ブロイラーに対してグルコース給与が耐暑機能にどのような効果を発揮するかを明らかにする目的で適温および高温環境において,飲水によりグルコースを給与し,飼料摂取量,飲水量,直腸温,血液性状および熱死発生に及ぼす影響を調べた。
実験では,4%のグルコース溶液を給与する区(G区)と水道水を給与する区(W区)を設け,48日齢からの3日間(1期)は17°Cと25°C,51日齢からの3日間(II期)は25°Cと33°Cに,それぞれ12時間ずつ感作し,54日齢(III期)には38°Cに12時間感作した。
飼料摂取量は各期,各温度下ともG区で少なく,飲水量はG区で多く,II期33°C感作においてG区とW区間に有意差(P<0.05)が認められた。環境温度上昇に伴う飼料摂取量の減少率と飲水量の増加率は,いずれもG区で大きかった。一方,I, II期の直腸温には,処理区間の差は認あられなかった。
III期における血漿中グルコース濃度は,G区で経時的に上昇する傾向にあったが,W区では減少し,感作8時間後の値は,開始時に比べ有意(P<0.05)に,また,G区と比較して有意(P<0.05)に低くなった。血漿中遊離脂肪酸濃度は,G区での変化は認められなかったが,W区では著しく増加し,感作8時間後の値は,開始時およびG区と比べ有意(P<0.05)に高かった。
38°C(III期)下における直腸温は,W区では感作2時間後より急激に上昇し,徐々に上昇するG区に比べ常に高い値で推移し,感作7時間30分後から処理区間に有意差(P<0.05)が認められた。熱死は,W区で感作9時間30分後までに4羽すべてに生じ,G区では感作11時間後に1羽生じた。
以上のことから,飲水からのグルコース給与は,熱死発生の抑制や発生を遅らせるものと思われた。

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本研究では,暑熱期にブロイラーの飼料摂取量が減少し飲水量が増加することに着目し,飲水によりグルコースを摂取させ,エネルギー不足を補い,生産性に及ぼす効果を調査したものである。試験は1994年と95年の暑熱期に,いずれも1,200羽規模で,35から58日齢までの24日間,4%のグルコース溶液を給与するグルコース給与区と水道水を給与する水道水給与区を設けて実施した。測定項目は,発死率,飼料摂取量,飲水量,ME摂取量,増体量,飼料要求率および1m²当たりの生産重量であった。
飼料摂取量は,雄,雌とも水道水給与区と比較しグルコース給与区で,それぞれ4.5%と4.8%少なく,その差は雄,雌とも有意であった。飲水量は,水道水給与区に比較してグルコース給与区で,その差は有意ではなかったが,雄で7.5%,雌で3.7%多かった。暑熱による発死率は,水道水給与区の雄が28.8%と最も多く,続いて水道水給与区の雌12.7%,グルコース給与区の雄8.7%雌3.2%の順となり,雌は雄と比較し両給与区とも有意に低く,また,グルコース給与区は水道水給与区と比較し雄,雌とも有意に低かった。増体量は水道水給与区に比較してグルコース給与区で,雄で3.1%,雌で6.0%と,いずれも有意に多かった。また,1m²当たりの生産重量についても水道水給与区に比較してグルコース給与区で,雄で35.0%,雌で16.2%多く,その差はいずれも有意であった。
以上のように,飲水からのグルコース給与によって,暑熱期におけるブロイラーの艶死率を著しく低下させ,増体の減少を抑制することができた。

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発生予測が困難な暑熱ストレス(HS)によるブロイラーの生産性低下に対する昼間の周期的絶食処置の有効性,ならびに絶食処置方法の差がその軽減に及ぼす影響について,2試験を実施し検討した。
試験1は21日齢のブロイラー800羽を供試し,22日齢より11:00から5, 6および7時間(各5, 6および7時間区)の絶食処置区および不断給餌区を設定し,49日齢までの28日間実施した。試験2は試験1と同様,21日齢のブロイラー800羽を供試し22, 29および36日齢(各22, 29および36日齢区)より11:00から6時間の絶食処置区および不断給餌区を設定し,56日齢までの35日間実施した。両試験とも艶死率,平均増体量,飼料要求率および1m²当たり増体量について比較検討した。
試験1では不断給餌区において4.5%のHSによる発死が認あられた。5, 6および7時間区はそれぞれ1.0, 1.5および0.5%に軽減され,7時間区は不断給餌区と比較し有意に低い驚死率を示した。6時間区の1m²当り増体量は不断給餌区と比較し16%多く,有意に改善された。試験2においても不断給餌区では18.0%のHSによる発死が認められた。22, 29および36日齢区はそれぞれ11.0, 9.0および13.0%に軽減され,29日齢区は不断給餌区と比較し有意に低かった。22および28日齢区の1m²当り増体量は不断給餌区と比較し16および17%多く,有意に改善された。
以上の結果,絶食処置はその時間および開始日齢を問わず,周期的に施すことにより不測のHSによる生産性低下の軽減に有効であり,1m²増体量を指標にすると,特に22もしくは29日齢から6時間絶食処置を施すことがより有効であることが示された。

