Effects of maturity stage, temperature and photoperiod on growth and nutritive value of timothy (Phleum pratense L.)

The aim of this experiment was to investigate effects of temperature and photoperiod on growth characteristics, chemical composition and indigestible fibre (IaNDF) in timothy harvested at three defined maturity stages. Two cultivars of timothy, Engmo (69oN) and Grindstad (59oN) were grown in a controlled environment using a phytotron, and were exposed to two different temperature regimes (21/15 °C and 15/9 °C, 12 h/12 h) and photoperiods (18 and 24 h). Plants were harvested at beginning of heading (BH), full heading (FH) and anthesis (AN). Leaves and stems were separated prior to chemical analyses and ruminal in situ incubation for 288 h was used to determine indigestible aNDF (IaNDF) content. Plants grown at low temperature used almost twice the number of days to reach AN, compared to the highest temperature regime. This explained the lower leaf:stem ratio (LSR), higher aNDF content and lower crude protein (CP) content in low temperature plants. The effect of temperature was often dependent on maturity stage. However, the content of IaNDF and lignin(sa) was only affected by maturity stage at harvest. The content of IaNDF and lignin increased by 70% and 35% respectively from BH to AN. The lack of response in IaNDF and lignin(sa) content and dry matter digestibility to temperature was probably caused by a combination of direct and indirect temperature effects. Photoperiod affected growth characteristics, but had minor effects on chemical composition and IaNDF. Due to the lower LSR, Engmo had higher IaNDF and lignin(sa) content than Grindstad. This study showed a high positive correlation (0.93) between IaNDF and lignin(sa). Interactions between temperature and maturity stage affect the growth and nutritive characteristics of timothy. However, only maturity stage affected IaNDF and lignin(sa) content.