PDF(Pubmed)
Abstract：
Consumption of ergot alkaloids from endophyte-infected tall fescue results in losses to the livestock industry in many countries and a means to mitigate these losses is needed. The objective of this study was to evaluate intra-abomasal infusion of the dopamine precursor, levodopa (L-DOPA), on dopamine metabolism, feed intake, and serum metabolites of steers exposed to ergot alkaloids. Twelve Holstein steers (344.9 ± 9.48 kg) fitted with ruminal cannula were housed with a cycle of heat challenge during the daytime (32 °C) and thermoneutral at night (25 °C). The steers received a basal diet of alfalfa cubes containing equal amounts of tall fescue seed composed of a mixture of endophyte-free (E-) or endophyte-infected tall fescue seeds (E+) equivalent to 15 µg ergovaline/kg body weight (BW) for 9 d followed by intra-abomasal infusion of water (L-DOPA-) or levodopa (L-DOPA+; 2 mg/kg BW) for an additional 9 d. Afterward, the steers were pair-fed for 5 d to conduct a glucose tolerance test. The E+ treatment decreased (P = 0.005) prolactin by approximately 50%. However, prolactin increased (P = 0.050) with L-DOPA+. Steers receiving E+ decreased (P < 0.001) dry matter intake (DMI); however, when supplemented with L-DOPA+ the decrease in DMI was less severe (L-DOPA × E, P = 0.003). Also, L-DOPA+ infusion increased eating duration (L-DOPA × E, P = 0.012) when steers were receiving E+. The number of meals, meal duration, and intake rate were not affected (P > 0.05) by E+ or L-DOPA+. The L-DOPA+ infusion increased (P < 0.05) free L-DOPA, free dopamine, total L-DOPA, and total dopamine. Conversely, free epinephrine and free norepinephrine decreased (P < 0.05) with L-DOPA+. Total epinephrine and total norepinephrine were not affected (P > 0.05) by L-DOPA+. Ergot alkaloids did not affect (P > 0.05) circulating free or total L-DOPA, dopamine, or epinephrine. However, free and total norepinephrine decreased (P = 0.046) with E+. Glucose clearance rates at 15 to 30 min after glucose infusion increased with L-DOPA+ (P < 0.001), but not with E+ (P = 0.280). Administration of L-DOPA as an agonist therapy to treat fescue toxicosis provided a moderate increase in DMI and eating time and increased plasma glucose clearance for cattle dosed with E+ seed.
Fescue has become the dominant cool-season perennial grass in the southeastern region of the United States and is also found in other countries. Endophytes from a plant–fungus symbiotic relationship produce toxic alkaloids that have caused significant annual economic losses to the livestock industry. Treatments to alleviate this toxicosis are still demanded. This study evaluates the infusion of the dopamine precursor, levodopa (L-DOPA), to mitigate the toxicosis caused by ergot alkaloids. When L-DOPA was infused, eating duration increased and the decrease in feed intake caused by ergot alkaloids was less severe. Additionally, circulating dopamine and glucose clearance increased with L-DOPA. These results suggest that L-DOPA has the potential to aid in the mitigation of the toxicosis caused by ergot alkaloids.
Fescue has become the dominant cool-season perennial grass in the southeastern region of the United States and is also found in other countries. Endophytes from a plant–fungus symbiotic relationship produce toxic alkaloids that have caused significant annual economic losses to the livestock industry. Treatments to alleviate this toxicosis are still demanded. This study evaluates the infusion of the dopamine precursor, levodopa (L-DOPA), to mitigate the toxicosis caused by ergot alkaloids. When L-DOPA was infused, eating duration increased and the decrease in feed intake caused by ergot alkaloids was less severe. Additionally, circulating dopamine and glucose clearance increased with L-DOPA. These results suggest that L-DOPA has the potential to aid in the mitigation of the toxicosis caused by ergot alkaloids.
摘要：
从内生菌感染的高羊茅中消费麦角生物碱会导致许多国家的畜牧业损失，因此需要一种减轻这些损失的方法。这项研究的目的是评估多巴胺前体的鼻内输注，左旋多巴（L-DOPA），关于多巴胺代谢，饲料摄入量，和暴露于麦角生物碱的牛的血清代谢产物。在白天（32°C）和夜间（25°C）的热中性循环中放置了12只装有瘤胃套管的荷斯坦转向（344.9±9.48kg）。牛接受苜蓿立方体的基础饮食，其中含有等量的高羊茅种子，该种子由不含内生菌（E-）或内生菌感染的高羊茅种子（E）的混合物组成，相当于15µg麦角缬氨酸/kg体重（BW），持续9天，然后鼻内注水（L-DOPA-）或左旋多巴（L-mg/kg）9；母牛配对喂养5d，进行葡萄糖耐量试验。E+处理使催乳素降低(P=0.005)约50%。然而,催乳素随L-DOPA+增加(P=0.050)。接受E+的Steers降低了(P<0.001)干物质摄入量(drymatteradvance,DMI);然而,当补充L-DOPA+时，STI的降低不那么严重(L-DOPA×E，P=0.003)。此外，L-DOPA+输液增加进食时间（L-DOPA×E，P=0.012），当舵手接受E时。吃饭的数量，用餐时间,摄入率不受E+或L-DOPA+的影响(P>0.05)。L-DOPA+输注增加(P<0.05)游离L-DOPA,游离的多巴胺,总L-DOPA，和总多巴胺。相反，L-DOPA+时,游离肾上腺素和游离去甲肾上腺素降低(P<0.05)。L-DOPA+对总肾上腺素和总去甲肾上腺素无明显影响(P>0.05)。麦角生物碱不影响(P>0.05)循环游离或总L-DOPA,多巴胺,或者肾上腺素.然而,游离去甲肾上腺素和总去甲肾上腺素随E+降低(P=0.046)。葡萄糖清除率在15至30分钟后增加与L-DOPA+（P<0.001），但不与E+（P=0.280）。施用L-DOPA作为激动剂疗法来治疗羊茅中毒，可以适度增加STI和进食时间，并增加服用E种子的牛的血浆葡萄糖清除率。
羊茅已成为美国东南部地区主要的冷季多年生草，在其他国家也有发现。来自植物-真菌共生关系的内生菌产生有毒生物碱，对畜牧业造成了重大的年度经济损失。仍然需要减轻这种中毒的治疗方法。这项研究评估了多巴胺前体的输注，左旋多巴（L-DOPA），减轻麦角生物碱引起的中毒。当注射L-DOPA时,进食时间增加，麦角生物碱引起的采食量减少不那么严重。此外,循环多巴胺和葡萄糖清除率增加与L-DOPA。这些结果表明，L-DOPA具有缓解麦角生物碱引起的中毒的潜力。
羊茅已成为美国东南部地区主要的冷季多年生草，在其他国家也有发现。来自植物-真菌共生关系的内生菌产生有毒生物碱，对畜牧业造成了重大的年度经济损失。仍然需要减轻这种中毒的治疗方法。这项研究评估了多巴胺前体的输注，左旋多巴（L-DOPA），减轻麦角生物碱引起的中毒。当注射L-DOPA时,进食时间增加，麦角生物碱引起的采食量减少不那么严重。此外,循环多巴胺和葡萄糖清除率增加与L-DOPA。这些结果表明，L-DOPA具有缓解麦角生物碱引起的中毒的潜力。
