The following was downloaded from the ARI Academy website - https:www.arilist.com
EPD TRAIT DESCRIPTIONS
Estimated Progeny Differences (EPDs) are calculated for many fleece traits from data collected from standardized fiber analysis. Growth and maternal traits are also included in the launch of the ARI EPD program (birth weight, weaning weight, and birthing ease).
EDPs provide an estimate of the average difference in an individual’s progeny performance as compared to the national herd OR as compared to another individual animal. EPDs cannot predict the outcome of a single breeding, but rather predict the progeny performance on average over a number of progeny. Utilization of EPDs for traits of interest in breeding plans which include selection for desired traits will, over time, move the herd’s performance in the desired direction.
EPDs are ONE tool in a breeder’s toolbox of methods for making informed breeding decisions. Conformation is not yet addressed by the ARI EPD program. Other traits such as maternal characteristics are also not yet addressed by the program. More to come!
Fiber samples are collected from the alpaca mid-side during annual shearing of the entire herd or entire group which has been maintained under the same environmental conditions (contemporary group). It is simple, but very important, to send representative fiber samples for testing. The integrity of sampling (the careful and proper selection of a sample) is the most critical factor involved in measurement of fiber diameter in individual animals. The samples must be taken at the middle of the side in the blanket location.
Yocom-McColl Testing Laboratory, utilized for fiber analysis for the ARI EPD program, is equipped with the state-of-the-art instrumentation for measuring animal fibers. The Sirolan Laserscan, developed by CSIRO, and Optical Fiber Diameter Analyzer (OFDA), developed by BSC Electronics are used by the laboratory. Both companies are located in Australia. These instruments are calibrated using Interwoollab s tops, the only recognized supplier of calibration tops to the worldwide textile industry. A diagnostic and calibration check is performed daily on analytical instruments. The accuracy of measurement of average fiber diameter is ± 0.3 microns and the tests are performed under standard conditions of 65% ± 2% relative humidity (RH) and a temperature of 70° ± 2°F.
The ARI EPD histogram provides data on the following fiber measurements. EPDs will not be calculated from all of the data as described below.
Average Fiber Diameter (AFD) or Mean Fiber Diameter (MFD)
AFD is measured from a sample of fiber collected from the mid-side of the alpaca. A four by four inch sample should be taken and kept in staple alignment. The fiber testing laboratory maintains the staple configuration and cuts across the base of the staples generating many 2mm snippets which are measured using an analytical instrument known as OFDA100. A histogram is generated which shows the number of fibers, as a percent of the total counted, in one or two micron increments. The base of staple AFD provides data on the fleece at a given point in time (shearing). The use of base of staple measurement supports contemporary group quality, critical to the development of valid and accurate EPDs.
The AFD EPD may be used by breeders to select for animals which produce fleece finer than the average of the overall national herd as well as within individual herds. A negative EPD value indicates that the animal’s progeny will have, on the average, finer fleeces than the breed average.
Standard Deviation (SDAFD)
Standard deviation of the set of measured fibers is also determined. SDAFD shows how much variation or dispersion there is from the average (mean). The smaller the standard deviation the more uniform is the sample.
The SDAFD EPD will aid the breeder in selecting animals which produce uniformly sized fibers. A negative EPD value indicates that the animal’s progeny will have, on the average, more uniform fiber diameter than the breed average.
Co-efficient of Variation (CV)
No EPD will be reported for this derived value that is reported on the histogram.
The Coefficient of Variation is the Standard Deviation divided by the AFD multiplied by 100 and reported as a percentage. The CV is used in the statistical analysis of different populations of fiber (different animals). CV can be made smaller (more desirable) by either a lower SD or a higher AFD and therefore could result in undesirable consequences if used as a selection factor.
Spin Fineness (SF)
Spinning Fineness is expressed in microns and provides an estimate of the performance of the wool when it is spun into yarn.
Spinning Fineness is calculated from the measured Mean Fibre Diameter and the measured Coefficient of Variation of Diameter. The Spinning Fineness is the same as the Mean Fibre Diameter when the Coefficient of Variation is 24%. Wools with a CV of less than 24% will have Spinning Fineness less than the Mean Fibre Diameter.
Percentage of Fibers > 30 microns (%F>30)
An EPD for % fibers > 30 microns can be used by breeders to select for animals that produce more uniform fleeces (in conjunction with SDAFD) as well as for animals with finer primary fibers. While primary fibers cannot be eliminated entirely it is possible to select for animals that produce finer primary fibers and for those that produce higher ratios of secondary to primary fibers.
The % fibers >30 EPD will aid the breeder in selecting for more fleeces with more uniform fiber size and smaller primary fibers. A negative EPD value indicates that the animal’s progeny will have, on the average, fewer fibers more than 30µ in diameter than the breed average.
