Some evidence suggests that there might be a species difference in the effect of intracerebroventricularly administered (ICV) prolactin-releasing peptide (PrRP) between rodents and sheep. We compared the levels of cortisol (CORT) and prolactin (PRL), rectal temperature (RT) and behavioral responses to ICV bovine PrRP (bPrRP) in steers. ICV bPrRP (0.2, 2 and 20 nmol/200 µL) tended to evoke a dose-related increase in CORT concentrations and 0.2 nmol of bPrRP induced transient increase in PRL concentrations. A significant time-treatment interaction was observed for the percent change of CORT (P<0.05) and PRL (P<0.05) from pre-injection value. The time-treatment interaction for changes in RT was not significant (P=0.50). There tended to be a difference among the four treatments in terms of maximum change in RT from the pre-injection value between 0 and 90 min (P<0.1). Stress-related behavioral signs were not observed in the present experiment. These findings indicate that ICV bPrRP increased CORT and PRL levels, suggesting that central PrRP might participate in controlling the hypothalamo-pituitary-adrenal axis and PRL release in cattle, unlike sheep. In contrast, central PrRP is unlikely to be involved in controlling the behavior of this species because ICV bPrRP did not induce marked changes in their behavior.

ABSTRACTEndogenous relationship to restraint and human handling were studied with growing–fattening steers. Thirty‐five crossbred (Japanese Black × Holstein) steers aged 6–10 months were randomly assigned to three pens. They had free access to an Italian ryegrass hay and a restricted amount of high‐concentrate diets (total digestible nutrients (TDN) 70.5%, digestible crude protein (DCP) 10.0%) for the first 6 months of trial. Then they had free access to an oat hay and another vitamin A‐restricted diet (TDN 72.0%, DCP 10.0%) until slaughter. The steers were individually driven into a restraint stall, and bodyweight was recorded. Blood samples were then collected under haltered conditions. These serial handling procedures started at 2 h after the morning feeding were conducted in months 1, 3, 5 (growing stage, GS) and in months 7, 9, 11 (fattening stage, FS) of the trial. Mean peripheral blood concentrations of epinephrine (A; GS, 117.4 ± 76.4 pg/mL; FS, 64.1 ± 34.2 pg/mL), norepinephrine (NA; GS, 257.7 ± 95.0 pg/mL; FS, 125.9 ± 44.1 pg/mL), cortisol (GS, 1.6 ± 0.8 µg/dL; FS, 1.2 ± 0.4 µg/dL), glucose (GS, 83.1 ± 7.5 mg/dL; FS, 71.9 ± 6.9 mg/dL), non‐esterified fatty acid (NEFA; GS, 0.13 ± 0.06 mEQ/L; FS, 0.10 ± 0.06 mEQ/L) and vitamin A (GS, 90.5 ± 24.6 IU/dL; FS, 37.2 ± 21.3 IU/dL) were higher (allP < 0.01) in the GS than in the FS, whereas those of insulin (GS, 1.06 ± 0.82 µU/mL; FS, 1.36 ± 0.61 µU/mL) and leptin (GS, 4.5 ± 1.8 ng/mL human equivalent (HE); FS, 6.8 ± 2.4 ng/mL HE) were lower (bothP < 0.01). The metabolite that correlated with A and NA was glucose (A:r = 0.61,P < 0.001; NA:r = 0.53,P < 0.01) in the GS, and the metabolites correlating with A, NA and cortisol were NEFA (A:r = 0.31,P < 0.10; NA:r = 0.32,P < 0.10; cortisol:r = 0.41,P < 0.05) and triglyceride (A:r = −0.37,P < 0.05; NA:r = −0.39,P < 0.05) in the FS. Vitamin A was a mediator between A (r = −0.38,P < 0.05) and NA (r = −0.42,P < 0.05) and insulin (r = 0.31,P < 0.10) in the GS, and between NA (r = −0.33,P < 0.10) and leptin (r = 0.38,P < 0.05) in the FS. In conclusion, when changing from the growing to the fattening stages, the stress of handling and restraint had caused the pathways to shift from carbohydrate metabolism to lipid metabolism. In addition, vitamin A seemed to be an important mediator in the endogenous pathways in both stages.

