Micron-Adjusted Standard Deviation. Our “Secrets” Revealed, Part One
Our “Secrets” Revealed, Part One
This is the first of a series of three blog posts where we will introduce and describe several proprietary analytical measures we calculate and use here at Little Creek to help assess our animals’ genetic propensity to produce specific, desirable fleece qualities in their offspring.
We calculate these measures because we find they help us target specific genetic improvements more accurately with our breeding decisions. If, as you read about these measures, you think they might be useful to you also, your next question might be “how can I calculate these measures for my own herd?” The answer is simple – we will tell you how we do it. And we will even do the analysis for your herd ourselves if you wish.
The first measure we will introduce you here is the micron-adjusted standard deviation. We use this measure to help us breed for animals that are exceptionally uniform without being exceptionally fine. This is, in our opinion, the most important genetic step we can take as an industry to improve the prices we receive for our fleece. We have written a detailed article on the calculation and validation of this measure that you can find in our library on this website if you wish.
Micron-Adjusted Standard Deviation (MASD)
What is it? MASD reveals the impact on micron uniformity of elements of animal’s genotype that are not linked to those that are associated with fineness. A negative MASD is good because it implies that this portion of an animal’s genotype appears to be contributing incremental uniformity compared the average of the animals under consideration.
The image above shows the histogram summary for a two-year-old working male that was bred to maximize his genetic propensity to produce micron uniformity in his offspring without maximizing the genetic potential for fineness. The SD and %>30 on this histogram are much lower than typically evidenced by animals with fleeces of this AFD. This histogram reflects what expected to see in the phenotype of such an animal, and we achieved it by using MASDs to select his parents.
How can you use it? MASD is a helpful tool to use when you are trying to breed for animals with improved micron uniformity at a targeted degree of fineness. As an example, if you breed for improved standard deviations alone, you will also be favoring ever-increasing fineness, but if you pair animals in your herd to produce offspring with better than average propensities to produce uniformity (negative MASDs) along with, say, (to set a specific target) average propensities to produce fineness (EPD AFD), the crias produced will, on average, be more uniform without being finer.
How is it calculated? An animal’s MASD is the difference between its actual EPD SD and what would be predicted based on the typical relationship between EPD AFDs and EPD SDs within the herd or other group under consideration.
How do you know MASD really reflects genetic differences, and not something else? This is not a question we can answer directly with our data. However, we find in our own herd that animals with particularly low or high MASDs have a higher average degree of kinship (that is, they are more related) than the herd as a whole. What is more, the shared ancestry includes animals that we associate anecdotally (that is, by personal observation) with the production of offspring that are particularly uniform, or particularly non-uniform. Finally, the regression analysis and individual observations passed some important statistical tests of validity. This is good circumstantial evidence that MASD does indeed reflect genetic attributes that are being passed from generation to generation.
How can I calculate my own herd’s MASDs, or use the ones calculated for Snowmass or Accoyo America Animals? We can help you calculate the MASDs for your own intra-herd comparisons based on a downloaded EPD report for your herd. The results will show which animals in your own herd are likely to carry genetic attributes that will improve or reduce micron uniformity relative to fineness in your herd via their offspring. This is quick and straightforward to do so do not hesitate to ask us for some help if you are interested. If you do not have EPDs calculated for your animals, we can also do a similar analysis for you based on a spreadsheet of your histograms, though it will require more contextual interpretation because unlike EPDs, histogram results themselves are not adjusted for animal age differences and other factors. Again, contact us for more detail.
The MASDs for Snowmass and Accoyo America animals can be used to help you compare animals within and across those herds to help identify animals or bloodlines that might be incrementally useful in your own program. They will not be directly comparable to the MASDs calculated for your own herd, but we can essentially “convert” them to a comparable number if you are interested. Of course, we also use our MASDs for intra-herd breeding decisions, based on the individual herds’ genetic improvement goals.
Where can I see your specific analysis? Please read our article on this topic in our library.