N+1 Singer has maintained a 'sell' rating for Devro after the sausage skin maker effectively delivered a profit warning on Monday.The company said that volumes were lower in the first quarter despite strong sales in certain key markets. Meanwhile, it has decided to bring forward plans to streamline its manufacturing footprint as it moves from older, higher-cost production lines.The combination of volume underperformance and actions to lower manufacturing capacity is expected to reduce profits by 8% in 2014, "a circa 22% downgrade", according to N+1 Singer."Today's statement further underlines our longstanding concerns around volume and competitive pressure in Devro's core markets," said Analyst Sahill Shan."We applaud the decisive cost action but ultimately until the top-line stabilises and improves, earnings on a 12-18 month view are likely to remain under pressure."Shan also expressed concerns with the likelihood of Devro's leverage ratio rising from 0.6 times last year to 2.0 times in 2015 given the ongoing uncertainty surrounding profits.Ahead of Monday's update the stock was trading at 13.2 times prospective earnings, falling to a multiple of 12.5 on 2015 estimates. Shan sees it de-rating further towards a price-to-earnings ratio of just 10-11 on next year's forecasts."We feel vindicated with our long-standing 'sell' recommendation and maintain a negative stance."The stock was down 11.1% at 210.75p by 10:09.BC