High Fat Rations for Dairy Cows. Effects on Feed Intake, Milk and Fat Production, and Plasma Metabolites

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Abstract
High fat diets (2.9-10.8% ether extract in total diet dry matter) for cows in early lactation were compared in two 4 .times. 4 Latin squares. Total diets and their ether extract (percent) were: 1) control 3.2; 2) ground raw soybeans 5.9; 3) hydrolyzed fat 5.7; and 4) hydrolyzed fat 10.8. While dry matter intake of Holsteins was lowest with diet 2 and highest with diet 3, milk production, fat and protein were not different. Jerseys produced the most fat-corrected milk per unit metabolic body size on diet 4. In trial 2 two concentrations of total diet ether extract and crude protein were arranged factorially in isoenergetic diets. Dry matter intake and milk production were not different among diets. Mean milk fat (percent) of low and high fat diets was 2.7 and 3.4. In 32 digestion trials, high fat diets increased digestibility of ether extract and did not reduce digestibility of any other nutrient. In some instances fat increased digestibility of crude protein but not N balance. Digestibility of acid detergent fiber was increased nonsignificantly. Seven to 8% fat can be included in lactation total diets to increase diet energy density or increase the forage to concentrate ratio to maintain milk fat percent, without negative effects on digestibility.