| Co-Investigator(Kenkyū-buntansha) |
TAKEMURA Yuji Tokyo University of Agrioulture and Technology, Faculty of Agriculture, Associate Professor, 農学部, 助手 (80197334)
KAMADA Toshihiko Tokyo University of Agrioulture and Technology, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (70015121)
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| Research Abstract |
Under hot environment, adaptability of crossbred cattle between Holstein and Japanese black (F1) and Holstein cattle (H), was compared, on several physiological parameters. Experiments were carried out using two H and F_1, calves aged 8 months. The calves were exposed to high temperature (30 ℃) for two days in the climatic chamber. Total digestible nutrients (TDN) intake and rectal temperature (RT) were measured and pneumotachogram and electrocardiogram were recorded. Blood samples were taken via jugular vein Blood samples were used for measurement of packed cell volume (PCV), hemoglobin concentration (Hb), red blood cell count (RBC), and white blood cell count (WBC). The other blood samples was separated to plasma for measurement of plasma concentration of total protein (TP), glucose (Glc), free fatty acid (FFA), and Nmethylhistidine (MeHis). TDN intake was decreased by heat stress, especially in H calves. RT in H was elevated to 40-41 ℃by heat stress, while that in F, was kept on abo
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ut 39 ℃. Respiratory rate (RR) in both calves was increased by heat stress. However, from first day to second day of 30 ℃, RR in F_1 was increased but that m H decreased. Heart rate(HR) in FI was increased by heat stress, while Holstein was decreased From these results, it is presumed that Holstein obliged to suffer the elevation of RT in spite of the decrease in heat production suggested from the decrease in TDN and HR. While F_1 could avoid the elevation of RT by the promotion of heat loss estimated from the increase in panting. The influence of heat stress on PCV, Hb, RBC, WBC, TP, and FFA in the both calves were almost not recognized. However, TP in Holstein calf were higher than that in F_1. Plasma Glc levwls were maintained within normal range through experimental periods. Plasma MeHis in the both calves was increased by heat stress. Plasma MeHis of Holstein was more increased by heat stress than that of F_1. Especially, MeHis as well as TDN intake in H-1 was greately changed. It is known that plasma MeHis of animal under energy deficient is increased due to myofibrillar protein degradation and MeHis released from myofibril increase in blood. It was presumed, therefore, that the increase in MeHis by heat stress in this study were partially caused due to decreased TDN intake. The results of this study suggest that F_1 is superior in heat tolerance to Holstein, and the characteristics of the heat tolerance in F1 are represented as the effctiv heat loss. Less
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