Hisashi Hidari

The effect of growth hormone-releasing peptide-2 (KP102) administration on plasma insulin-like growth factor (IGF)-1 and IGF-binding proteins in Holstein steers on different planes of nutrition

This study was conducted to investigate the nutrition-dependent changes in insulin-like growth factor (IGF)-1 and IGF-binding proteins (IGFBPs) with growth hormone releasing peptide-2 (D-Ala-D-betaNal-Ala-Trp-D-Phe-Lys-NH(2); GHRP-2 or KP102) treatment in growing Holstein steers. Eight 13 month-old Holstein steers were grouped on two levels of feed intake (high intake (HI); 2.43% body weight or low intake (LI); 1.22%) and each group was daily injected with KP102 (12.5 microg/kg body weight/day) or saline solution into the jugular vein during 6-day period. The concentration of plasma GH showed an increase after an i.v. bolus injection of KP102 on Day 1 and Day 6 in both the LI and HI groups. Plasma IGF-1 began to increase 10 hr following an i.v. bolus injection of KP102, but this was only observed in the HI group (P < 0.05). Also, the plasma IGF-1 in the HI group with daily injections was significantly greater than the LI group from Day 1 of KP102 administration (P < 0.05). It reached maximum values of 125.1 +/- 7.6 ng/ml after Day 2, and returned to pre-injection levels after Day 4, however, no change in plasma IGF-1 was observed in LI with administration of KP102. During 6 days of treatment, plasma 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 were significantly higher in KP102 treated steers but only in the HI group (P < 0.05). Plasma 34 kDa IGFBP-2 decreased in the HI group and did not show any change following an injection of KP102. In conclusion, the effect of stimulated endogenous GH with KP102 administration increased plasma IGF-1, 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 levels in the HI group of growing Holstein steers, but not in the LI one. Thus, we strongly believe that the plasma IGF-1 and IGFBPs response to KP102 treatment is modulated by the nutritional status of growing Holstein steers and the increased plasma IGF-1 concentration with KP102 treatment may be regulated by plasma 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 in Holstein steers.

Effect of cholinergic blockade on inhibited GH secretion by feeding and intraruminal SCFA infusion in sheep

The effect of cholinergic blockade on suppressed growth hormone (GH) secretion caused by feeding or the intraruminal infusion of an acetate, propionate, and butyrate mixture (107 and 214 mumol.kg-1.min-1 over 6 h) was examined in ovariectomized ewes. Intraruminal infusion at the rate of 107 mumol.kg-1.min-1 increased peripheral plasma short-chain fatty acid (SCFA) concentrations to approximately the physiological levels noted after feeding. Plasma GH was markedly suppressed by feeding and at both the 107 and 214 mumol.kg-1.min-1 SCFA infusion rates; however, cholinergic blocking agents completely blocked the suppressed GH secretion after feeding and only at the 107 mumol.kg-1.min-1 infusion rate. Plasma glucose increased at both infusion rates, and the plasma free fatty acids decreased after feeding and at both infusion rates. However, both metabolites were unchanged relative to the saline control after the injection of the cholinergic antagonists. It is suggested that the decrease in plasma GH observed after feeding and a near-physiological ruminal SCFA increment is mediated via the parasympathetic nerve and not by pharmacological ruminal SCFA increments attributed to other pathways.The effect of cholinergic blockade on suppressed growth hormone (GH) secretion caused by feeding or the intraruminal infusion of an acetate, propionate, and butyrate mixture (107 and 214 μmol ⋅ kg-1 ⋅ min-1over 6 h) was examined in ovariectomized ewes. Intraruminal infusion at the rate of 107 μmol ⋅ kg-1 ⋅ min-1increased peripheral plasma short-chain fatty acid (SCFA) concentrations to approximately the physiological levels noted after feeding. Plasma GH was markedly suppressed by feeding and at both the 107 and 214 μmol ⋅ kg-1 ⋅ min-1SCFA infusion rates; however, cholinergic blocking agents completely blocked the suppressed GH secretion after feeding and only at the 107 μmol ⋅ kg-1 ⋅ min-1infusion rate. Plasma glucose increased at both infusion rates, and the plasma free fatty acids decreased after feeding and at both infusion rates. However, both metabolites were unchanged relative to the saline control after the injection of the cholinergic antagonists. It is suggested that the decrease in plasma GH observed after feeding and a near-physiological ruminal SCFA increment is mediated via the parasympathetic nerve and not by pharmacological ruminal SCFA increments attributed to other pathways.

