13th April 2002
News
13th April 2002
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Making sense of EBI for bulls
By Pat O' Keeffe
The introduction of the Economic Breeding Index (EBI) has given farmers a more accurate tool in bull selection. This year sees the introduction of some improvements - this article summarises the changes and the following are some points to consider when making your choice.
Have a look behind the high EBI and see what it is made up of. Try to pick the bull with the combination of strong points most suited to your needs. If high fertility is your priority, focus on these figures.
Don't heavily use individual bulls with low reliability. Reliability is a measure of how accurate the figures are and depends on the number of daughters that contributed to the bull's rating. If the reliability is low, the figures are more likely to change.
Give preference to bulls with Irish daughters, regardless of where the bull originally came from. Don't forget that the majority of "Irish" bulls have very similar blood to their "foreign" competitors.
Just because someone is from Brazil doesn't automatically make them a great soccer player. Likewise, not every bull from New Zealand America or any particular country is automatically better than the rest. Judge a bull on their individual merits, not their country of origin.
Avoid bulls with extremely low scores for udders and feet and legs. These traits have proven links to longevity. There is no need for major emphasis on them - simply exclude bulls with strongly negative scores under these headings.
Don't be a slave to fashion. If a bull did well for you in the past and is still available with a good EBI, use him again. Of course keep an eye on the risks of inbreeding.
Inbreeding is on the increase, as more and more bulls are from the same bloodlines. It could be affecting your herd already. Spend a little time going through your breeding chart and note the sires of the cows. Be particularily careful of Irish bulls such as Linde Bartho (LBO), Galtee Merci (GMI) and Mars Ferro (MFX). They have large numbers of daughters on the ground and are still in widespread use.
Don't expect bulls with good scores for survival and calving interval to solve herd fertility problems overnight. Breeding is only a partial solution.
Avoid the bulls sold on their "outstanding udders" or "superb legs and feet". A good salesperson can sell virtually any bull on some specific strong point - look for the best all-rounders.
How is the EBI value calculated?
The Economic Breeding Index (EBI) combines information on milk, fat and protein ratings, as well as survival and calving interval. Bulls are given figures for each of these traits on the basis of their daughters' performance. These figures are then combined in a "weighted index" to produce one single EBI value.
A "weighted index" means that the traits that have the most impact on profit have the greatest effect on the final EBI value. Protein kilograms has the heaviest weighting, due to its economic importance.
Crossbreeding
Crossbreeding potentially has much to offer and Teagasc now actively promote this choice. However, herdowners should tread carefully. Genetic merit that takes generations (years) to accumulate can be undone in one bad cross.
As a"toe in the water," there may be merit in using a panel of Jersey, Montbeliarde or Norwegian Red bulls on a portion of the more "extreme" young cows in the herd. Bear in mind of course that crossbreeding has yet to be fully evaluated in a large scale study under Irish conditions.
Consider the pros and cons. The positives are that crossbred animals tend to have better health and fertility than their parents. In the case of the Jersey breed, the downsides would obviously include higher butterfat, smaller calves/cows and the lower bull calf value.
If you opt for crossbreeding, remember that individual bull selection remains crucial. So once you have chosen a breed, select a panel of good bulls that match your criteria.
How does the EBI measure fertility?
The EBI index includes figures for two traits closely related to cow fertility - survival and calving interval.
The daughters of some bulls have a better ability to stay in the herd than others and the EBI rewards these bulls with higher scores for "survival".
Calving interval is the length of time from one calving to the next. A bull whose daughters have a longer than average calving interval is penalised. Bulls with good daughter fertility will have negative scores for calving interval - less days from one calving to the next.
Survival ratingson foreign bulls
This year also sees survival and calving interval ratings placed on an increased number of foreign bulls. Many of these bulls do not yet have Irish daughters - in these cases, data from their home countries is converted to Irish equivalents.
The accuracy of these conversions is a contentious issue in the AI industry, but it offers useful guidance to farmers.
Where the foreign bulls have Irish daughters, there can be no arguments, as the scores achieved by the bull is a reflection of how their daughters performed under an Irish sky.
Predicting longevity
This year four "predictor" type traits are also included in the analysis. These are Angularity, Body Condition Score, Foot Angle and Udder Depth. They are the best available early indicators of likely survival.
So, for example, when the first crop of daughters of a bull calve down, there is no information available on how they "survived" their first lactation, or how long a calving interval they had.
In this case, scoring them on the four type traits gives the best estimate of likely survival. So, for example, if all the daughters of the bull score very poorly on udder depth (they have very deep udders), they are likely to have poor survival.
The bull with the highest Economic Breeing Index (EBI) in Ireland is the Progressive Genetics bull Newhouse Sjoerd (NHS). Let us go through his figures in detail in order to better understand what EBI is all about.
An example of how to read the figures
The bull NHS has an EBI value of €82. This means that NHS daughters will generate €82 more profit per lactation than offspring from an average bull with an EBI of
€0.
NHS received that rating based on 45 daughters milking in 32 Irish herds. They produced moderate yields of milk with extremely high fat and protein content. The bull scores 0.5 for calving interval - this means that the length of time from one calving to the next is half a day above average. This is not a major worry, unless you are looking for the best bulls on fertility, in which case you would look for a bull with a -2 or -3 for calving interval. The score for udders, legs and feet is average. Highly positive scores are better than negative ones, and bulls with large minus values should be avoided.
The main weak point in the figures for this bull is the low reliability score. This will only increase as more daughters are added. Low reliability means a higher risk that the figures will change.
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Copyright © : The Irish Farmers Journal 2002 |
