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家畜氨基酸需要量受日粮、环境和基因的影响很大。利用剂量响应试验表达包括必需氨基酸在内的所在因素几乎是不可能的。所以猪营养学家首先将体重不同的猪对各必需氨基酸需要量表达为相对于赖氨酸的比例。这一方法的理论基础是 :受许多因素影响 ,氨基酸的总需要量会不断变化 ,但是各必需氨基酸相对于赖氨酸的比例只会在日龄有较大变化时才会产生变化。因此 ,获知在一定阶段内一种必需氨基酸相对于赖氨酸的理想比例 ,就可精确计算在变化情况下赖氨酸的需要量 ,从而就可应用氨基酸模型得知其它几种必需氨基酸的需要量 ,这也正是理想氨基酸模型… 相似文献
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C Kerr L Bouré S Pearce C Martin WN McDonell 《Veterinary anaesthesia and analgesia》2003,30(2):113-113
The purpose of this study was to evaluate the cardiopulmonary effects of anesthetic induction with diazepam/ketamine or xylazine/ketamine with subsequent maintenance of anesthesia using isoflurane in foals undergoing abdominal surgery. Seventeen foals underwent laparotomy at 7–10 days of age and a laparoscopy 7–10 days later. Foals were randomly assigned to receive xylazine (0.8 mg kg?1)/ketamine (2 mg kg?1) (X/K)(n = 9) or diazepam (0.2 mg kg?1)/ketamine (2 mg kg?1) (D/K)(n = 8) for induction of anesthesia for both procedures. In all foals, anesthesia was maintained with isoflurane in oxygen with the inspired concentration adjusted to achieve adequate depth of anesthesia as assessed by an individual blinded to the treatments. IPPV was employed throughout using a tidal volume of 10 mL kg?1 adjusting the frequency to maintain eucapnia (PaCO2 35–45 mm Hg, 4.7–6.0 kPa). Cardiopulmonary variables were measured after induction of anesthesia prior to, during, and following surgery. To compare the measured cardiopulmonary variables between the two anesthetic regimes for both surgical procedures, results were analyzed using a three‐way factorial anova for repeated measures (p < 0.05). During anesthesia for laparotomy, mean CI and MAP ranged from 110 to 180 mL kg?1 minute?1 and 57–81 mm Hg, respectively, in the D/K foals and 98–171 mL kg?1 minute?1 and 50–66 mm Hg in the X/K foals. Overall, CI, HR, SAP, DAP, and MAP were significantly higher in foals in the D/K group versus the X/K group during this anesthetic period. During anesthesia for laparoscopy, mean CI and MBP ranged from 85 to 165 mL kg?1 minute?1 and 67–83 mm Hg, respectively, in the D/K group, and 98–171 mL kg?1 minute?1 and 48–67 mm Hg in the X/K group. Only HR, SAP, DAP, and MAP were significantly higher in the D/K group versus X/K group during this latter anesthetic period. There were no significant differences between groups during either surgical procedure for end‐tidal isoflurane, PaO2, PaCO2, or pH. In conclusion, anesthesia of foals for laparotomy and laparoscopy with diazepam/ketamine/isoflurane is associated with less hemodynamic depression than with xylazine/ketamine/isoflurane. 相似文献
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This article examines the question of whether the traditional view of a complementary relationship between universities and local businesses is still appropriate or whether auxiliary activities and other competitive elements have changed this relationship. Cross-sectional data on over 3100 counties and 3300 institutions are used to analyze the effects of university enrollment and auxiliary activities on county-level employment in the retail, financial, and service sectors. Findings indicate that the negative effects of university auxiliary activities are confined to relatively small counties, are small in magnitude, and are more than offset by the positive effects of spending by universities and students. The overall impact is positive, is more pronounced in more populous counties, and has increased over time. 相似文献
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FJ Teixeira Neto WN McDonell W Black S Durongphongtorn 《Veterinary anaesthesia and analgesia》2003,30(2):111-112
