LAUSR

Objective This study was conducted to investigate hematological and vasodilator characteristics for high altitude acclimatization in Holstein heifers ascended to high altitude. Methods Holstein heifers resided at low altitude (LH; Beijing, China 43 meter), and Holstein heifers ascended to high altitude (Lhasa city, Tibet; 3,658 meter) after one year exposure including hypoxia acclimated Holstein heifers (AH; with mean pulmonary arterial pressure mPAP < 41 mmHg) and Holstein heifers affected by high altitude pulmonary hypertension (HAPH; with mPAP > 49 mmHg) and crossbred cattle (CB; Holstein × Tibet cattle) born and resided in Tibet were selected to compare parameters of blood gas, blood cells and vasodilators. Each group included 15 animals with 16 to 18 month of age. Results The HAPH had greater mPAP than other cattle classes (P < 0.01). Alveolar ventilation (as indicated by partial pressure of carbon dioxide; PaCO2) was improved in AH and HAPH compared to LH, but it was lower in HAPH than in CB and AH (P < 0.05). In addition, LH had the greatest and HAPH had the lowest partial pressure of oxygen (PaO2) among the four cattle classes (P < 0.05). Erythropoietin and mean corpuscular hemoglobin concentration were greater in AH and HAPH than LH (P < 0.05). Serum iron was greater in AH than LA and HAPH (P < 0.05). Hypoxia exposure increased plasma nitric oxide and endothelin-1 in cattle resided in Tibet compared to LH. Additionally, AH had greater brain natriuretic peptides than HAPH and LH, and AH had greatest C-type natriuretic peptides than the other groups (P < 0.05). Conclusion High altitude hypoxia acclimatization was achieved in Holstein heifers ascended to high altitude via augmented alveolar ventilation, serum iron, mean corpuscular hemoglobin concentration, natriuretic peptides and nitric oxide, it enables them to tolerate the high altitude.