Detection of yield-independent forage quality differences among timothy genotypes

Abstract

The trade-off between forage yield and quality would be minimized by selecting a genotype that produces high-quality forage regardless of yield. This paper attempts to detect forage quality differences among timothy (Phleum pratense L.) genotypes that are independent of yield. Two separate field experiments were conducted from 1993 to 1995 on an Ando loamy sand in Hokkaido, Japan. For exp. 1, timothy plants (cv. Nosap) were harvested at various maturity stages for the first, second, and third cuts in 1994 and 1995 to evaluate the relationships of crude protein (CP) and neutral detergent fibre (NDF) yields with dry matter (DM) yield. The relationship between NDF and DM yields was positive and linear across different cuts (r2 = 0.98–0.99), and was slightly affected by year. In contrast, the relationship between CP and DM yields depended on the cuts (r2 = 0.01–0.98). In exp. 2, four genotypes were evaluated in 1994 to compare the coefficients of the NDF vs. DM yield regressions using ANCOVA. The comparison showed that the NDF yields of Kitami 20, Kitami 21, and Hokuo were less than that of Nosap (P < 0.01) for a wide range of DM yields (150–700 g m-2). Thus, NDF concentrations were lower in the former genotypes across varying forage yields. Using the regression lines as indices could facilitate selection of timothy genotypes that reduce the trade-off between yield and quality, although further experiments are needed to confirm the usefulness of this method. Key words: Acid detergent fibre, crude protein, forage yield, neutral detergent fibre, timothy