**8. Manure management consideration**

production and consequently increasing distiller grain availability, feeding wheat distiller grain to dairy cattle has been spread recently not only as protein source but also as energy or fibre sources [31]. In fact, high-producing dairy cows are often at risk of subacute rumen acidosis, a common digestive disorder usually caused by feeding a diet containing highly fermentable carbohydrates with insufficient effective fibre to maintain rumen health [32]. Because the distiller grain contain low starch which is highly fermentable in the rumen, and high digestible fibre as well as relative high fat, it was suggested that feeding distiller grain in dairy cow diets could be potentially reduce the incidence of rumen acidosis while maintain milk production. Numbers of studies have been conducted to assess wheat distiller grain as a fibre and energy source to partly replace grain, or roughage or both. Penner et al. [33] evaluated wheat distiller grain to include 10% of wheat distiller grain in the ration showed that feeding wheat distiller grain as a forage substitute increased milk yield by 7% and milk protein content by 9%, whereas milk fat content decreased from 3.36 to 3.04% even though milk fat yield was not affected. Zhang et al. [34] reported that feeding wheat distiller grain in partial replacement of barley grain had no negative effect on dairy cow production. Feeding wheat distiller grain as a partial replacement of barley silage can improve dairy cow production, but, it may decrease chewing time, ruminal pH and milk fat concentration [35]. Overall, substitution of wheat distiller grain for part of concentrate or roughage in dairy cow diets improves milk production as a result of increase of feed consumption without negatively impacting milk fat. In contrast, feeding wheat distiller grain to partly replace roughage may reduce milk fat content due to reduction of chewing activity and rumen pH. Thus, dairy producers and nutritionists formulate dairy rations to ensure cow chewing time is sufficient to maintain rumen pH which is linked to maintaining milk fat

Abundant distiller grain from ethanol production can be used as alternatives to feed grains and other premium ingredients in sheep feeding to reduce feeding costs for sheep farmers. However, most of the studies with feeding wheat distiller grain are with cattle or pigs. With our best knowledge, only one study was conducted using growing lambs fed diets containing wheat distiller grain. O'Hara et al. [36] reported that wheat distiller grain could replace a mixture of barley grain and rapeseed meal at 20% dietary dry matter without negatively affecting feed intake, daily gain and carcass traits of growing lambs. Replacing part of barley grain with 20% of wheat distiller grain in finishing lambs also maintained a healthy rumen function, growth performance and carcass characteristics [36]. McKeown et al. [37] also found that triticale-based distiller grain could replace up to 60% barley grain without adversely affecting on growth performance or carcass traits of lambs. Inclusion of wheat distiller grain in growing or finishing lamb diets is likely a viable feeding management since wheat distiller grain can entirely replace protein supplement to meet protein requirement of growing lambs, and simultaneously used as energy and fibre source because of its high contents of protein,

concentrations [34].

302 Wheat Improvement, Management and Utilization

energy and fibre.

**7. Feeding distiller grain for small ruminants**

Ammonia emitted from animal feeding operations is a major air and water pollutant contributing to eutrophication, soil acidity, aerosol formation, and impaired visibility. Although ammonia is not a greenhouse gas, it may indirectly contribute to agricultural emissions of nitrous oxide, a potent greenhouse gas with a global warming potential of approximately 300 times that of CO<sup>2</sup> . During last decade, dramatic increase of high-protein by-products feeding in livestock animals as a result of increased production of corn and wheat distiller grain. Consequently, inclusion of the distiller grain in cattle diets as protein and energy source has been becoming a common practice in cattle production because of high nutritional value. With the increased use of high protein distiller grain in cattle diets, the potential for increased manure nitrogen is a concern. For instance, finishing diets that contain 30% wheat distiller grain have more than 20% (dry matter basis) crude protein, compared to the animal's requirement of about 12%. As a result, the excess nitrogen is excreted in manure (feces, urine and bedding) leading to greater NH3 and N2 O emissions. In feedlot cattle, only a small percentage of the protein consumed by feedlot cattle is retained in animal tissue and as a result 80–90% is excreted in urine and feces, mostly in urine since digestibility of feed protein is relatively high for most types of feeds. Li et al. [38] reported that increased nitrogen intake due to increased distiller grain feeding quantitatively increased nitrogen retention, excretion in feces and urine, whereas, proportionally, nitrogen excretion in urine increased (primarily in the form of urea) and nitrogen excretion in feces decreased. The study clearly identified that urinary nitrogen is the principal source of NH3 -N volatilized from cattle manure during the initial 10 days of storage, accounting for an average of 90% of the emitted NH3 -N. Thus, from an environmental point, it is important to match dietary protein supplies as closely as possible to rumen microbial and animal needs. However, when the distiller grain is included at high proportion as energy source in cattle diets, high nitrogen excretion is not avoidable, a factor that needs to be considered for manure management.

Wheat distiller grain also contains high concentrations of phosphorus and sulphur [11]. The resulting manure from cattle fed wheat distiller grain, with high phosphorus content, can be beneficial for crop production, but it may also have a negative environmental impact due to increased phosphorus accumulation in crop lands surrounding feedlots [39]. Environmental concerns regarding phosphorus excretion are primarily associated with pollution of surface water. Dietary phosphorus intake was positively associated with the amount of phosphorus excreted in livestock manure [40]. Concentration of sulphur in wheat distiller grain was reported to range from 3.9 to 11.4 g/kg in dry matter [6, 11]. The high sulphur in distiller grain is mostly from chemicals added during the ethanol fermentation to control pH and for cleanup. Excreted sulphur can contribute to H2 S emissions from livestock manure [41]. Li et al. [38] reported that increasing substitution of wheat distiller grain for barley grain and barley silage in diets fed to finishing cattle increased urinary phosphorus excretion. Thus, potential environmental implications of liquid runoff from the feedlot surface and potential phosphorus contamination of surface water need to be considered. In addition, the increased intake and urinary excretion of sulphur as a result of increased inclusion of distiller grain in feedlot diets [38] may increase ammonia and H<sup>2</sup> S emissions from the feedlot, in particular when combined with increased nitrogen excretion. Therefore, cattle producers that replace grains or forages with distiller grain need to take appropriate steps to develop nutrient management programs in order to minimize nutrient loss to the environment and to maximize use of both nitrogen and phosphorus.
