Genetic Selection at Tamarack Lamb & Wool

In Uncategorized by Janet McNally10829 Comments

Genetic Selection and Performance testing

Friday, January 29, 2016

8:49 PM

My philosophy about breeding sheep, is that I want to select sheep that perform within the environment that they will be used in without crutches to help them attain desired production goals. Therefore I stopped feeding grain to ewes and lambs by 1996. The only animals that ever see a small amount of oats are replacement ewe lambs and ram lambs during their first winter just to replace some of the nutrients lacking in our local hay. The rest of our breeding flock and all lambs up until market time, live their lives without anything but hay or pasture and a trace mineral supplement.


Lambs are recorded at birth noting birth type, and what I call management ease codes MMUB. The first M is for Milk, does the ewe have adequate milk to feed her brood no matter how many lambs she gave birth to? The second M is for mothering, does she keep her lambs together, clean them, and assure they suckle? U is for udder, does she have a nice high udder above the hocks, with proper sized and positioned teats to assure survival? And B is for birth, was the birth easy and unassisted? Or did she require assistance? Ewes are assessed in a pasture lambing environment. I have not jugged ewes for nearly 20 years. Teepees are occasionally used during severe weather but usually only needed for newborn lambs born during an exceptionally cold rain or sleet.


Lambs are weighed at 60, 100, and 150 days of age.  At 150 days of age, lambs are scanned for loin eye depth and back fat.   We are one of very few white faced breeds that actually scan lambs in the USA.



All of this information is processed by Lamb Plan

To provide us breeding values for Maternal Weaning Weight, Weaning Weight, Post Weaning weight, Eye Muscle Depth, Fat Depth, Number of Lambs Born, and Number of Lambs weaned.   I then use this information for selecting the next generation of replacements.

The breeding values on all of our sheep are available here:

To find the data for Tamarack Lamb & Wool just type  in “Tamarack” in the “Stud” field and click on search.  A hint, when you first arrive at our data, it is arranged chronologically, i.e. the oldest animals from the 2000s are at the top of the list. To re arrange the order, double click on the heading of the trait you are interested in, and it will sort from lowest to highest EBV in that trait.  Double click on the header again,   and you will sort the animals from the highest performing animals in that trait to the lowest. Numbers encased in a blue box are trait leaders. The EBV s for the Tamarack flock are currently all within flock EBVs.

2015 non booroola rams data

rams for sale in 2016. Click on image to enlarge

In addition to EBVs and management ease codes, I evaluate overall structure and balance, along with teeth, toes, and testicles before making my final selections. Ewes in poor body condition, or that produce a lamb in poor body condition are culled.

Turnaleary Dollar

Turnalearydollar Ile de France ram from which semen was imported in 2007.

Most matings use Tamarack or Tamarack Prolific rams, but to avoid too much inbreeding, new genetics are sourced from Ile de France rams in Ireland via AI. The only live rams we bring in are grass based British influenced Dorset rams from KbarK Dorsets.


Tamarack Lamb & Wool’s Pasture reared lambs at weaning time

The results of decades of dedication to performance and fitness to perform in a pasture environment are sheep that you can depend upon to consistently produce well muscled lambs that can grow within an all grass system as well as ewes with the milk and mothering ability to raise those lambs.

The following charts show 19 years of  genetic progress of the Tamarack Flock in the following traits:  Post Weaning Weight (Pwwt), weaning weight (wwt), Post weaning eye muscle depth (Pemd),maternal weaning weight (Mwwt or milk),   and Post weaning fat depth (Pfat).  not shown are Number of lambs born (nlb) and Number of lambs weaned (nlw) simply because these two traits have remained steady.  These bar charts show that it is not the exact % IDF or Dorset in our breeding, but the continued selection for growth, muscle, and maternal ability that make the difference.

2015 avg pwwt bar chart

2015 avg wwt bar chart

2015 avg pemd bar chart

2015 avg mwwt bar chart

2015 avg pfat bar chart