Effects of d-cloprostenol dose and corpus luteum age on ovulation, luteal function, and morphology in nonlactating dairy cows with early corpora lutea

Abstract

Luteolysis is a key event in cattle reproduction. A standard dose of exogenous PGF(2α) will induce full luteolysis in the majority of cows with a matured corpus luteum (CL). However, this will not occur in cows with a CL <5d old. To date, it is not known whether a larger dose will have a more potent luteolytic effect in cows during early diestrus. The objective of this study was to characterize the effect of 2 doses of d-cloprostenol (150 and 300 μg) on the progesterone concentration, luteal diameter, and ovulation rate in nonlactating dairy cattle 96 to 132 h postovulation. Twenty nonlactating dairy cows were included in the study. Each cow received 2 treatments of d-cloprostenol in 2 consecutive cycles: a standard dose of 150 μg and a double dose of 300 μg. The cows were allocated randomly to 1 of 4 groups (5 cows in each group) according to the age of the CL at the time of treatment: 96, 108, 120, and 132 h. The exact time of ovulation was known within 12h, because of twice per day ultrasound examination. The CL diameter and progesterone concentration were measured before treatment (d 0) and 2 and 4d after treatment. Within each CL age group, the effect of d-cloprostenol dose on luteolysis was determined. More cows treated with double dose tended to have full luteolysis compared with the standard dose (8/10 vs. 4/10, respectively). This effect was only apparent in cows with CL of 120 and 132 h but not in earlier CL. The interval from treatment to ovulation was shorter (3.3 ± 0.1d) in cows treated with a double dose than in cows treated with the standard dose (4.5 ± 0.4d).

The Effect of Dose and Type of Cloprostenol on the Luteolytic Response of Dairy Cattle during the Ovsynch Protocol under Different Oestrous Cycle and Physiological Characteristics

“…A superior luteolytic effect of a double dose of d‐CLO was also shown in cows treated at early stages of the oestrus cycle (Valldecabres‐Torres et al. ). A similar study also found a superior luteolytic response in mares treated with higher doses of PGF at early stages of the oestrus cycle (Cuervo‐Arango and Newcombe ).…”

“…; Valldecabres‐Torres et al. ). However, in cows from Experiment II, the presence of an older CL at the time of PGF treatment appeared to override the luteolytic resistance of the younger accessory CL.…”

“…In a recent experiment, as little as 20% of cows underwent full luteolysis when a single standard dose of d‐CLO was administered 4.5–5 days post‐ovulation (Valldecabres‐Torres et al. ). It is not surprising that in the present study, full luteolysis only occurred in 50% of cows, treated with a standard dose of d‐CLO 5.5 days post‐ovulation (Experiment I).…”

“…Recently, it has been shown that an increase in the dose of PGF can enhance the luteolytic response of non‐lactating dairy cattle with early CL compared with cows treated with the standard dose (Valldecabres‐Torres et al. , ). However, the latter studies did not test the effect of increasing the dose of PGF during an Ovsynch protocol.…”

“…It is reasonable to think that providing a higher dose of exogenous PGF 2a or cloprostenol would override to some extent the antiluteolytic effect resultant from the increased availability of PGDH and reduced concentration of ET-1 in the early CL. Recently, it has been shown that an increase in the dose of PGF can enhance the luteolytic response of non-lactating dairy cattle with early CL compared with cows treated with the standard dose (Valldecabres-Torres et al 2012, 2013. However, the latter studies did not test the effect of increasing the dose of PGF during an Ovsynch protocol.…”