Eastern Alliance for Production Katahdins


NSIP – What Is in It for Me?

For most of us, raising sheep is a business. All successful businesses continually and objectively evaluate their products for performance, accuracy, and predictability. Estimated Breeding Values (EBVs) as provided by the National Sheep Improvement Program (NSIP), allow shepherds to convert performance records for economically important traits into information about an animal’s genetic merit while increasing accuracy and predictability for those traits. EBVs provide a science-based selection tool to improve or enhance preferred traits but do not take the place of direct evaluation of an animal’s physical appearance, health, or structural correctness.

There are multiple ways to use the power of EBVs to minimize the guesswork of breeding selection and to improve your operation whether you are a commercial or a seedstock producer. You can receive EBVs on your animals by joining and submitting data to NSIP. If the cost and extra management tasks are not practical, you may still reap the benefits of EBVs by purchasing sheep, especially rams, with EBVs. The benefits, requirements, and costs of joining NSIP are outlined below.

Benefits of EBVs

You may be wondering what benefit EBVs would provide over the performance data you already use to evaluate your flock. Environmental or non-genetic effects account for most of the differences you see among animals. EBVs help by measuring the part due specifically to genetic effects. For instance, EBVs make it possible to compare the growth of animals born in different years, under different management, or from different farms. Without EBVs, it is difficult to compare a current lamb crop to lamb crops from previous years. A case in point, inclement weather, disease or changes in management leads to differences in lamb performance from one year to the next. EBVs remove the environmental noise and allow better selection across years.

EBVs factor in the performance of the animal itself, as well as the performance of its relatives. This inclusion of multi-generational performance data helps to more accurately predict how an animal’s offspring will perform. When comparing two lambs with the same low fecal egg count (FEC), the lamb whose relatives also had low FECs will have better fecal egg count EBVs than the lamb whose relatives had moderate or higher FECs. Animals whose relatives perform similarly have a higher chance of passing on that trait to their offspring.

EBVs also adjust for a lambs’ age, sex, birth type, rear type, and age of its dam so that accurate comparisons can be made. Two lambs may have the same weight at weaning but if one is a single out of an adult ewe that was born at the end of the lambing period and the other is a twin out of a yearling ewe born on the first day, their genetic potential may be very different. You can use adjustment factors to calculate some of these differences, but that can be time consuming and much less accurate. EBVs will do the calculations automatically with the added benefit of estimating which part of the weaning weight is due to growth potential of the lamb vs milk production of its dam.

Some economically important traits like mothering ability or milk production, cannot be easily quantified making comparisons between ewes difficult. NSIP is able to perform complex calculations and provide EBVs to estimate genetic merit for these traits. Some traits are unrealistic to measure on your whole lamb crop, such as yearling weights, since most of the lambs will be sold before they reach one year of age. EBVs can estimate traits, like yearling weights, that take a long time to measure by looking at the performance of relatives that had yearling weight measured as well as the measurement of correlated traits such as post-weaning weight which is a good indicator of yearling weight.

The number of lambs a ewe produces each year is important because ewes that have singles frequently do not pay their way. Without EBVs, most people try to select for multiple births by only keeping twin or triplet born ewe lambs. EBVs look at the lifetime performance of the ewe lamb’s dam as well as her sire and dam’s female relatives thus giving an accurate and definitive evaluation of her genetic merit for prolificacy. A single ewe lamb out of an older ewe that historically produces triplets should have a higher genetic merit for multiples than a twin born ewe out of a dam that historically singles.

When there are enough genetic connections with other flocks enrolled in NSIP, EBVs allow comparisons of animals from different flocks, different management systems, and different ages. When looking for a new ram, it is difficult to compare a nine-month-old supplemented ram to a six-month-old grass-fed ram that is 40 pounds lighter. If both farms are in NSIP and are genetically linked, one can simply look at their weight EBVs and compare them one to one.

Benefits of NSIP Membership

There are many benefits to joining and submitting data to NSIP including:

  1. Free flock management software (Pedigree Master) provided to organize and submit your data so that EBVs can be calculated for your flock.
  2. Easy access to all animals with EBVs in the NSIP database through the Online Searchable Database on the NSIP website.
  3. A percentile report on the NSIP website that can be used to compare your animals to all lambs born during the past two years.
  4. Unlimited data submissions and updated reports provided from Lamb Plan for the current lamb crop. Data can be submitted at any time and reports are generated twice a month and include any updated calculations. These reports include:
    1. An Individual Listing Report: This report includes the complete and updated EBVs on each sire used, the dams that lambed, and the lambs born during the current lambing season. Each time more data is collected and submitted, the EBVs will change slightly. Weight and FEC EBVs are direct measurements for the current lamb crop, while maternal traits are considered “pedigree” measurements until the lambs start producing offspring themselves. Each EBV has an accuracy associated with it. As more data is submitted for an individual animal, their accuracies as well as their relatives’ accuracies for those traits increase.
    2. Sire Summary: A list of sires used each year including the number of male and female progeny.
    3. Genetic Trends: Traits are charted showing how your flock compares to the average Katahdin NSIP flock and tracks the progress made annually for each trait.
    4. Database Summary: This includes the number of lambs born and raised each year by sex and the data collected at each collection point: birth, weaning, early post-weaning, postweaning and adult. The data collected on each flock is used to compile the percentile reports listed on the NSIP website.
  5. A listing of your farm on the NSIP website which can serve as a marketing aid.
  6. Newsletters and updates sent to members periodically by email.
  7. Educational materials and webinars also provided by NSIP.

