Impacts of age on residual feed intake and its effect on reproductive parameters and profitability in ewes

Project Overview

Project Type: Graduate Student
Funds awarded in 2011: $24,990.00
Projected End Date: 12/31/2012
Grant Recipient: University of Wyoming
Region: Western
State: Wyoming
Graduate Student:
Principal Investigator:
Dr. Kristi Cammack
University of Wyoming

Annual Reports


  • Animals: sheep


  • Animal Production: general animal production

    Proposal abstract:

    Due to the limited research available, the sheep industry has yet to adopt residual feed intake (RFI) as a measure of feed efficiency as seen in the swine and poultry industries. To be an appropriate measure of feed efficiency for genetic selection, RFI must not be unfavorably correlated with carcass merit, growth traits or reproductive efficiency. Initial research has implicated that age may affect RFI ranking, and that reproduction may be negatively affected. Additionally, no economic data is currently available for sheep producers to demonstrate the potential economic impact of selecting for improved RFI. Therefore, we propose to 1) determine how puberty affects RFI ranking, 2) estimate heritability of RFI in sheep and determine the impact of selecting for low RFI (more efficient) on reproductive efficiency, and 3) investigate the economic impacts of RFI selection on the sheep industry.

    Project objectives from proposal:

    • Objective 1. Determine how age affects RFI ranking. This will be accomplished by comparing RFI measurements of forage-fed ewe lambs before and after attainment of puberty.

    • Objective 2. Estimate heritability of RFI in sheep and determine the impact of selecting for RFI on reproductive efficiency. This will be accomplished by 1) regressing lamb RFI estimates on respective dam RFI estimates, and 2) estimating correlations between dam RFI measurements and reproductive performance measurements.

    • Objective 3. Investigate the economic impacts of RFI selection on the sheep industry. This will be accomplished by performing cost-benefit analyses in collaboration with agricultural economist Dr. John Ritten. Information needed for this analysis, such as input costs, labor costs, etc., will be solicited from Western region sheep producers.

    Timeline for performance targets:

    Year 1
    - Producer Advisory Committee meeting
    - Ewe RFI measurements using GrowSafe system
    - Blood collection to ascertain attainment of puberty

    Year 2
    - Breed ewes
    - Blood collection for LH, FSH and P4 analyses and ultrasound for follicular measurements
    - RFI measurements on lambs using GrowSafe system
    - Statistical analyses of performance and reproduction data
    - Economic analyses and dissemination of results

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.