|NICOL, ALASTAIR - Lincoln University - New Zealand|
Submitted to: Animal Production Science
Publication Type: Review Article
Publication Acceptance Date: 6/28/2016
Publication Date: 8/19/2016
Citation: Nicol, A.M., Klotz, J.L. 2016. Ergovaline, an endophytic alkaloid. 2. Intake and impact on animal production, with reference to New Zealand. Animal Production Science. 56:1775-1786. http://dx.doi.org/10.1071/AN14963.
Interpretive Summary: A review of the New Zealand data shows that in only a small proportion (15%) of formal comparisons has feed intake or animal production been depressed (up to around 15%) on endophyte-containing pasture compared with ergovaline-free pasture. These have been associated with an ergovaline intake of > 0.07 mg /kg LW0.75/day. Furthermore, less than 20% of pasture samples show ergovaline concentrations (> 0.7 mg/kg DM) high enough to risk depressing animal performance. The incidence of high pasture ergovaline concentrations is greater in summer and in the basal horizons (< 5cm) of the pasture and is less when high levels of animal production are required, e.g. when grazing is restricted to the upper pasture horizons. Threshold upper critical temperature and THI will be lower for animals consuming ergovaline, but the extent of these changes is not known. However, under these conditions various mitigation strategies can be invoked to reduce ergovaline intake.
Technical Abstract: Based on published reports the daily intake of the alkaloid, ergovaline, from the consumption of endophyte-containing ryegrass in New Zealand ranges from 0.008 to 0.287 mg ergovaline/kg LW0.75/day. Most of these reports are based on the use of standard endophyte-containing ryegrass and thus it is difficult to disassociate the impact of ergovaline consumption from that of lolitrem B. However, physiological effects of ergovaline consumption, such as reduced circulating prolactin concentration, vasoconstriction and elevated core temperature have been detected at relatively low ergovaline intake, whereas decreased feed intake, liveweight gain and milk production have not generally been observed at an intake below 0.07 mg ergovaline/kg LW0.75/day. Intakes above this value represent only 17% of published values. There are insufficient data to suggest a threshold ergovaline intake associated with heat stress with animal welfare implications. The relationship between published ergovaline intake and the corresponding ergovaline concentration in pasture is poor (R2 = 0.48), but on average an intake of 0.07 ergovaline/kg LW0.75/day is associated with a ergovaline concentration in ryegrass of 0.70 mg/kg DM. Around 16-18% of published ergovaline concentrations in ryegrass pasture exceed this value. The ergovaline concentration in ryegrass is greater in the basal parts of the plant than in the leaf and during the late summer-autumn than spring. Animals grazing in the lower sward horizons are more at risk of high ergovaline intake although the reduction in grazing intake induced by grazing at low pasture height aids to limit ergovaline intake. As pasture growth rate decline in late summer, supplementary feed may be used to maintain stocking rate and, if such feeds have zero ergovaline concentration, they serve to dilute the mean dietary ergovaline intake. Ergovaline-containing ryegrass pastures are widely used in New Zealand. It appears that farmers consider the risks of depressed animal production on these pastures to be less than the benefits ergovaline bestows through its deterrent effect of specific insect attack and thus greater survival and pasture persistence.