Ram performance testing programs in Virginia

Prices paid for yearling rams were influenced (P < .001) by TSC, BT, YW and FW. The importance of YW increased with time, while the role of TSC declined in later time periods, suggesting that buyers were willing to pay more for superior performance and less for subjective conformation and type in later years than when the test began. A larger ram with an equivalent performance record was worth more than a smaller ram. The relative importance of FW and YW in defining price changed. In early years superiority in both traits was worth approximately the same, while in later years a higher YW brought about 2 1/2 times the premium of the same increase in FW. Prices paid for ram lambs were affected by TSC, BT, DG and FW, but the time period involved was too short to draw conclusions concerning changes in their relative importance. Phenotypic trends for yearling rams' WW, FW, YW and DG were positive (P < .001), and rates of increase were different for breeds (P < . 001). The decrease in mean age of tested rams and the increase in DG contributed to a quadratic trend in YW and supported adjustment of the data for age. Environmental trends, analyzed by a within-sire analysis of 1885 progeny of 4:30 sires, were not significant. Estimated genetic gains due to sires were: 1.06 ± .30 kg/yr for FW, 1.16 ± .32 kg/yr for YW, .36 ± .18 kg/yr for WW and .0037 ± .0021 kg/d/yr for DG. Phenotypic trends for the ram lambs were: .906 ± .198 kg/yr for FW, .00956 ± .000880 for WDA and .00212 ± .00228 kg/d/yr for DG. Yearling rams' OW and FW were correlated (P < .001), as were the same traits for ram lambs. The yearling correlation was much lower than that of the lambs, however (r = .89 vs r = .66). The correlation (P < .001) of OW and DG was .22 and -.20 for yearlings and ram lambs, respectively. Age and DG were correlated (P < .001) with a coefficient of -.20 for both yearlings and ram lambs. Yearling rams' SHT, HHT and BLGTH were highly correlated ( P < . 001), and cannon length was moderately correlated (P < .005) to SHT and HHT. Suffolks were taller than Hampshires and Dorsets. All three breeds made similar gains in SHT within the same year. SC generally increased over the course of the test. The SC of the black-faced breeds sometimes regressed from April to May, but showed gains from 0 to 2.15 ± .24 cm for the overall measurement interval. Dorset SC always increased the most with gains ranging from 2.08 ± .93 cm to 3. 88 ± 1.10 cm. Suffolk ram lambs were tallest in the first 2 yr and were similar to Hampshires in the third. Gains in ram lamb SHT over short intervals were negated by the shearing which took place before the second measurement. Mean gains over the lengthened 1982 test period ranged from 6. 04 ± .68 cm for Hampshires to 7.37 ± .36 for Suffolks. SHT was correlated ( P < .001) with weight, generally moderately correlated (P < .05) with DG and not usually correlated with age. Only the Suffolk lamb SC consistently increased from July to August. The SC of all breeds increased from May to August, Suffolks by the greatest amount. SC was correlated (P < .05) with SHT and generally was correlated (P < .005) with weight. Only the final SC was correlated ( P < . 005) with DG, and SC and age were not usually correlated.

Name thesis:degree_name

M.S.

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Animal Science

Department dc:contributor.department

Animal Science

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1983

Author dc:creator

• Lester, Donya C.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/10919/101439

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/101439