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To determine crustal structure of the Neodani Fault zone, where the largest inland Nobi earthquake occurred in 1891, an active-source seismic experiment was carried out in the northern Mino region, central Japan. The shots were recorded by seismic array stations settled across the Neodani Fault Zone and we applied seismic reflection analysis to the data and obtained reflection profiles of the crust. Then we estimated crustal velocity by forward modeling using travel times of first break and reflected waves. We found significant reflections with duration of 2 s around 10 s two way travel time. Based on comparisons with other reflection profiles, we interpreted the events to come from the laminated lower crust within the overriding plate. The depth of the laminated crust varies across the Neodani Fault Zone, which is shallower in the southwest than in the northeast, implying that displacement along the Neodani faults extends to the deep crust. In the southwestern part of study area, the top of the Philippine Sea plate (PSP) estimated from travel time tomography is shallower than the lower limit of the laminated lower crust. We thus suggest that the subducting PSP may contact with the bottom of the overriding crust beneath the northern Mino district.

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We have investigated the waveform characteristics and source mechanisms of deep low-frequency earthquakes (DLFeqs) that occurred near the Osorezan volcano in the Shimokita Peninsula and near the Esan volcano in the Oshima Peninsula, northern Japan. The seismograms were collected by the temporal observation conducted for seven and six months in 1998 and 1999, respectively, using many broadband (with a flat velocity response up to 20 or 30s) and midband (up to 5s) seismometers. DLFeqs in both areas form clusters with focal depths ranging from the lower crust to the uppermost mantle. The most remarkable feature of seismograms is the dominance of low-frequency oscillation around 2Hz. The amplitude of source displacement spectra also shows a prominent peak at the same frequency and rapid decay with increasing frequency beyond the peak. Thus the source spectra of DLFeqs are different from the ordinary ones approximated by the omega-square model. From the broadband spectra we confirmed that the lower bound of significant seismic energy of DLFeqs is above 1Hz. A particle motion analysis exhibits the change in oscillation pattern with time in the major part of seismograms from well-excited S-wave to long-tailed S coda, suggesting the time variation of radiation characteristics of low-frequency waves from the source. The source type of DLFeqs inferred from the amplitude ratio of S- to P-waves is either single force or fault slip in low frequency range (1-5Hz), while the ratio in high frequency range (5-20Hz) shows good agreement with a type of tensile crack or single force. The waveform of initial part of P- and S-waves from one DLFeq can be relatively well explained by a moment tensor solution of a reverse faulting with little non-double-couple component. Though we could not constrain the source mechanism of DLFeqs uniquely from the results of above analyses, we propose the following model under the assumption of a source driven by magma. The pressurized magma in one reservoir extends the preexisting crack, producing high-frequency seismic radiation by a tensile crack. If the crack connects to the other reservoir, magma flow from one to the other excites low-frequency radiation of single force type, sometimes followed by reversed flow to balance the pressure between the reservoirs.

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We have investigated a stress field in the source region of the 2004 Mid-Niigata Prefecture (Niigata-Chuetsu) earthquake (M=6.8) by using P-wave polarity data obtained by a dense temporal seismic observation. The earthquake took place in central Japan near the eastern border of the Niigata-Kobe Tectonic Zone characterized by E-W contraction. The purpose of this study is to get insight into the stress heterogeneities in the source area including quite complex fault system with two parallel, westerly dipping fault planes and one conjugate plane. About two-thirds of well-constrained 514 focal mechanisms are reverse-fault type with WNW-ESE trending P-axes, which is consistent with the regional stress field in the area. Minor strike-slip events are distributed in the northern and central part of aftershock zone. Ten normal-fault events that are rare in the northeastern Japan are scattered mostly outside the major earthquake faults and occurred in a short period, suggesting that they reflect local stress field. Stress tensors derived from the focal mechanisms exhibit the compressional stress field characterized by nearly horizontal maximum principal stress that is consistent with the average direction of P-axes in the whole aftershock zone. Horizontal rotation of maximum principal stress axis is evident from WNW-ESE in the northeastern part of aftershock zone to E-W in the southwestern part. The direction of intermediate principle stress axis also changes from NE-SW in the northeastern part to NNE-SSW in the southwestern part. The fold axes in the area show similar strike variation. An interesting feature of stress distribution found in this study is the change in dip angle of the maximum principle stress axes. The axes through the aftershock zone dip gently to WNW, but those for earthquake clusters of mainshock fault dip steeply in a similar direction. Judging from the stress ratio, the horizontal compression is dominant near the mainshock hypocenter while the state in the surrounding areas is relatively close to isotropic stress. Though the difference in dip angle may not significant by considering the estimation error of stress axes, the combined anomalies with the stress ratio suggest that the mainshock occurred in an area of local stress inhomogeneity. We further examined the spatial distribution of earthquakes that have inconsistent focal mechanisms with the estimated stress tensors. Such earthquakes are distributed in the northeastern edge of the aftershock zone, in the southern edge of easterly dipping fault plane, and in a shallow earthquake cluster that is located between the faults of mainshock and the largest aftershock. The location of these events indicates small-scale stress heterogeneities in the source area superposed on the larger-scale stress variation mentioned above.

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