Wheat is used in ruminant diets as an energy source. It can replace maize as a high-energy ingredient in concentrates, with the additional benefit that it requires less protein supplementation than maize due to its higher protein content. While slightly less rich in net energy than maize (96% of maize NE), wheat, when adequately processed, is highly digestible for ruminants (more than 86%) (Sauvant et al., 2004). Due to its higher protein content and lower fibre, wheat has a higher energy value for ruminants than barley (Sauvant et al., 2004), though similar growth rates from wheat and barley have been reported in steers fed grass silage (Steen, 1993). Wheat is very palatable if not ground too finely (Blair, 2011).
The rapid rate of starch digestion, as well as the gluten component of the protein, makes wheat more difficult to feed than other grains. The rate of in vitro disappearance of starch of dry-rolled wheat has been reported to be higher than that of dry-rolled maize (Stock et al., 1990). Wheat is more rapidly, extensively, and somewhat erraticly, fermented than other cereal grains (Fulton et al., 1979). This can result in digestive problems such as bloat, laminitis and acidosis when too much grain is fed, when there are too many fines or when animals have been introduced too rapidly to the diet (Blair, 2011). As noted in Potential concerns above, the viscosity of finely milled wheat may lead to digestive upsets due to the formation of dough.
Low test weight and damaged wheats
Low test weight or damaged wheats generally give performances similar to regular wheats. Low test weight wheats tested in beef cattle produced very similar performance compared to higher test weight grains (Lalman et al., 2011). No relation was found between test weight and metabolizable energy (ME) in ewes (Wilkinson et al., 2003). Feeding sprouted wheats did not affect performance, feed efficiency and feeding value, but it was recommmended to limit the inclusion rate at 20% (diet DM) to minimize the risk of reduced feed intake (Lalman et al., 2011). Severely frosted wheat grains fed to wethers had a slightly lower ME (6% less) than unfrosted wheat but those values fell within the normal observed ME range for wheat (Richardson et al., 2001).
Wheat can be included at up to 40-50% in the diet of milking cows, though different levels are recommended depending on the processing and on the other ingredients of the diet (Ewing, 1997; Blair, 2011). For instance, 4-5 kg/d (25-30% of diet DM) of processed (rolled or ground) wheat fed to cows after an adaptation period is considered safe, but it is possible to include up to 8-10 kg/d in the diet of grass hay-fed cows. More than 5 kg/d of wheat given to cows fed silage maize is reported to decrease intake (Laurent, 1988).
Cows should be introduced progressively to a wheat-based concentrate over 2 or 3 weeks, with an initial level not exceeding 10% of the concentrate (Blair, 2011). Dairy cows cannot utilize efficiently whole wheat grains (Laurent, 1988) and processing, such as grinding, rolling and pelleting, can substantially increase their digestibility. In general, wheat grain is fed dry and rolled or ground. A general recommendation is that coarse rolling should be used to break the kernel into two or three pieces, and good results have been obtained with coarsely ground wheat (hammer mill screen size of 4.5-6.4 mm) (Blair, 2011). It was shown that rolled wheat gave a better response than ground wheat, but only in early lactation (Laurent, 1988). Tempering wheat by adding moisture has been shown to be effective in reducing fines and maintaining milk yield and composition (Blair, 2011). It has been noted that crushed wheat grain fed with pasture hay (grass or legumes) to dairy cattle reduced the pH of rumen fluid and the digestibility of fibre (Leddin et al., 2009; Leddin et al., 2010), though this effect was limited when wheat was included at less than 30% of the diet (DM) (Laurent, 1988).
Heat processes can be used: 20% steam-rolled wheat included in the diet of dairy cows did not compromise production or cause subacute rumen acidosis, when adequate fibre was provided and the diets were correctly formulated and mixed (Doepel et al., 2009). In France, in cows fed a maize and grass silage diet supplemented with wheat processed by different methods (23% diet DM), ground and pelleted wheat gave higher milk yields and higher milk fat yields than dry-rolled or moist-rolled wheat. None of the processes caused acidosis (Cabon et al., 2002).
