Contrasting effects of progesterone on fertility of dairy and beef cows

Abstract

The role of progesterone in maintaining pregnancy is well known in the bovine. Subtle differences exist between dairy and beef cows because of differing concentrations of progesterone during recrudescence of postpartum estrous cycles, rate of follicular growth and maturation, proportions of 2- and 3-follicular wave cycles, and other effects on pregnancy outcomes per artificial insemination (P/AI). Because proportions of anovulatory cows before the onset of the artificial insemination (AI) period are greater and more variable in beef (usually ranging from 30 to 70%) than dairy (25%) cows, AI programs were developed to accommodate anovulatory and cycling beef cows enrolled therein. Incorporating a progestin as part of an AI program in beef cows improved P/AI by reducing the proportion of cows having premature luteal regression and short post-AI luteal phases. In both genotypes, prolonged dominant follicle growth in a reduced progesterone milieu resulted in increased (1) LH pulses, (2) preovulatory follicle diameter, and (3) concentrations of estradiol and a subsequently larger corpora lutea (CL). In contrast, the progesterone milieu during growth of the ovulatory follicle in an ovulation control program does not seem to affect subsequent P/AI in beef cows, whereas in dairy cows follicle development in an elevated compared with a low progesterone environment increases P/AI. Progesterone status in beef cows at the onset of ovulation synchronization is not related to P/AI in multiparous cows, whereas P/AI was suppressed in primiparous cows that began a timed AI program in a low-progesterone environment. In timed AI programs, elevated concentrations of progesterone just before PGF2α and reduced concentrations at AI are critical to maximizing subsequent P/AI in dairy cows, but seemingly much less important in beef cows. By inducing ancillary CL and increasing concentrations of progesterone, human chorionic gonadotropin may increase P/AI when administered to beef cows 7d after AI or at embryo transfer, and its success seems to depend on induction of ancillary CL, whereas in dairy cows increased fertility was detected in cows with multiple CL, human chorionic gonadotropin-enhanced progesterone from original CL, or both. Pregnancy losses after AI are less frequent in beef cows and are not associated with pre-AI progesterone or cycling status, whereas losses in dairy cows are inversely related to progesterone and adversely affected in anovular dairy cows. Genotype and nutritional management likely influence several physiological differences including circulating concentrations of progesterone and responses to supplemental progesterone.

Effect of a second treatment of prostaglandin F2α during the Ovsynch program on fixed‐time artificial insemination conception rates and luteolysis in split‐calving, pasture‐fed dairy cows

“…Differences in progesterone concentrations across studies are likely to be due to the use of different assays (e.g. chemiluminescence in this study versus radioimmunoassay in others), differences in the proportion of cows in post‐partum anoestrus at the start of treatment programs and differences between beef and dairy cows . Although P4 a cutoff of <1 ng/mL has been used in other studies to classify cows as having undergone luteolysis, in our data, there appears to be a distinct cut‐off point of 3 ng/mL at the time of AI in the OV group (Figure ) and a cut‐off point of 2 ng/mL at the time of AI in the MO group (Figure ).…”

“…Since the rate of luteolysis increases with the age of the CL, a second dose of PGF 24 h after the first would be expected to coincide with the time of responsiveness of the CL to PGF administration of PGF . In this study, concentrations of progesterone at the time of FTAI were higher than that recorded in other studies where cows were sampled 48–72 h after administration of PGF using GnRH‐based treatment protocols . Differences in progesterone concentrations across studies are likely to be due to the use of different assays (e.g.…”

Oral progesterone supplementation for beef cattle after insemination in TAI programs

“…According to previous studies, several factors may affect the conception rates of animals supplemented with P4, and this complexity can be noted in the experiments of Larson et al (2009), who found positive effects on fertility, when dairy cows were supplemented with a progesterone intravaginal device; however, these authors found no improvement in beef cows that received the same treatment, at the same time, which suggested that there was a difference in response to treatment according to the type of animal that was treated (beef or dairy). Stevenson and Lamb (2016) proposed that physiological differences, including the circulating concentrations of progesterone and responses to supplemental progesterone, affected by the genotype and nutritional management of the animals, could account for the variation.…”

“…bras., Brasília, v.53, n.1, p.105-112, Jan. 2018 DOI: 10.1590/S0100-204X2018000100012 preimplantation phase, and provided an adequate uterine environment for conception (Davoodi et al, 2016). Furthermore, adequate concentrations of E2 during the final follicular growth were positively correlated with the preovulatory follicle diameter and luteal function, which facilitated the establishment and maintenance of pregnancy (Bridges et al, 2012;Stevenson & Lamb, 2016).…”

Characterization of the Endometrial Transcriptome in Early Diestrus Influencing Pregnancy Establishment in Dairy Cattle after Transfer of In-Vitro Produced Embryos

“…Regarding endometrial receptivity, experiments performed in Nellore cows and Simmental heifers 19,21,22 , after estrus synchronization, have unveiled important differences in the endometrial transcriptome at day 6 or 7 of animals that become pregnant after AI or embryo transfer (ET), respectively, compared to the non-pregnant ones. However, disparities in embryo survival between heifers and lactating cows 2 , the different effects of progesterone on the fertility of dairy and beef cows 23 and the variations in hormonal concentration and uterine thickness between induced or natural estrus 17 , indicate the need of further studies for a better comprehension of the mechanisms controlling endometrial receptivity.…”