ABSTRACT: Introducing forage in dairy calf dietsduring the preweaning period stimulates developmentof rumen capacity and function and gut wall integrity.It was hypothesized that calves fed alfalfa hay (AH)at greater levels (up to 25% of DM) would result inan increase in starter diet intake and growth performance.The objective of this study was to determinethe effects of increasing levels of supplemental AHon growth performance, rumen fermentation, bloodmetabolites, and feeding behavior in intact male dairycalves. For this purpose, 45 Holstein male calves (3 dof age and 41 ± 2.5 kg of BW) were randomly assignedto 1 of the following 3 starter diets differing in theirforage level: 1) diet without AH (control), 2) diet with12.5% AH on a DM basis, and 3) diet with 25% AHon a DM basis. Supplementation of AH in the starterdiets linearly increased total DMI and ADG during thepostweaning (P < 0.01) and overall (P = 0.02) periods.Alfalfa hay supplementation linearly increased (P <0.01) ruminal pH on d 35 and 70 of the study. The concentrationsof total VFA (P = 0.85), acetate (P = 0.74),propionate (P = 0.93), and butyrate (P = 0.91) were notaffected by treatments. Furthermore, forage supplementationtended (linearly, P = 0.08) to increase theacetate to propionate ratio compared with the controlcalves. Blood β-hydroxybutyrate (BHBA) concentrationsin the control calves were less (P = 0.03) than inthe AH-fed calves on d 70 of the study. Among all themeasured variables of skeletal growth, supplementationof AH in the starter diets linearly increased heartgirth (P = 0.05) and abdominal girth (P < 0.01) on d 70of the study. These results indicate that the feed intake,feeding behavior, rumen fermentation parameters, andblood BHBA concentration may be affected by rationsdiffering in AH level so that providing calves with25% AH can improve calf performance.
