Liquid feeding strategies to provide equal nutrient intake to dairy calves: increased liquid volume versus diet concentration.

The aim of this study was to compare the effects of feeding Holstein calves 750 g of daily milk replacer (MR) at either 12.5% of dry matter [(DM); 6 L/d] or 16.7% DM (4.5 L/d) on intake, growth performance, ruminal fermentation, apparent nutrient digestibility, urinary excretion, postprandial glucose and insulin dynamics, health, and behavior during the preweaning and immediate postweaning periods. Thirty calves were randomly assigned to one of 2 treatments delivering 750 g of MR powder per day but differing in concentration and volume: control (CON, 12.5% of DM, 6 L/d) or increased dry matter (IDM, 16.7% of DM, 4.5 L/d). Daily measurements included MR, starter, and water intake and health scores; weekly assessments included behavior, body weight (BW), average daily gain (ADG), body biometric measurements, and every 2 weeks blood insulin and glucose concentrations and ruminal fermentation parameters. Apparent nutrient digestibility was assessed at 30 - 34 and 52 - 56 d of age, and postprandial glucose and insulin response curves were evaluated through 13 serial blood samples on d 20 of life. Treatment did not affect nutrient intake, growth performance, or mean glucose and insulin concentrations every 2 weeks (P > 0.05). Postprandial glycemia was equivalent between groups, with virtually identical glucose area under the curve (AUC; P = 0.67). However, IDM calves exhibited greater total postprandial insulin exposure (AUC; P = 0.032), suggesting a possible reduction in insulin sensitivity. Ruminal ammonia nitrogen (N-NH3) concentration was lower in IDM calves (P = 0.04), and urinary volume and weight were reduced by approximately 25 - 28% in both digestibility periods (P < 0.01), consistent with the 40% greater osmolality of the IDM diet (629 vs. 450 mOsm/kg), with no adverse effects on hydration status or health. Calves in CON exhibited greater frequency of non-nutritive oral behaviors (NNOB; P = 0.04). Moderately increasing MR concentration to 16.7% DM, while maintaining the same daily solids allowance did not compromise growth or nutrient utilization, and reduced NNOB of Holstein calves, and may represent a viable alternative to conventional dilution practices, offering flexibility in liquid diet management without detrimental effects on calf development.