Abstract This review examines the growing challenge of managing overabundant wildlife populations in the context of increasing human–wildlife conflicts. Traditionally, population control has relied on lethal methods such as culling, but these approaches are increasingly restricted due to concerns over environmental harm, non-target effects, human safety, and shifting societal values favouring more humane solutions. Fertility control has emerged as a promising non-lethal alternative, aiming to regulate populations by reducing reproductive success rather than increasing mortality. Its effectiveness depends on species-specific life-history traits: it can rapidly reduce populations of short-lived, highly fecund species, while effects in long-lived animals are delayed. Various fertility control methods are available, including endocrine suppression, immunocontraceptive vaccines, synthetic hormones and non-endocrine approaches such as zona pellucida vaccines. A major limitation to field applications of fertility control is the development of efficient delivery systems, particularly for small or free-ranging species where oral delivery must overcome challenges of palatability, stability, and species-specificity. Animal welfare considerations depend on species, contraceptives and contexts and involve trade-offs between reduced mortality and potential impacts on behaviour, physiology, and reproduction. Nevertheless, fertility control may offer welfare advantages over lethal methods and can reduce the transmission of infectious agents by maintaining social stability. Despite its potential, widespread implementation is constrained by economic and regulatory barriers. Overall, fertility control represents a valuable tool within integrated wildlife management strategies, though continued technological innovation and regulatory adaptation are essential for widespread application in the future.
Pregnancy losses constitute a major economic burden in cattle farming and are caused by developmental failures occurring mostly during the first month of gestation. This review integrates knowledge gathered from direct and indirect estimations of embryo survival at critical developmental periods with knowledge obtained from functional in vivo and in vitro studies to elucidate the developmental origins of pregnancy loss in cattle. Fertilization failures and embryonic arrest prior to the blastocyst stage, estimated based on morphological observation of flushed structures, average 10 to 20 and 10 to 30%, respectively. Reduced oocyte competence arises as the major driver of the underlying developmental failures, including impaired embryonic genome activation, loss of totipotency and defective first lineage differentiation. To estimate embryonic losses from blastocyst to implantation, direct observation of embryo development and indirect proxies of pregnancy have been employed. Indirect proxies such as nonreturn to oestrus or biochemical markers such as Interferon Stimulated Genes or Pregnancy Associated Glycoproteins inform on the development of extra-embryonic membranes, but do not distinguish between viable pregnancies and anembryonic pregnancies, where embryo-devoid structures formed by extra-embryonic membranes are able to maintain the corpus luteus to day 37. Merging data from recovery rates of early elongated structures and incidence of embryo-devoid structures, embryonic mortality from blastocyst hatching to pregnancy recognition oscillates between 12-79% for in vivo derived and 40-86% for in vitro produced embryos. The exclusion of anembryonic pregnancies diminishes embryonic mortality between day 16 and the time when the embryo proper is clearly identifiable by ultrasound (days 31-42) to less than 10%. The manuscript also provides an update on novel tools used to elucidate embryonic metabolic and signalling requirements, as well as on the molecular regulation of key developmental landmarks that must be achieved during developmental windows most susceptible to pregnancy loss.
The main objective of implementing embryo transfer programs in beef operations is to accelerate the rate of genetic progress in the herd. The main factors that affect the use of this technology are related to nutrition, management, category and breed of the recipients and the estrus synchronization programs implemented. As a result of research conducted over the last 30 years, recipient utilization has increased by applying protocols that synchronize ovulation and allow for embryo transfer without the need for estrus detection, usually referred to as fixed-time embryo transfer (FTET). Although these protocols have performed adequately for several years, recent attention has been directed to the effect of estrus expression, proestrus length and restriction to some hormonal treatments in some countries. The experiments reviewed herein demonstrate that several programs can be effectively used today to obtain high pregnancy per ET (P/ET) and reduced pregnancy losses, especially in recipients receiving in-vitro-produced embryos.
Intrafollicular immature oocyte transfer (IFIOT) represents an intermediate approach between in vitro embryo production (IVP) and conventional in vivo-derived embryo systems, combining key advantages of both. Similar to IVP, it enables repeated use of donor females through ovum pick-up without gonadotropin-based superstimulation, while allowing oocyte maturation, fertilization and early embryonic development to occur under physiological in vivo conditions. The development of IFIOT has progressed from early experimental demonstrations of intrafollicular maturation to ultrasound-guided applications and, more recently, to the production of viable embryos and live offspring, confirming its biological feasibility. However, efficiency remains limited, with embryo recovery rates of 3-17%, reflecting constraints such as oocyte retention, follicular disruption and suboptimal injection conditions. Beyond embryo production, IFIOT provides a valuable model to investigate follicular function and oocyte competence, with emerging applications in oocyte cryopreservation, embryo production from prepubertal donors, and somatic cell nuclear transfer. Therefore, IFIOT should be viewed not only as an embryo production alternative, but as a physiological platform for in vivo oocyte maturation with broad applications in farm animals and wildlife species, while further technical refinement may enable its consolidation as an efficient system for embryo production.
Over the past four decades, reproductive biotechnologies have profoundly transformed cattle breeding by accelerating genetic progress and enabling the dissemination of elite genetics. In this article, I present a perspective based on more than 40 years of practical experience in embryo technologies within Auriva-Elevage, a cooperative organization serving 30,000 farmers in southern France. The development of embryo transfer in France was closely linked to genetic and sanitary challenges, particularly the introduction of North American Holstein genetics and the restrictions on live animal imports due to infectious diseases such as Infectious Bovine Rhinotracheitis. These constraints stimulated the development of national expertise in embryo transfer. Over the years, our team has implemented and adapted a wide range of reproductive technologies including in vivo embryo production and embryo transfer, cryopreservation, embryo sexing, ovum pick-up (OPU), in vitro embryo production (IVP), embryo biopsy, genomic evaluation of embryos, and laser-assisted biopsy techniques. The genomic revolution dramatically increased the strategic value of OPU-IVP for the rapid multiplication of elite donor females. In addition to technological developments, the success of these programs has depended heavily on internal training, collaboration with national organizations such as ELIANCE (previously UNCEIA, ALLICE) and research institutes including INRAE and Toulouse veterinary school, as well as strong international exchanges through scientific networks. Practical examples such as the use of embryo biopsy to prevent genetic diseases demonstrate the applied value of these technologies in breeding programs. This review highlights the technical evolution, organizational structures, and human expertise that have shaped the implementation of reproductive biotechnologies in cattle breeding and discusses the importance of anticipating future needs to ensure continued genetic progress.
