groups, becoming detectable from d 1 after birth and
reaching a maximum value at the end of this study
(20 d). In general, no differences in complement system
activity were found between study groups, although we
found that lambs fed sheep colostrum showed a higher
TCA at d 3, 4, and 5 compared with lambs fed goat
colostrum. Despite these findings, no differences were
observed between groups at d 20. As no differences in
ACA were found, we can assume that the increase of
the TCA was produced by activation of the classical
complement system activity pathway. In accordance
with these findings, Eckblad et al. (1981) suggested that
complement system components in colostrum might
play an essential role in the development of complement
system activity in newborn animals through gut
absorption. Our findings suggest that lambs fed sheep
colostrum could have earlier activation of the classical
complement system pathway compared with those fed
with goat colostrum. According to Tabel (1996), the
ACA pathway does not require antibody for activation,
whereas activation of the classical pathway is antibody
mediated. In our study, the greater phylogenetic affinity
of sheep immunoglobulins present in the sheep colostrum
compared with goat immunoglobulins present in
goat colostrum could produce higher activation of the
classical pathway in lambs. Results of the current study
indicate that TFCF (2 h vs. 14 h after birth) did not
affect the complement system development, although
colostrum source (goat vs. sheep) may partly affect it.