Shifts in uterine bacterial communities associated with endogenous progesterone and 17ß-estradiol concentrations in beef cattle.

The relation between circulating concentrations of progesterone and 17ß-estradiol prior to insemination play a key role in optimizing fertility in cattle. This study aimed to determine the impact of endogenous progesterone (P4) and estradiol (E2) concentrations on uterine bacterial community abundance and diversity in beef cattle. Angus-influenced heifers were subjected to an industry standard estrous synchronization protocol. Uterine flushes were collected on d -2 (endogenous P4) and d 0 (endogenous E2) and used for targeting the V4 hypervariable region of 16S rRNA bacterial gene. Plasma was collected on d -2 and 0 for quantification of P4 and E2 concentrations by radioimmunoassay, respectively. Heifers were allotted to one of the following groups: High P4 + High E2 (H-H; n = 11), High P4 + Low E2 (H-L; n = 9), Low P4 + High E2 (L-H; n = 9), Low P4 + Low E2 (L-L; n = 11). Results indicated that Shannon's diversity index tended to be greater for H-L heifers compared to L-H heifers on d 0 (P = 0.10). For H-L heifers from d -2 to d 0, the relative abundance of Actinobacteria decreased and Tenericutes increased (P < 0.01). Within phylum Actinobacteria, the relative abundance of Corynebacterium decreased from d -2 to d 0 in treatment groups H-H, H-L, and L-L (P < 0.05); however, did not differ by d for L-H heifers. Within phylum Tenericutes, the relative abundance of Ureaplasma increased from d -2 to d 0 for H-L heifers (P = 0.01). Additionally for H-L heifers, the relative abundance of Bacteroidetes tended to increase from day -2 to on d 0 (P = 0.07). For H-L heifers, uterine pH increased from day -2 to d 0 (P = 0.05). These results suggest that differing endogenous concentrations of P4 and E2 may be associated with shifts in uterine microbiota and pH, and this could ultimately impact fertility outcomes in beef cattle.

Pregnancy maintenance following sequential induced prostaglandin pulses in beef cows.

The relationship between the maternal endocrine environment and late embryonic mortality (> 28 d of gestation) in cattle is poorly defined. A definitive rise and alterations in secretion patterns of prostaglandin F2α (PGF2α) concentration without luteal regression is a trademark of this period. The objective was to evaluate whether consecutively induced PGF2α pulses would alter steroid hormone production and luteal blood perfusion potentially influencing pregnancy success. Pregnant beef cows (n = 12) were selected to receive either an oxytocin injection (OT, n = 8) or saline injection (CON, n = 4) on d 30 and 31 of gestation to stimulate sequential prostaglandin releases 24 h apart. Blood samples were collected every 30 min for 1 h before and continuing for 4 h post oxytocin administration. Luteal blood perfusion was measured via Doppler ultrasound at the beginning and end of the OT challenge. Concentrations of prostaglandin F2α metabolite (PGFM) were quantified to show effectiveness of the treatment while concentrations of progesterone, estradiol and pregnancy-associated glycoproteins (PAG) were measured to examine the effect of PGF2α release. Control animals exhibited no changes in any quantified hormone and an expected numerical increase in circulating PAG concentrations. Peak concentrations of PGFM in OT cows were observed 2 h post OT administration and concentrations returned to basal levels by the end of the sampling period. Peak concentrations of PGFM were decreased on d 31 compared to d 30. Following OT administration, progesterone and estradiol concentrations did not change in response to PGF2α release but were decreased on d 31 compared to d 30. There were no changes in luteal blood perfusion in response to PGF release on d 30 or d 31. Repeated PGF2α release may alter steroid hormone production; however, it does not negatively affect pregnancy status during the transition between early and late embryonic development.

Decisive points for pregnancy losses in beef cattle.

Beef cattle producers rely on each of their cows to produce a marketable calf each year to maintain a sustainable operation. Within the first month of gestation, pregnancy failures have been recorded to be upwards of 40-50%. From fertilisation to birth, there are numerous factors contributing to pregnancy failure. From the beginning of gestation oocyte competence is often a large factor impacting fertility as the dam contributes all mRNA for initial embryo development. Other factors contributing to early embryonic infertility include hormonal concentration and heat stress. After the embryo enters the uterus, it becomes critical for the uterus to be receptive to the developing conceptus. The embryo then begins to elongate and secrete interferon-tau to initiate maternal recognition of pregnancy; a requirement to establish and maintain bovine pregnancies. After a pregnancy completes these steps, placentation actively begins around day 22 of pregnancy and lasts until organogenesis. The fetal phase follows the embryonic phase where disease and/or toxins are often the cause of pregnancy failure at this period. However, fetal mortality has been reported to occur in less than 10% of pregnancies. Understanding of the many factors influencing infertility needs to be further investigated to increase pregnancy success in beef cattle.

[New aspects of rabies control]. / Nouveaux aspects de la lutte contre la rage.

Rabies still causes about 60,000 human deaths per year, mainly in poor populations in Africa and Asia. However, since Louis Pasteur developed the first vaccine 130 years ago, prophylactic measures have been considerably improved and simplified. They now consist of the vaccine combined with purified rabies immunoglobulins of equine or human origin. In general, however, post-exposure prophylaxis protocols are long and expensive. Furthermore, the immunoglobulins used for associated serotherapy are costly and not widely available in developing countries. Approaches have been developed to deal with these two issues that offer hope for a paradigm shift for the benefit of exposed populations. Finally, mass rabies vaccination in dogs, which are the most cost-effective measure for preventing rabies in humans, are difficult to implement and sometimes have moderate effectiveness. The identification and analysis of the epidemiological drivers conditioning the circulation of the virus in dog populations allow a better understanding of the key control points that need to be associated with these campaigns for a better efficacy.