Variation in immunoglobulin transfer from ewes to lambs.

The IgG1 concentrations in two-day-old lambs were significantly correlated with litter size, date of lambing, length of gestation and age of the dam. When these and other effects were allowed for significant breed differences were found, the concentrations being relatively high in Finnish Landrace, Welsh Mountain and Soay lambs, and relatively low in Border Leicester, Oxford Down and Southdown lambs. The concentrations in crossbred lambs were related to those in the parent breeds. The effects of the various factors on the yields of colostrum and total IgG1 by ewes were similar to their effects on the lamb serum concentrations. The yields were highly correlated with milk production. The heritabilities for IgG1 concentration in lambs and for total IgG1 production by ewes were estimated at 0.10 and 0.45, respectively.