Table 2

Multilevel Poisson regression model results

N farmsN obsEstimateStd. errorZ valueExponentiated estimateEffectPr(>|z|)
(Intercept)18−1.1300.919−1.2290.3230.219
Sheep category Ewe (>=1 year)18291Ref.
Sheep category Lamb(younger than 1 year)1696−0.2900.090−3.2140.748−25%0.001**
Sheep category Ram513−0.1770.280−0.6310.8380.528
Pasture length>10 cm (long)11145Ref.
Pasture length 6–10 cm (medium)16192−0.1830.089−2.0540.832−17%0.040*
Pasture length up to 5 cm (short)15182−0.3840.114−3.3750.681−32%<0.001***
Pasture type forage crop29Ref.
Pasture type new leys6270.4870.4711.0351.6280.301
Pasture type permanent184870.3880.4510.8601.4740.390
Season autumn10177Ref.
Season spring111150.3660.1382.6581.44244%0.008**
Season summer91000.4940.1194.1351.63964%<0.001***
Season winter121270.6940.1644.2322.002100%<0.001***
Selenium concentration18521−1.8500.735−2.5160.157−84%0.012*
Precipitation (2 week mean)18521−0.0340.024−1.4520.9660.147
Maximum temperature (3 day mean)185210.0290.0132.2441.0293%0.025*
Flock size: up to 5015171Ref.
Flock size: 51–10017173−0.2920.122−2.3920.746−25%0.017*
Flock size: 101–20014102−0.4430.149−2.9710.642−36%0.003**
Flock size: 201–400773−0.7130.173−4.1140.490−51%<0.001***
Bedrock type SLAR210Ref.
Bedrock type LSSA231−0.8800.992−0.8870.4150.375
Bedrock type MDSS281−0.8730.624−1.3990.4180.162
Bedrock type MSLS13397−1.6230.816−1.9900.197−80%0.047*
R squared: 0.31 (marginal), 0.94 (conditional)
Significance codes: ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05
Random effects:
GroupsNameVarianceStd.Dev.
Farm(Intercept)0.49230.7016
Field(Intercept)0.44260.6653
Date(Intercept)0.38020.6166
  • Number of obs: 519, groups: N_intfield, 177; Nperfield, 21; Num_farm, 18.

  • LSSA, limestone with subordinate sandstone and argillaceous; MDSS, mudstone, siltstone and sandstone; MSLS, mudstone, siltstone, limestone and sandstone; SLAR, sandstone, limestone and argillaceous rocks.