The present study aimed to investigate metabolic and physiological changes induced by pregnancy, as well as the expression of key genes linked to the absorptive and proliferative activity of the ruminal epithelium towards the end of the gestational period in zebu beef heifers. Twelve ruminally cannulated Zebu beef heifers were randomly assigned into two experimental treatments: a pregnant group (n = 7) and a control group (non-pregnant; n = 5). All heifers received the same diet throughout the experiment. Respiratory and heart rates and plasma glucose levels were assessed just before and four hours after morning feeding at 110, 171, 206, 242, 266, and 286 days of pregnancy (DOP). Blood samples were collected for serum non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), and urea analysis prior to the morning feedings at 110, 206, 266, and 286 DOP. At 215 and 272 DOP the ruminal epithelium was biopsied to evaluate the mRNA expression of key genes involved in remodeling, inflammation, and transport. The respiratory rate was similar (P ≥ 0.79) between groups over days. However, the heart rate increased (P = 0.01) in late-pregnant heifers compared to controls. Blood concentrations of NEFA (P = 0.11) and BHB (P = 0.67) did not vary over the gestation period in pregnant heifers. Glucose concentrations, before morning feeding, were similar during all collection periods with an exception at 286 days (DOP × physiological status interaction; P = 0.05) when glucose was lower in pregnant (83 mg/dL) compared to non-pregnant (107 mg/dL) heifers. The mRNA expression of genes related to cellular remodeling (PCNA and CASP3), inflammation (KLK9 and KLK10), and transport of volatile fatty acids (SLC16A1 and SLC16A3), H⁺ (SLC9A1), HCO₃⁻ (SLC26A3 and SLC26A6), and glucose (SLC5A1) in the ruminal epithelium were downregulated at late gestation. These results suggest that the ruminal epithelium saves energy at late pregnancy to benefit fetal development. In addition, the increase in heart rate coupled with tissue mobilization can be considered homeorhetic mechanisms that help meet fetal nutrient requirements.

本研究旨在调查妊娠期末母牛在妊娠期末由妊娠引起的代谢和生理变化，以及与瘤胃上皮的吸收和增殖活性有关的关键基因的表达。将十二个瘤胃插管的瘤牛小母牛随机分为两种实验处理：怀孕组（n  = 7）和对照组（未怀孕；n = 5）。在整个实验过程中，所有小母牛都接受相同的饮食。在妊娠110、171、206、242、266和286天（DOP）刚进食前和进食后四个小时评估了呼吸和心率以及血浆葡萄糖水平。在早晨以110、206、266和286 DOP喂养之前，采集血样进行血清非酯化脂肪酸（NEFA），β-羟基丁酸酯（BHB）和尿素分析。在215和272 DOP对瘤胃上皮进行活检，以评估参与重塑，炎症和转运的关键基因的mRNA表达。呼吸率相似（P 数天集团之间≥0.79）。但是， 与对照组相比，晚期妊娠小母牛的心率增加（P = 0.01）。血液中NEFA的浓度（P = 0.11）和BHB（P  = 0.67）在怀孕的小母牛的妊娠期间没有变化。在早晨采食之前，所有收集期间的葡萄糖浓度都相似，但在286天时（DOP×生理状态相互作用；P  = 0.05）除外，当时孕妇的葡萄糖（83 mg / dL）低于未妊娠的葡萄糖（107 mg） / dL）小母牛。有关细胞重塑（基因的mRNA表达PCNA和CASP3），炎症（KLK9和KLK10），和挥发性脂肪酸（传输SLC16A1和SLC16A3），ħ ⁺（SLC9A1），HCO ₃ ^-（SLC26A3和SLC26A6）和瘤胃上皮中的葡萄糖（SLC5A1）在妊娠后期被下调。这些结果表明，瘤胃上皮在妊娠晚期可以节省能量，从而有利于胎儿发育。此外，心率增加和组织动员可以被认为是顺应性机制，可以帮助满足胎儿的营养需求。