The effect of breed and breed-by-flock interaction on summer mortality of free-ranging lambs in Norwegian sheep

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• 作者：Geir Steinheim^a ; ^{geir.steinheim@umb.no} ; Leiv S. Eikje^b ; ¹ ; ^{sigbjorn.eikje@nsg.no} ; Gunnar Klemetsdal^a ; ² ; ^{gunnar.klemetsdal@umb.no} ; Tormod &Aring ; dnø ; y^a ; ³ ; ^{tormod.adnoy@umb.no} ; Jø ; rgen Ø ; deg&aring ; rd^c ; ⁴ ; ^{jorgen.odegard@nofima.no}
• 关键词：Genotype by environment interaction ; G  ; × ;   ; E ; Lamb mortality ; Rangeland pasture ; Threshold model
• 刊名：Small Ruminant Research
• 出版年：2012
• 期刊代码：94_09214488
• 类别：abs
• 出版时间：June, 2012
• 卷：105
• 期：1-3
• 页码：79-82
• 文件大小：293 K

摘要

We studied breed and breed by environment interaction effects on lamb mortality during the summer grazing period. One hundred forty-six Norwegian sheep farms that stocked the two most common breeds - Norwegian White Sheep (NWS) and Sp忙lsau together and grazed both in the same free-range grazing areas were used. Average summer mortality of lambs on the study farms was 8.7%for NWS and 6.3%for Sp忙lsau. For 110 of the 146 sheep flocks Sp忙lsau had the lower lamb mortality during summer. The higher mortality observed amongst NWS lambs may suggest a higher environmental sensitivity for this breed, which coincides well with results previously obtained for lamb autumn weights of the same two breeds. Analysing genotype by environment interactions with a probit threshold model revealed that the breeds differed significantly in lamb mortality, and that they ranked their flock environments in a slightly, albeit significantly, different way, i.e., breed by environment interactions did affect lamb mortality. The consequences of the threshold model's assumptions and the constraints on interpretation of results are discussed.