Comparison of Selected Endocrine Parameters During Luteal Phase and Pregnancy in German Shepherd Dogs and Beagles

Abstract

Contents Concentrations of progesterone, prolactin and relaxin in serum at predetermined intervals after ovulation (day 0) in non‐pregnant and pregnant normocyclic Beagles were assayed and results compared with those observed in German Shepherd dogs (GSD) in a previous study. The goal was to determine possible reproductive hormone specificities related to the GSD breed. Furthermore, the effects of medroxyprogesterone acetate (MPA)‐treatment in non‐pregnant Beagles and of progesterone supplementation in pregnant Beagles on the hormone concentrations were examined. Mean concentrations of progesterone and prolactin were not different in the non‐pregnant Beagles compared with those seen in non‐pregnant GSD, except at days 50–60, when progesterone concentrations were found to be higher in Beagles (p < 0.05). Mean progesterone concentrations in pregnant Beagles at days 50–60 after ovulation (day 0) were higher (p < 0.05) than in GSD at that time, but not at earlier time periods. Prolactin concentrations were higher (p < 0.05) in Beagles throughout pregnancy compared with those in the GSD. Mean relaxin concentrations were numerically but not significantly lower in GSD than in Beagles throughout pregnancy. A 10‐day oral MPA treatment did not affect progesterone or prolactin secretion in normocyclic non‐pregnant Beagles. Medroxyprogesterone acetate serum concentrations were approximately 3.9 ng/ml during treatment and decreased to 0.42 and 0.021 ng/ml within 5 and 15 days after end of treatment, respectively. Intramuscular progesterone supplementation from days 30 to 40 in pregnant Beagles resulted in higher concentrations of progesterone in the 36‐ to 45‐day time periods; prolactin and relaxin concentrations were not significantly affected during or after treatment compared with administration of placebo. The results suggest a tendency towards deficient luteal function in the short‐cycle GSD bitches previously studied, which in pregnancy may reflect the observed decreased prolactin concentrations; the possibility that GSD relaxin secretion is deficiency required needs further study. As oral treatment with MPA did not affect progesterone and prolactin release, it may be useful for studying luteal function in pregnant bitches with suspected hypoluteoidism.

Serum Progesterone in Pregnant Bitches Supplemented with Progestin Because of Expected or Suspected Luteal Insufficiency

“…approximately 0.7 mg/kg) given orally in the mid‐luteal phase did not affect the secretion of either P 4 or PRL in normocyclic non‐pregnant beagle bitches (Günzel‐Apel et al. ). In the present study, treatment was not started before day 30 after ov to ensure the completion of embryonic organogenesis.…”

“…Significantly lower PRL values were found throughout pregnancy in GSD dogs compared to pregnant beagle bitches, both groups with a normal cycle length (Günzel‐Apel et al. ). In GSD bitch I (case 3) and in the first pregnancy of GSD bitch II (case 4a), PRL values were at markedly lower level than in the second pregnancy of GSD bitch II (case 4b), in which also a more pronounced PRL increase was observed, indicating intra‐individual differences both in luteal and pituitary hormone secretion.…”

“…Pregnancies in bitches with short interoestrous intervals had significantly lower concentrations of PRL and RLN between days 20 and 60, which suggest a secondary luteal deficiency because of reduced PRL and perhaps RLN. Comparing normocyclic pregnant GSD bitches with beagles, there were significantly lower P 4 values in GSD only in the late luteal phase (days 50-60 after ov; p < 0.05), whereas PRL was significantly (p < 0.05) lower, and RLN tended to be lower in the GSD throughout pregnancy (Gu¨nzel-Apel et al 2009).…”

“…Comparing normocyclic pregnant GSD bitches with beagles, there were significantly lower P 4 values in GSD only in the late luteal phase (days 50–60 after ov; p < 0.05), whereas PRL was significantly (p < 0.05) lower, and RLN tended to be lower in the GSD throughout pregnancy (Günzel‐Apel et al. ).…”

“…However, monitoring the ovarian P 4 secretion in pregnant bitches is not possible if exogenous P 4 is administered (Günzel‐Apel et al. , ; Verstegen et al. ).…”