2/20/2013 Recent Studies in The Genetics of Genetic Resistance to Parasite Resistance • • Parasite Infection in Ruminants •Worm resistance clearly has a heritable genetic component David Notter •Large differences in parasite resistance exist among breeds Department of Animal & •But there are also clear and Poultry Sciences substantial genetic differences Virginia Tech within breeds Opportunities to Enhance Parasite Resistance Opportunities to • Parasite resistance is a quantitative Enhance Parasite performance trait—no different from Resistance weaning weight or wool quality—and will respond to selection in any breed . • Innate levels of parasite resistance are highest in Caribbean hair breeds such as the St. Croix and Barbados Blackbelly, African breeds such as the Red Maasai and naturally selected wool breeds such as the Gulf Coast and Florida Natives 1
2/20/2013 Measuring parasite resistance Opportunities to Enhance Parasite • Measures of parasite resistance Resistance include: fecal egg counts , packed cell volume (hematocrit), FAMACHA • Must measure resistance when worms • The Katahdin breed was created by crossing are present—cannot just set a Caribbean hair breeds with temperate wool calendar date breeds in the USA and shares some of the • Must coordinate measurements with genetically mediated resistance from its hair the deworming schedule and protocol sheep ancestor. Understanding and Utilizing Parasite Understanding and Utilizing Parasite Resistance Resistance • With regard to parasite resistance, all hair • Document and utilize breed diversity sheep are NOT created equal • Develop program for breed improvement • Breeds of Caribbean origin have generally – Data collection—classic genetic evaluations high levels of resistance – EBVs • Dorper is much less resistant, as expected • Functional genomic strategies—build from its origins as an arid-lands breed. understanding • Genome-wide screening and marker detection – What animals, what populations? 2
2/20/2013 Mean Packed Cell Volume Following Mean Fecal Egg Counts Following Natural Infection of Wether Lambs Natural Infection of Wether Lambs Dorset cross Dorper cross Katahdin Hair sheep crosses Dorset cross Dorper cross Katahdin Hair sheep crosses 2000 36 Fecal egg count 34 32 1500 PCV, % 30 28 1000 26 24 500 22 20 0 2001 2002 2001 2002 Year Year Katahdin 2003-05 Fecal Egg Measuring parasite resistance Count EPD Study (fecal egg counts) in Katahdin Spring-born Maintain normal parasite mgmt. • Six flocks; each with at least 2 sires lambs (FAMACHA, etc) and a minimum of 10-12 lambs per sire (Optional for Katahdin) • 850 lambs by 26 sires over 3 years If >10-20% dewormed, then Monitor parasite deworm ALL lambs. Otherwise • Average ages of ~8 and ~22 weeks levels (we will) exclude recently (FAMACHA) • Heritabilities for FEC dewormed lambs from the data – 0.48 at 8 wks Collect fecal samples – 0.54 at 22 weeks at first deworming Collect a fecal sample 4 to – genetic correlation of 0.50. (Innate resistance) 5 wk after deworming (Acquired resistance) 3
2/20/2013 Heritabilities from Ohio Parasite Katahdin 2006-07 Fecal Egg Count Project EPD Study • 10 Flocks • Measure lambs at approximately 8 wk (n = • Three measurement times: 244), 13 wk (n = 289), and 17 wk (n = 139) – Early-season FEC (innate resistance) at 35 to 92 days. 8 wk 13 wk 17 wk Mean FEC – Mid-season FEC shortly after weaning at 65 to 8 wk 0.41 568 epg 127 days. – Late-season FEC at 92 to 184 days. 13 wk 0.52 1,486 epg • Only groups with Mean FEC > 500 epg 17 wk 0.54 1,061 epg Correlations among FEC at Heritability and Litter (maternal) different ages variance components for High FEC Contemporary Groups High FEC Data Early- Early- Mid- High FEC Data Mid Late Late Early Mid- Late Genetic 0.85 0.76 0.99 Heritability 0.27 0.65 0.51 Phenotypic 0.55 0.38 0.95 Litter (Maternal) 0.34 0.11 0.29 4
