Introduction: Laparoscopic artificial insemination (LAI) is widely used in goat breeding, yet the influence of sheath needle design on reproductive outcomes remains unclear. This study aimed to evaluate the effects of three different LAI sheath designs (IMV, Minitube, and TLRI) on pregnancy rate, kidding rate, and average litter size in Alpine does.Methods: A total of 300 Alpine does (2–3 years old) were enrolled in two experiments. In Experiment 1, does were inseminated into either the middle-horn (M-H) or the horn-body junction (H-BJ) of one uterine horn using each of the three sheath types. In Experiment 2, the IMV and TLRI sheaths were used to deposit semen either unilaterally or bilaterally. Pregnancy rate, kidding rate, and average litter size were recorded for all treatment groups. Statistical significance was set at p < 0.05.Results: In Experiment 1, overall pregnancy rates with TLRI and IMV sheaths were significantly higher than with the Minitube sheath (p < 0.05) regardless of site. The lowest kidding rate occurred with the Minitube sheath at the H-BJ site (p < 0.05), while the highest was observed with the TLRI sheath at the M-H site (p < 0.05). No significant differences in kidding rate or average litter size were found among the remaining groups (p > 0.05). In Experiment 2, there were no significant differences in pregnancy rate, kidding rate, or average litter size between unilateral and bilateral inseminations using either the IMV or TLRI sheath (p > 0.05).Discussion: These findings demonstrate that both TLRI and IMV sheath designs outperform the Minitube sheath in terms of pregnancy and kidding rates, particularly when targeting the M-H site. Moreover, unilateral insemination with these sheaths does not compromise reproductive performance and offers a time-efficient alternative to bilateral deposition. Adoption of optimal sheath designs and insemination strategies can enhance LAI efficiency and success in goat breeding programs.

Modern genetic selection for high productivity has created a physiological conflict in ruminants, where the metabolic demands of lactation compete directly with the energy requirements of reproduction. This review provides a mechanistic synthesis of how key nutritional factors modulate the endocrine and cellular pathways governing reproductive success in cattle and sheep. Negative energy balance (NEB), characteristic of the early postpartum period, suppresses the hypothalamic–pituitary–gonadal (HPG) axis by impairing the pulsatile secretion of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH), mediated through reduced kisspeptin signaling, growth hormone (GH) resistance, and decreased circulating insulin, insulin-like growth factor-1 (IGF-1), and leptin. At the macronutrient level, excess rumen-degradable protein elevates blood urea nitrogen and impairs the uterine environment, while omega-3 polyunsaturated fatty acids inhibit prostaglandin F2α synthesis to support corpus luteum maintenance. At the micronutrient level, selenium, copper, and zinc are essential antioxidant cofactors protecting gametes and embryos from oxidative stress, while vitamins A, D, and E regulate gene expression in reproductive tissues. Furthermore, maternal nutrition during critical gestational windows programs the reproductive capacity of offspring through epigenetic modifications, with profound implications for long-term herd fertility. Understanding these nutritional–reproductive interactions is crucial for developing precision feeding strategies that optimize herd fertility, improve animal welfare, and ensure the economic sustainability of livestock management. A thorough understanding of these nutritional–reproductive interactions is essential for developing precision feeding strategies that optimize fertility in high-producing ruminants.

Ensuring boar sperm quality before insemination is crucial for maximizing field fertility and efficient pig production. The computer-assisted sperm analysis (CASA) and fluorescence probes combined with flow cytometry (FC) are commonly used techniques for evaluating sperm kinematics and functions, closely related to animal fertility. However, their high cost and complex operations make it challenging to apply them in laboratories or pig breeding farms with limited resources. Here, our aim was to develop a new protocol using a resazurin redox dye to assess boar sperm quality for practical application. We first created simulated semen samples with different levels of sperm quality (0, 20, 40, 60, 80, 100%) at concentrations of 300 and 150 × 10⁶ cells/mL. Subsequently, the simulated semen was used to establish an optimal standard protocol based on the results of the resazurin colorimetric assay. Finally, the condition that showed the strongest correlation between resazurin redox rate and sperm parameters was selected to perform a linear regression test. Two optimal working conditions were identified, involved incubating 10 µL of resazurin reagent with 100 µL of semen for either 20 or 40 min, depending on the sperm concentration of either 300 or 150 × 10⁶ cells/mL. We subsequently conducted a linear regression analysis using data that included the resazurin reaction rate and measurements of sperm parameters. Finally, we obtained two sets of five equations, allowing directly convert the absorbance of the resazurin assay into values for sperm quality parameters. These parameters include total motility, progressive motility, viability, acrosome integrity, and mitochondrial activity. This new protocol is valuable for sperm evaluation because it is cost-effective, time-efficient, and labor-saving.