Intake and digestibility in cattle fed tropical forage based diets

The objective of this trial was to investigate the effects of diets containing corn silage, bermudagrass hay, or elephantgrass silage on intake and apparent total tract and partial digestibilities of nutrients in cattle. A forage to concentrate (soybean meal) ratio of 90:10 was used. Six ruminally and omasally fistulated bovines averaging 351 kg of initial body weight were used in two replicated 3 x 3 Latin squares. Each experimental period lasted 16 days with 10 days for animal adaptation and six days for samples collection. The internal marker indigestible neutral detergent fiber (INDF) was used to estimate abomasal DM flow and fecal DM excretion. No significant difference in DM intake was observed between corn silage and bermudagrass hay diets. However, total digestible nutrient intake was greater on corn silage than bermudagrass hay. Animals fed the bermudagrass hay diet had the greatest NDF intake (4.52 kg/day) while those fed corn silage showed the highest NFC intake (1.95 kg/day). In addition, the corn silage diet also resulted in the greatest apparent total tract digestibilities of DM (66.3%), OM (68.9%), NDF (55.7%), and total carbohydrates (68.21%). Rumen was the main site for digestion of total carbohydrates and NDF in all four diets. It was observed an inverse relationship between apparent total tract DM digestibility and INDF intake. Therefore, forage INDF content can be used to estimate digestibility of tropical grasses. Estimated NFC true digestibility averaged 96.6% across diets in the present study.