Prolongation of the oestrous cycle in cows and ewes after passive immunization with PGF antibodies

Abstract

Three cows and 2 sheep were passively immunized against prostaglandin (PG) F on Day 16 and Days 13-15 of the oestrous cycle respectively. The PGF antiplasma was raised in ovariectomized ewes against a PGF-2 alpha-bovine serum albumin complex and showed 100%, 12.5%, 0.3%, less than 0.05% and less than 0.01% cross-reactivity with PGF-2 alpha, PGE-2, PGA-2, PGB-2 and arachidonic acid, respectively. Control animals were given an equivalent amount of ovariectomized ewe plasma. In all passively immunized animals there was evidence of a persistent corpus luteum as indicated by plasma progesterone concentration and the failure of the animals to return to oestrus until at least 29 days after treatment. These data are consistent with previous proposals that PGF-2 alpha is the uterine luteolytic factor in sheep and cattle.

Effects of oxytocin on the bovine corpus luteum of early pregnancy

“…In non-pregnant cows and sheep, there is evidence that PGF-2a of uterine origin is the physiological luteolysin (Fairclough et al, 1981). Towards the end of the oestrous cycle, therefore, increased oxytocin secretion is thought to trigger the production of uterine PGF-2a which then acts locally on the ipsilateral corpus luteum to bring about its regression .…”

“…In-vitro studies have shown that oxytocin stimulates the release of PGF-2a from uterine tissue (Roberts, McCracken, Gavagan & Soloff, 1976), while in-vivo experiments have demonstrated a temporal relationship between plasma levels of oxytocin-associated neurophysin I/II and the prostaglandin F metabolite (13,14-dihydro-15-ketoprostaglandin F) at the end of the oestrous cycle . The luteolytic role of prostaglandins has been repeatedly shown (Horton & Poyser, 1977;Fairclough, Smith & McGowan, 1981).…”

Effect of active immunization of pre-partum and post-partum cows against prostaglandin F-2 on lifespan and progesterone secretion of short-lived corpora lutea

“…Prostaglandin F-2a has been proposed as the uterine luteolysin in numerous species including cattle (Horton & Poyser, 1976;Knickerbocker et al, 1988 Baird, 1976;Fairclough et al, 1981) and cattle (Fairclough et al, 1981;Chang et al 1987). In the present study, active immunization against PGF-2a extended the lifespan and function of corpora lutea anticipated to be short-lived.…”

“…Both active and passive immunization against PGF-2a lengthened the functional lifespan of corpora lutea in sheep (Scaramuzzi & Baird, 1976;Fairclough et al, 1981), guinea-pigs (Horton & Poyser, 1974;Poyser & Horton, 1975) and cattle (Fairclough et al, 1981;Chang et al, 1987). Therefore, the objective of this study was to determine whether active immunization of pre-partum and post-partum cows against PGF-2a would extend the lifespan and progesterone secretion of short-lived corpora lutea.…”

Comparison of techniques for synchronisation of oestrus and subsequent fertility in beef cattle

“…The smallest amount of progesterone that could be measuredwithprecision was0.15ng/mlserum. The intra-and inter-assay coefficients of variation for a plasma pool assayed on 16 consecutive occasions and containing progesterone at a concentration of 0.9 ng/ml were 9.6 and 10.9% respectively (Fairclough et al 1981).…”