Perspectives for reproduction and production in grazing sheep and cattle in Australasia: The next 20 years.

We offer a perspective on the major challenges that are confronting the management of reproduction in sheep and cattle in Australia and New Zealand, over the next two decades. An important context is the dominance of grazing systems in which large flocks or herds are managed over large areas where it is challenging to manage reproduction with precision. Consequently, the variable forage supply usually dominates reproductive outcomes, a problem that will be exacerbated by global heating.

The role of the oviduct environment in embryo survival.

Context: Declining fertility is an issue in multiple mammalian species. As the site of fertilisation and early embryo development, the oviduct plays a critical role in embryo survival, yet there is a paucity of information on how the oviduct regulates this process.

Aims: We hypothesised that differences in steroid hormone signalling and/or immune function would be observed in a model of poor embryo survival, the peripubertal ewe.

Ewes with higher embryo survival rear lambs that grow faster.

A key economic driver of a meat producing sheep flock is the total kilograms of lamb liveweight at weaning per ewe exposed to the ram. Optimization of key reproductive steps is required to achieve peak performance of a sheep flock. The goal of this paper was to use more than 56,000 records from a commercial flock to investigate the key reproductive steps affecting flock reproductive performance.

High pressure frozen oocytes have improved ultrastructure but reduced cleavage rates compared to conventionally fixed or vitrified oocytes.

Context: Live birth rates are lower for cryopreserved oocytes than for fresh IVF cycles, indicating a need for improved methodologies.

Aims: The aim of this study was to determine if high pressure freezing (HPF) could improve both ultrastructural preservation and cryopreserved oocyte quality when compared to conventional fixation and vitrification methods.

Methods: Sheep oocytes and embryos were prepared by HPF or vitrification, with or without cryoprotectants.

The first week following insemination is the period of major pregnancy failure in pasture-grazed dairy cows.

A 60% pregnancy success for inseminations is targeted to optimize production efficiency for dairy cows within a seasonal, pasture-grazed system. Routine measures of pregnancy success are widely available but are limited, in practice, to a gestation stage beyond the first 28 d. Although some historical data exist on embryonic mortality before this stage, productivity of dairy systems and genetics of the cows have advanced significantly in recent decades.