Because of the challenges of goat herding, milking each animal tends not to occur daily. In some instances, goats are milked weekly, which violates regulations specified for grade A milk in some countries. Commercial production of goat's milk is challenging because herds tend to be small, widely scattered, and distant from processing facilities. The study by the American Institute for Goat Research at Langston University took milk samples, storing them for up to seven days in bulk tank storage. The somatic cell count (SCC) - an indicator of milk quality, pH, and microbiological quality -- were tested daily. Duplicate farm bulk tank samples were taken daily after the morning milking for seven consecutive days each month during the lactation season. Samples were analysed immediately for all variables except free fatty acids. Scientists found that there were no significant changes detected in milk fat, protein, lactose, nonfat solids, SCC, or pH during extended storage, although significant effects of stage of lactation were observed. Tests found that after six days of storage the mean standard plate count -- an indication of the level of microorganisms present -- increased beyond the grade A limit for US milk. With a growing number of people suffering allergies to cow's milk, goat-derived products are often suggested as an alternative. Nutritionally, goat milk is similar to that produced by cows, but the most significant difference is its ease of digestion. According to UK's largest goat's milk producer, St Helens Farm, the market value of the 20 million litres produced each year is about €30 million in Britain, the largest market in Europe. Mike Hind, sales and marketing manager at St Helens Farm, said that the market had increased by up to 15 per cent in recent years, driven by an increased prevalence of cow's milk intolerance and consumer demand for products perceived as more natural. "Some of the growth is driven by availability," he told FoodQualityNews. "Five years ago it was difficult to find goat's milk on the shelves, now every supermarket in the country stocks it."