Studies on the Relationship between Heart Rate and Heat Production of Dairy Steers, as Compared with the Results of Dairy Bull Calves

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  • 乳用種去勢牛の心拍数と熱発生量の関係について
  • ニュウヨウシュ キョセイ ウシ ノ シンパクスウ ト ネツ ハッセイリョウ ノ
  • 雄子牛との比較

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Abstract

In previous report, the method of removing individual difference from the relationship between heart rate (HR) and heat production (HP) of dairy bull calves was demonstrated. One of the purposes of this study is to investigate the linear regression between HR and HP of dairy beef steers, and the other is to indicate that the relationship between HR and HP in both dairy bull calves and dairy steers may be expressed by an equation of linear regression. 1. Experiment was carried out in the university farm with six dairy beef steers, weighing about 400-500kg, under the conditions of various eating levels. 2. A close relationship between HR and HP was shown to exist in five of the six steers (r=0.802-0.891, P<.01), but in one steer (No. 4) somewhat less correlation coefficient (r=0.647, P<.05) was found in this relationship. The main reason of this result might be the narrow range of HR (56-76 beats/min) in No. 4 steer, as compared with other steers of HR range. However, the individual difference in estimated HP (Kcal/kg•hr) could not be found clearly in the range of HR from 50 to 90 beats/min. 3. The clear differences between dairy bull calves and dairy beef steers could be found to exist in the range and the level of both HR and HP, associated with the relationship between HR and HP. To remove this differences in HR and HP, the HR needed to be converted to the RHR (relative heart rate) by the basic HR, which was measured during the resting before feeding in the morning. The HP in Kcal/kg•hr needed to be converted to the HP in Kcal/W0.75•hr or to the RHP (relative heat production) instead of using the HP itself. The RHP was calculated by estimating the basic HP from the each basic HR. Then, the close correlation coefficient between RHR and HP/W0.75•hr or RHP could be shown to exist in pooled data of dairy bull calves and dairy beef steers. 4. It was concluded that the reasonable equation of linear regression between RHR and HP or RHP would be expressed by the following two equations. (1) y=4.6409x-0.3982 [x: RHR, y: HP Kcal/W<, SE of regression coeffcient: ±0.1759∗∗, SD of estimate: ±0.5866] (2) y=0.9704x+0.0352 [x: RHR, y:RHP, r=0.914∗∗, SE of regression coefficient: ±0.0296∗∗, SD of estimate: ±0.0990]∗∗P<, 01.The method of RHR to indicate HP or RHP may be applied to the studies of the energy expenditure from dairy bull calves to dairy beef steers.

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