Bovine Nutritional Needs: Digestibility of Dry and Ensiled Forages when Feeding Young Dairy Heifers

The diets fed to growing animals are very important to ensure that young animals have the proper nutrients available for growth. When feeding dairy heifers, a farmer’s goal is to feed a very digestible diet that will provide nutrients to keep dairy heifers healthy and allow them to grow faster, while spending less money on feed. The objective of this study was to determine whether feeding heifers diets containing dry or ensiled forage (haylage) improved digestibility. Our hypothesis was that incorporating hay into the diet of 16-week-old dairy heifers would provide a more digestible source of nutrients. For this study, 12 heifers were randomly assigned to treatments, with 6 heifers fed hay-based diets and the other 6 heifers fed haylage-based diets. The heifers were housed in individual pens and fed individually on a daily basis for 8 days. Fecal samples were collected during the last 3 days of the feeding period. The fecal collection was achieved by collecting fecal samples from individual heifers every 6 hours over a 3-day period. Digestibility of the diets and nutrients were determined using chromic oxide as an external marker. In order to determine the digestibility of haylage or hay diets fed to the heifers, the percent of chromic oxide in feed was compared to the percent of chromic oxide in feces. The neutral detergent fiber (NDF) of the feeds and feces was determined using the Ankom Fiber Analysis System. Data were analyzed using the Proc Mixed procedure of the Statistical Analysis System. The dry matter digestibility of the diets were similar between treatments (P = 0.19) and was 68.4% for the hay diet and 66.6% for the haylage diet. The NDF digestibility was also similar between diets (P = 0.21) with an NDF digestibility of 68.4% for hay and 66.1% for haylage diets. In summary, feeding dairy heifers hay-based diets did not significantly improve either the dry matter or NDF digestibility of the diets.