Effect of 0.3% sorghum ergot (Claviceps africana) in sow diets on plasma prolactin, lactation and piglet growth: regulatory implications

Abstract

The safety of 0.3% sorghum ergot in a sow diet was evaluated, this being the currently regulated limit for stock food in Queensland. The alkaloid content (mg/kg) of the test diet was: dihydroergosine (DHES), 1.1; dihydroelymoclavine, 0.15; and festuclavine, 0.05. The test diet was fed to 16 sows from ~6 weeks prior to farrowing, until weaning of piglets 4 weeks post-farrowing. Compared to 16 sows fed a control diet, there were no significant effects on either onset of lactation, piglet mortality, or litter performance. There was a trend for ergot to reduce plasma prolactin concentrations at farrowing, particularly in first-litter sows, but this did not meet the test for significance and there were no corresponding trends for reduced performance. The results support shorter-term investigations showing that a diet with 0.3% sorghum ergot is tolerated by sows, when it contains 1 mg DHES/kg or less. Data are presented indicating a significant correlation between % ergot and DHES in 26 different sources of infected sorghum. However, while a sample containing 0.3% ergot is most likely to contain 1 mg DHES/kg or less, this can range from <0.1 up to 5 mg DHES/kg, depending on maturity of ergot sclerotia present in infected grain. Consequently, the risk that occasional batches of grain with 0.3% ergot can contain up to 5 mg DHES/kg must be taken into account, and regulations should probably be revised, either to reduce ergot concentrations to 0.1%, or to incorporate maximum alkaloid (DHES) concentrations of 1 mg/kg, for sow feeds.