| Popis: |
Ad libitum intake is achieved by offering a diet at amounts in excess of expected consumption; however, the amount of excess may alter the intake of certain diets and challenge this definition of ad libitum intake. The objectives of these trials were to measure feed intake, milk production, and composition of the orts of lactating cows offered total mixed diets at different amounts of excess feed. Three diets that differed in form and amount of forage were examined, one in each of three trials with lactating Holstein cows [n = 27 (trial 1) or n = 16 (trials 2 and 3)]. Treatments consisted of different amounts of feed to achieve an amount of orts of 5 or 30% of feed offered; for trial 1, a 15% rate also was included. Actual refusal rates achieved were close to target values, averaging 7.1, 15.0, and 28.3% across all trials. Intake of dry matter was not different among treatments for cows fed a low forage diet based on silage (trial 1) or for those fed a diet based on chopped hay (trial 2); however, dry matter intake was 39% higher at the higher feeding rate for cows fed a high forage diet based on silage (trial 3). Neither milk production nor composition of orts differed with treatment. High amounts of excess feeding may increase feed intake. Recommendations that refusal rates of 10% are adequate for maximum intake in research and commercial feeding situations need to be evaluated across a variety of diets, feeding systems, and climates. |
