Three studies were conducted to evaluate the effect of
gonadotropic stimulationonthe reproductiveperformance
of nulliparous females. The first study utilized ewe lambs
of mixed breeding (N = 191) born in mid-October through
mid-December of 2010 and 2011 and was conducted during
the mid-anestrous period (May to early July) of 2011
and 2012 on five farms located in West Virginia and southwestern
Pennsylvania. The second and third studies were
conducted beginning in May (study 2) and late August
(study 3) at a farm located in southwestern Pennsylvania.
The animals used in these studies consisted of springborn
Dorset X Texel yearlings (N = 120, 15-months-old and
N = 104, 17-months-old for studies 2 and 3, respectively).
In the third study a single blood sample was collected
via jugular venipuncture and assayed for progesterone as
described by Sheffel et al. (1982). The limit of detection
was 0.1 ng/mL, and the intra and interassay coefficients
of variation were 7.1 and 18%, respectively. Animals with
concentrations of progesterone >1 ng/mL (N = 11) were
considered to be ovulatory and were removed from the
study. Animals were not previously exposed to rams and
were managed on mixed grass:legume pastures with ad
libitum access to water and shade.