Feeding tallow triglycerides of different saturation and particle size to lactating dairy cows

Five multiparious Holstein cows, arranged in a 5×5 Latin square design, were fed a control diet (no supplemental fat) and diets containing 5% of the following fat supplements: flaked tallow with a low iodine value of 14.4 (FTL), prilled tallow with a low iodine value of 14.5 (PTL), prilled tallow with a medium iodine value of 25.8 (PTM) and fancy bleachable tallow with a high iodine value of 62 (BTH). Diets consisted of 50% forage and 50% concentrate and the fat supplements replaced corn in the control diet. Diets were isonitrogenous and blood meal was added to provide a similar concentration of rumen undegradable protein among diets. Each period consisted of 28 days; 14 days were for adaptation and 14 days were for data collection. Intake and milk yield were similar among cows fed the hydrogenated fat sources. Fatty acid digestibility appeared to be lowest for flaked tallow but similar between the prilled tallow supplements. The fancy bleachable tallow depressed dry matter intake and milk fat percentage. Total tract digestibility of neutral detergent fiber was lower for fancy bleachable tallow (32.8%) than for prilled tallow with low iodine value (50.2%). Feeding 5% tallow with an iodine value of 62 appeared to have caused detrimental effects on ruminal fermentation and resulted in poor performance by the dairy cows. The prilled and flaked tallow fed in this study appeared to be ruminally inert, but flaked tallow may be of low digestibility.