ABSTRACTThe differential variables for carcass grades were identified from morphological, behavioral and physiological measurements of young steers at a commercial farm. Thirty‐five Japanese Black × Holstein steers aged 6–10 months were randomly assigned to three pens. The steers had free access to ryegrass hay and a restricted amount of concentrate diet for the first 6 months of trial. They were then given oat straw ad libitum and an additional concentrate diet until slaughter. Behavioral observations (15 categories) were carried out once every 2 weeks for 2 h after feeding. Bodyweight was measured, blood sampled (for seven metabolic hormones and five metabolites), ultrasonic scanning conducted and physical measurements taken (10 parts for each animal) in months 1, 3 and 5 (early fattening stage, EFS) and in months 7, 9 and 11 (middle fattening stage, MFS) of the trial. Temperament scores during these procedures, entry order into restraint stalls, social rank and average daily gain were also assessed. A factor analysis and one‐way anova were used to identify clusters of variables which had different factor scores between carcass grades. As for the carcass yields, a cluster of chest girth and depth, bodyweight, withers and hip height, and rump length (P < 0.01), and a cluster of the frequency of scratching the body with facilities (P < 0.05) were identified as differential variables in the EFS. In the MFS, a cluster of concentrations of cortisol and epinephrine, and the frequency of eating straw were identified (P < 0.10). As for the carcass quality grade, a cluster of social rank, triglyceride concentration and the frequencies of stand‐chewing cud and eating hay, and a cluster of the frequency of investigating facilities (both P < 0.10) were identified in the EFS. In the MFS, a cluster of hip height, bodyweight, cannon circumference, chest depth, withers height and chest girth, and a cluster of the frequencies of eating a concentrate diet and stand‐chewing the cud, and social rank (both P < 0.10) were identified. In conclusion, bodyweight, chest girth and depth, withers and hip height were identified as good differential variables for future carcass grades of young steers. Facility enrichment that encourages steers to eat hay in the EFS, and to eat a concentrate diet in and after the MFS would be effective in upgrading carcass grades. High incidence of investigating and scratching the body with facilities and stand‐chewing the cud might lead to lower carcass grades.

Twelve crossbred (Japanese Black (cid:2) Holstein) bull calves aged 2* days were individually stroked gently by brush for / minutes per day for ,. days after weaning to improve tractability. All of them performed mock-fighting (MF) with the handler during this gentling period. The frequencies of MF with the handler were quite di # erent among calves, making it possible to classify the High Mock-Fighting group (HMF) and the Low Mock-Fighting group (LMF). HMF performed statically both maintenance behaviour and social behaviour during the experimental periods, and showed a little stronger cardiac response to dropping of bucket and a little weaker plasma cortisol response after castration. In addition, HMF had higher usual plasma testosterone level than LMF. On the other hand, LMF performed variably both maintenance behaviour and social behaviour, and showed di # erent physiological response to stress and usual plasma testosterone level from HPG. These results suggest that HMF calves seemed to be “active coper” with environmental challenges from the physiological and behavioural characteristics.

離乳後の交雑種雄子牛12頭を用い，馴致処理により発生したヒトに対する模擬闘争行動を罰訓練により制御する試験を実施した．1日5分，延べ120分の馴致処理期間中に全ての個体がヒトに対する模擬闘争行動を行った．その後，電気鞭（直流，9,000V, 480mA）による行動制御を試みた結果，1頭を除くほとんどの個体で16試行中4回以下（χ2検定，P＜0.05）となり，ヒトに対する模擬闘争行動の抑制が認められた．罰訓練時の服装とは異なる試験者に対する模擬闘争行動の発生もなく，学習効果は般化したことから罰訓練による問題行動の制御が可能であることが示唆された．馴致処理時と罰実施時の試験者が同じ服装であった場合，学習成立までに7.2±1.8試行要したが，異なる服装では4.0±2.3試行と有意に（P＜0.05）早期の学習が成立した．扱い易さの指標としたウシのヒトに対する許容反応評点は罰実施前より罰実施後に有意に（P＜0.01）高く，許容的となった．逃避反応距離は罰実施前に0.99±0.48mであったが，実施後では0.37±0.30mと有意に（P＜0.01）短縮した．これらのことから，馴致処理によって発生するウシのヒトに対する模擬闘争行動は，逃避反応性を阻害することなく罰訓練により限定的に制御できることが明らかとなった．

