Digestibility and Associative Effects of Protected Tallow

Abstract

Two Guernsey heifers were fed three mixtures: corn silage and a wheat-corn-soy bean concentrate at 35 or 55% dry matter or this concentrate at 35% plus a protected tallow product (HE, Alta Lipids, Boise, ID) at 18%. Food intakes and fecal outputs were measured daily for 5-day periods, then pooled for analysis. Digestibilities were calculated for each of the rations, then digestibilities of each ingredient were solved by simultaneous equations. For protected tallow, digestibilities were dry matter 78%, energy 83%, fat 91%, protein 86%, nitrogen-free extract 83%, acid-detergent fiber −24%, calcium −76%, and magnesium −5%. Gross energy of protected tallow was calculated from analysis, 6.34Mcal/kg, so digestible energy was 5.28 Mcal/kg. The heifers were weighed at the start and finish of each period, and changes in body weight were related to intakes of digestible energy above maintenance, 7.1±3.3 Meal digestible energy per kilogram change in body weight. The negative associative effects on fiber, calcium, and magnesium warrant further investigation because they may determine the upper limit of protected tallow in ration formulation.