A MULTILEVEL MODEL OF DATA WITH REPEATED-MEASURES OF THE EFFECT OF LAMB DIARRHEA ON WEIGHT

Over a 1-year period, data were collected from three flocks of sheep. A total of 213 lambs were examined routinely from birth to 32 kg (2178 examinations in total). Diarrhoea was seen in lambs of all ages but d id not appear to make them systemically ill. The effect of diarrhoea o n lamb weight was investigated using MLn, a multi-level modeling progr am. The data were set at three hierarchical levels: level one, the rep eated examinations on each lamb; level two, the lamb; and level three, the litter. Age, the quadratic of age, litter size, sex and farm of o rigin, all had significant effect on the weight of the lambs. There wa s also significant random variation in examinations within lambs, betw een individual lambs and between litters of lambs. There was a reducti on in absolute weight of lambs for each week until four weeks after an episode of diarrhoea. (C) 1998 Elsevier Science B.V.