Requirements for NSIP Membership

Membership in NSIP is theoretically open to all sheep breeds that meet a minimum set of requirements and is independent of breed registry. The sheep do not need to be from registered seedstock. To ensure that EBVs are accurate and meaningful, there are some basic criteria required.

  1. EBVs cannot be compared across breeds so best results are produced with purebred sheep (commercial or seedstock). Crossbreeding programs can boost some performance traits due to hybrid vigor over what their genetics dictate.
  2. There is no minimum or maximum flock size required for NSIP. However, accuracy is greatly improved when a flock has a contemporary group of at least 10-20 lambs per sire born within a 35-day period and managed the same. Lambs born after that 35-day period will be placed in a separate contemporary group for more accurate comparisons. The more lambs you have in each contemporary group, the more accurate their EBVs will be.
  3. The ability to individually identify your sheep is critical. Tagging lambs early, assigning them to the correct dam and sire, and recording data carefully is essential for accurate EBVs. In addition, all animals in NSIP are assigned a 16-digit ID that reflects its breed, flock, and individual ID for data submission.
  4. Using at least two sires per breeding season allows comparisons of the genetic merit of each ram based on their progeny’s performance compared to their contemporaries. This is usually done using individual breeding groups, pairing one ram with his own group of ewes. Multiple sire breeding groups (multiple rams used with one large group of ewes), will require parentage testing on all the lambs. It is possible for lambs in one litter to have different sires. Relying on breeding harness marks alone to decide parentage in a multiple sire breeding scenario may give you sire mismatching and therefore inaccurate EBVs.
  5. You must be willing and able to collect, record, and submit the following information on all lambs born. You cannot just submit your best lambs.
    1. ID number of the lamb, its sire and dam
    2. Birth and rear type (single, twin, triplet, etc., and dead, artificially reared, and grafted lambs)
    3. Birth weight (recorded within 24 hours of birth)
    4. A weight on all the lambs on one day when the average age for the group is 60 days old (45-90 days) which is used to calculate Weaning Weight (WWT) EBVs. This will probably not be the date that you actually wean your lambs. At 60 days, ewes are still producing a fair amount of milk which enables representative estimates of the ewe’s milk production and mothering ability (Maternal Weaning Weight, MWWT).
  6. Although not required, another weight collected on one day at around 120-150 days of age is suggested. Post-Weaning Weight (PWWT) EBVs can be calculated based on the 60-day weaning weight, but including an actual weight at 120-150 days will improve accuracy.
  7. Optional data to collect and submit:
    1. Weaning and post-weaning fecal egg counts (WFEC and PFEC) to measure parasite resistance.
    2. Carcass trait ultrasound measurements for loin eye depth (EMD) and fat cover (PFAT).
    3. Scrotal circumference (PSC).
    4. Later weights to calculate yearling weights (YWT) and hogget weights (HWT). There is not an adult weight EBV currently, but yearling and hogget weights can be used in your flock as a good indicator for adult weights.


There are two sets of fees for member flocks: an enrollment fee and a database fee. The flock enrollment fee for 2021 consists of a flat $100 enrollment fee plus $2.50 per breeding ewe, capped at a total of $500 per year. The database fee for 2021 is $3.50 per lamb for any animal with post-birth measurement submitted, except those designated with CU or CO in their IDs. You will not receive EBVs on the animals marked CU or CO, so make sure it is only used for animals not destined for breeding. Their data is still useful and will be included in the calculations for their family members’ EBVs. The CU or CO coding is restricted to 30% of the lamb crop if used. The database fee is charged only one time in an animal’s life, with unlimited data submissions possible.

Other Considerations

If you think you may want to join NSIP at some future date, start keeping the necessary records now. This way you can see how collecting the relevant data fits into your system. When you do join, all data previously collected can be submitted at one time giving you improved accuracy from the beginning.

The use of EBVs has dramatically improved sheep production in the U.S. through increases in lambing rates, milk production, and growth rates. There are two ways to take advantage of this exciting technology: enroll in NSIP, submit data and receive EBVs for your flock; or purchase rams or ewes from NSIP flocks. The latter option works especially well for commercial producers, owners of small flocks, or producers that don’t have the time to invest in data collection. This option also allows you to acquire high quality genetics to improve traits of interest to you without having to join NSIP and it supports the work of the producers with the desire to collect and maintain the data.


Estimated Breeding Values for enhanced lamb and wool production, Tom Murphy

By EAPK Communications Committee

Kathy Bielek, Roxanne Newton, Isabel Richards

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