EPD

Expected Progeny Differences or EPDs

EPDs can take many pages to explain; here is a brief overview. EPD is a powerful tool based on quantitative genetics used by livestock breeders for decades to aid in sire selection and dam/progeny evaluation. The technology takes measurable, quantitative (and in some cases qualitative) data and applies a set of equations designed to discount the contribution of all inputs to a specific trait except the genetics of the individual animal of interest to predict the outcome “on the average” of matings of that animal to a set of females of similar quality.

EPDs can also be used to help evaluate traits of economic importance such as fiber fineness. Using this technology will help breeders to select sires that help to produce finer fleeced herds. This trait may be evaluated in conjunction with other production traits such as yearling and/or two-year old weight as breeding for fineness tends to produce smaller and smaller animals over just a few generations.

An example of a trait for which most livestock industries develop an EPD is birth weight—bigger babies, whether they be crias or calves, increase the chance of birthing difficulties. Most livestock industries consider it important for a sire to contribute to smaller or at least not bigger babies, on average. Birthing difficulties bring significant costs in terms of animal loss, time and money. Therefore, a consideration along with improvement of economic traits of importance is a neutral to negative impact on birth weight.

EPDs have been used in other livestock for decades, most notably in the dairy industry for milk production and beef industry for marbling. Sheep fiber producers have also adopted the use of EPDs as have many Australian alpaca producers.  Use of EPDs in the U.S. alpaca industry is in its infancy; the 3rd calculation was just completed in March 2012. Historically, it takes about 5 years for EPDs to be accepted and used by producers. RobAsia is proud to be a part of this herd improvement technology and we look forward to its evolution in the Alpaca Fiber Industry.

EPDs are yet another tool of objective data for herd improvement.

An Explanation of Expected Progeny Differences (EPDs) as released from ARI for each trait.

 

Average Fiber Diameter (AFD)

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.

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.

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.