FTSE 250 sausage skins maker Devro said first half sales of edible collagen are expected to rise modestly from a year earlier and it remains confident of a strong second half and growth in full year earnings.The Scotland-based firm said sales are expected to increase 1% while the average price per unit sold has increased around 2%, equivalent to recent input cost increases.Volumes of Select, its premium product range, has surged 13%, after particularly strong growth in Germany and Japan. Steady volume growth was seen in the US & Canada, South East Asia, and China.Elsewhere sales in Continental Europe and Russia remained at the same level as last year, despite general retail sales volumes of food being lower. "In some countries sales of processed meats have declined temporarily due to various factors including colder weather and lower levels of consumer spending," the group explained.The group's Australasia and UK businesses saw lower sales volumes, amid tough retail conditions for its customers.Looking ahead to the second half, it said operations are running well at all manufacturing sites, with a particularly notable improvement in the US, following a strengthening of its management team."We expect further growth in sales during the second half, as additional capacity becomes available in Europe, manufacturing output has increased in our US plant and sufficient inventory is now in place for China, SE Asia and Japan," Devro said. CJ