caa a22 4500 388060972 CHVBK 20180307125120.0 cr unu---uuuuu 161130e199810 xx s 000 0 eng 10.1017/S1357729800010043 doi S1357729800010043 pii (NATIONALLICENCE)cambridge-10.1017/S1357729800010043 Faecal nematode egg counts in lactating ewes from Romney flocks selectively bred for divergence in lamb faecal egg count [Elektronische Daten] Faecal nematode egg counts (FECs) were examined in lactating ewes from divergent flocks of Romney sheep which had been selectively bred from 1979 to 1996 for or against FEC in 4 to 7 month old lambs. Faecal samples were obtained from the ewes while under normal grazing management, 1 to 2 months after lambing in spring for each of 6 years between 1987 and 1996 (no. = 785 records; 298 animals). Analyses were carried out on loge (FEC + 100)-transformed data using animal-model maximum likelihood procedures, accounting for repeated records on ewes, within and between lactations. An examination of non-genetic effects indicated that there was no significant effect of age class of ewe on FEC but ewes which gave birth to single lambs had significantly lower post-parturient FECs than those bearing twins (back-transformed means of 184 v. 276 egg per g, respectively; P < 0·001). In relation to genetic effects, post-parturient FECs were significantly lower in ewes from the flock bred for low lamb-FEC than in their counterparts from the flock bred for high lamb-FEC, with ewes from the most recent birth years (1991 to 1994) showing a nine-fold difference (back-transformed means of 33 and 305 eggs per g faeces respectively; P < 0·001). This was equivalent to 69% of the divergence observed between loge (FEC + 100) in their lambs in the same years. Heritability and repeatability estimates for loge (FEC + 100) in ewes were 0·37 (s.e. 0·06) and 0·46 (s.e. 0·03) respectively. Genetic correlation estimates between a ewe's post-parturient loge (FEC + 200) and her loge (FEC + 100) as a lamb, based on analysis of (co)variance or realized responses, were 0·70 or 0·58 respectively. The phenotypic correlation between a ewe's loge (FEC + 100) and that of her lamb(s) in the same lactation was 0·29 (s.e. 0·06) (P < 0·001). From the results it is clear that substantial genetic changes in post-parturient FECs of breeding ewes can be induced through a correlated response to selective breeding for or against reduced FEC in lambs. This may have important implications for the epidemiology of nematode parasite infections in spring-born lambs, a possibility which is currently being investigated. Copyright © British Society of Animal Science 1998 disease resistance nationallicence faecal egg count nationallicence parasitic nematodes nationallicence selection nationallicence sheep nationallicence Morris C. A. 1AgResearch, Ruakura Agricultural Research Centre, Private Bag 3123, Hamilton, New Zealand Bisset S. A. 2AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand Vlassoff A. 2AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand West C. J. 2AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand Wheeler M. 1AgResearch, Ruakura Agricultural Research Centre, Private Bag 3123, Hamilton, New Zealand Animal Science Cambridge University Press 67/2(1998-10), 283-288 1357-7298 67:2<283 1998 67 ASC https://doi.org/10.1017/S1357729800010043 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S1357729800010043 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Morris C. A. 1AgResearch, Ruakura Agricultural Research Centre, Private Bag 3123, Hamilton, New Zealand NATIONALLICENCE 700 1- Bisset S. A. 2AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand NATIONALLICENCE 700 1- Vlassoff A. 2AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand NATIONALLICENCE 700 1- West C. J. 2AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand NATIONALLICENCE 700 1- Wheeler M. 1AgResearch, Ruakura Agricultural Research Centre, Private Bag 3123, Hamilton, New Zealand NATIONALLICENCE 773 0- Animal Science Cambridge University Press 67/2(1998-10), 283-288 1357-7298 67:2<283 1998 67 ASC CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge