Two experiments are described in which dairy cows in early lactation were individually offered ad libitum complete diets containing firstly rolled barley, wheat or oats comprising proportionately 0·6 of the total dry matter (DM) and seeondly, whole oats, rolled oats or whole oats soaked in sodium hydroxide comprising proportionately 0·5 of the total DM. Organic-matter (OM) digestibility was measured using chromium III oxide as an external faecal marker and production of milk, milk fat and milk protein were monitored. Rumen digestion rates of each grain type were measured in sacco using non-lactating cows.
In the first experiment, voluntary DM intakes did not differ between diets, OM digestibilities were, in decreasing order, wheat > barley > oats, and faecal starch concentrations were, in decreasing order, barley > wheat > oats. Cows given oats produced the most milk and milk fat while cows given wheat produced the most milk protein. Digested OM was used most efficiently by cows given oats and their greater productivity was attributed partly to higher levels of dietary fibre and lipid.
In the second experiment, cows fed alkali-treated oats had higher (though non-significant) DM intakes and produced the most milk, milk fat and milk protein. Excretion rates of whole grain from cows given treated or untreated whole oats did not differ, but grain weight loss in transit through the gut was higher with the alkali-treated grain. Food intakes and yields of milk and milk solids were similar in cows given either whole untreated or coarsely rolled oats.