ホルスタイン種とその黒毛和種との交雑種育成牛の高温感作に対する体温調節性生理反応の反応差について

概要

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The thermoregulatory responses of heifers of Holstein and Holstein crossed with Japanese Black Cattle were compared in order to explain breed differences in terms of thermosensitivity. The heifers were exposed to environmental temperatures (Te) of 23,28,33 and 38 PC under controlled conditions of heat production (HP) from ingested feed both during the day and during the night. HP was greater in Holstein than in cross bred heifers both during the day and night. Against increased Te, the vaginal temperature (Tv), mean skin temperature (mTs), mean body temperature (Tb), respiration rate (RR), heart rate (HR) and standing time (ST) increased significantly (P<0.05) during the day and/or night. During the night, against Te the Tv, Tb and ST of Holstein heifers was significantly greater than that of cross bred heifers. These differences between breeds were explained using thermosensitivity as was done in an earlier study. Thermosensitivity was greater in cross bred than in Holstein heifers and during the day than during the night, because in cross bred heifers at high Te and during the day, heat balance was maintained at a lower body temperature than in Holstein and during the night. These breed and day-night differences in thermosensitivity are important in breed selection and thermal management in warm and hot conditions. Jpn. J. Livest. Management, 33(1) : 9-15. 1997. Received January 16,1997. Accepted March 17,1997.
1997-06-20