In Canada, feeding high moisture wheat to dairy cattle (6.1 kg/d DM, 30% diet DM) resulted in lower feed costs than feeding high moisture maize, due to the need for less protein supplementation and more milk being produced, possibly the result of a more digestible diet. High moisture wheat was considered to be a good alternative for dairy cows in areas where maize does not grow, because wheat requires a shorter growing season than maize (Petit et al., 1996).
Feeding wheat to beef cattle requires the same precautions as for dairy cows. In moderate to high grain rations (50% or more concentrate), wheat should be fed in combination with more fibrous or slowly fermented feed grains and limited to 40% of the diet. Beef cattle should be adapted by introducing wheat into the ration at low levels (10 to 15% of the diet) and increasing the level in steps after a period of several days of constant intake and appetite. Cattle should not be offered higher concentrate levels until intakes are consistent. The feed should be offered two, or more times, per day, in restricted amounts, with plenty of roughage, and in a total mixed ration. Self-feeding wheat should be avoided (Lardy et al., 2000).
Coarse-rolled durum wheat fed to beef cattle resulted in poorer intake, weight gains and feed conversion than hard red spring wheat, perhaps due to its higher gluten strength. Inclusion rate of durum wheat for beef cattle should not exceed 30% (Lardy et al., 2000).
Wheat grains can be fed to sheep. Recommendations are up to 25% for lambs and 35% for ewes (Ewing, 1997). Feeding wheat to sheep (ewes and lambs) has been extensively studied in Australia, particularly in the "wheat-sheep zone" in southern Australia. In this region, wheat (as well as oats and barley) are commonly used as energy supplements during short seasonal droughts. During long-term droughts (6-18 months), wheat grain can be the cheapest source of energy for supplementary feeding to sheep (McGregor, 2006). Wheat-dominant diets and even wheat-only diets are used (Jolly et al., 2007; McManus et al., 1973), but a minimum of 10-20% roughage is recommended in Australia to prevent acidosis and mortality in both lambs and ewes. For instance, ewes fed only wheat grain failed to produce adequate quantities of milk, resulting in increased lamb mortality (Reynolds et al., 1972).
Unlike cattle, processes such as rolling, flaking and grinding are not advisable in sheep as they increase fermentation rates and the risk of acidosis (Pulina, 2004). Lambs have been found capable of digesting whole grains as efficiently as the processed forms: lambs fed whole or rolled wheat had significantly higher average daily gains than lambs fed pelleted wheat (Tait et al., 1973). However, in a later experiment with lambs, pelleted wheat was found to be more digestible than whole wheat (Orskov et al., 1974a; Orskov et al., 1974b). However, responses to either the physical form or mode of presentation of the ration appear inconsistent. Feeding whole grain was also preferable to processed grain to avoid the production of soft fat associated with high levels of propionic acid (Jolly et al., 2007). With early-weaned and artificially-reared lambs, pelleting can improve the palatability of wheat grain (Bell, 2003)..
Few data are available about the use of wheat grain in goats. In China, growing castrated goats fed a maize stover-based diet containing either 25% (diet DM) wheat or maize grain had similar intakes but growth rate was higher with maize (Yang et al., 2012). In Argentina, dairy goats fed an alfalfa silage-based diet with 33-36% of either wheat grain, sorghum grain or dried citrus pulp had similar milk yields, indicating that the three sources of energy were interchangeable (Danelon et al., 2010). In the wheat-sheep zone of Australia, wheat grain is fed to goats during seasonal or longer droughts. In an experiment with castrated Angora goats, it was found that long-term feeding of whole wheat required the provision of 25% hay in the diet to ensure adequate energy intake and animal health. Animal losses during the experiment showed that wheat-fed goats had to be protected against acidosis, enterotoxemia and vitamin E deficiency (McGregor, 2006).