Compared to other cereals, rye is nutritious at the early stages of growth (vegetative to boot) as a highly digestible green chop or grazing crop that is also high in protein; in contrast, barley and wheat stand out as excellent high yielding, nutritious silage sources at the soft dough stage (Edmisten et al., 1998).
Digestibility
Organic matter digestibility varies widely according to the stage of growth, falling from 84 to 59% between the stem elongation and dough stage (INRA, 2007). Comparable values are reported for silage (55% when harvested at 32% DM, i.e. late milk-early dough stage, Emile et al., 2007), and for hay (57% at the dough stage, Andueza et al., 2004). Changes in digestibility are less marked through the hard dough stage, as observed in vitro (Edmisten et al., 1998). The decrease in nutritive value with maturity is associated with a rapid decrease in the leaf:head DM ratio after the boot stage (Moon et al., 1992).
Pasture
Data on voluntary intake of fresh rye forage are scarce. In rams, it ranks from 76 to 58 g DM/kg W0.75, depending on growth stage, with an only moderate effect of ensiling (Ferri et al., 1993). Much lower and questionable values have been reported in Holstein heifers for fresh rye forage at the vegetative and flowering stages (20 to 26 g DM/kg W0.75, Moon et al., 1992).
In the Southern Plains of the USA, many beef cattle systems utilize winter wheat and rye from November through May to improve the seasonal balance of forage availability (Gillen et al., 2005). In Florida, small-grain rye is used in association with annual ryegrass (Lolium multiflorum Lam.) to feed weaned beef calves or heifers (Vendramini et al., 2006; Vendramini et al., 2008a; Vendramini et al., 2008b; Roso et al., 2000). A mixture of rye forage and sorghum was fed to Holstein yearling steers (Cardozo, 1984). Mixing rye and wheat in pastures resulted in some cases of grass tetany (see Potential constraints above) in mature beef cows (Bohman et al., 1983).
Goats fed on pure stands of rye had the same growth rate as goats fed on triticale and higher growth than goats fed on fescue (Lema et al., 2007).
Silage
Rye can also be used as silage and is particularly valuable if harvested at late milk-early dough grain stage. As opposed to summer crops, the use of whole-plant winter cereals would spare water resources and highlight low-input management systems (Emile et al., 2007). It is preferable to ensile the crop before heading (Moon et al., 1992). The optimal harvest time is very limited and critical because the quality and palatability of the forage decrease more quickly than other cereals at heading stage (Bagg, 2005).
Intake and milk yield of dairy cows appeared lower with rye than with maize silage (Fisher et al., 1987). Whole crops of rye harvested at 37.2% DM (relatively immature, but stemmy) ensiled with NaOH (51 g/kg) improved the digestibility of all feed components other than nitrogen (Tetlow et al., 1987).
Hay and wilted forage
Rye can also be used as hay or wilted forage. Compared to other cereals at the same stage (dough), intake of rye hay is close to that of barley (av. 54 g DMI/BW0.75 in sheep), but lower than that of oats and triticale (av. 66 DMI/BW0.75) (Andueza et al., 2004). Careful drying of rye fodder at air temperatures up to 320-350°C does not alter digestibility of energy and crude protein whereas severe drying at air temperatures up to 350-450°C reduces digestibility significantly, especially that of crude protein (Jentsch et al., 1973).
The proportion of N intake excreted in faeces and urine, and methane yield, are not affected by stage of growth (heading vs. boot stage) (Moon et al., 1995).
Straw
Rye can also be used as straw. Treatment of straw with alkali (NaOH, Janicki, 1991; Bergner et al., 1989) improves its degradation, as observed both in sacco (Deschard, 1980) and in vivo in sheep. A dose of 50-60 g NaOH/kg rye straw DM can be used (Piatkowski et al., 1974).
