Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Animal Science


Reproductive and economic traits were evaluated and compared for fall and spring lambing using 1/4 Finn x 1/4 Dorset x 1/2 Targhee ewes at the SDSU Sheep Teaching and Research Station in Brookings, South Dakota. Animals used in this experiment were offspring of Finnsheep x Dorset rams mated to Targhee ewes, poroducing 524 1/4 Finn x 1/4 Dorset x 1/2 Targhee (FDT) ewes and offspring from Hampshire (H) rams mated to FDT ewes to produce 80 Hampshire x FDT (HFDT) ewes. Data was collected from 1995 through 1999, with 482 ewes being exposed in April for fall lambing and 461 ewes being exposed in September for spring lambing. Replacements from the original 524 FDT and 80 HFDT ewes were selected according to birth type, birth date, growth ratio and reproductive and structural soundness. Shed lambing was used for both flocks. The reproductive and performance traits that were analyzed were lambing percent per ewe exposed, lambs born per ewe exposed and per ewe lambing, percent lambs born alive, lambs weaned per ewe exposed and per ewe lambing, and percent lambs weaned excluding and including bum lambs. Weaning weight and weaning weight adjusted to 75 days of age were also analyzed for both flocks. The economic traits that were evaluated and compared between flocks were price received for feeder and slaughter lambs, value of lambs at weaning and slaughter, ewe expenses and post weaning feed costs, net value at weaning and slaughter, and the increase in value from weaning to slaughter. The spring flock had greater performance in percent ewes lambing (P=0.0136), lambs born per ewe exposed (P=0.0003) and lambing (P=0.0002), lambs weaned per ewe exposed (P=0.0008) and lambing (P=0.0022). No difference was found for weaning weight (P=0.4247) and adjusted weaning weights (P=0.2319). The fall flock had a greater percent survival at weaning when lambs that were bummed were excluded (P=0.0108), however, no difference was found when they were included (P=0.9095). No difference was found in the percentage of lambs alive at birth between the fall and spring flocks. The economic traits that were analyzed were all greater for the spring flock, except expenses per ewe (P=0.0041), which was lower for the fall flock, and post weaning feeding costs, which were not different between flocks (P=0.2643). The spring flock was superior to the fall flock in reproductive performance and received more net return per ewe exposed. Alternatives to improve net returns of the fall flock are discussed.

Library of Congress Subject Headings

Ewes -- South Dakota -- Reproduction
Ewes -- Breeding
Lambs -- Economic aspects -- South Dakota



Number of Pages



South Dakota State University