Piglet serum IgG concentration and birth weight had
the greatest effect of any of the variables measured on survival
percent at weaning. Stone and Leymaster [17] used a
statistical model that fitted the combined effects of serum
albumin and birth weight and found that they accounted
for 57% of the variation in survival. Hendrix et al. [18]
showed that the concentration of IgG in piglet plasma
shortly after birth was positively correlated with survival.
We selected piglets with birth weight greater than 0.68
kg because very low birth weight piglets die to a much
greater extent than their heavier littermates and this
would have limited our blood sampling at 2 d of age. A
low-birth weight piglet is disadvantaged when competing
with its littermates a) because of its size [7], b) it has a
larger surface area when compared to its weight [19,20]
and c) it differs physiologically from its littermates and
has an increased risk of mortality [21]. Milligan et al.
[22] also emphasized that this disadvantage is exacerbated
in large litters and litters from older sows. Various
researchers [23-25] have argued that low-birth weight
piglets lack the ability to successfully extract colostrum
from the teats and this reduces their chances of suckling
later on, as nursing becomes synchronized.