Effects of ad libitum or restricted access to total mixed ration with supplemental long hay on production, intake, and rumination.

Limiting feeding time has been a concept used in growing and nonlactating ruminant animals with good success, especially in improving feed efficiency while maintaining normal rumen function and fiber digestibility. This study evaluated the physiological and productive responses of cows fed a total mixed ration (TMR) available for 24 or 19 h/d with or without access to additional long hay. Eight multiparous Holstein cows were used in a replicated 4 × 4 Latin square design with 21-d periods. Rations were formulated to mimic a TMR used in the Parmigiano Reggiano cheese production area of Italy, consisting of all dry and nonfermented components. Intakes were reduced by 2.49 kg/d in cows with restricted TMR access and 1.16 kg/d without supplemental hay. Rumen characteristics were similar for all groups with improvements in energy-corrected milk. The results show that once cows adapted to diet changes, few differences were observed when offering TMR continuously or with limited access. Energy-corrected milk feed efficiency was improved in cows having access to feed 19 versus 24 h/d. In addition, the presence of long hay during the TMR restriction offered the optimal conditions for ruminal function and pH stability, yet no effects were observed on body weight change. A Latin square with 21-d periods could have a carry-over effect on energy storage, and mobilization of fat reserves might be able to mask negative energy balance during restriction. Restricted feeding could be used as a strategy to manage feed availability according to cow production and metabolic condition, to maximize the use of nutrient resources, reducing the cost of milk production and improving the cows' welfare and health.