Terminal sire crossbreeding systems which improve growth performance while maintaining parasite resistance have the potential to enhance the profitability of hair sheep enterprises. Katahdin (KT, n = 4), Suffolk (SU, n = 3), and Texel (TX, n = 3) rams were randomly mated to KT ewes over two years (Y1, Y2) at the Virginia Tech Southwest Agricultural Research and Extension Center. Post-lambing until weaning (80 d), pairs were managed on fescue pasture. At weaning, lambs (n = 192) were moved to an ungrazed pasture and provided a concentrate pellet daily for a 90 d grazing trial. During this time, BW, strongylid egg count (FEC), FAMACHA score and packed cell volume (PCV) were collected every 14 d. FAMACHA score - 3 was utilized as the basis for anthelmintic treatment. Post-grazing, lambs were fed to approximately 50 kg BW. Lambs were harvested at the Virginia Tech Meat Center and carcass evaluation performed 1 d post-harvest. Statistical analyses were conducted using SAS (SAS Institute Inc., Cary, NC) with Proc MIXED for repeated measures analysis and Proc GLM with Tukey?s test for mean separation. No differences existed between sire breeds for adjusted number of lambs born or number of lambs weaned. Adjusted birth BW was greater for SU-sired lambs than KT-sired and TX-sired (P < 0.05) in Y2. Adjusted weaning BW was smallest for KT-sired lambs compared to SU- and TX-sired lambs (P < 0.05) in both years. During the grazing trials, BW, ADG, lnFEC, FAMACHA and PCV varied over time (P < 0.001) with lower FAMACHA scores for KT-sired lambs than SU- and TX-sired lambs in Y1 (P < 0.05). A greater proportion of SU-sired lambs tended to require deworming than KT-sired lambs (P = 0.08). Adjusted BW post weaning was greater for TX-sired lambs than KT-sired lambs (P < 0.05) in Y1. Post-grazing, BW and ADG varied over time (P < 0.01) with no sire breed differences for ADG. At harvest, SU-sired lambs were heavier than KT-sired lambs (P < 0.05). TX-sired lambs had greater LM area than KT-sired lambs (P = 0.05). KT-sired lambs had the smallest leg scores (P < 0.05). These results indicate the potential of terminal sires (SU- and TX-sires) to improve lamb growth and carcass merit. TX-sired lambs had more similar parasite resistance characteristics to KT-sired Iambs and may have potential as terminal sires in forage based hair sheep production systems. / Master of Science / Katahdin hair sheep have been developed as an easy-care breed adaptable to forage-based production systems. Their enhanced resistance to gastrointestinal parasites has resulted in their rise in popularity among sheep producers in the southeastern United States. However, their lower cutability (muscle to fat ratio) and lighter carcass weights have resulted in economic concerns. Therefore, other breeds (Texel and Suffolk) have been considered for crossbreeding to increase carcass size and muscle improving the market value of lambs produced. Here, Katahdin, Suffolk and Texel sires were mated to Katahdin ewes over two years at the Southwest Virginia Agriculture Research and Extension Center. Lambs were grazed with their dams until weaning at approximately 70 days of age. Post-weaning, lambs were grazed for approximately 90 days during which time body weights and parasite resistance indicators were recorded every two weeks. Lambs were dewormed based on anemia level measured by mucus membrane color (FAMACHA score). After grazing, lambs were fed until they reached approximately 50 kg. Lambs were harvested at the Virginia Tech Meat Center for carcass evaluation. There were no differences between the sire breeds for number of lambs born or weaned per ewe. Suffolk-sired lambs were heaviest at birth in year 2 and at weaning Suffolk- and Texel-sired lambs were heavier than Katahdin-sired in both years. In year 1, Texel-sired lambs were heaviest at the end of the grazing period. FAMACHA scores tended to be lower for Katahdin-sired lambs and Suffolk-sired lambs tended to require greater deworming. At harvest, Suffolk-sired lambs were heavier than Katahdin-sired lambs while the Texel-sired lambs had greater loin muscle area. These results indicate the potential of terminal-sires (Suffolk and Texel) to improve lamb growth. Texel-sired lambs were more similar to Katahdin-sired lambs for resistance traits while increasing carcass muscling and may be a potential terminal option for forage-based production systems.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/80300 |
| Date | 10 October 2017 |
| Creators | Weaver, Andrew Ryan |
| Contributors | Animal and Poultry Sciences, Greiner, Scott P., Notter, David R., Zajac, Anne M. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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