A comparison of tall fescue and orchardgrass silages for lactating cows

Abstract

The feeding value of tall fescue silage (Festuca arundinacea schreb.) harvested at the boot stage of maturity with a crude protein (CP) content of 15.4% was compared to that of orchardgrass silage (Dactylis glomerata) harvested at the same stage of maturity with a CP content of 12.5%. Two feeding trials with lactating cows were used in this comparison. The first trial employed 10 cows in a 2 × 2 Latin- square, with treatment period 35 d in length. In the second experiment five cows were used in a preference trial where individual feed intakes, duration of feeding, and rate of forage consumption were monitored electronically for a period of 9 d.In the first trial, the cows consumed more tall fescue than orchardgrass silage (P < 0.05) (14.08 vs. 12.90 kg d−1 dry matter (DM)) but there were no differences between cows fed the two silages in milk yield (30.4 vs. 29.8 kg d−1) or milk compositon. Source of silage did not influence rumen fluid pH, molar percent of volatile fatty acids or plasma glucose; however, plasma urea-N levels were significantly higher (P < 0.05) (17.00 vs. 15.14 mg dL−1) when cows were fed tall fescue silage compared with when they were fed orchardgrass silage. In the preference trial employing electronically monitored forage feeding gates, all five cows demonstrated a preference for the tall fescue silage consuming a daily average of 9.83 kg DM for tall fescue compared with 3.73 kg for orchardgrass silage. Cows spent more time (P < 0.05) (68.3 vs. 14.1 min−1) and ate faster (69.6 vs. 54.0 g DM min−1) from the gates offering tall fescue silage compared with the gates offering orchardgrass silage. From the results of these two trials it was concluded that tall fescue silage was comparable to orchardgrass in supporting milk production and superior to orchardgrass in terms of palatability. Key words: Tall fescue, silage preference, lactating cows