Plasma progesterone and gonadotrophin concentrations and ovarian activity in post-partum dairy cows

Abstract

Summary. Plasma

Endocrine regulation of postpartum ovarian activity in cattle : a review

“…Prolactin release is not systematically connected with suckling (Gimenez et al, 1980 ;Convey et al, 1983). Moreover, anoestrus length was observed by some (Chang et al, 1981) but not others (Webb et al, 1980) to be closely correlated with plasma prolactin concentrations. Finally, the injection of prolactin (Forrest et al, 1980) or of bromocryptin (Williams and Ray, 1980), an inhibitor of prolactin release, influences neither the variations of LH or FSH concentrations nor the resumption of cyclic activity after calving delay at least in bovines.…”

“…According to different authors, the first rise of progesterone appears between 16 and 69 days after calving in dairy cows (Webb et al, 1977(Webb et al, , 1980Pirchner et al, 1983) and between 56 and 96 days in suckled cows (Fonseca et al, 1980 ;Peters and Riley 1982 ; Jainudeen et al, 1982 Jainudeen et al, /1983Montgomery et al, 1985).…”

“…In dairy cows, the pulsatile release of LH and the sensitivity of the pituitary to hypothalamic GnRH appears 10 days after calving and is greater between 12 and 15 days after calving (Echterkamp and Hansel, 1973 ;Kesler et al, 1977Kesler et al, , 1979Peters et al, 1981 Suckling may have an effect at three levels. It reduces the frequency Walters et al, 1982a ;Edwards, 1985) and amplitude of LH release (Radford et al, 1978 ;Troxel et al, 1980 ;Webb et al, 1980, pituitary sensitivity to GnRH (Carruthers et al, 1978 ;Smith et al, 1981) and pulsatile release of GnRH by the hypothalamus Walters et al, 1982c ;Schallenberger and Peterson, 1982 (Schams et al, 1973 ;Kesler et al, 1977 ;Webb et al, 1977 ;Schallenberger et al, 1978 ;Smith et al, 1981 ;Walters et al, 1982c).At last, as well as a diminution in the interval between injection of oestradiol or GnRH and the LH peak, there is also an increase in the amplitude of this peak during the first 4 weeks after calving (Stevenson et al, 1983 ;Azzazi et al, 1983). The magnitude of the GnRH-induced release of LH was directly proportionnal to follicular diameter (Smith et al, 1983 ;Lishman et al, 1979) and oestrogen concentrations in postpartum cattle (Fernandes et al, 1978 Manns et al, 1983) but tend to increase during the first few days after calving (Webb et al, 1980 ; Peters et al, 19811.…”

“…They diminish slowly during the final 3-4 weeks and rapidly 2-3 days before calving (Short, 1958 ;Randel and Erb, 1971 ;Smith et al, 1973 (Webb et al, 1977 ;Lishman et al, 1979 ;Kesler et al, 1980 ;Fonseca et al, 1980 ;Sheffel et al, 1980 ;Troxel et al, 1983) or after early weaning (Odde et al, 1980) or limited suckling with (Dunn et al, 1985) or without (Flood et al, 1979) GnRH injection. Many hypotheses have been put forward to explain this.Morphological and endocrine studies (Manns et al, 1983) (Ramirez-Godinez et al, 1982a).Progesterone might be formed by a follicle which has failed to ovulate (Tribble et al, 1973 ;Corah et al, 1974 ;Webb et al, 1980). The absence of differences in LH plasma concentrations observed before or after an oestrus associated with a short cycle does not lead one to a conclusion of an insufficient LH synthesis (Ramirez-Godinez et al, 1982a).…”

“…It is possible to detect ovarian follicles by rectal palpation in both milked and suckled cow from the second week after calving (Saiduddin et al, 1968 ;Callahan et al, 1971 ;Kesler et al, 1979 ;Webb et al, 1980 ;Kesler et al, 1980 ;Stevenson et al, 1983 (Wiltbank et al, 1962(Wiltbank et al, , 1964Dunn et al, 1969 ; Lammond, 1970 ;Corah et al, 1975 ;Whitman et a/., 1975 ;Duffour, 1975 ;Holness et al, 1978 ;Carstairs et al, 1980 ;Dunn and Kaltenbach, 1980 ; Gauthier and Thimonnier, 1982 ;Peters and Riley, 1982 ; Mc Leod, 1983/1984 ;Rutter and Randel, 1984). Some authors have found that overfeeding improves ovarian (Wiltbank et al, 1962(Wiltbank et al, , 1964Hansen et al, 1982) or pituitary (Beal et al, 1978 ;Jordan and Swanson, 1979 ;Lishman et al, 1979 ;Moss et al, 1982) function.…”