Corpus Luteum Development and Function after Supplementation of Long‐Acting Progesterone During the Early Luteal Phase in Beef Cattle

Abstract

Strategic supplementation of P4 may be used to increase conception rates in cattle, but timing of supplementation in relation to ovulation, mass of supplementary P4 and formulation of the P4-containing supplement has not been determined for beef cattle. Effects of supplementation of long-acting progesterone (P4) on Days 2 or 3 post-ovulation on development, function and regression of corpus luteum (CL) were studied in beef cattle. Cows were synchronized with an oestradiol/P4-based protocol and treated with 150 or 300 mg of long-acting P4 on Day 2 or 3 post-ovulation (6-7 cows/group). Colour-doppler ultrasound scanning and blood sample collection were performed from Day 2-21.5. Plasma P4 concentrations were greater (p < 0.05) from Day 2.5-5.5 in the Day 2-treated groups and from Day 3.5-5.5 in the Day 3-treated cows than in the control group. CL area and blood flow during Day 2-8.5 did not differ (p > 0.05) among groups, suggesting no effect of P4 treatment on luteal development. The frequency of cows that began luteolysis before Day 15 was greater (p < 0.04) in cows treated with 300 mg than in the controls, but there were no differences between non-treated and 150 mg-treated cows. The interval from pre-treatment ovulation to functional and structural luteolysis was shorter (p < 0.01) in the combined P4-treated groups than in the control cows. In conclusion, was showed for the first time that long-acting P4 supplementation on Day 2 or 3 post-ovulation increases P4 concentrations for ≥3 day, has no effect on luteal development, but anticipates the beginning of luteolysis in beef cattle.

Follicle and corpus luteum size and vascularity as predictors of fertility at the time of artificial insemination and embryo transfer in beef cattle

“…For the gray-scale mode, the brightness and contrast controls of the monitor and the gain controls of the scanner were standardized to constant settings . For color Doppler mode, all scans were performed at a constant color-gain setting and a velocity setting of 5cm/s (Pugliesi et al 2014). All scans were recorded by video clips for further analyses using specific software (MyLab Desk; Esaote Healthcare, Genova, Italy).…”

The Role of Progesterone in Maternal Recognition of Pregnancy in Domestic Ruminants

“…Paradoxically, depending on the timing of administration, exogenous P4 can have a negative effect on CL life span, resulting in shortened interestrous intervals due to premature CL regression (Ginther 1970 ;Garrett et al 1988a ;Burke et al 1994 ;Pope et al 1995 ;O'Hara et al 2014a ;Pugliesi et al 2014 ;Randi et al 2015 ) while at the same time advancing conceptus development due to the changes induced in the endometrium by P4 ). This situation is clearly not compatible with successful maintenance of pregnancy.…”

<b>Ação do 17&#946;-estradiol na síntese de PGF2&#945; endometrial em vacas</b>

“…Foi observado em novilhas que a permanência de dispositivos de liberação de P4, com maiores concentrações de P4, entre os dias 8 e 21 do ciclo, promoveu maior número de picos de PGF2α e duração do ciclo (DUCHENS et al, 1995). Em estudos recentes relatou-se que a aplicação de P4 injetável no início do diestro, em vacas de corte, também resulta na antecipação da luteólise (PUGLIESI et al, 2014). Lafrance e Goff (1988) mostraram que os efeitos de 17β-estradiol e ocitocina na liberação de PGF2α dependem do tempo de exposição à P4, de forma que maiores períodos de exposição à P4 potencializam os efeitos do estradiol e ocitocina (LAFRANCE;GOFF, 1988).…”