Towards progressive regulatory approaches for agricultural applications of animal biotechnology.

Traditional breeding techniques, applied incrementally over thousands of years, have yielded huge benefits in the characteristics of agricultural animals. This is a result of significant, measurable changes to the genomes of those animal species and breeds. Genome editing techniques may now be applied to achieve targeted DNA sequence alterations, with the potential to affect traits of interest to production of agricultural animals in just one generation. New opportunities arise to improve characteristics difficult to achieve or not amenable to traditional breeding, including disease resistance, and traits that can improve animal welfare, reduce environmental impact, or mitigate impacts of climate change. Countries and supranational institutions are in the process of defining regulatory approaches for genome edited animals and can benefit from sharing approaches and experiences to institute progressive policies in which regulatory oversight is scaled to the particular level of risk involved. To facilitate information sharing and discussion on animal biotechnology, an international community of researchers, developers, breeders, regulators, and communicators recently held a series of seven virtual workshop sessions on applications of biotechnology for animal agriculture, food and environmental safety assessment, regulatory approaches, and market and consumer acceptance. In this report, we summarize the topics presented in the workshop sessions, as well as discussions coming out of the breakout sessions. This is framed within the context of past and recent scientific and regulatory developments. This is a pivotal moment for determination of regulatory approaches and establishment of trust across the innovation through-chain, from researchers, developers, regulators, breeders, farmers through to consumers.

Dose and administration protocol for FSH used for ovarian stimulation affect gene expression in sheep cumulus-oocyte complexes.

The present study evaluated the effect of four ovarian stimulation protocols on the follicular population and molecular status of cumulus-oocyte complexes (COCs). Twelve Santa Inês ewes (in a cross-over design) received 80 or 120mg FSH alone in a multiple-dose (MD80 and MD120) regimen or in combination with 300IU equine chorionic gonadotrophin (eCG) in a one-shot (OS80 and OS120) protocol. The follicular population, COC recovery rate, mean COCs per ewe and the rate of brilliant Cresyl blue-positive (BCB+) COCs were similar among treatments (P>0.05). The expression of markers of oocyte competence (ZAR1, zygote arrest 1; MATER, maternal antigen that embryo requires; GDF9, growth differentiation factor 9; BMP15, bone morphogenetic protein 15; Bcl-2, B-cell lymphoma 2; BAX, Bcl-2 associated X protein) and the steroidogenic pathway (ERα, oestrogen receptor α; LHr, LH receptor; FSHr, FSH receptor; STAR, steroidogenic acute regulatory protein) was affected by stimulation. Specifically, the expression of markers of the steroidogenic pathway was reduced with increasing FSH dose in the OS protocol. FSH at a dose of 80mg reduced the expression of FSHr and ERα in the OS versus MD protocol. Conversely, in MD protocol, only LHr was affected by increasing FSH dose. In conclusion, 80mg FSH in the MD or OS protocol was sufficient to promote the development of multiple follicles and obtain fully grown (BCB+) oocytes. The MD protocol may be more appropriate for the production of better-quality oocytes.

Interrelationships among morphology, echotexture, and function of the bovine corpus luteum during the estrous cycle.

It has been suggested that ultrasound image attributes are a potential indicator of physiological and functional status of the corpus luteum (CL) in several species, including cattle. The aims of this study were to evaluate CL morphological, functional and echotextural characteristics, and also to investigate the hypothesis that those attributes are correlated and change similarly throughout an estrous cycle. Ovaries of crossbred (Bos taurus taurus x Bos taurus indicus) heifers were evaluated using ultrasonography daily throughout an interestrus interval using a B-mode, real-time ultrasound machine equipped with a 5 MHz linear-array rectal transducer, during a natural estrous cycle (Experiment 1; n=12) or during a shortened cycle, with luteolysis induction 10d after estrus (Experiment 2; n=6). Blood samples were collected for assay of plasma progesterone concentrations. Corpora lutea areas were measured and daily images of each CL were videotaped and digitized for computer-assisted analysis using custom-developed software. In Experiment 1, area of luteal tissue increased until a maximum value 10d after estrus (P<0.001), followed by a plateau phase, and then a decline beginning 14 d after estrus. Luteal tissue area was highly correlated to plasma progesterone concentrations (r=0.86; P<0.001). When luteolysis was induced in Experiment 2, loss of CL function (decrease in plasma progesterone concentrations to metestrous values) preceded tissue regression by 48 h (24h compared with 72 h; P<0.001). The mean pixel value of ultrasound images did not change in Experiment 1 (P>0.70), but a day effect on this attribute was observed in Experiment 2 (P=0.052). In contrast, mean pixel value was correlated to plasma progesterone concentrations in Experiment 1 (r=-0.63; P<0.05), but not in Experiment 2 (r=-0.28; P>0.10). In regard to CL heterogeneity, defined as the standard deviation of the mean pixel value of the luteal tissue, a time effect was observed following both natural (Experiment 1; P<0.009) and luteolysis-induced (Experiment 2; P<0.05) estrous cycles (P<0.05). Moreover, this variable was correlated with plasma progesterone concentrations (r=-0.71 and -0.58 in Experiments 1 and 2, respectively; P<0.01), indicating that CL images were more heterogeneous during metestrus and after luteolysis (functional regression). In summary, morphological and echotextural attributes were correlated with CL function and underwent similar changes during the estrous cycle. Luteal tissue heterogeneity, assessed by ultrasonography, is considered a potential indicator of CL functional status, because it is correlated to circulating progesterone concentrations.