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Heritability of Fur Characters and Birth Weight in Karakul Lambs¹

U. S. Department of Agriculture

Abstract

The records of eight lamb fur characters and birth weight from 728 purebred and grade Karakul lambs and their 207 dams and 22 sires raised at the Agricultural Research Center, Beltsville, Maryland, from 1942 through 1949, were used to calculate heritability estimates. The estimates were also computed separately in the purebred and three grade groups—Karakul x Blackfaced Highland, Karakul x Corriedale and Karakul x Navajo. Three methods—paternal half-sib correlation, intra-sire regression on dam, and mid-parent regression—were used in the estimation. The variances for lambs, dams and mid-parents and the covariances between lambs and dams, and between lambs and mid-parents were corrected with the variances and covariances caused by breed, year and sire differences.

The nine characters were divided into three heritability groups: high heritability group—curl size (36.0–67.6), tightness (16.5–60.2), luster (15.2–44.3); medium heritability group—desirability (10.1–17.7), curl type (25.2), birth weight (17.7–34.5); and low heritability group—pattern (2.0–10.4), texture (13.1), and hair length (9.2). Different breeding groups had different heritability estimates. Purebred Karakuls had the highest heritability in curl size (59.7) with half-sib method, in luster (75.8) and birth weight (63.8) with intra-sire regression method, and again in luster (81.7) with mid-parent regression method. The Karakul x Blackfaced Highlands had the highest heritability in tightness (67.6, 72.0, 68.1) by all three methods, in curl size (55.9, 54.6) with both regression methods, and in desirability (31.3) with the intra-sire regression method. The Karakul x Navajo had the highest heritability only in birth weight (51.3) with the half-sib method. The characters which had high heritability could be expected to give the most response in selection, while the characters with low heritability may be improved when line selection and cross breeding systems are practiced.

¹ This work was conducted jointly by the sections of Sheep and Goat Husbandry, Animal Fiber, and Fur Farming Investigations, Animal Husbandry Division, Bureau of Animal Industry, A.R.A., U.S.D.A.