Complete diets given ad libitum to dairy cows: the effect of straw content and of cubing the diet

Publisher Website
Google Scholar
Abstract
Twelve Friesian cows were given six complete diets ad libitum in an experiment designed as a double 6 × 6 Latin Square balanoed for residual effects. The main energy components of the diets were rolled barley and 20, 35 or 50% chopped barley straw. The diets were given either as a loose mix or extruded through a fin. die. Dry-matter intake, milk yield and solids not fat % declined while butter fat % increased progressively with increased levels of straw in the complete diets which were fed in the loose form. In comparison with the loose diet containing 20% straw, the corresponding cubed diet was associated with a depression in dry matter intake and a decreased butterfat %. In contrast, the oubed diets containing 35 and 50% straw supported higher dry-matter intakes, higher solids oorrected milk yield but lower butter fat % than the corresponding loose diets. The effect of cubing the 35 and 50% straw diets was to make the voluntary dry-matter intakes and lactational performances comparable to those obtained with the loose mixes containing 20 and 35% straw respectively. In general the voluntary intake data agrees with a previously proposed model. However, the depressed intake obtained with the 20% straw diet in the cubed form would not have been predicted by the model. It is suggested that complete diets could be used in large units to combine the low labour costs of self feeding of dry feed with a high degree of control over nutrient intake and laotational performance.