The relative effects of farm management versus climate on lamb autumn weights

Abstract

Abstract In this study I ask if farm management have such large effects on sheep (Ovis aries) production that climatic studies could be improved by taking it into account. The relative effects of climate and farm management on autumn live weights of lamb were studied in Troms, northern Norway. A mixed method approach was used, including analyses of multiple databases, as well as qualitative, semi-structured interviews with sheep farmers. The results combine the farmer’s statements with the quantitative data on production and climate. A total of 30 farms in three climatic areas (coast, fjord and inland), were selected from the Norwegian Sheep Recording System’s (NSRS) database, which was based on the highest contrasts in autumn live weights. In the climatic analyses 34 831 free ranging lambs were studied over a ten year period. Spring and summer temperature and precipitation, and the Arctic Oscillation (AO) index were used as climatic parameters. Interviews on farm management included general treatment, feeding, outdoor and socioeconomic factors. The results indicate that both climate and farm management is important for autumn live weights. The main climatic effects were captured by the AO index for July/August, while the effects of temperature and precipitation did not show any clear pattern. Grazing at cultivated pastures in spring and herd size had negative effects, while the length of the grazing period had a positive effect on the weights. As effects size for management and climate were of similar magnitude, I suggest that the accuracy of climatic studies could be improved by taking into account some of the farm management variables.