HERITABILITY OF PHYSICAL PROPERTIES AND OTHER QUALITY TRAITS IN TIMOTHY

Abstract

An important aspect in breeding for improved quality is to identify and evaluate new selection criteria. The purposes of this work were (1) to evaluate genetic variability for three physical properties in timothy (Phleum pratense L.): packed volume (PV), water retention (WR) and water solubility (WS); these traits being potential indicators of voluntary intake, (2) to estimate their heritability, and (3) to determine the genetic relationship between these physical properties and some other quality traits. In this study, 25 clones and their half-sib families were evaluated over a 3-yr period for dry matter yield (DMY), crude protein (CP), digestibility (IVDMD), neutral detergent fiber (NDF), acid detergent fiber (ADF) and three physical properties. The genetic analysis revealed that most genetic variability was additive for these traits. Narrow sense heritability estimates for PV (0.77–0.93), WR (0.70–0.96) and WS (0.33–0.67) suggest that genetic gains could be expected from selection. The phenotypic correlations indicated that PV, WR and WS were positively correlated with CP and IVDMD but negatively correlated with NDF and ADF. The exception was WS, which was not correlated with CP. According to these results, selection for either lower PV or lower WR would have a detrimental effect on CP, IVDMD, NDF and ADF while selection for WS would have little if any effect on these traits.Key words: Digestibility, packed volume, water retention, water solubility, fiber