Biofuel co-products as livestock feed - Opportunities and challenges

88Biofuel co-products as livestock feed – Opportunities and challengesTABLE 18Feeding value of wet distillers grains with solubles (WDGS) in dry-rolled maize (DRC) or combinations of high-moisturemaize (HMC) and DRC diets at 0 to 40 percent DM inclusion for calves and yearlingsDiet (see notes)0WDGS 10WDGS 20WDGS 30WDGS 40WDGSCalvesDRC, feeding value — 136 136 136 136DRC:HMC, feeding value — 124 124 124 124YearlingsDRC, feeding value — 167 159 151 143DRC:HMC, feeding value — 154 146 138 132Notes: Feeding value = difference in G:F between WDGS treatment level and 0% WDGS inclusion, and divided by % of WDGS inclusion. Diets are0WDGS = 0% WDGS; 10WDGS = 10% WDGS; 20WDGS = 20% WDGS; 30WDGS = 30% WDGS; 40WDGS = 40% WDGS. Diets expressed as a percentage ofdiet DM. Source: Adapted from Bremer et al., 2010a.DRC-based diets, 27.5 percent WDGS in HMC-based diets,and 15 percent WDGS in SFC-based diets. In addition,when 40 percent WDGS was included in DRC diets, cattleperformed just as efficiently as cattle fed any of the SFCdiets. A greater performance response to WDGS inclusionin diets based on less intensely processed grain may renderthem an economically attractive alternative compared todiets based on more intensely processed grains. Cattleperformance is improved by steam flaking corn when dietscontain WCGF. It is unclear why steam flaking did notimprove performance when diets contained WDGS.In the meta-analysis of 20 experiments for feedingincreasing dietary levels of WDGS conducted by Bremeret al. (2010a), they evaluated feeding value differences ofWDGS when fed in either DRC or DRC plus HMC blendeddiets, and when fed to calves or yearlings. Feeding valuewas calculated based on the G:F difference between a dietincluding WDGS and the predominately maize based diet,then divided by the percent inclusion of WDGS. For bothcalves and yearlings, greater feeding values resulted fromincluding WDGS in DRC-based diets compared with theDRC plus HMC blended diets (Table 18). This further agreeswith previous research that greater performance responsesare observed when WDGS is included in diets with lessintensely processed maize. Greater feeding values were alsoobserved when WDGS was included in DRC or DRC plusHMC based diets for yearlings compared with calves. Thissuggests that cattle producers can feed WDGS to yearlingsand get a greater performance response to WDGS comparedwith a predominately maize-based diet than withcalves. It is unclear why the energy response to feedingWDGS is greater with yearlings than calves.SULPHURSulphur concentration in maize is 0.10 to 0.15 percent ofDM, but S content in DGS is commonly 0.7 to 0.8 percent.Normally, nutrients are concentrated in DGS by a factor ofthree from that in maize, but ethanol plants typically usesulphuric acid to control pH, thereby increasing proportionatelythe S content in the DGS. Therefore, diets can behigh in S if a large quantity of DGS is included in diets orif the S content in the DGS is abnormally high. The commonconcern with feeding high dietary S is that S can beconverted to hydrogen sulphide (H 2 S) in the rumen andresult in polio encephalo malacia (“polio” or PEM). This conditionis commonly referred to as ‘brainers’, in which cattleexperience lack of coordination. Brainers is a general termcovering central nervous system problems that can be dueto numerous causes, including PEM. Cattle that are chronicbrainers do not recover from this condition and, if theysurvive, they probably will not recover in terms of performance.The key to treating cattle with PEM is early diagnosisand intravenous infusion of thiamine (Gould, 1998; Brentand Bartley, 1984). The occurrence of PEM appears to befairly random, but is still highly correlated with dietary Sconcentration (and probably even more so to ruminallydegradable S intake). It should be noted that while PEM isa concern, producers using less than 40 percent inclusion ofany co-products (DM basis) should expect few if any casesof PEM. It should also be noted that a small incidence ofPEM has been common in the feedlot industry, even beforethe use of DGS. However, increasing S intake exacerbatesthe challenge and can result in very high incidences of PEMif not monitored. Water should be tested for sulphates andaccounted for in total S intake.NRC (1996) states that 0.4 percent dietary S is consideredto be a concentration that can result in PEM conditions.However, many research experiments have beenconducted with co-product-containing diets where dietaryS concentrations exceeded 0.4 percent, but with low PEMincidences. Thus Vanness et al. (2009) summarized severalresearch experiments involving 4143 cattle in which coproductswere fed to evaluate S content in the diet andincidence of PEM. Polio was defined as either identificationand treatment of PEM by the health crew in the feedlot,or death due to PEM confirmed by necropsy. Very lowlevels of sulphates were present in the drinking waterin this research feedlot (less than 100 ppm sulphate). Asmall incidence of PEM (0.14 percent) was observed whendiets contained 0.46 percent S or less. Incidences of PEM