Biofuel co-products as livestock feed - Opportunities and challenges

Utilization of feed co-products from wet or dry milling for beef cattle 81TABLE 3Wet and dry distillers grains for calvesSupplement ADG Protein efficiency (1) ADINUrea 0.45 — —WG 0.66 2.6 —DDGS 0.65 2.0 9.7DDGS 0.67 1.8 17.5DDGS 0.70 2.5 28.8Notes: ADIN = acid-detergent-insoluble N; WG = wet grains; DDGS =dried distillers grains with solubles. (1) kg gain/kg supplemental protein.Wet grains were compared with dry grains and thevalue of the protein was similar (Table 3). This suggests thatthe high escape protein value of DGS is due to the innatecharacteristics of the protein and not to drying or moisturecontent, and does not appear to be influenced by aciddetergent-insolubleprotein, which is a common measureof heat damaged protein.Distillers grains contain approximately 65 percent UIP (aspercentage of CP), consequently diets that include DGS fedas an energy source (generally greater than 15 percent dietDM) are commonly deficient in DIP but contain excess MP.Cattle convert excess MP to urea, which can be excretedin the urine or recycled to the rumen to serve as a sourceof DIP. Jenkins et al. (2011) fed DDGS to finishing cattleat either 10 or 20 percent of diet DM, with or withoutadded urea. No advantage was observed for cattle supplementedwith urea (DIP) or not, suggesting recycling wasoccurring in finishing diets that included 10 or 20 percentDDGS. However, some numerical differences suggested aconservative approach to balancing diets based on proteinneeds would be to follow NRC (1996) guidelines for DIPsupplementation if DGS are provided at less than 20 percentof diet DM. Jenkins et al. (2011) also fed 0, 0.5 and1.0 percent urea (DIP) to dry-rolled maize (DRC)-baseddiets containing 25 percent WDGS. The diet containing1.0 percent urea was the only diet that was calculated tomeet DIP requirements. In the first 61 days on feed of the142-day feeding period, dry matter intake (DMI) was similaracross urea levels, but average daily gain (ADG) increasedwith added urea, resulting in an increased gain:feed (G:F)ratio. However, there were no cattle performance differencesover the entire feeding period. These data suggestthat when DGS are fed with DRC at inclusions greater than20 percent of diet DM, then recycling occurs and is sufficientto meet the DIP requirements.ENERGY REPLACEMENTThe feeding value of DGS and CGF is dependent onwhether the co-products are fed wet or dry, and the levelof dietary inclusion. Although the feeding value of WCGF isbetter than maize (100 to 112 percent of the feeding valueof maize), the feeding value of DCGF is 88 percent of DRCwhen fed at 25 to 30 percent of diet DM (Green, Stock andKlopfenstein, 1987; Ham et al., 1995).There have been several research experiments conductedto evaluate inclusion levels of WDGS, MDGS and DDGSon cattle performance. To summarize these experiments,statistical meta-analyses were conducted to evaluate eachof these types of DGS and account for differences observedacross experiments conducted at the University of Nebraska(Bremer et al., 2011). The inclusion of DGS replaced equalDM portions of DRC and/or high-moisture maize (HMC). Inthe meta-analysis that summarized 20 trials for feeding upto 40 percent WDGS (of diet DM), quadratic effects wereobserved for DMI, ADG and G:F (Table 4).Optimum inclusion of WDGS was observed at 15.8 percentfor DMI, 28.4 percent for ADG, and 40 percent for G:F,calculated from the first derivative of the quadratic equation.These improvements in G:F resulted in 30 to 40 percentgreater feeding value for WDGS compared with maizeat inclusions of 10 to 40 percent. Although these werequadratic relationships, feeding 40 percent WDGS resultedin greater ADG and G:F compared with a traditional maizebaseddiet. Greater 12th rib fat thickness and marblingscores result from feeding WDGS, and were also quadraticrelationships. The meta-analysis that summarized MDGS infour feeding trials up to 40 percent diet DM also indicatedquadratic relationships for DMI, ADG and G:F (Table 5).Optimum inclusion of MDGS for DMI was at 22.5 percentand 29.4 percent for ADG, and 40 percent for G:F.These improvements in cattle performance resulted in15 to 30 percent greater feeding value for MDGS comparedwith maize, in which cattle had greater ADG and G:F forall inclusions up to 40 percent. A quadratic relationshipwas observed for 12th rib fat thickness and a linearrelationship for marbling score for feeding MDGS. TheseTABLE 4Performance measurements for cattle fed increasing levels of wet distillers grains plus solubles (WDGS)Control diet 10% WDGS 20% WDGS 30% WDGS 40% WDGSDMI (kg/day) (1) 10.5 10.6 10.6 10.5 10.2ADG (kg) (1) 1.60 1.71 1.77 1.79 1.76G:F (1) 0.155 0.162 0.168 0.171 0.17312th rib fat (cm) 1.22 1.32 1.37 1.40 1.40Marbling score (2) 528 535 537 534 525Notes: Levels are as a % of diet DM. DMI = dry matter intake; ADG = average daily gain; G:F = gain-to-feed ratio. (1) Quadratic response to level ofWDGS in the diet (P < 0.01). (2) Marbling score: 400 = Slight, 500 = Small, 600 = Modest. Source: Adapted from Bremer et al., 2011.