Location: Range Sheep Production Efficiency Research
Project Number: 2056-31610-007-000-D
Project Type: In-House Appropriated
Start Date: Jun 21, 2022
End Date: Jun 20, 2027
Objective:
Objective 1: Develop ecologically-oriented sheep genetic resources applicable towards increasing lifetime production efficiency and grazing utility of sheep originating from extensive rangeland systems.
Subobjective 1.A: In sheep, quantify the association between taste sensitivity towards bitter flavor and herbivory of browse species.
Subobjective 1.B: In sheep, identify genetic markers/candidate genes that are associated with taste sensitivity towards bitter flavor.
Objective 2: Develop non-antibiotic solutions for increasing sheep longevity in the production system.
Subobjective 2.A: Determine the utility of chlorate salts to mitigate anti-productive effects of sub-clinical mastitis in early and near-peak lactation ewes on annual weight of lamb weaned.
Objective 3: Provide novel strategies to seedstock sheep breeders to increase the effectiveness of participation in national genetic evaluation through sampling methods and increased flock connectivity.
Sub-objective 3.A: Develop solutions for seedstock sheep breeders to cost-effectively sample sheep for inclusion in national genetic evaluation and in establishing a reference population for genomic selection.
Objective 4: Develop Estimated Breeding Values for lamb survivability and ewe longevity.
Sub-objective 4.A: Develop lamb survivability (LS) estimated breeding values (EBVs) and identify associated genes and pathways for the LS trait.
Sub-objective 4.B: Develop ewe longevity (EL) estimated breeding values (EBVs) and identify areas of adaptation or selection for the EL trait in the Range Sheep Production Efficiency Research (RSPER) Polypay.
Approach:
For Objective 1, we will develop a series of tests to identify sheep with low to high taste sensitivity towards bittering compounds placed in the feed, determine the herbivory preferences of sheep based on sensitivity towards bitter flavor, and further validate use of genetic markers to identify sheep with specific taste sensitivities and herbivory preferences. Experimental goals specific to Objective 1 are: 1) Develop a feed-based, bitter-taste sensitivity classification method that generates precise classification results in agreement with Hensley et al. (2019); 2) Develop a high-throughput, feed-based, bitter-taste sensitivity classification method where multiple sheep in group-fed environments can be simultaneously classified; 3) Determine if bitter-taste sensitivity can be used as an accurate predictor of sheep herbivory of shrubs in an actual grazing application; and 4) Identify genetic markers/candidate genes that are useful for identifying and predicting herbivory of sheep.
For Objective 2, we will extend previous efforts in evaluating the effect of adding sodium chlorate to the drinking water of periparturient ewes to reduce diseases associated with pathogenic Enterobacteria. The experimental hypothesis (alternative) specific to Objective 2 is: Ewe consumption of sodium chlorate (via drinking water) at early and near-peak lactation reduces occurrence of Escherichia coli-induced subclinical mastitis in sheep and, thus, mitigates anti-productive effects of mastitis. Specific focus will be placed on evaluating performance and productivity of ewes and lambs from an environment where measures are taken to reduce the likelihood of disease.
For Objective 3, sampling to capture the genetic diversity of the flock will enhance genetic evaluation and genetic connectedness across flocks. We aim to facilitate selection of genetically superior sheep, which includes sheep adapted to their rangeland environment. Sampling in a way that allows us to assess the full range of diversity across the flock is the key to cost-effective genetic improvement.
For Objective 4, a comprehensive quantitative and molecular evaluation of factors influencing the composite traits of lamb survivability and ewe longevity in a rangeland environment will provide the opportunity to improve long-term production efficiency for the sheep industry. As an additional cooperative component of Objectives 3 and 4, we will continue to submit phenotype data to NSIP and generate pertinent genotype and standard and novel phenotype data supporting the multi-ARS location cooperative approach to extend the scope and applicability of national sheep breeding programs.
