provides additional important information such as testes development, muscling, meat yield and marbling to name a few (see Bull Selection and Performance Testing). Vastrap alone has contributed over 35% of all the recorded phase-D bulls tested in the Boran stud industry.

We can therefore assure you that the EBVs of Vastrap animals, even those older ones where their individual performance data was not measured, is as accurate as it can be. You can rely on the EBVs of Vastrap animals published in the Vastrap Auction sale catalogue and these EBV will provide you with an extra tool to assess the animals you like, over and above build, looks and parentage. This should help you to make a more informed decision about which animals will fit into your herd.

Below are examples of the production data and EVBs drawn from Logix for Jackie VST 12-04, and one of our three-year old bulls that went through performance testing VST 14-84. The first column of data shows all the data on the animal that has actually been measured. This data is important for the animal’s parents and their progeny, who will have EBVs based on the performance of their parents until they get their own data.

Jackie VST 12-04 (Jackie MHB 05-08 x Co-Jack CI 08-30)