J. Anim Sci.
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J. Anim Sci. 1986. 62:1555-1562.
© 1986 American Society of Animal Science
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Reproductive Parameters of Crossbred Ewe Lambs Sired by Romanov, Finnish Landrace, Dorset and Western Range Rams

J. A. Vesely and E. E. Swierstra

Agriculture Canada Research Station, Lethbridge, Alberta T1J 4B1

Abstract

Crossbred ewe lambs of eight genetic types (Dorset x 3/4 Dorset, DD; Dorset x 3/4 Finn, DF; Finn x 3/4 Dorset, FD; Finn x 3/4 Finn, FF; Romanov x 3/4 Dorset, RD; Romanov x 3/4 Finn, RF; Romanov x Western, RW; and Western x Western, WW) were used to determine age and weight at conception, conception rate, ovulation rate, litter size and prenatal mortality. Ninety-eight percent of lambs were pregnant. Age at conception in days, ovulation rate (number of corpora lutea) and litter size for the eight groups were as follows: DD, 236 ± 5, 1.5 ± .1, 1.3 ± .2; DF, 218 ± 4, 1.5 ± .1, 1.4 ± .1; FD, 234 ± 5, 2.2 ± .1, 1.8 ± .1; FF, 228 ± 4, 2.6 ± .1, 2.3 ± .1; RD, 209 ± 5, 2.2 ± .2, 2.0 ± .1; RF, 213 ± 3, 2.7 ± .1, 2.4 ± .1; RW, 222 ± 5, 2.1 ± .2, 2.1 ± .2, 2.1 ± .2; WW, 247 ± 5, 1.0 + .1, 1.0 ± .2. Lambs sired by Romanov conceived at an earlier (P<.01) age than those sired by Dorset and Finn rams (210 ± 3 vs 225 ± 3 and 220 ± 3 d). Ovulation rate and litter size were similar for Romanov- and Finn-sired lambs (2.5 ± .1 and 2.2 ± .1 vs 2.4 ± .1 and 2.1 ± .1) and smaller for Dorset-sired lambs (1.5 ± .1 and 1.4 ± .1). Romanov additive effects, expressed as deviations from Dorset Horn, were negative for age at conception (P<.05) and positive for ovulation rate and litter size (P<.01). Maternal effects of Romanov could not be estimated due to incompleteness of the mating design. Finnish Landrace additive effects for ovulation rate and litter size were also positive and significant (P<,01), but somewhat lower than those of the Romanov. Finnish Landrace maternal effects on weight and age at conception and ovulation rate were negative and significant as compared with Dorset Horn. Prenatal mortality was not significantly different among the crosses. Prenatal mortality was a function of ovulation rate. Lambs ovulating 1,2,3 and 4 ova had a prenatal mortality of 0, 13, 17 and 18%, respectively.




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E. Casas, B. A. Freking, and K. A. Leymaster
Evaluation of Dorset, Finnsheep, Romanov, Texel, and Montadale breeds of sheep: II. Reproduction of F1 ewes in fall mating seasons
J Anim Sci, May 1, 2004; 82(5): 1280 - 1289.
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Copyright © 1986 by the American Society of Animal Science.