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Interpretive Summary: Comparison of three maternal composite sheep breeds managed under pasture lambing and purebred or terminal mating systems: ewe body weight, reproductive efficiency, and longevity

By: Tom W Murphy, Brad A Freking, Gary L Bennett

Production systems across the U.S. sheep industry are diverse, ranging from intensive management to lower-input and extensive operations. Extensive flocks are more nutritionally reliant on grazing, have lower labor costs, and have limited housing for animals. Most extensively managed sheep operations in the United States are in the western states, where approximately 60% of lambs are born outside and with little intervention. Predation, recurrent drought, and limited nutritional value of forages are common in this region and are antagonistic to rearing multiple lambs. However, large breed differences in ewe maternal ability exist and can be utilized to improve lamb production through strategic crossbreeding. The Composite-IV is a sheep population developed at the U.S. Meat Animal Research Center and has been selected for enhanced reproductive efficiency in a lower-input system. Composite-IV ewes were evaluated alongside Katahdin and Polypay ewes, two other popular maternal sheep breeds, over 4 yr in a lower-input, pasture lambing system. Total number and weight of lamb marketed per ewe was greatest for Composite-IV, but all three breeds had much greater reproductive performance than the current U.S. average. Results highlight the importance of applying existing and novel genetic tools to optimize sheep performance for specific production systems.

Read the full article in the Journal of Animal Science.