Project Number: 5438-31000-068-00
Project Type: Appropriated

Start Date: Jul 31, 2002
End Date: Jul 30, 2007

Objective:
Objective 1: Evaluate growth, composition, and meat quality of breeds representing an extensive range of biodiversity. Objective 2: Evaluate wool and hair breeds for production efficiency under intensive and extensive management systems. Objective 3: Identify QTL and exploit allelic differences for reproduction, growth, carcass composition, and meat tenderness. Objective 4: Estimate genetic relationships among component traits affecting biological efficiency.

Approach:
Objective 1. In September of 2001, 2002, and 2003 rams of nine breeds (Composite, Dorper, Dorset, Finnsheep, Katahdin, Rambouillet, Romanov, Suffolk, and Texel) will be single-sire mated to a common flock of ewes. Five rams per breed will be used each year and then replaced by a new set of rams the following year. Effects of each breed for carcass and meat quality traits will be estimated from information collected on about 90 lambs per breed using a serial slaughter design. Carcass traits will include leg score, kidney-pelvic fat weight, carcass weight, 12th-rib fat thickness, longissimus area, and chemical composition of the longissimus and one side of the carcass. Shear force and sensory traits (tenderness, juiciness, and flavor) will be recorded. Objective 2. Dorper, Dorset, Katahdin, and Rambouillet rams will be single-sire mated to 360 Romanov ewes during 2000, 2001, and 2002. Six rams per breed are used in October and December breeding seasons each year and then replaced by a new set of rams. Resulting crossbred ewes of each type will be multi-sire mated to Suffolk and Texel rams to produce terminally-sired progeny. The productivity of crossbred ewes in intensive and extensive production systems will be evaluated over three parities. Objective 3. A three-generation resource population was produced using Dorset and Romanov breeds to provide genotypic and phenotypic data for detection of chromosomal segments that affect growth, carcass, meat quality, and reproductive traits. A genomic scan will be directed using microsatellite markers to detect quantitative trait loci and test for interactions with the callipyge locus. In another experiment, the callipyge mutation is being introgressed from the Dorset into a terminal sire composite population. Composite flocks homozygous for alternative callipyge alleles are being created to support future research. Objective 4. Phenotypic data will be analyzed to estimate genetic parameters for reproductive, survival, growth, feed intake, composition, and meat quality traits. Estimates of genetic and phenotypic variance-covariance matrices will be used to derive conventional selection indexes for development of breeds by selection.

Project Team

Leymaster, Kreg Van Vleck, Lloyd - Dale Freking, Bradley - Brad

Project Annual Reports

FY 2003