Growing bovine oocytes represent a potential source of embryos, but this has not been adopted in practice. Although several offspring were produced following a two-week culture period, further optimization of the culture system is required. In vivo, the outermost granulosa cell layer is in direct contact with the basement membrane (BM); however, this interaction is absent in cultured oocyte–granulosa cell complexes (OGCs). Since the BM is known to have regulatory roles, this study examined the effects of BM components on oocyte growth by treating membrane inserts with laminin, a major BM constituent, or with the laminin-containing protein mixture Matrigel^®. OGCs containing growing oocytes (90–106 μm in diameter) were cultured from Day 0 to Day 14 on plain membranes or on membranes with spots of Matrigel or laminin. A modified minimum essential medium α supplemented with 5% fetal bovine serum, 4% polyvinylpyrrolidone (average molecular weight, 360,000), steroid hormones, and 3 mM hypoxanthine was used. Granulosa cell migration was more pronounced in the treated spots, particularly in the Matrigel-treated group where migration extended across the entire treated area. Oocyte volume increased to 147% in the control group, 158% in the Matrigel group, and 160% in the laminin group, with Day 1 values normalized to 100%. Oocytes cultured on laminin-treated membranes were significantly larger than those in the control group (P < 0.05). Following in vitro fertilization, approximately 5% of the oocytes in each group developed to the blastocyst stage. Overall, the interaction between granulosa cells and laminin-treated membranes positively influenced the growth of bovine oocytes in vitro.

Improving and sustaining the health and productivity of dairy cows require integrated strategies that combine management and appropriate nutrition. This review adopts two complementary perspectives: optimizing periparturient management to support high productivity without compromising animal health and improving gestational nutrition to produce healthy replacement heifers. Several studies have examined how maternal nutritional and metabolic status before and after calving influence postpartum reproduction, productivity, placental development, and offspring health. Prepartum energy status is a key determinant of early postpartum ovarian function, with a timely first ovulation associated with adequate insulin-like growth factor-I exposure during follicular development. Insufficient β-carotene intake in energy-prioritized feeding systems adversely affects ovarian resumption. Uterine recovery is also nutrition-sensitive; cows with endometritis exhibit signs of impaired liver function, whereas delayed uterine involution is associated with inefficient ruminal nitrogen utilization. Supplementation with lysine, the first limiting amino acid in corn-based diets, further promotes uterine recovery. From a developmental perspective, maternal insulin resistance is associated with low birth weight and altered endocrine profiles in calves, which are indicative of long-term metabolic vulnerability. In contrast, lysine supplementation during the dry period supports neonatal protein synthesis and growth. Furthermore, in growing primiparous cows, greater milk yield during early pregnancy was associated with reduced anti-Müllerian hormone concentrations in female calves, suggesting a lower ovarian reserve. Collectively, these findings highlight the importance of gestational and peripartum nutritional management not only for improving dairy cow fertility and productivity but also for optimizing the health and reproductive potential of the next generation.

Artificial insemination (AI) is the predominant reproductive technology in Japanese cattle breeding, particularly for genetic improvement of dairy and beef cattle. This review outlines the historical development, current status, and recent advances in semen production technologies for AI in Japan and addresses the remaining challenges and future directions. The adoption of AI accelerated after the Act on Improvement and Increased Production of Livestock was implemented in 1950, with frozen semen replacing liquid semen by the mid-1960s. Advances in cryobiology and genomic selection have improved breeding efficiency; however, fertility issues persist. In dairy cattle, conception rates have declined primarily due to high milk yield, negative energy balance, and heat stress. In beef cattle, particularly Japanese Black cattle, conception rates remain stable overall, but subfertile sires still occur despite normal post-thaw semen quality. Studies on sperm motility, acrosomal integrity, and genomic variants have identified a single nucleotide polymorphism (SNP) marker linked to extreme subfertility in Japanese Black bulls. Japan has developed innovative technologies such as the two-layer semen straw (FCMax), which enhances post-thaw sperm function through in-straw dilution and supplementation. Field trials have suggested potential improvements in conception rates; however, large-scale validation studies are still ongoing. Furthermore, sexed semen technology has been widely adopted in Japan and achieved conception rates comparable to those of conventional semen. Emerging challenges include labor efficiency in large-scale farms, prompting interest in improved thawing protocols or liquid semen alternatives. Future priorities include integrating genomic tools, refining cryobiological techniques, and implementing practical innovations to sustain cattle reproduction in evolving production systems.