Lamb Production Related to the Body Weight of the Ewe

Master Thesis by Marie Lillehammer, 2004

Abstract from
Lammeproduksjon i forhold til kroppsvekt hos sau

Norwegian University of Life Sciences
Department of Animal and Aquacultural Sciences


Marie together with one of her sons, Trygve

My whole life, I have been surrounded by animals. I grew up on a small farm in the southern part of Norway and had sheep, rabbits, cats and other pets as a child. However, my big fascination of sheep and Norwegian sheep breeds did not start until I worked one year on a sheep farm when I was 18 years old. During that year I decided to study animal breeding. This thesis is the result of that choice.

Currently I live together with my husband and two sons in Ås in Norway. I am working on my PhD degree in animal breeding and genetics.

I hope you will enjoy this English abstract of my thesis. I am sorry that the full thesis is written in Norwegian, and thereby is unavailable for all of you that do not read Norwegian.

For readers of Scandinavian languages, Sheep-Isle strongly recommend reading the whole Master Thesis, or even take contact to Marie Lillehammer by e-mail:

For the Norwegian version of the master thesis, click here.





Marie Lillehammer  


The relationship between the weight of the ewe and the number of lambs, averaged weaning weight of the lambs, averaged EUROP-classification of the lambs and production efficiency of the ewe was investigated for the breeds cheviot, "spæl" and "nks" (norwegian white sheep). Field data from farmers, who after notice in the magazine "Sau og Geit" weighed their sheep and reported the weights into "sauekontrollen", were used. Production data were also collected from "sauekontrollen". The data set contained observations from 86 cheviot, 1164 spæl and 865 nks, that were from 1.5 to 6.5 years old. The datas were analyzed using proc mixed in SAS. The connection between ewe weight and number of lambs was positive in the breeds cheviot and spæl, but there was no connection in the breed "nks". In addition the age of the ewe had a significant effect on the number of lambs. The connection between ewe weight in kg and averaged weaning weight in kg of her lambs was positive within the breeds spæl and nks. There could not be detected any effect of ewe weight on average weaning weight of the lambs within the breed cheviot. The regression coeffisients were quite similar in all the breeds, ranging from 0.08 to 0.11. Other factors having a significant effect on the average weaning weights of the lambs were the age of the ewe, the age at where the lambs were weighed and the sexes of the lambs. There was no significant effect of breed after correcting for weight. As it comes to EUROP-classification, all the breeds differed significantly from each other. Cheviot got the highest score, and spæl got the lowest. In addition there was a positive significant effect of ewe weight within the spæl-breed. A significant negativ, linear relationship between ewe weight and production efficiency, measured as kg lambs weaned divided by the metabolic weight of the ewe was detected within the breeds spæl and nks. The regression coeffisients were -0.23 for spæl and -0.24 for nks. There could not be detected any difference in production efficiency between these two breeds. By comparing production efficiency in all the three breeds at their average weight within every age class, the spæl-sheep was the most efficient in every age class and all the breeds became more effective the older they got. It also looked like it could be an interaction between ewe weight and production environment. In some environments there were detected a stronger negative effect of ewe weight on the efficiency than in others. None of the herds had a positive significant effect of ewe weight on production efficiency. The negative relationship between ewe weight and production efficiency could be a product of that the Norwegian sheep is heavier than the optimal weight in the Norwegian production environment.

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