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Recently, interest in supplementing vitamin D (Vit D) to improve aspects of health, mainly in human fertility, has emerged. Still, supplementation of Vit D above the minimum required levels has yet to be explored in cattle despite evidence for Vit D receptors in reproductive tissues. The objective of this study was to establish if a dose–response relationship exists between Vit D exposure and success of in vitro production (IVP) of embryos and, if acute supplementation of Vit D improves pregnancy rates during timed artificial insemination (TAI) of dairy cows. Cumulus-oocyte complexes (COCs) were obtained from ovaries acquired from a local abattoir and cultured in five different IVP treatments from three separate collections (Control, 50, 100, 150, and 200 ng/mL of 1,25(OH)2D3; n = 20–30 COCs/group). In Experiment 2, dairy breed cows (n = 100) were synchronized for TAI with the PresynchOvsynch protocol. Cows received 150,000 IU of Vit D (n = 48) or castor oil as control (n = 53) along with gonadotropin-releasing hormone (GnRH) 24 h before TAI. Serum samples were collected before and 24 h after treatment. A small cohort of cows (n = 4) received the same treatments in two separate cycles and follicular fluid (FF) was collected after 24 h for calcidiol (25OHD) analyses. Increased concentrations of Vit D resulted in decreased rates of maturation of COC (150 and 200 ng/mL vs. control and 50 ng/mL; P = 0.01). Supplementation with 50 ng/mL resulted in greater numbers of early blastocyst and blastocyst stage embryos (P < 0.009). Pregnancy at first breeding did not differ (P = 0.13) between groups, but serum 25OHD increased in treated females after 24 h (P = 0.002). The FF 25OHD levels were reflective of serum levels, however, the observed increase in the treatment cycle (P = 0.04) was parallel to an overall increase in serum 25OHD during the entire second cycle, likely due to increased environmental sunlight exposure (March, control vs. May, treatment). A similar increase in the serum 25OHD in the lactating commercial herd maintained in covered housing was not observed, although experiments were conducted during a similar timeframe. This herd had levels of 25OHD near the low end of sufficiency according to National Research Council (NRC) guidelines. We conclude mild Vitamin D supplementation with concentrations at the higher end of NRC guidelines can improve maturation rates of recovered COCs. However, longer term supplementation may be needed to appreciate any benefits on fertility. [ABSTRACT FROM AUTHOR]

Study Question: What is the impact of prolonged exposure to hyperandrogenemia (T), Western-style diet (WSD) and the combination on metabolic and reproductive function in female rhesus macaques, particularly in the post-partum period?Summary Answer: Combined T + WSD worsened measures of insulin sensitivity and parameters of cyclicity following prolonged (5 years) exposure, but there was no effect on post-partum metabolic function.What Is Known Already: Women with hyperandrogenemia due to polycystic ovary syndrome are at higher risk for gestational diabetes and Type 2 diabetes post-partum, but it is unknown if this is related to hyperandrogenemia. Hyperandrogenemia in the presence of a WSD worsens metabolic function in female nonhuman primates.Study Design, Size, Duration: Female rhesus macaques began treatment near menarche (roughly 2.5 years of age) consisting of either cholesterol (control; C) or testosterone (T) implants (average serum levels 1.4 ng/ml) and exposure to standard monkey chow or a WSD (15 vs 36% of calories from fat, respectively). The four groups were maintained on treatment for 3 years, underwent a fertility trial in Year 4 and continued with treatments through Year 5.Participants/materials, Setting, Methods: Metabolic measurements (glucose tolerance tests and double X-ray absorptiometry scans) were performed yearly, and results from 5 years of treatment are reported for all animals. Animals were bled daily for 30 days at 5 years to capture changes in ovarian cycle hormones, and ultrasound measurements were performed during the early follicular and luteal phase.Main Results and the Role Of Chance: After 5 years of treatment, WSD exposure moderately increased body weight and body fat, although control animals also had a high body mass index due to ad libitum feeding. Animals in the T + WSD group had increased fasting insulin and insulin secretion during an intravenous glucose tolerance test. WSD exposure also altered ovarian cycles, delaying the time to the E2 surge, decreasing progesterone and anti-Müllerian hormone levels and increasing the number of antral follicles present by ultrasound. Longitudinal assessment of metabolic function for only those animals that became pregnant in Year 4 of treatment revealed no differences in post-partum metabolism between groups, although WSD resulted in overall elevated weights, body fat and measures of insulin resistance.Large Scale Data: None.Limitations, Reasons For Caution: The small sample size and heterogeneity in metabolic effects observed in the T + WSD group are limitations of the current study, with only a subset of animals in this group showing impaired insulin resistance relative to controls. In addition, obesity in the C group prevented comparisons to lean animals.Wider Implications Of the Findings: Hyperandrogenemia combined with WSD had a greater impact on insulin sensitivity and ovarian function than either treatment alone.Study Funding/competing Interest(s): This work was supported by NIH grant P50 HD071836 to C.T.R., J.H. and C.T. and P51 OD011092 for support of the Oregon National Primate Research Center. All authors declare no competing interests. [ABSTRACT FROM AUTHOR]

Vitamins A and D are important for immunity, reproduction, and overall health. The need for supplementation is often overlooked in beef cattle production because it is assumed that beef cows receive adequate amounts of these micronutrients from their environment. However, there is an increasing incidence of vitamin A and D deficiencies in beef cattle due to challenges of environment, forage access and quality. It is well known that nutrition has a major effect on reproduction, but direct effects of vitamins A and D on beef cow reproduction and fertility are understudied. We previously reported increased rates of fertilization after co-culture of bovine embryos with vitamin A and D in vitro. The objective of this study is to determine how vitamin A and D supplementation in mid-to late gestation affects calving ease and birth weights of calves at parturition, as well as cow fertility at the following breeding. Angus and Angus crossbred females (Bos taurus) of first (n = 20) or second (n = 10) parity were selected based on pregnancy status and gestational age and then randomly assigned to treatment groups. Starting in October 2021, pregnant cows were injected monthly with either a vehicle (control) or a commercial supplement made up of 300,000 IU vitamin A and 45,000 IU vitamin D (Vitamin AD, Vet One; n = 15/treatment group). Blood samples were collected before each injection for analysis of vitamin and hormone concentrations. All cows were monitored from January-April 2022 for signs of parturition to determine calving date and time, calving ease, birth weight, and to provide assistance if necessary. Serum samples were collected from the calves within 12 hours of parturition for analysis of vitamin D concentrations. There was no effect of vitamin A and D treatment on calving ease (Generalized Linear Model analyses; P = 0.58; 1.44 ± 0.2 treated, 1.29 ± 0.19 control group) or on birth weight (Generalized Linear Model; P = 0.52, 32.6 ± 1.24 kg treated, 33.8 ± 1.38 kg control group). Estrus synchronization, additional blood sampling, vitamin/vehicle injections, and artificial insemination (AI) was performed in late April 2022. Conception rates were determined by transrectal ultrasonography 30 to 40 days post-AI. Interestingly, 7 of 15 controls were determined to be pregnant by AI, while this improved to 10 of14 in AD-injected females (one female could not undergo AI due to late calving). Cows not pregnant by AI were pastured with a bull of proven fertility, and rectal palpation was used in the fall to determine overall pregnancy rates and any pregnancy loss. These data suggest a modest increase in serum vitamin A and D will improve pregnancy rates after AI. Additional studies should reveal if these treatments improve markers of calf health. Supported by The Oregon Beef Council (C. Bishop). [ABSTRACT FROM AUTHOR]