Treatment of bradycardia in horses has been historically ignored because of the motility depressant effects of nonselective antimuscarinics. This study evaluated the cardiopulmonary effects of a cardioselective (M2) muscarinic antagonist, methoctramine (MET), in anesthetized horses. In a previous in vitro study, we determined that supraphysiological doses of MET were necessary to inhibit acetylcholine‐induced longitudinal jejunal smooth muscle contractions in this species. Six adult horses were allocated to two treatments in a randomized complete block design. Anesthesia was induced with xylazine/ketamine, and maintained with halothane (1% end‐tidal) and a constant infusion of xylazine (1 mg kg?1 hour?1) under mechanical ventilation. Invasive hemodynamic variables were monitored at baseline (approximately 45 minutes after induction) and for 120 minutes after MET or saline (control) had been injected. MET was titrated at 10‐minute intervals (10 µg kg?1 IV) until the heart rate (HR) increased at least 30% above the baseline, or a maximum cumulative dose of 30 µg kg?1 had been injected. A person blinded to the treatment evaluated recovery scores and monitored intestinal auscultation until 24 hours after the end of anesthesia using previously published methods. Cardiovascular parameters were analyzed by anova followed by a Dunnet's test, and nonparametrical data were analyzed by a Mann–Whitney U‐test (p < 0.05). Values were mean ± SEM unless otherwise stated. MET significantly increased HR from baseline to 120 minutes post‐injection (from 29 ± 1 to 36 ± 2 beats minute?1 at 20 minutes). Thermodilution cardiac output (CO) and mean arterial pressure (MAP) were increased from baseline to 75 minutes post‐MET injection (from 13.9 ± 0.8 to 19.4 ± 2.0 L minute?1 for CO at 20 minutes, and from 82 ± 3 to 103 ± 5 mm Hg for MAP at 20 minutes). Recovery characteristics and bowel auscultation scores did not differ among the groups. The return to at least 75% of the maximum auscultation score occurred at 10 (8–18) hours [median (range)] for controls and at 9 (8–12) hours for MET. It was concluded that MET increased HR and improved hemodynamic function during halothane/xylazine anesthesia with no apparent effect on return to full‐bowel motility, as assessed by auscultation. Accordingly, M2 muscarinic antagonists might be represented as a safer alternative to treat intraoperative bradycardia in horse. 相似文献
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Factors affecting pregnancy rate in Holstein-Friesian cattle mated during summer in a tropical upland environment 总被引：1，自引：0，他引：1
SUMMARY The relationships between some environmental factors and reproductive rates of dairy cattle during summer in a tropical upland area were studied using records for Holstein-Frieslan milking cows and non-lactating growing helfers maintained at the Kalri Research Station on the Atherton Tableland in north Queensland. The Station is situated in a tropical upland environment with warm, wet summers and dry, cool winters. Data were collected over a 12-year-period (1977 to 1988) for cows grazing nitrogen (N)-fertilised grass pastures and receiving either no supplement or about 3.5 kg molasses/cow/day. Cattle were mated over a 10-week period starting from mid-January to early February, with 32 to 36 cows and 5 to 42 heifers used in each year. There was considerable variation among years in the pregnancy rate after 3 Inseminations, with a low of 39% and a high of 94% pregnancy. This variation from year to year was reduced for cows grazing pastures receiving 300 kg N/ha/yr after molasses feeding commenced in 1984–85. Pregnancy rates after molasses Introduction were higher for cows grazing pastures receiving 300 compared with 100 kg N/ha/yr. Pregnancy rate in cows and heifers was reduced from 80 to 55% as mean daily maximum temperature increased from 26°C to 27.5°C. At mean maximum temperatures above 27°C for cows and 27.6°C for heifers pregnancy rates to 3 Inseminations were consistently below 60%. Much of the year to year variation in pregnancy rate was related to rainfall during the mating period. There was a positive association between pregnancy rate and rainfall up to 1000 mm, and this was associated with differences in growth rate of pasture. In years of very high rainfall, above 1500 mm, there was a depression in pregnancy rate, which may be related to the intense humidity in very wet years causing heat stress in cows and associated problems such as feet infections, or a deterioration in pasture quality. We conclude that much of the variation in pregnancy rate during summer may have been related to heat stress and the level of feed supply in the form of pasture and supplements. 相似文献