Biofuel co-products as livestock feed - Opportunities and challenges

Utilization of feed co-products from wet or dry milling for beef cattle 95finishing diet. Inclusion level of wheat DGS had no effecton G:F, but increasing levels of maize DGS resulted in aquadratic increase in G:F. Wierenga et al. (2010) measuredcattle performance on finishing diets with 20, 25 or and30 percent triticale DDGS replacing barley silage in the diet.The triticale DDGS was similar in fat and NDF content towheat DDGS, but lower in CP. Increasing inclusion levelsof triticale DDGS tended to linearly increase G:F (P = 0.06)with no effect on ADG (P = 0.56).Impact of fat and fat removalResearch has shown that feeding DGS improves cattleperformance. One likely reason for DGS resulting in betterperformance than maize is due to the high fat content inDGS. The fat content of DGS can be affected by the processand by how much solubles are added back to the wetgrains. Another factor that can affect the fat content ofDGS is whether some of this maize oil is isolated in theprocess (similar in concept to complete removal in the wetmilling industry). Numerous processes are currently beingexplored by ethanol plants to remove a portion of the maizeoil for other purposes. It is therefore important to know theimpact of the fat content in DGS on performance.Gigax et al. (2011) evaluated feeding 35 percent WDGS(DM basis) with normal fat content (13.0 percent of DM)or low fat (6.7 percent of DM), and compared this with aDRC-and HMC-based control diet. Cattle consumed equalDMI, but feeding the high fat WDGS improved ADG andG:F (Table 25). Cattle fed the low fat WDGS had equivalentADG and G:F to cattle fed the maize control diet. Thesedata suggest that the improved performance due toTABLE 25Effect on cattle performance of feeding a low- or highfatwet distillers grains with solubles (WDGS) at 35% DMinclusion compared with a maize-based control dietControl Low-fat WDGS Normal-fat WDGSDMI (kg/day) 11.2 11.2 11.2ADG (kg) 1.55 a 1.55 a 1.69 bG:F 0.139 a 0.139 a 0.152 bNotes: DMI = dry matter intake; ADG = average daily gain; G:F = gainto-feedratio. a,b = Means within the same row without a commonsuffix differ (P < 0.05). Source: Adapted from Gigax et al., 2011.feeding WDGS is at least partially due to higher fat contentin the WDGS.In this study, the primary difference in these two productswas the amount of distillers solubles added back to thewet grain. Although WDGS typically has 11 to 13 percentfat, this amount can vary due to the amount of distillerssolubles (18–26 percent fat) that is added back to the wetdistillers grains (~8 percent fat).Godsey et al. (2009) conducted a feeding trial evaluatingthe proportion of solubles added to WDG at WDG:solublesratios of 100:0, 85:15 and 70:30.They fed these ratios in DRC-based diets at 0, 20 and40 percent of diet DM. No interactions resulted for ratio ofgrains to solubles or for level of WDG±DS fed. Althoughthere was no effect for DMI, linear improvements wereobserved for ADG and G:F as the level of WDG±DS wasincreased (Table 26). Optimum inclusion was observed at40 percent DM inclusion. No effects of WDG to solublesratio were detected in this experiment, suggesting that, forimproving cattle performance, the level of WDGS is moreimportant than the grain to solubles ratio.The fat in DGS is maize oil originating from the maizegrain. Maize oil is high in unsaturated fatty acids (doublebonds within the fatty acids). Feeding unsaturated fatsources to cattle generally has a negative impact on therumen microbes (particularly forage-digesting microbes).During rumen fermentation, rumen microbes will saturatethe fatty acids by bio hydrogenation and produce saturatedfatty acids that leave the rumen and are available forabsorption in the small intestine. Therefore, unless the fatis “protected” against bio hydrogenation by the microbes,the majority of the fat will be saturated fatty acids at thesmall intestine. It is important to note that fatty acids arenot absorbed in the rumen or metabolized by the rumenmicrobes, except for bio hydrogenation. The primary site ofmaize oil is in the maize germ, which may be “protected”from rumen microbes.Vander Pol et al. (2009) evaluated different fat sources,including wet distillers grains plus solubles, in both feedingand metabolism studies. The ratio of unsaturated fattyacids relative to saturated fatty acids increased at the smallintestine in steers fed WDGS compared with maize-basedTABLE 26Effect on cattle performance of feeding increasing levels of WDG with or without distillers solubles and the ratio of WDGto distillers solublesLevel of WDG ±DS (1) Ratio of WDG:DS (2)0 20 40 100:0 85:15 70:30DMI (kg/day) 11.6 11.6 11.4 11.5 11.4 11.6ADG (kg) (3) 1.68 1.76 1.77 1.76 1.75 1.80G:F (3) 0.144 0.152 0.156 0.153 0.154 0.156Notes: DMI = dry matter intake; ADG = average daily gain; G:F = gain-to-feed ratio. (1) Level of wet distillers grains with or without distillers solubles(DS). Represented as a % of diet DM. (2) Ratio of wet distillers grains (WDG) to distillers solubles (DS). Represented as a proportion of the total WDGSproduct. (3) Linear effect for level of WDG±S fed (P