Animal Evaluation of Forages Following Several Methods of Field Renovation

Sod-seeding is the only practical method to introduce improved forage species on many fields. Animal data are needed to adequately evaluate the viability of sod-seeding. This study determined animal responses to changes in forage composition following several methods of renovation. Two fields with fine, sandy loam soils were used. Bradford Field (Typic Dystrochrepts) was dominated by smooth brome (Bromus inermis L.). Walker Field (Typic Fragiochrepts) was low in fertility and had a diverse sward. Treatments consisted of an N-fertilized control and sod-seeding of legumes following either paraquat (1,1'-dimethyl-4,4'-bipyridinium ion) or glyphosate [N-(phosphonomethyl)glycine] application. Additionally, red clover (Trifolium pratense L.) and timothy (Phleum pratense L.) were seeded conventionally at the Walker site. Nutritive value of three harvests from Bradford Field and one harvest from Walker Field was determined in feeding trials with 250-kg dairy heifers (Bos primigenius). Greater legume content of renovated swards (avg. 720 g kg⁻¹ the year following seeding) compared to N-fertilized controls (avg. 230 g kg⁻¹) resulted in greater forage crude protein (CP) content (all four harvests) and greater dry matter (DM) intake (two of four harvests), greater N intake (NI) (all four harvests), and greater body tissue retention of N (three of four harvests) by dairy heifers. Metabolizable and digestible energy were similar for all harvests and improvement methods. There were no differences in animal response to forages from sod and conventional seedings, except that NI was greater from sod-seedings. The year following seeding, there was an average 48 and 75% increase in digestible DM and CP yield, respectively, from treatments introducing legumes compared to N-fertilized controls. These results show that when existing species are not highly responsive to N, improved forage species can be seeded without tillage and without N, and result in improved forage quality and animal performance.