Orchardgrass Ley for Improved Manure Management in Wisconsin: II. Nutritive Value and Voluntary Intake by Dairy Heifers

Published in Agron. J. 103:1106–1114 (2011) Posted online 5 May 2011 doi:10.2134/agronj2011.0054 Copyright © 2011 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. C dairy cattle feeding programs in the Midwest are typically forage based. Historically, dairy producers have relied on alfalfa silage; however, they have increased reliance on corn silage in recent years because of its superior energy density, yield, and harvest efficiency. In addition, alfalfa forages often can be too high in crude protein (CP) to optimize milk production (Broderick, 2003), thereby resulting in inefficient N-usage and increased potential for N to be lost to the environment (Wattiaux and Karg, 2004; Castillo et al., 2000). Also problematic are energy-rich corn silage rations for lactating cows that can lead to rumen acidosis or subacute acidosis. This not only reduces milk production but also contributes to laminitis (Nordlund, 2002), and it is estimated that 20 to 25% of Wisconsin’s dairy cows suffer from this problem (Cook, 2003). Relying heavily on corn silage within diets of replacement dairy heifers can cause overconditioning, which can reduce milk production during first lactation due to excessive fat tissue deposits in the mammary gland (Hoffman et al., 2007; Radcliff et al., 2000). On the other hand, offering moderate energy diets during the dry period has been shown to reduce postpartum disorders such as ketosis and displaced abomasum (Dann et al., 2006). As a result, dairy farmers using a corn silage-based ration for heifer and dry cows often cut or reduce nonfiber carbohydrates of the diet with chopped straw, soy hulls, corn gluten feed, etc. to avoid overconditioning (Greter et al., 2008; Combs, 2011). However, the market value of these purchased inputs has increased dramatically in the past few years, increasing the cost of these ration adjustments. In other dairy regions of the world, an alternative to corn and alfalfa silages is to rely on perennial cool-season grass forages as the core component of the feeding program (Barnes et al., 1995). Only recently have cool-season grasses become more prominent and acceptable in U.S. dairy cattle rations (Cherney and Cherney, 1998); in part, this change has been propelled by the success of management-intensive grazing systems (Jackson-Smith et al., 1996; Fales et al., 1993). Improved, disease-resistant, and more palatable cultivars are now widely available, and management strategies for producing high-quality grass forages continue to be evaluated in university research trials. Concurrently, many forage analysis labs are now reporting relative forage quality (RFQ) rather than relative feed value (RFV) because RFQ ranks grasses more appropriately (Jeranyama and Garcia, 2004; Undersander and Moore, 2004) and properly credits the greater digestibility of cool-season grasses because of their lower lignin concentration. Although perennial cool-season grass pastures do not fit easily into confinement production systems, several researchers have begun working with small grain forages as annual cropping options for producing good quality grass forage for the various livestock classes within dairy herds. Most of this research in the upper Midwest has focused on oats (Avena sativa L.) (Coblentz and Walgenbach, 2010; Contreras-Govea and Albrecht, 2006), rye (Secale cereale L.) and wheat (Triticum aestivum L.) (Coblentz ABSTRACT Confinement dairy feeding operations in the Upper Midwest could benefit from using a wider range of forages than alfalfa (Medicago sativa L.) and corn silage (Zea mays L.). A short-term ley of orchardgrass (Dactylis glomerata L.) (OG) frequently treated with manure, was compared with corn silage (CS) in a 2 × 2 factorial trial conducted across 3 yr at two locations in Wisconsin. Nutrients were applied as either manure (M) or fertilizer (F) to meet crop N needs. Weighted on the basis each cut contributed to the total annual yield of OG, concentrations of crude protein (163 g kg–1) and 48-h neutral detergent fiber (NDF) digestibility (657 g kg–1 NDF) were suitable for incorporation into the diets of dairy cows (Bos taurus) and replacement heifers. Tissue concentrations of P and K were 3.7 and 32.0 g kg–1, respectively. High tissue concentrations of P can help with soil-test P drawdown, and reduce purchases of supplemental dietary P. Although heavy manuring resulted in high tissue K, especially in late-season cuts, K concentrations were not significantly greater in the hay-production years relative to the seeding year in either M or F. Based on results with 483 ± 37.6 kg Holstein heifers, there were no differences in voluntary intake by heifers offered commercially fertilized compared to manured OG hays. These results indicate that an OG ley system could be part of a larger alfalfa–corn silage rotation, providing confinement dairies with an alternative forage option, and additional manuring opportunities during summer months.