Project Number: 5364-31000-011-00
Project Type: Appropriated

Start Date: Oct 08, 2012
End Date: Oct 07, 2017

Objective:
This location will focus on the following objectives over the next five years. Objective 1: Enhance the understanding of control points during the first 24 months of a ewe’s life to improve reproductive efficiency and lifetime production, and develop methods for managing these critical control points to optimize production efficiencies in range sheep flocks. Subobjective 1.A: Quantify relationships among age at puberty of Targhee ewe lambs, ability of Targhee ewes to lamb at 1 year of age, and scrotal circumference of Targhee ram lambs from weaning until approximately 8 months of age, and quantify the response to EBV-based selection strategies on the ability of ewes to lamb at 1 year of age. Subobjective 1.B: Describe the dose-response effects of subacute sodium chlorate exposure on ewe and lamb health and fecal Escherichia coli concentrations, and bactericidal efficacy of chlorate naturally secreted in milk. Objective 2: Evaluate germplasm, selection criteria, and mating systems to improve maternal and paternal genetic lines of sheep to best match western rangeland environments and industry targets for reproductive efficiency, growth, feed/forage efficiencies and meat quality. Subobjective 2.A: Evaluate Polypay, Rambouillet, and 1/4 Romanov × 1/4 White Dorper × 1/2 Rambouillet ewes for lifetime production in a western rangeland, terminal crossbreeding system. Subobjective 2.B: Develop and evaluate a white-faced, composite, paternal genetic line of sheep adapted to extensive rangeland management systems.

Approach:
Market lambs are the primary source of income for United States sheep producers. The mission of the U.S. Sheep Experiment Station is to increase production efficiency of sheep, which includes improving animal well-being, weight of lamb produced during a ewe’s lifetime, lamb growth performance, and carcass merit of lambs. Genetic merit of maternal and paternal lines, reproductive rate, nutrition, health, and management system are some of the factors affecting production efficiency. Our objectives are to 1) enhance the understanding of control points during the first 2 years of a ewe’s life to improve reproductive efficiency and lifetime production, and develop methods for managing these control points to optimize production efficiencies in range-sheep flocks, and 2) evaluate germplasm, selection criteria, and mating systems to improve maternal and paternal genetic lines of sheep to best match western rangeland environments and industry targets for reproductive efficiency, growth, feed/forage efficiencies, and meat quality. The research will focus on 1) determining whether estimated breeding value-based selection strategies can be used to improve the ability of ewes to lamb at 1 year of age, 2) determining whether subacute sodium chlorate exposure will reduce fecal Escherichia coli concentrations and be an effective agent for reducing the incidence of neonatal diarrhea, 3) evaluating maternal genetics for lifetime production in a western rangeland, terminal crossbreeding system, and 4) developing and evaluating a white-faced, composite, paternal genetic line of sheep adapted to extensive rangeland management systems. This research is expected to produce 1) data that can be used to determine the feasibility of actively selecting for the ability of ewes to lamb at 1 year of age (i.e., ewe lamb fertility) and of using scrotal circumference of ram lambs to improve ewe lamb fertility; 2) a sodium chlorate treatment protocol for postpartum ewes and(or) their neonatal lambs that will reduce the incidence of lamb diarrhea and reduce the overall enteropathogenic bacterial load in ewe flocks; 3) data to inform decisions about the genetics of ewe flocks that are suitable for western rangeland, terminal crossbreeding systems; 4) data to inform decisions about crossing paternal genetic lines of rams with maternal genetic lines of ewes to produce terminal-cross market lambs in extensive rangeland production systems; and 5) an alternative terminal-sire genetic line that is suitable for extensive rangeland production systems.