The effects of growth hormone-releasing peptide-2 (GHRP-2) on the release of growth hormone and growth performance in swine

The effects of GHRP-2 (also named KP102), a new growth hormone-releasing peptide, on the release of growth hormone (GH) and growth performance were examined in swine. The single intravenous (i. v.) injection of GHRP-2 at doses of 2, 10, 30 and 100 microg/kg body weight (BW) to cross-bred castrated male swine stimulated GH release in a dose-dependent manner, with a return to the baseline by 120 min. The peak GH concentrations and GH areas under the response curves (GH AUCs) for 180 min after the injections of GHRP-2 were higher (P < 0.05) than those after the injection of saline. The GH responses to repeated i.v. injections of GHRP-2 (30 microg/kg BW) at 2-h intervals for 6 h were decreased after each injection. The chronic subcutaneous (s.c.) administration of GHRP-2 (30 microg/kg BW) once daily for 30 days consistently stimulated GH release. The GH AUCs for 300 min after the injections on d 1, 10 and 30 of treatment in GHRP-2-treated swine were higher than those in saline-treated swine. However, chronic administration of GHRP-2 caused a partial attenuation of GH response between d 1 and 10 of treatment. The chronic s.c. administration of GHRP-2 also increased average daily gain for the entire treatment period by 22.35% (P < 0.05) and feed efficiency (feed/gain) by 20.64% (P < 0.01) over the saline control values, but did not significantly affect daily feed intake. These results indicate that GHRP-2 stimulates GH release and enhancing growth performance in swine.

Effects of the administration of growth hormone-releasing peptide-2 (GHRP-2) orally by gavage and in feed on growth hormone release in swine

The experiments were conducted to determine the effects of the administration of growth hormone-releasing peptide-2 (GHRP-2, also named KP102), both orally by gavage and in feed, on the release of growth hormone (GH) in swine and to investigate whether attenuation of the GH response occurs after short-term treatment with the peptide in feed. In the first experiment, saline or GHRP-2 at doses of 1, 4.5 and 9 mg/kg body weight (BW) was dissolved in 15 ml saline and administered orally as a bolus by gavage to cross-bred castrated male swine (n = 6). Orally administered GHRP-2 stimulated dose-related increases in peak concentrations of GH, with a return to basal by 120 min. After administering GHRP-2 orally, peak concentrations of GH and areas under the GH response curves (GH AUCs) for 180 min were higher (P < 0.05) than those in saline controls. In Experiment 2, GHRP-2 at doses of 0 (served as control), 1, 4.5 and 9 mg/kg BW was mixed in 150 g of feed and offered to cross-bred castrated male swine (n = 6) at 0900 hr and 1700 hr daily for a 3-d period. Administration of 1 mg/kg BW GHRP-2 to swine in feed failed to stimulate the release of GH, but GHRP-2 at doses of 4.5 and 9 mg/kg BW significantly (P < 0.05) increased plasma concentrations of GH after initial and final treatments at 0900 hr on Days 1 and 3 of treatment, respectively. Peak concentrations of GH and GH AUCs for 180 min after the initial and final treatments in the 4.5 and 9 mg/kg BW GHRP-2-treated swine were higher (P < 0.05) than those in controls. After 3 d of treatment with GHRP-2 in feed at doses of 4.5 and 9 mg/kg BW, GH responses to the peptide were maintained. The results of the present study indicate that the administration of GHRP-2 orally by gavage and in feed stimulates the release of GH in swine, and that the GH-releasing effect of the peptide does not become desensitized after short-term administration in feed.

Lying Posture of Dairy Cows and Various Types of Cow Stalls

乳牛舎のけい留方式やストールの構造がウシの居住感に与える影響をウシの横臥姿勢の面から分析する方法について検討するため,放し飼いされたウシの横臥姿勢を四肢の伸縮,頸の曲げ方によって分類し,その出現率を調べるとともに,けい留牛舎における横臥牛への適用,比較を試みた.まずフリーストール型休息場を持つ放し飼い施設に収容する85頭およびスタンチォン式牛舎にけい留する5頭について,15分ごと5日間にわたり横臥牛の姿勢を記録,分類した.次いでスタンチォン式•チェーンタイ式•コンフォートストール式のけい留牛舎それぞれ3ないし4牛舎,72～134頭について,夜間15分ごと2時間の観察を行ない,放し飼い施設における同時間帯の横臥姿勢と比較した.放し飼い施設(バーンヤードとフリーストール)における1日の横臥時間は623±121分でスタンチォン式牛舎より平均約30分長かった(P>0.05).左坐りは右坐りよりやや多く(P<0.01),放し飼い施設で横臥時の肢をその位置によって上側と下側に分けると,左坐りと右坐りの間に各種横臥姿勢出現の差はほとんど認められず,四肢を縮めた姿勢が平均40.7%を占め,肢を伸ばしたものは,上側のみ,下側のみ,両側の順に,後肢でそれぞれ31.4,1.3,24.1%,前肢で1.7,13.3,2.1%となり,後肢は上側を前肢は下側の肢を伸ばす率が高かった.横臥時間や各種横臥姿勢出現率は昼間と夜間で異り,夜間は70～90%の個体が横臥し,肢を伸ばし頸を後方に曲げて休む姿勢が多かった.バーンヤードとフリーストールの間には横臥姿勢に著明な相異は認められず,けい留牛舎では一般に四肢を縮めた姿勢や前肢を伸ばす姿勢が少なかった.けい留方式についてはスタンチォン式牛舎で頸を後方に曲げる姿勢の少ない点がめだった.しかし同じけい留方式でも牛舎によって各種横臥姿勢出現率の違いが大きく,牛床と飼槽の間にある縁石(curb)の高さ,牛床の長さ,床の状態なども横臥姿勢と関連があるようで,それらの点も含めた総合的な考慮が必要と考えられる.