Effect of Campylobacter fetus on in vitro fertilization and embryonic development of preimplantation bovine embryos.

Campylobacter fetus is an important veterinary pathogen that causes campylobacteriosis. This disease causes decreased productivity of cattle by inducing reproductive losses. Although several virulence factors have been recognized in C. fetus, including a cytolethal distending toxin (CDT), the exact mechanism responsible for embryonic death remains unknown. The aim of this work was to evaluate the effect of C. fetus subsp. fetus (Cff) and C. fetus subsp. venerealis (Cfv), and their toxin activity on the in vitro fertilization of bovine ova and early embryonic development. Two different experiments were performed. In Experiment 1, a total of 1524 cumulus-oocyte complexes (COCs) were inseminated, distributed into three groups: two of them infected with the microorganism (Cff, Cfv) and a control group. Percentages COCs cleaved were similar among groups (p = 0.1243); however, the embryonic development rate (blastocyst at day 7) in the control group was greater (p < 0.001) than those obtained in Cff and Cfv groups. In experiment 2, a total of 746 COCs were inseminated, divided into three groups: two of them treated with the bacterial-free culture filtrates to test toxin activity (Cff-CDT, Cfv-CDT) and a control group. Both cleavage and embryonic development rates were greater (p < 0.001) in the control group than those obtained in Cff-CDT and Cfv-CDT groups. This study provides evidence that both subspecies of C. fetus do not interfere with fertilization but do affect in vitro embryonic development. It is the first report on the biological effect of the CDT on bovine embryonic development.

Effects of two protocols of ovulation synchronization on corpus luteum size and blood flow, progesterone concentration, and pregnancy rate in beef heifers.

The objective of this study was to evaluate the effect of 7-day estradiol-progesterone-based [Treat(C)] and 5-day Co-Synch plus progesterone [Treat(Co-Sy)] protocols on ovulation time, pre-ovulatory follicle diameter, corpus luteum (CL) size and blood flow, progesterone (P4) concentration and pregnancy rate (PR) in beef heifers. In Experiment 1, a crossover design was applied (n = 9). For Treat(C), a progesterone intravaginal (PI) device was inserted, plus 2 mg of estradiol benzoate (day 0). On day 7, 500 µg of cloprostenol plus 0.5 mg of estradiol cypionate were administered, and PI was removed. For Treat(Co-Sy), on day 0, a PI was inserted plus 100 µg gonadotropin-releasing hormone (GnRH). On day 5, PI was removed, plus 500 µg of cloprostenol and 100 µg of GnRH were administered at 69-70 h later. From day one to ovulation day, dominant follicle was evaluated by ultrasonography. On days 4 and 8 post-ovulation, CL was evaluated by color Doppler, and P4 concentration was determined by chemiluminescence. In Experiment 2, a split-plot experimental design was used. Protocols followed were the same as in Experiment 1 [Treat(C); n = 310 and Treat(Co-Sy); n = 314]. Heifers were fixed-time artificially inseminated. Pregnancy was determined on day 41. In Experiment 1, the interval between PI removal and ovulation time was different between protocols (P < 0.01). In addition, P4 concentration was related to the CL size (P < 0.001), CL blood flow (P < 0.01) and protocols (P < 0.03). In Experiment 2, PR did not differ between protocols.

Effects of Campylobacter fetus on bull sperm quality.

Campylobacter fetus is a gram-negative, motile, spiral or S-shaped bacterium, which induces campylobacteriosis. This disease causes decrease productivity of cattle. Although considerable research has been done on the role of C. fetus on female fertility, little is known about the effect on bulls. The aim of this work was to evaluate the effect of C. fetus subsp. fetus (Cff) and C. fetus subsp. venerealis (Cfv) on bull sperm quality. Samples of frozen semen (n = 29 straws) were each distributed into three groups: two of them incubated with the microorganism (Cff, Cfv) and a control group. The proportions of live spermatozoa, with functional membrane and true acrosomal reaction in control group were significantly (P < 0.01) greater than those observed in Cff and Cfv groups. However, no significant differences (P > 0.05) were found in sperm chromatin structure among treatments. In adhesion assay, proportions of spermatozoa with adhered Campylobacter were similar for both subspecies. Results confirm that Cff and Cfv have the same ability to bind in an irreversible way to bull spermatozoa and to affect sperm quality. It is proposed that adherence could be considered as the main cause of sperm alterations, and also an important step of pathogenesis and venereal transmission.

Estradiol benzoate given 0 or 24 h after the end of a progestagen treatment in postpartum suckled beef cows.

The objective of Experiment 1 was to compare the effects of estradiol benzoate (EB) given 0 or 24h after the end of a progestagen treatment on ovulation and CL formation in anestrous cows. Twenty cows were treated with an intravaginal sponge containing 250 mg of medroxiprogesterone acetate (MPA). At sponge insertion, each cow received 3 mg EB and 10 mg MPA im. At device removal, cows received 0.7 mg EB either at that time (EB0) or 24h later (EB24). Ultrasound examinations and blood sampling to determine plasma progesterone concentrations were performed to detect ovulation and CL formation. Ovulation occurred in 77.8 and 81.8% cows in the EB0 and EB24 groups, respectively. Diameter of the ovulatory follicle (EB0 = 10.9 +/- 0.5mm; EB24 = 12.1 +/- 0.8 mm; P = 0.26) and the interval from sponge removal to ovulation (median = 3 days; P = 0.64) did not differ between treatments. Among the cows that ovulated (n = 16), short-lived CL were present in 2/7 and 2/9 cows in the EB0 and EB24 groups, respectively. Plasma progesterone concentrations and CL area did not differ between treatments (P > 0.05). In Experiment 2, cows were treated with the same protocol as in Experiment 1, but at sponge withdrawal all cows received 250 microg cloprostenol and timed artificial insemination (TAI) was performed 48 h after sponge removal. In Replicate 1 (n = 204 multiparous cows), pregnancy rates were 45.0 and 47.5% for EB0 and EB24, respectively (P > 0.05). In Replicate 2 (n = 69 primiparous cows) pregnancy rate did not differ between EB0 and EB24 (51.4% versus 52.9%). In conclusion, EB given 0 or 24h after the end of a progestagen treatment had the same effect on ovulation rate, time to ovulation, diameter of the ovulatory follicle, incidence of short-lived CL, luteal tissue area, and plasma progesterone concentrations of normal lifespan CL, and pregnancy rate after TAI in suckled beef cows.