Nasir Y. Iman

Document Type

Dissertation - University Access Only

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Animal Science

First Advisor

A.L. Slyter


Lifetime (5 years) lamb and wool production from 207 straightbred Targhee (T) and 474 1/4-Finn 1/4-Dorset 1/2-Targhee (FDT) crossbred ewes managed in a range or farm flock system were evaluated for ewe fertility, prolificacy, lamb birth weight, lamb survival, lamb weaning weight, ewe fleece weight, and total lamb weight weaned per ewe exposed. Data included 2620 ewe exposures, 2384 parturitions, 4638 lambs born and 3498 lambs weaned. Ewes were born in 1984 through 1987 and lambed the first time as 2-yr-olds. The basic model included main effects of ewe breed, management system, and age of ewe. Lamb birth type and lamb sex were added for lamb birth weight, weaning weight and survival analyses. Expressed as mean annual values ewe fertility rate was similar (90. 6 vs 89.3%, P = .2755) between the FDT and T ewes. Range flock ewes had a higher (P < .01) fertility rate than farm flock ewes (93.3 vs 86.5%). Targhee ewes had heavier lambs at birth (5.1 vs 4.6 kg, P < .01) and weaning (25.8 vs 25.4 kg, P = .0521) than FDT ewes. Finn-Dorset-Targhee ewes had heavier (P < .01) lamb weaning weights (26.2 vs 25.0 kg) and had higher lamb survival (74.9 vs 70.7%) than Tewes. Range flock ewes had higher (P < .01) lamb survival rates than farm flock ewes (75.4 vs 70.2%). Over the 5 yr period of the study for ewes entering the experiment, FDT ewes had higher (P < .01) cumulative number of lambs born (7.42 vs 5.70), number of lambs weaned (5.48 vs 4.38) and total lamb weight weaned (131.7 vs 110.5 kg) per ewe exposed than Tewes. Targhee ewes produced more (P < .01) wool (16.1 vs 13.6 kg) than the FDT ewes. Farm flock ewes had produced more wool (15.2 vs 14.5 kg, P < .01) than range flock ewes. Ewes in the range flock had a higher cumulative number of lambs born (6.74 vs 6.38, P < .05), number of lambs weaned (5.39 vs 4.48, P < .05) and total lamb weight weaned (135.8 vs 106.5 kg, P < .01) per ewe exposed than farm flock ewes. Percent of ewes remaining in the flock at the end of the study was higher (P < .01} for the range flock (53.3 vs 40.5%) and FDT ewes (48.5 vs 43.0%} compared to the farm flock and T ewes, respectively. Incorporation of Finnsheep and Dorset breeding increased the reproductive performance in both management systems but decreased wool production. Finn cross ewes produced equally as well under range management as in a farm flock situation.

Library of Congress Subject Headings

Ewes -- Reproduction
Ewes -- Breeding -- South Dakota




South Dakota State University



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