Digestibility of diets differing in rumen degradability of protein as affected by sex and species

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Insufficient information is available on Whether significant differences exist between digestive efficiency of pregnant cattle and sheep and that of the corresponding male castrates. The latter animals are invariably used to obtain digestibility values for foods or diets Which are applied to other ruminant animals including pregnant females. Three experiments have been undertaken in Which the digestibility of two diets fed at two levels Was compared in eWes and Wethers (two experiments) and steers and heifers (one experiment). For each species the females Were in the last trimester of pregnancy.The diets were similar to those used in recent Work on pregnant cows and designed to contain a similar amount of RDP, but different amounts of UDP i.e. 0.17 (low) and 0.29 (high) of total crude protein. The low UDP diet contained (on dry matter basis) barley straw (0.39), barley grain (0.40), molassed meal (0.Z0) and urea (0.01). The high UDP diet contained (on DM basis) barley straw (0.38), barley grain (0.18), malt distillers dark grains (0.11) and special propietary cubes (0.33). The levels of feeding were 1.0 and 1.5 x maintenance.