Productivity of Russian wildrye as fall pasture with and without non-protein nitrogen supplementation

Abstract

Russian wildrye (Psathyrostachys junceus) is recommended for fall pasture but little data are available from grazing trials to substantiate this advice. This study was initiated to evaluate forage yield and quality, and carrying capacity of Russian wildrye as fall pasture. The experiment was conducted at Swift Current, Saskatchewan from 1983 to 988 with Hereford cows and calves as the grazing units. Stockpiled yields of forage, available for grazing, averaged 650 kg ha−1 when determined in September. In vitro organic matter (OM) digestibility averaged 53% and nitrogen content of the forage averaged 1.3%. Yield of forage supported 34 animal-unit grazing days per hectare, when grazed with Hereford cows (540 ± 60 kg) and calves (190 ± 30 kg) for 4–7 wk in September and October. Cows weights were maintained, and calves gained, on average, 0.95 kg d−1. Supplementation with liquid urea-molasses, provided free choice in lick tanks, had no effect on stocking rate or average daily gain of cows or calves. Daily forage intake (OM basis), as measured by chromic oxide dilution, was 2.8% of cow body weight (BW). Daily forage intake by the calves was 1.6% of BW in 1987 and 2.2% of BW in 1988 when OM digestibility of the forage was 54 and 63%, respectively. Forage intake was not affected by supplementation. However, cows allowed access to the supplement grazed 1 h less each day than cows receiving no supplement (7.7 vs. 8.7 h). Russian wildrye provided excellent fall pasture for cows and calves but its production and, consequently carrying capacity, were below levels reported previously. Key words: Psathyrostachys junceus, forage intake, stocking rate