caa a22 4500 388061049 CHVBK 20180307125120.0 cr unu---uuuuu 161130e199810 xx s 000 0 eng 10.1017/S1357729800010092 doi S1357729800010092 pii (NATIONALLICENCE)cambridge-10.1017/S1357729800010092 Genetic parameters for lamb birth weight in spring and autumn lambing [Elektronische Daten] Genetic parameters for birth weight were estimated for two sets of spring-born and one set of autumn-born lambs of the same breed composition and genetic origin using a model that included random additive, additive maternal, permanent environmental maternal, litter and residual effects. Litter effects were significant for all data sets, indicating that within-year effects of common environment and (or) non-additive genotype were important for birth weight and should be included in genetic evaluation programmes. Estimates of variance components for autumn-born lambs differed significantly from those obtained from spring-born lambs or from the combined data. In contrast, estimates obtained for the two sets of spring-born lambs did not differ from those obtained when data on all spring-born lambs were pooled. The estimate of h2 for birth weight in spring-born lambs was over twice as large as that obtained for autumn-born lambs (0·26 v. 0·22).In contrast, the across-year repeatability of ewe effects was much larger in autumn lambs (0·41 v. 0·26) as was the full-sib littermate correlation (0·73 v. 0·49). Mean birth weights were also 0·4 to 0·6 kg less in autumn lambs. These results suggest that negative effects on birth weight that have been reported for lambs gestated during summer in equatorial and subtropical regions are also manifested (albeit at reduced levels) in less extreme climates (in this case, 37°, 15' N latitude and 654 m elevation) and that maternal variation exists in the ability of the ewe to maintain adequate lamb birth weights in autumn lambing systems. Copyright © British Society of Animal Science 1998 birth weight nationallicence genetic parameters nationallicence seasonal variation nationallicence sheep nationallicence Al-Shorepy S. A. Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0306, USA Notter D. R. Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0306, USA Animal Science Cambridge University Press 67/2(1998-10), 327-332 1357-7298 67:2<327 1998 67 ASC https://doi.org/10.1017/S1357729800010092 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S1357729800010092 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Al-Shorepy S. A. Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0306, USA NATIONALLICENCE 700 1- Notter D. R. Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0306, USA NATIONALLICENCE 773 0- Animal Science Cambridge University Press 67/2(1998-10), 327-332 1357-7298 67:2<327 1998 67 ASC CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge