Effects of propylene glycol or elevated luteinizing hormone during follicle development on ovulation, fertilization, and early embryo development.

Seventeen nonlactating Holstein cows were superovulated in a Latin-square designed experiment to determine the effects of increased propylene glycol (PROP) and luteinizing hormone (LH) during antral follicle development on ovarian function, fertilization, and early embryo quality. PROP was orally drenched every 4 h for 7 days to induce hyperinsulinemia and associated metabolic changes. LH concentrations were altered by increasing LH (3-fold) during last 2 days of superovulation. Treatment groups were as follows: (1) control-oral drenching with water plus low-LH preparation; (2) high LH(HLH)-water plus HLH preparation; (3) PROP-drenching with PROP plus low LH; (4) PROP/HLH-PROP plus HLH. PROP increased glucose (P < 0.05) and insulin (P < 0.02) concentrations at all time points analyzed. Neither PROP nor LH affected numbers of follicles > 9 mm at time of gonadotropin-releasing hormone-induced LH surge, although percentage of these follicles that ovulated was decreased by both PROP (P = 0.002) and LH (P = 0.048). In addition, PROP tended (P = 0.056) to decrease total number of ovulations. PROP reduced (P = 0.028) fertilization rate, while LH tended (P = 0.092) to increase fertilization rate. There was no effect of either PROP or LH on any measure of embryo quality including percentage of embryos that were degenerate, quality 1, or quality 1 and 2 of total structures collected or fertilized structures. These results indicate that acute elevation in insulin during the preovulatory follicular wave can decrease percentage of large follicles that ovulate, particularly when combined with increased LH, and reduce fertilization of ovulated oocytes.

Use of a single injection of long-acting recombinant bovine FSH to superovulate Holstein heifers: a preliminary study.

Our objective was to compare several experimental preparations of a single injection of long-acting recombinant bovine FSH (rbFSH; types A and B) to a porcine pituitary-derived FSH (Folltropin) to superovulate Holstein dairy heifers. Nonlactating, nonpregnant virgin Holstein heifers (n = 56) aged 12 to 15 months were randomly assigned to one of four superstimulatory treatments. Beginning at a random stage of the estrous cycle, all follicles greater than 5 mm were aspirated. Thirty-six hours later, heifers received an intravaginal P4 device and superstimulatory treatments were initiated. Treatments were (1) 300 mg of pituitary-derived FSH (Folltropin) administered in eight decreasing doses over a period of 3.5 days; (2) a single injection of 50 µg of A-rbFSH; (3) a single injection of 100 µg of A-rbFSH; and (4) a single injection of 50 µg of B-rbFSH. All heifers received 25 mg PGF2α at 48 and 72 hours after the insertion of P4 device. At 84 hours after insertion, P4 devices were removed, and ovulation was induced 24 hours later with hCG (2500 IU). Heifers were inseminated at 12 and 24 hours after hCG treatment. The number of ovulatory follicles was greatest for heifers treated with Folltropin and B50-rbFSH, least for heifers treated with A50-rbFSH, and was intermediate for heifers treated with A100-rbFSH (25.7 ± 3.2, 18.9 ± 3.2, 5.9 ± 0.9, and 16.6 ± 3.1, respectively; P < 0.001). The number of corpora lutea was greatest for heifers treated with Folltropin, B50-rbFSH, and A100-rbFSH, and least for heifers treated with A50-rbFSH (19.1 ± 2.4, 16.1 ± 3.0, 15.9 ± 2.9, and 2.6 ± 0.9, respectively; P < 0.001). The number of good-quality embryos differed among treatments and was greatest for heifers treated with B50-rbFSH, Folltropin, and A100-rbFSH and least for heifers treated with A50-rbFSH (7.6 ± 2.4, 6.5 ± 1.7, 4.3 ± 1.5, and 0.8 ± 0.5, respectively; P < 0.001). In conclusion, a single injection of a preparation of long-acting rbFSH (either 100 µg of A-rbFSH or 50 µg of B-rbFSH but not 50 µg of A-rbFSH) produced similar superovulatory responses resulting in the production of good-quality embryos when compared with a pituitary-derived FSH preparation administered twice daily for 4 days. More studies using different types of cattle and different doses of rbFSH are needed to confirm the findings reported in this preliminary study.

Patterns of gene expression in the bovine corpus luteum following repeated intrauterine infusions of low doses of prostaglandin F2alpha.

Natural luteolysis involves multiple pulses of prostaglandin F2alpha (PGF) released by the nonpregnant uterus. This study investigated expression of 18 genes from five distinct pathways, following multiple low-dose pulses of PGF. Cows on Day 9 of the estrous cycle received four intrauterine infusions of 0.25 ml of phosphate-buffered saline (PBS) or PGF (0.5 mg of PGF in 0.25 ml of PBS) at 6-h intervals. A luteal biopsy sample was collected 30 min after each PBS or PGF infusion. There were four treatment groups: Control (n = 5; 4 PBS infusions), 4XPGF (4 PGF infusions; n = 5), 2XPGF-non-regressed (2 PGF infusions; n = 5; PGF-PBS-PGF-PBS; no regression after treatments), and 2XPGF-regressed (PGF-PBS-PGF-PBS; regression after treatments; n = 5). As expected, the first PGF pulse increased mRNA for the immediate early genes JUN, FOS, NR4A1, and EGR1 but unexpectedly also increased mRNA for steroidogenic (STAR) and angiogenic (VEGFA) pathways. The second PGF pulse induced immediate early genes and genes related to immune system activation (IL1B, FAS, FASLG, IL8). However, mRNA for VEGFA and STAR were decreased by the second PGF infusion. After the third and fourth PGF pulses, a distinctly luteolytic pattern of gene expression was evident, with inhibition of steroidogenic and angiogenic pathways, whereas, there was induction of pathways for immune system activation and production of PGF. The pattern of PGF-induced gene expression was similar in corpus luteum not destined for luteolysis (2X-non-regressed) after the first PGF pulse but was very distinct after the second PGF pulse. Thus, although the initial PGF pulse induced mRNA for many pathways, the second and later pulses of PGF appear to have set the distinct pattern of gene expression that result in luteolysis.

Improving fertility to timed artificial insemination by manipulation of circulating progesterone concentrations in lactating dairy cattle.

This manuscript reviews the effect of progesterone (P4) during timed AI protocols in lactating dairy cows. Circulating P4 is determined by a balance between P4 production, primarily by the corpus luteum (CL), and P4 metabolism, primarily by the liver. In dairy cattle, the volume of luteal tissue is a primary determinant of P4 production; however, inadequate circulating P4 is generally due to high P4 metabolism resulting from extremely elevated liver blood flow. Three sections in this manuscript summarise the role of P4 concentrations before breeding, near the time of breeding and after breeding. During timed AI protocols, elevations in P4 are generally achieved by ovulation, resulting in an accessory CL, or by supplementation with exogenous P4. Elevating P4 before timed AI has been found to decrease double ovulation and increase fertility to the timed AI. Slight elevations in circulating P4 can dramatically reduce fertility, with inadequate luteolysis to the prostaglandin F2α treatment before timed AI being the underlying cause of this problem. After AI, circulating P4 is critical for embryo growth, and for establishment and maintenance of pregnancy. Many studies have attempted to improve fertility by elevating P4 after timed AI with marginal elevations in fertility. Thus, previous research has provided substantial insights into mechanisms regulating circulating P4 concentrations and actions. Understanding this prior research can focus future research on P4 manipulation to improve timed AI protocols.