Finch S C, Thom E R, Babu J V, Hawkes A D, Waugh C D
AgResearch Limited, Ruakura Research Centre, Hamilton, New Zealand.
N Z Vet J. 2013 Jan;61(1):11-7. doi: 10.1080/00480169.2012.704626. Epub 2012 Sep 18.
To determine the concentrations of fungal endophyte toxins in the milk of cows fed perennial ryegrass containing wild-type or AR37 endophyte.
Groups of 10 multiparous Holstein-Friesian cows were fed wild-type (containing lolitrem B) or AR37 (containing epoxy-janthitrems) endophyte-infected perennial ryegrass (Lolium perenneL.). Animals were kept indoors and fed for 12 days. Over this period, animals were regularly assessed for ryegrass staggers and herbage intake measured. At the conclusion of the 12-day indoor-feeding period, cows were grazed on AR1 (toxin-free) pastures for a further 8 days. Daily individual milk samples and milk yields were collected over the complete 20-day period. Milk samples were analysed for endophyte toxins using HPLC methods developed during this study. Daily herbage samples were also taken and concentrations of endophyte toxins measured.
Methods were successfully developed for the analysis of lolitrem B and epoxy-janthitrems in milk which allowed the concentrations of these compounds in milk to be compared with the concentrations in feed consumed by the animals. Both toxin types could be detected in milk after only 1 day of exposure to respective treatment pastures. The maximum concentration of endophyte toxins in milk was 5 ng/mL lolitrem B and 109 ng/mL epoxy-janthitrems from cows fed wild-type and AR37 endophyte-infected ryegrass pastures, respectively. Concentrations of epoxy-janthitrems present in herbage were much higher than for lolitrem B (Day 1-12 average of 14.6 and 1.8 ppm, respectively). Despite the high concentrations of epoxy-janthitrems consumed by cows fed AR37 endophyte-infected pastures no signs of ryegrass staggers were observed over the experimental period, whereas those cows fed wild-type endophyte-infected pastures all showed signs of ryegrass staggers. This is consistent with the view that epoxy-janthitrems are low potency tremorgens. At the conclusion of the toxin feeding period, endophyte toxin concentrations in milk quickly dropped to almost zero after 8 days. A comparison of the quantities of lolitrem B and epoxy-janthitrems consumed by each cow with the quantities secreted in milk showed that only very low proportions of the total amount ingested are secreted in milk (0.23% lolitrem B and 0.49% epoxy-janthitrems).
Lolitrem B and epoxy-janthitrems can be detected in the milk of cows consuming wild-type and AR37 endophyte-infected perennial ryegrass, respectively. Concentrations detected were low and changed quickly in association with the amounts being consumed by the cows. Available evidence gives no indication that these compounds may pose a threat to human health.
测定食用含野生型或AR37内生真菌的多年生黑麦草的奶牛乳汁中真菌内生毒素的浓度。
将10头经产的荷斯坦-弗里生奶牛分为几组，分别喂食含野生型（含洛利特rem B）或AR37（含环氧-詹替毒素）内生真菌感染的多年生黑麦草（Lolium perenneL.）。动物饲养在室内，喂养12天。在此期间，定期评估动物是否出现黑麦草蹒跚症，并测量牧草摄入量。在为期12天的室内喂养期结束后，奶牛在AR1（无毒素）牧场上再放牧8天。在整个20天期间收集每日个体乳汁样本和产奶量。使用本研究开发的HPLC方法分析乳汁样本中的内生毒素。每天还采集牧草样本并测量内生毒素浓度。
成功开发了分析乳汁中洛利特rem B和环氧-詹替毒素的方法，可将这些化合物在乳汁中的浓度与动物食用的饲料中的浓度进行比较。仅在接触相应处理牧场1天后，两种毒素类型均可在乳汁中检测到。食用野生型和AR37内生真菌感染的黑麦草牧场的奶牛乳汁中内生毒素的最大浓度分别为5 ng/mL洛利特rem B和109 ng/mL环氧-詹替毒素。牧草中环氧-詹替毒素的浓度远高于洛利特rem B（第1 - 12天的平均浓度分别为14.6和1.8 ppm）。尽管食用AR37内生真菌感染牧场的奶牛摄入了高浓度的环氧-詹替毒素，但在实验期间未观察到黑麦草蹒跚症的迹象，而那些食用野生型内生真菌感染牧场的奶牛均表现出黑麦草蹒跚症的迹象。这与环氧-詹替毒素是低效震颤原的观点一致。在毒素喂养期结束时，乳汁中的内生毒素浓度在8天后迅速降至几乎为零。将每头奶牛摄入的洛利特rem B和环氧-詹替毒素的量与乳汁中分泌的量进行比较，结果表明摄入总量中仅有极低比例分泌到乳汁中（洛利特rem B为0.23%，环氧-詹替毒素为0.49%）。
在食用野生型和AR37内生真菌感染的多年生黑麦草的奶牛乳汁中可分别检测到洛利特rem B和环氧-詹替毒素。检测到的浓度较低，且与奶牛的摄入量相关迅速变化。现有证据表明这些化合物可能不会对人类健康构成威胁。
