Oocyte quality and viability in Nguni and Hereford cows exposed to different levels of dietary protein.

High blood urea nitrogen (BUN) concentration decreases fertility in ruminants. Nguni cattle are reported to maintain BUN concentration more efficiently than other beef breeds. Our objectives were to determine if BUN concentration differed between Nguni and Hereford cows exposed to a high protein ration, and if breed or BUN and serum protein concentrations at the time of oocyte pick-up affected oocyte quantity, quality, and viability. Twelve Nguni and 10 Hereford cows were randomized into high or normal BUN-inducing diets in a crossover design. Ultrasound-guided oocyte pick-up was performed twice weekly; oocytes were counted, visually graded and the viable oocytes were pooled by treatment and breed for in vitro maturation, fertilization, and culture. Nguni cows on the highest protein ration achieved lower mean BUN concentration than Herefords (P < 0.05), and Nguni cows reached BUN concentrations above 20 mg/dL less frequently than Herefords (P = 0.03). Donor BUN concentration above 20 mg/dL at the time of oocyte pick-up, but not breed, independently decreased the number of good quality oocytes harvested. Increasing weighted mean serum albumin of donor cows was independently associated with the number of oocytes that cleaved by day 2 and that reached morula stage by day 7 (P = 0.01). In conclusion, Nguni cows reached the critical threshold of 20 mg/dL BUN less frequently than Herefords; BUN of donor cows above 20 mg/dL negatively affected visual oocyte quality independent of breed, and increasing serum albumin of donor cows improved viability of bovine oocytes.

The effect of a warmed enema during ovum pick-up on subsequent in vitro oocyte maturation in Southern white rhinoceros (Ceratotherium simum simum).

BACKGROUND: Rhinoceros are currently one of the most threatened mammal species globally. Slow population growth, increased poaching and habitat destruction have led to increased conservation efforts for each species. Assisted reproductive technologies (ART) have been implemented in an attempt to aid reproductive outputs for the conservation of these endangered species. Developing species-specific ART programmes for wildlife have been challenging. Temperature control during oocyte recovery is essential for ensuring in vitro success. OBJECTIVE: This study is the first to investigate the effect of enema warming prior to trans-rectal ovum pick-up (OPU) on in vitro oocyte maturation in Southern white rhinoceros (Ceratotherium simum simum). METHODS: OPUs were performed on 20 rhinoceros cows from three different game farms in South Africa; oocytes were transported to one of two in vitro fertilisation laboratories for culture. The enema fluid was either warmed to 32 °C or not warmed prior to the OPU. Location of the farm, the different laboratories, ambient temperature, season, aspiration probe temperature, media type and enema temperature were investigated as predictor variables for oocyte maturation success. RESULTS: After considering all other potential covariates, warming of the enema fluid was the only independent predictor of in vitro oocyte maturation success during this study. CONCLUSION: Oocytes retrieved from rhinoceros cows that received an enema warmed to 32 °C were 2.3 times more likely to mature in vitro compared to oocytes from cows that received an unwarmed enema; the findings can be implemented in other rhinoceros ART programmes and in conservation efforts of other endangered mammalian species.

The potential effects and interactions of oxidative stress and trace minerals on fresh and frozen semen in bulls - a review.

Reproduction is one of the most important factors determining successful cattle farming systems. Management practices, such as nutritional supplementation, can influence the reproductive performance of cattle. The objective of this literature review is to determine the potential value of injectable trace mineral administration on fresh and cryopreserved semen quality of bulls. A search of keywords related to the topic was performed on published articles and textbooks. The search was narrowed to the 40 most relevant references. Several studies have demonstrated a positive association between trace mineral supplementation and bull semen quality. Moderate amounts of reactive oxygen species (ROS) play an important role in normal spermatogenesis, but oxidative stress (OS), as experienced with adverse environmental conditions or disease, can contribute to idiopathic male infertility by negatively impacting spermatogenesis. Trace minerals such as selenium, copper, zinc, and manganese have been demonstrated to have antioxidant effects in mammals. Due to the complexity of oral ingested trace mineral bioavailability, injectable trace mineral supplementation prior to physiological periods with known deficiencies or increased requirement can benefit the animal. The potential benefits of injectable trace mineral supplementation to minimise oxidative damage to spermatogenesis in breeding bulls need further investigation. Positive results from such studies can lead to the implementation of injectable trace mineral supplementation strategies prior to the breeding season to minimise the detrimental effects of OS and can improve semen quality.