The evaluation of fungal endophyte toxin residues in milk.

AIM: To determine the concentrations of fungal endophyte toxins in the milk of cows fed perennial ryegrass containing wild-type or AR37 endophyte. METHODS: 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. RESULTS: 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). CONCLUSION: 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.

Effects of novel and wild-type endophytes in perennial ryegrass on cow health and production.

AIM: To measure the effects of AR37, AR1 and Wild-type endophytes in perennial ryegrass on cow health and milk production. METHODS: Four indoor and six grazing experiments were used to evaluate a perennial ryegrass cultivar containing either novel (AR37, AR1) or Wild-type (HE or Standard) endophytes or no endophyte (Nil). Three hectares of each ryegrass/endophyte association were sown with a white clover cultivar in April 2005 and either grazed or cut for indoor feeding from July 2005 to March 2009. The novel endophytes were distinguished by the production of epoxy-janthitrems by AR37 and peramine only by AR1, both of which deter insect attack. This is the first assessment of the effects of AR37 endophyte on dairy cow health and production. In all experiments, cows were monitored for indications of ryegrass staggers (RGS) by visual scoring, respiration rate as an indicator of heat stress and, in some instances, packed cell volume (blood haematocrit), blood serum albumin concentrations and skin elasticity as indicators of dehydration. Milk production and composition were measured routinely. Pasture production, composition and alkaloid content were determined, as well as temperature and humidity in the indoor feeding facility. Indoor experiments enabled accurate measurement of dry matter intakes, as well as water consumption in some instances. RESULTS: Cows eating AR37 or AR1 ryegrass did not develop RGS. During indoor feeding experiments in summer and autumn, cows eating ryegrass infected with Wild-type (Wild-type ryegrass) always developed RGS, while under rotational grazing, onset of RGS was less predictable and rarely affected all animals in the group. Severity of RGS was related to the concentration of lolitrem B in ryegrass. No cows demonstrated signs of extreme heat stress in any situation. During summer indoor feeding, cows eating ryegrass infected with AR1 endophyte (AR1 ryegrass) sometimes produced more milk and milksolids (MS) compared to ryegrass infected with AR37 (AR37 ryegrass). The dry matter intakes of cows fed AR37 ryegrass were sometimes higher than those fed AR1, and intakes were lowest when Wild-type ryegrass was fed. Water intakes of cows fed Wild-type ryegrass indoors were lower than those of cows fed AR1 or AR37 ryegrass in two of the three summer indoor experiments. The cows fed AR1 ryegrass indoors always produced more MS than cows fed Wild-type ryegrass. Under grazing, the same trends were detected, but production over three full lactations was similar for AR1 and AR37 ryegrass. CONCLUSIONS AND CLINICAL RELEVANCE: The absence of animal health and management problems, especially RGS, makes the novel endophytes AR37 and AR1 attractive alternatives to Wild-type ryegrass. Total MS production over three consecutive lactations was not affected by endophyte treatment. The choice of novel endophyte for pasture renewal will depend on local insect pest populations.