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Parasite Immunology Lab

Research Activity

Katahdin Crossbreeding Project (Terminal Sire Project)

Results from our preliminary study were used by a colleague at Virginia Tech to apply for an internal grant at Virginia Tech. The concept driving this experiment was to compare the effects of utilizing Texel, Suffolk or Katahdin sires on lamb performance when mated to Katahdin ewes.

This project has been conducted in 2015, 2016 and 2017 and data from each year have been or will be presented at the Southern Section of Animal Science annual meeting. Abstracts from each year can be found at under the key words sire breed and parasite resistance .


The Katahdin hair sheep is the fastest growing breed in the United States. This composite “easy-care” breed was developed from crosses of African hair sheep and a variety of wool breeds with selection for a hair coat, prolificacy, and conformation. Along with these traits, an enhanced level of resistance to gastrointestinal nematodes has been maintained. This, in combination with their moderate mature size, has resulted in their adaptability to the forage based production systems of the Southeastern U.S. and their rise in popularity among commercial sheep producers in this region. However, their reduced carcass merit compared to wool breeds is well documented and has been of concern among sheep producers.

Over three years, terminal sire breeds (Suffolk and Texel) were mated to Katahdin ewes at the Southwest Virginia Agriculture Research and Extension Center (Glade Spring, VA) for progeny evaluation of growth and carcass characteristics as well as parasite resistance. Lambs were randomly allocated at birth to a pasture or feedlot management group. The feedlot management group was transported to West Virginia University (Morgantown, WV) at weaning.

Grazing Trial

Lambs were born in mid-March and moved to pasture with their dams upon leaving the jug. All pairs were managed together until weaning at approximately 75 days of age in early June. At weaning, lambs were moved to a clean pasture and grazed for approximately 90 days rotated as necessary.

Number of Lambs Born (NLB)/Number of Lambs Weaned (NLW) by Sire Breed

chart of NLB/NLW by Sire Breed 
Figure 1: This first chart shows that the number of lambs born (NLB) and the number of lambs weaned (NLW) by the sire breed were comparably the same in all 3 breeds (Katahdin, Suffolk, Texel).

Birth and Weaning Weights by Sire Breed

chart of birth weights of Katahdin, Suffolk, Texel chart showing weaning weights of Katahdin, Suffolk, Texel

Figure 2: These charts show that at birth and weaning, there were no differences in litter size between the purebred Katahdin, Suffolk or Texel pairings and no observed differences in survivability. Lamb body weights at these time points were also similar across years of the project.

Three-Year ADG, FAMACHA, FEC and PCV Performance

ADG rate of 3 groups of sheep in 3 year study FAMACHA of 3 groups of sheep in 3 year study

FEC of 3 groups of sheep in 3 year study PCV of 3 groups of sheep in 3 year study

Figure 3: These charts show the three-year summary of the grazing performance in the areas of average daily gain (ADG), average FAMACHA score, average fecal egg count (FEC), and packed cell (PVC) over the 90-day grazing trial. Grazing performance post-weaning was similar across sire breeds. Fecal egg counts (FEC) and red blood cell percentage (PCV) did not differ; however, purebred Katahdin lambs tended to have lower FAMACHA scores compared to Suffolk-sired lambs.

Lambs were selectively dewormed at a FAMACHA score greater than or equal to 3. In the first year of the project, purebred Katahdin lambs took a greater number of days before requiring deworming compared to Texel-sired lambs. At the time of deworming, Suffolk-sired lambs had the lowest FEC while tending to take a fewer number of days before requiring deworming compared to the Texel-sired lambs (year 2 of the project). In both year 1 and 2, purebred Katahdin lambs tended to require less deworming compared to the Suffolk-sired lambs.

Following the conclusion of the grazing trail, lambs were fed to approximately 110 pounds and then harvested at the Virginia Tech Meat Center for carcass evaluation. Suffolk-sired lambs had greater live and carcass weights with no differences in dressing percentages. Fat was similar across the sire breeds. 

three hanging sheep carcasses--1) Texel-sired, 2) Purebred Katahdin, 3) Suffolk-sired 

However, loin muscle area was consistently greater for Texel-sired lambs with purebred Katahdin lambs having lower leg scores compared to the terminal-sired lambs. With similar growth performance between the sire breeds, the added muscle found in Texel-sired lambs resulted from a difference in composition of growth. Texel sires have the potential to improve carcass quality in progeny raised in a forage-based production system.

two sheep carcasses showing a comparison
Caption: Purebred Katahdin carcass on left vs. 50% Katahdin /50% Texel carcass on right

Feedlot Trial

After arrival at the WVU Animal Science Farm the lambs were placed into a feedlot fitted with GrowsafeTM bunks. The GrowsafeTM bunks provide the opportunity to evaluate feed efficiency through a measure called Residual Feed Intake (RFI). The lambs remained on test until late September and carcass measures were recorded. Carcass measures were conducted using ultrasound measures of loin muscle area. All lambs were infected with Haemonchus contortus (Barber Pole Worm) to measure parasite resistance in a controlled environment. Weights and fecals were collected weekly for the duration of the study.

Three Year Summary of Feedlot Performance

3 year ADG 3 year avg challenge FEC  

3-Year REA 3-Year RFI

Figure 4. The three-year summary of feedlot performance showing the average daily gain (ADG), average fecal egg count (over the infection period, ribeye area (REA) nat the conclusion of the grazing period and residual feed intake.

Average Daily Gain (ADG) across all three years favored lambs sired by Suffolk rams and both Texel and Katahdin-sired lambs had a similar ADG. Fecal egg count (FEC) breed averages are listed across all three years and FEC remained relatively low across all three breeds. This low FEC would be indicative of a low level of infection. Ribeye area was calculated using ultrasound at the conclusion of the feedlot period. As expected, lambs sired by terminal breeds (Suffolk and Texel) have improved REA compared to the purebred Katahdin progeny. RFI was calculated across all three years and showed observable differences favoring Texel sired lambs, but data was not statistically significant.

In summary, the superior growth and muscling of terminal sired lambs support the use of these breeds for market lamb production. With a low level of parasitism across breeds, differences in parasite resistance are not well illustrated. With a greater level of infection on pasture, the grazing study should be referenced for resistance measures. RFI data provides early evidence of a possible feed efficiency advantage to Texel sheep although further work is need to ensure these differences are significant.

50% Suffolk/ 50% Katahdin 50% Texel/ 50% Katahdin Purebred Katahdin

Caption: 50% Suffolk/50% Katahdin (left), 50% Texel/50% Katahdin (middle), Purebred Katahdin (right).