2/20/2013 Rapid Genetic Improvement Is Average PFEC EBVs by sires--sires with at least Possible for Fecal Egg Counts 10 and minimum accuracy of 0.75 for WFEC or PFEC EBVs (N = 127) • Heritabilities are relatively high at 25% and 500 appear to be very high (near 50%) in 450 400 Average PFEC EBV, % Katahdin 350 300 250 • Very high levels of variation for FEC 200 150 • Animals can be successfully evaluated early 100 50 in life 0 -50 • In pedigree flocks with EPDs, progeny -100 -150 testing can occur along with the individual -200 evaluations Sires Predicted genetic change Functional (in %) over 20 years with single-trait selection for: Genomics 5
2/20/2013 Abmasal Lymph Node Count 10 8 6 #LN 4 2 Experimental Design Abomasal Lymph Nodes 0 0 3 5 7 Hair Sheep Total of 48 Jan./Feb. ’07 spring -born lambs Wool Sheep • N=24 N=24 Lambs were primed with 2,000 H. Lymph Node Weight contortus L 3 larvae for 4 weeks prior to infection. 8 • Dewormed 6 • Final infection of 10,000 L 3 H. 0 3 5 7 0 3 5 7 WT (g) contortus larvae 4 Days post infection Days post infection • Divided into 3 blocks 2 0 0 3 5 7 Slaughter lambs at 3, 5, and 7 d July 19 July 25 July 31 • Days PI 2007- Harvest Dates Hair Wool after infection Sample abomasal mucosa & abdominal • 7 6 5 4 3 2 1 0 Block A •Lymph node weight: significant effects of type and lymph nodes day*type interaction (p=0.004) 7 6 5 4 3 2 1 0 Block B 7 6 5 4 3 2 1 0 Block C 2007- Day 7 Infection July 7 July 18 July 24 White Blood Cell Counts Histology A a 14000 b: Lymphocytes 1800 12000 10000 10000 1600 * 1400 8000 8000 cells / μ l cells / μ l 6000 1200 6000 4000 8001000 4000 2000 cells/mm2 2000 0 0 600 0 3 5 7 0 3 5 7 D 400 Days PI c: 200 d: Neutrophils 250300 0 5000 * 150200 0 3 5 7 4000 * cells / μ l cells / μ l * D 3000 50 100 W H 2000 1000 0 0 0 3 5 7 0 3 5 7 •By day 3, there is a noticeable difference in tissue D Days PI neutrophils W H •Are neutrophils playing a role in early immune response to PMN: model (p=0.0231), type (p=0.0003), day (p=0.2155) Haemonchus contortus? 6
0 60 2/20/2013 Fold Change Fold Change 0 3 5 7 (A) IL-4 40 20 (C) IL-33 0 0 3 5 7 IL-13 and IL-33 in abomasal Fold Change IL-4 in abomasal mucosa at 0, (B) IL-13 mucosa at 0, 3, 5, & 7 days 3, 5, & 7 days postinfection Fold Change Fold Change postinfection 3 5 7 Days after infection (A) IL-4 0 3 5 7 0 3 5 7 Hair Wool 80 * (B) IL-13 (C) IL-33 4 3 *** 60 Fold Change 3 Fold Change Fold Change *** 2 2 3 5 7 40 1 1 0 Days after infection 20 0 3 5 7 0 Days after infection 0 3 5 7 Hair Wool Hair Wool 0 0 3 5 7 (C) IL-33 (B) IL-13 Fold Change Fold Change Genomics: g enotype 100 progeny-tested (A) IL-4 80 * Katahdin rams using 700K SNP chip IL-4, IL-13 60 Fold Change ≥ 0 3 5 7 40 and IL-33 in FEC EBVs of sires with 10 or more progeny and Days after infection 20 0 3 5 7 minimum FEC EBV accuracy of 0.80 (N = 94) Hair Wool abomasal 0 300 0 3 5 7 (C) IL-33 (B) IL-13 250 mucosa at 0, 3 4 200 Fold Change *** Average PFEC EBV, % 2 3, 5, & 7 days 150 1 3 Fold Change 100 0 after 0 3 5 7 2 50 (C) IL-33 0 4 1 infection *** Fold Change 3 -50 2 0 -100 1 0 3 5 7 0 -150 0 3 5 7 Days after infection Days after infection -200 Hair Wool Hair Wool Sires 7
2/20/2013 Questions? http://www.toledotel.com/~smokeyvly/sheep6%20004.jpg 8
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