St. Anderson et al., ADVANCEMENT OF PUBERTY IN EWE LAMBS BY ACTIVE IMMUNIZATION AGAINST INHIBIN EARLY IN LIFE, Animal reproduction science, 44(2), 1996, pp. 111-125
Active immunisation of lambs early in life with inhibin can advance pu
berty and increase ovulation rate but these effects appear not to be m
ediated through changes in FSH concentrations. The aims of this study
were to advance puberty in ewe lambs and determine if increased plasma
concentrations of gonadotropins are responsible for the advancement o
f puberty. Ewe lambs were immunised at 3, 7 and 15 weeks of age agains
t either a synthetic inhibin alpha subunit peptide 1-32 conjugated to
human serum albumin (HSA), or an inhibin preparation purified from por
cine follicular fluid (porcine monoclonal purified inhibin; pMPI), or
HSA alone (control immunogen). Immunisation with inhibin alpha peptide
1-32 produced antibodies which bound iodinated native bovine inhibin
and advanced puberty (time of first ovulation) and increased ovulation
rate but did not significantly increase plasma FSH concentrations, al
though LH concentrations were lower (P < 0.01) on a number of occasion
s. In contrast, immunisation with pMPI significantly (P < 0.01) increa
sed FSH and LH concentrations following the first booster immunisation
, although FSH was only transiently elevated. Despite these increases
in gonadotropins, no advancement of puberty was observed in PMPI immun
ised ewe lambs. This study confirms that active immunisation of ewe la
mbs early in life against inhibin advances puberty via a mechanism whi
ch does not significantly increase plasma gonadotrophin concentrations
. Immunisation to advance puberty also results in persistent increases
in ovulation rates in later breeding seasons.