BY PAUL WILLIAMS TBTS TECHNICAL OFFICER
TECHTALK APRIL 2014DOWNLOAD ARTICLE HERE
One of the most common questions asked by seedstock breeders is "What size herd do you need to obtain effective results from BREEDPLAN?" Whilst there is no minimum herd size requirement for herds wishing to participate in BREEDPLAN, the nature of the BREEDPLAN analysis means that there are a number of additional considerations that small herds need to make to ensure the performance information that they record for their animals can be analysed effectively by BREEDPLAN.
There are two main concepts that all herds, regardless of size, need to understand if they going to obtain effective results from BREEDPLAN. These concepts are contemporary group formation and the creation of genetic linkage. Small herds in particular should look to implement management strategies which maximise the size of their contemporary groups and create genetic linkage both within the herd and with other herds in the breed.
Although the BREEDPLAN analysis is underpinned by a very sophisticated analytical model, the basic mechanism by which it works is to directly compare the performance of an animal with the performance of other "similar" animals within the same contemporary group. Put simply a contemporary group can be described as animals from the same herd, of a similar age and run under the same conditions i.e. animals that have had the same opportunity to perform.
For most performance traits, calves will be analysed in the same contemporary group if they:
Therefore small herds must try and ensure there are at least two animals that meet the above criteria if their performance records are to be analysed effectively by BREEDPLAN. When there is only one animal represented in a contemporary group, there are no other "similar" animals to which its performance can be directly compared and thus the performance submitted for it will not be used in the BREEDPLAN analysis, rendering it ineffective.
The effectiveness of an individual animal's performance record increases as more animals are represented within each contemporary group. The effect of the contemporary group size on the effectiveness of the performance is illustrated in the graph on the following page. The general aim for all herds should be to maximise contemporary group size where possible.
Genetic linkage gives the BREEDPLAN analysis the ability to compare the performance of animals from different contemporary groups. This is particularly important for animals running under different conditions in different herds, but also relates to animals in different contemporary groups within a herd. For example, animals born in the same herd but in different years. For BREEDPLAN to compare animals from different contemporary groups, each contemporary group must have some performance recorded progeny from common animals (typically common sires) so that the performance recorded animals in each group are genetically linked.
As a simple example of genetic linkage, consider the scenario below where 3 different mobs of calves (either on the same property or different properties) are compared. There are environmental differences between the groups – Contemporary Group 1 (CG1) has relatively poor nutrition, Contemporary Group 3 (CG3) is average and Contemporary Group 2 (CG2) is relatively good. All of the progeny in each group are by different sires (Nifty, Lofty & Curly), with a common link sire (Admiral) existing in each contemporary group. This link sire makes it possible to compare the progeny of the different sires represented in each group.
When compared to the link sire Admiral, Curly in contemporary group 3 can be considered to have the highest genetic value for 400 day weight performance, followed by Nifty in group 1, followed by Lofty in group 2. Graphically, these differences are shown in Figure 2. For the purpose of this exercise, we will assume all sires are joined to cows of equal genetic merit, although in practice, BREEDPLAN accounts for any genetic differences that exist between the dams.
Understanding the concepts of contemporary group formation and genetic linkage, it becomes obvious that small herds, if not managed with these concepts in mind, may struggle to maximise the effectiveness of their performance recording. Because of their low animal numbers, small herds tend to have high numbers of single animal contemporary groups, and may struggle to create genetic linkage, thereby reducing the effectiveness of their performance recording. There is however a variety of management strategies small herds can implement to increase the effectiveness of their performance recording.
There are a number of ways breeders can manage their herd to create effective contemporary groups.
There are a number of ways breeders can manage their herd to create effective genetic linkage.
This article only touches on the basic concepts of the BREEDPLAN analysis. Recently SBTS & TBTS ran a webinar for small herds , titled "Small Herds – Obtaining Effective Results from BREEDPLAN". This webinar is available for viewing on the SBTS and TBTS websites and expands on the concept of how BREEDPLAN works, contemporary group formation and genetic linkage. Additional information is also available from the tip sheets section of the BREEDPLAN website (http://breedplan.une.edu.au) or by contacting staff at SBTS or TBTS.