Comfort Factor is simply 100 – the % fibers > 30 microns. An EPD will not be reported for this value.
Mean Curvature (MC)
EPDs will be reported for the trait of curvature. Curvature is a way of looking at crimp, but it can be deceiving. The method of measuring curvature is to determine the degrees of curvature observed over the length of the 2mm snippets that are generated by the base of staple sampling methodology. Higher curvature is observed in fleeces that show high frequency and fairly low amplitude waves. Fleeces that have very high amplitude waves may not generate as high a curvature measurement as might first be thought. This is due to the possibility of sampling within the straight part of the fiber in between the curves at the top and bottom of the waves. No EPD will be calculated on CV of Mean Curvature.
The MC EPD will aid breeders in selecting for higher frequency crimp styles. Care should be taken to also visually assess the crimp style as well. A positive EPD value indicates that the animal’s progeny will have, on the average, higher frequency crimp than the breed average.
Standard Deviation of Curvature (SDMC)
SDMC EPD is reported. This trait assesses the uniformity of curvature within the fleece sample. Curvature (and crimp) is variable in alpaca fiber. The value of Standard Deviation of Curvature data available from OFDA100 analysis has not been agreed on by researchers but it is definitely secondary to Mean Curvature when used for assessment or selection of individual animals. (from McColl, Angus “An Inside View of Fiber Testing” Alpacas Magazine, Herd Sire Issue 2009)
% Medullated Fibers (%M)
Medullation, or the occurrence of a hollow core or hollow sections within the fleece, can be measured for white or very light colored fleeces. The medullation is measured by shining bright light through the snippets sample and capturing the percentage of the fibers which can be observed to have a hollow core. Values are reported in the fiber analysis only for white and light fleeces, as the measurement cannot be done on darker colored fleeces. However, because of genetic correlations within the data it is possible for EPDs to be calculated for all color fleeces and this trait will have a EPD reported for all colors of animals. Medullation was thought to only be observed in primary fibers but with further examination has been found in the very finest of fibers even down to as small as 10 microns. The full impact of medullation in fleece remains a question at this point in time.
Using IWTO nomenclature, a kemp fiber is classified as an “objectionable fiber” when measured on the OFDA100. A medulla in mammalian hair fibers is the more or less continuous cellular marrow inside the cortical layer in most medium and coarse alpaca fibers. By definition (ASTM), a kemp fiber is a medullated fiber in which the diameter of the medulla is 60% or more of the diameter of the fiber. (from McColl, Angus “An Inside View of Fiber Testing” Alpacas Magazine, Herd Sire Issue 2009)
A negative EPD value indicates that the animal’s progeny will have, on the average, less overall fiber medullation than the breed average.
Mean Staple Length (MSL)
EPDs will be reported for the trait of staple length to aid in selecting for the production of longer staple lengths. Production of sufficiently long staples for ease of processing is a desirable long term trait.
The MSL EPD will aid breeders in selecting for animals which produce longer staple lengths or that maintain or minimize loss of staple length when selecting for finer fleeces. A positive EPD value indicates that the animal’s progeny will have, on the average, longer staple length per growth period than the breed average.
Fleece Weight (FW)
EPDs for fleece weight will be reported. This value may be used to help breeders select for animals that produce higher fleece weights. It should be noted that one way of producing higher fleece weights is the production of higher micron fibers. Care should be taken in selecting for this trait alone.
A positive EPD value indicates that the animal’s progeny will have, on the average, heavier fleeces than the breed average.
EPDs will be reported for birth weight when sufficient data is accumulated. Birth weight can be an important
characteristic for breeders in considering mates for maiden females, especially if the female is smaller. Birth weight data is reported directly to ARI by breeders through their account pages.
A negative EPD value indicates that the animal’s progeny will be, on the average, smaller than the breed average.
EPDs will be reported for weaning weight when sufficient data is accumulated. Weaning weight may or may not be a trait of interest to most breeders. Weaning weight data is reported directly to ARI by breeders through their account pages.
A positive EPD value indicates that the animal’s progeny will be, on the average, larger at weaning than the breed average.
EPDs will be reported for birthing ease when sufficient data is accumulated. Birthing ease data is subjective and reported by the breeder by selecting one of the 4 categories describing the ease of birth for individual females. This trait is important for husbandry of herds of alpacas. In other livestock species this trait has been shown to be heritable by the daughters of sires and the EPD will be reported for both males and females. When reported for males it will reflect the genetic impact the sire has on his daughter’s birthing capability.
A negative EPD value indicates that the animal’s progeny will, on the average, birth with less difficulty than the breed average (this does not, by any means, indicate that females will not have birthing difficulties!!).