Christopher Schauer

Objectives were to evaluate impacts of divergent planes of nutrition on body weight (BW), hormone and metabolite concentrations, and semen characteristics in rams. Mature Rambouillet rams (n = 24, BW = 83.1 ± 2.64 kg) were individually housed and randomly assigned to positive (POS; n = 8), maintenance (MAINT; n = 8), or negative (NEG; n = 8) planes of nutrition for 84 d. Rams were fed a common diet with feed allocations adjusted weekly based on BW to achieve targeted weight gain or loss (approximately 12% initial BW). On d 0, 28, 56, and 84, body condition scores (BCS) and scrotal circumference (SC) were recorded, and blood and semen were collected. Blood was analyzed for triiodothyronine (T3), thyroxine (T4), testosterone, insulin-like growth factor-1 (IGF-1), glucose, and non-esterified fatty acids (NEFA). Semen was collected via electroejaculation and analyzed by Computer Assisted Semen Analysis. Data were analyzed with the GLM or MIXED procedure of SAS, with ram as experimental unit and significance determined at P < 0.05. By design, BW was influenced by a treatment × day interaction (P < 0.0001), and daily weight change was greater (P < 0.0001) for POS (0.11 ± 0.011 kg) than MAINT (0.01 ± 0.011 kg), which was greater (P < 0.0001) than NEG (-0.12 ± 0.011 kg). Consequently, BCS, and SC were greater for POS than NEG as evidenced by a treatment × day interaction (P < 0.0001). Concentrations of T3, IGF-1, and NEFA were increased in POS compared with NEG and MAINT by day 84 (P ≤ 0.03), whereas T4, testosterone, and glucose remained unaffected (P ≤ 0.39). No differences were observed among treatments for semen volume/concentration, motility, or morphology (P ≤ 0.49). Collectively, BW, hormone, and metabolites differed among treatments, indicating a potential for epigenetic alterations which could influence offspring outcomes.

We have shown that maternal nutrient restriction during pregnancy impairs an EDHF‐like pathway that is mediated via BK _Ca activation in fetal coronary arteries (CA). We hypothesized that BK _Ca activity is altered in CA of fetuses from malnourished ewes. Pregnant ewes were fed diets that differed only in metabolizable protein levels (control = 100% vs low protein = 80% of NRC recommendation) from day 100 – 130 of gestation. Fetal CA were then harvested and whole‐cell K currents (−70 to +50mV, 200 ms duration) were obtained in freshly isolated smooth muscle cells (n = 5–6 cells/fetus). In fetal CA smooth muscle cells from ewes fed a low protein diet, the I‐V curve was shifted to the left and peak current density was increased by 31% (low protein = 92.3 ± 7.5 vs. control = 70.5 ± 6.8 pA/pF; n=14). Iberiotoxin (100 nM) almost completely inhibited the K current in cells from the low protein group (72.3 ± 4.8% inhibition), but only partially inhibited this current in controls (31.5 ± 6.2% inhibition). Expression and localization of BK _Ca α‐ and β ₁ ‐subunits was similar in CA from both groups. Restricted maternal protein intake during late pregnancy enhances BK _Ca activity in fetal CA, without altering BK _Ca expression or localization, and may represent an adaptation to the dysfunction in the coronary arterial EDHF‐like pathway previously observed in offspring of ewes subjected to decreased nutrient intake during pregnancy (NIH R03HD061532) .