Previous work in this laboratory revealed that hormone analysis using fecal
samples may predict the number of fetuses carried by pregnant ewes at mid- to late
gestation. Reliable lambing number prediction is useful to the producer. Using gas
chromatography/mass spectrometry the 5α- and 5β-series of pregnanes and
selected 4- and 5-pregnenes were monitored in the feces of 36 black and white-face
cross ewes during early gestation. Feces were collected at d 5, 19, and 30 post-mating.
Endoscopy was used at d 6 to determine the number of corpora lutea, and
litter size data were collected at term. The number of copora lutea was not related
(P>.05) to hormone concentrations at any of the sampling times (ANOVA-GLM).
No differences in hormone levels were detected at d 5 in response to lambing
number. At d 19, 5β-pregnane-3,20-dione and 5β-pregnane-3β,20α-diol were
higher in ewes carrying triplets than ewes carrying twins (P≤.008). At d 30, 3α-hydroxy-5β-pregnan-20-one was higher in ewes carrying triplets than twins
(P<.05). Five progestins, including progesterone and 20α-hydroxy-4-pregnen-3-
one, were lower at d 5 in ewes that conceived (n=26) than in ewes that did not
conceive (n=6) at the first mating (P<.05). Concentrations of ten progestins were
different (P<.05) (some higher and some lower) between groups of ewes that
conceived at the first mating versus those that conceived at the second mating. In
ewes that conceived at the second mating, pregnenolone and 5β-pregnane-3,20-
dione were higher (P<.05) at d 5 than at d 5 of their previous non-conceptive cycle.
Of the six ewes that were mated a second time, two still did not conceive but had
elevated concentrations of three 5β-pregnanes (P<.05). Although there are
differences in progestin profiles in ewes carrying different numbers of fetuses,
concentrations alone are not adequate predictors of prolificacy at early gestation. It
is inconclusive whether detection of pregnancy is possible as early as d 5 of