Centamin has lowered annual forecasts for production from its flagship Sukari Gold Mine after plant productivity suffered a slowdown in October.Production, which is now expected to be between 370,000 and 380,000 gold ounces compared to previous forecasts of 420,000, was also affected by lower expected average grades for the fourth quarter from underground development ore.The new estimate represents an increase of between 4% and 7% on 2013 production of 356,943 ounces."Open pit mining continues to see an improvement in average ore grade for the fourth quarter compared with the third quarter and with the granted increase in ammonium nitrate usage having taken place during the quarter material movements from the open pit have also increased," the group said."Further increases in average plant throughput rates are expected during the remainder of this year and into 2015 as the expanded 10m tonnes per annum process plant continues to be optimised." It anticipates that the fourth quarter is expected to deliver a record quarterly gold production at the Sukari project, which will on an annualised basis see the achievement of its forecast post expansion production rate of 450,000 to 500,000 per annum.The stock was down nearly 11% at 46.73p by 09:04 on Wednesday.