Reproductive Seasonality Affects In Vitro Embryo Production Outcomes in Adult Goats

Field outcomes of laparoscopic ovum pick-up combined with in vitro embryo production in sheep: Effects of long-acting recombinant ovine FSH pre-stimulation, collection frequency, and donor breed

Laparoscopic ovum pick-up (LOPU) combined with in vitro embryo production (IVEP) is a technology platform that improves the utilization rate of the elite ewe's ovarian oocytes and increases the number of obtained offspring. This study aimed to evaluate the effects of FSH pre-stimulation, serial oocyte collection, and breed on LOPU-IVEP under field conditions. Donors were randomly assigned to five groups (group A: decreasing doses of pituitary FSH (p-FSH); group B: constant doses of p-FSH; group C: two doses of long-acting recombinant ovine FSH (ro-FSH); group D: single administration of a long-acting ro-FSH in; group E: no FSH stimulation). Oocyte yield following LOPU (average recovered oocytes: 20.9 ± 0.5; average viable oocytes: 17.2 ± 0.4) and oocyte developmental competence (average blastocysts: 7.0 ± 0.2) in group C were significantly better than these of group D and group E, and similar to these of groups A and B. Meanwhile, there were no differences in oocyte yield and developmental capacity using repeated LOPU session at 1-, 2-, and 3-month intervals (p > 0.05). Finally, we compared LOPU-IVEP outcomes among five sheep breeds. The results indicated that East Friesian × Chinese Mongolian crossbred sheep and purebred East Friesian sheep had the more recovered oocytes and viable oocytes compared with the Suffolk, Dorper, and Texel breeds, and average number of blastocysts in East Friesian × Chinese Mongolian sheep group was also highest among the groups (8.1 ±0.3, p < 0.05). In summary, the results of this study indicate long-acting ro-FSH pre-stimulation combined with 12 times LOPU sessions over one year maximizes embryo production of elite donor ewes under field conditions.

In vitro embryo production in small ruminants: what is still missing?

In vitro embryo production (IVEP) is an extremely important tool for genetic improvement in livestock and it is the biotechnology that has grown the most recently. However, multiple ovulation followed by embryo transfer is still considered the leading biotechnology for embryo production in small ruminants. This review aimed to identify what is still missing for more efficient diffusion of IVEP in small ruminants, going through the IVEP steps and highlighting the main factors affecting the outcomes. Oocyte quality is essential for the success of IVEP and an aspect to be considered in small ruminants is their reproductive seasonality and strategies to mitigate the effect of season. The logistics for oocyte collection from live females is more complex than in cattle, and tools to simplify this collection system and/or to promote an alternative way of recovering oocytes may be an important point in this scenario. The heterogeneity of oocytes collected from growing follicles in live females or from ovaries collected from abattoirs remains a challenge, and there is a demand to standardize/homogenize the hormonal stimulatory protocols and IVM protocols for each source of oocytes. The use of sexed semen is technically possible, however the low market demand associated with the high costs of the sexing process prevents the routine use of this technique, but its higher availability is an important aspect aiming for greater dissemination of IVEP. New noninvasive approaches for embryo selection are key factors since the selection for transfer or cryopreservation is another difficulty faced among laboratories. Embryo selection is based on morphological traits, although these are not necessarily reliable in predicting pregnancy. Several issues described in this review must be considered by researchers in other to promote the diffusion of IVEP in small ruminants.