本研究は150日齢でのマネキンに対する模擬闘争行動を発生した個体の特徴を行動学的および生理学的に明らかにすることを目的とした. 交雑種雄子牛10頭を供試し, ヒトの代替として設置したマネキンに対して模擬闘争を発生した6頭 (発生群) と発生がなかった4頭 (非発生群) を通常飼育下, 新奇環境下およびストレス刺激下での行動的・生理的反応に関して比較した. 通常飼育管理下では, 維持行動および常同行動に関して差はなかったが, 発生群の社会行動は多く, とくに闘争行動の6時間あたりの発生回数では発生群の3.3回に対し非発生群は1.6回, 模擬闘争行動では発生群の7.8回に対し非発生群では4.3回と有意に多かった (P<0.05). 新奇環境としてマネキンを設置したオープンフィールド (OF) 内における行動では, 発生群はOF全体を平均的に通過するのに対し非発生群はマネキン設置付近を有意に避けた (P<0.001). また, OFを囲う壁への探査行動は非発生群で200回に対し, 発生群では101回と非発生群が有意に多発し (P<0.05), マネキンに対する探査時間は発生群で109秒に対し非発生群では8秒と発生群が有意に長かった (P<0.05). 驚愕刺激前後の心拍数の変動率は, 発生群では118%に対し非発生群は115%と発生群が高い傾向にあった (P=0.10). 拘束前後の血清コルチゾール値の変動率では発生群の28%に対し非発生群では192%と非発生群が有意に大きかった (P<0.05). 血清テストステロン値は発生群の8.33ng/ml に対し非発生群は4.11ng/ml と発生群が有意に高かった (P<0.05). これらの結果から模擬闘争行動発生個体および非発生個体は, 積極型行動タイプと消極型行動タイプというストレス研究での類型化と一致する可能性が示唆された.

東北, 関東および東海地方における8県, 422戸の酪農家で飼育されている1,535頭の乳用雌牛 (ホルスタイン種) を対象とした搾乳気質についてのアンケート調査結果を解析した. 調査内容は, 対象牛の搾乳気質, 産次, 牛群内での社会的優位度, 繋留時間, 繋留方法, 飼養規模, 種雄牛で, 各項目について酪農家の回答を求めた. 搾乳気質評価は, 1 : 非常におとなしい, 2 : おとなしい, 3 : やや神経質, 4 : 神経質, 5 : 非常に神経質, の5段階として飼育者自身に評価を依頼した. 気質評価1と2にランクされ, 搾乳作業に支障がないと思われたウシは全体の63%であったが, ランク3のやや神経質と評価されたウシは27%, ランク4および5に評価され搾乳作業にやや支障があると思われるウシは9%存在した. 全調査牛の平均搾乳気質評点は2.31であった. 搾乳気質を従属変数とし, その他の項目を独立変数として最小2乗分散分析を行った結果, 産次 (P<0.03), 社会的順位 (P<0.0001), および種雄牛 (P<0.0001) において有意な効果が示されたが, 繋留時間 (P<0.13) および繋留方法 (P<0.22) の効果は有意ではなく比較的小さかった. また酪農家の飼養規模と搾乳気質の間には関連性は認められなかった. 以上の結果より, 本試験における対象牛では, 特定種雄牛を父に持ち, 経産牛でしかも社会的に中庸で繋留時間が短くフリーストール下で飼養されたウシはおとなしく搾乳される傾向のあることが示唆された.