Effect of feeding distillers grains on health in the feedlot
- Project No: 0009-001
- Lead Researcher(s): Dr. Steve Hendrick, Western College of Veterinary Medicine
- Year Completed: 2012
Background
Increased usage of DDGS in beef cattle diets has arisen from the rising costs of traditional feedstuffs. When wheat or corn are fermented and distilled, the starch is converted to alcohol. The fat, protein, and fiber from the grain are concentrated in the DDGS by-product, resulting in higher levels of those nutrients than the parent grains. It has been hypothesized that inclusion of DDGS in feedlot diets may mitigate acidosis due to its low starch content, but preliminary research (ABP project #0007-105), determined that inclusion of DDGS up to 40% of the diet did not reduce incidences of acidosis.
Unfortunately, the distillation process also concentrates minerals such as nitrogen, phosphorus and sulfur. This may negatively affect cattle health. For example, too much dietary sulfur may result in a neurological disease condition in cattle known as polioencephalomalacia (PEM or nutritional polio). Symptoms of nutritional polio may become blind, stumble, unable to stand up or have seizures. Several research studies have evaluated the performance of cattle fed DDGS, but very little has been reported regarding the effects of DDGS on cattle health.
Objective
To evaluate the animal health and performance of yearling cattle finished on a ration containing varying quantities of wheat-based dried distillers grains with solubles (DDGS), to investigate the sulfur metabolism of cattle being fed wheat-based DDGS, and to assess any differences in ruminal, hepatic, brain and distal limb lesions resulting from diets containing wheat-based DDGS.
What they did
A small-scale study involved 288 crossbred steers that were randomly assigned to one of four diets. The control diet consisted of 86.8% rolled barley, 5.8% supplement, and 7.4% barley silage. Diet treatments involved replacing 50% of the rolled barley with either wheat, corn or a 50:50 wheat/corn blend DDGS. Blood samples were taken from a random subset of steers in each pen just before the backgrounding phase, at the end of the backgrounding phase and after completion of the finishing phase. Feed samples were taken every two weeks from each pen’s feed bunk, and each load of feed had a sample taken when it arrived at the lot.
A larger field trial study involved 6815 crossbred steers in a commercial feedlot setting. Diet treatments involved 22.5% wheat-based DDGS, 22.5% corn-based DDGS or the control diet (no DDGS). Animal measures included final weight, weight gain, carcass weight, dressing percentage, days on feed, daily dry matter intake, average daily gain, feed to gain ratio, carcass quality and yield grade, BRD treatment rate, laminitis observation rate, bloat treatment rate, overall mortality rate, BRD mortality rate, metabolic disease mortality rate and miscellaneous mortality rate. Animals that died or were euthanized had a full necropsy performed, including histopathological examination of tissues. At slaughter, all carcasses were scored for liver abscesses.
The final study involved 16 cannulated heifers to evaluate the impact of dietary sulfur and grain on rumen, blood and urine parameters. Heifers were fed one of the following diets: high grain/high sulfur, high grain/low sulfur, low grain/high sulfur, and low grain, low sulfur. High grain diets contained 50% barley, 35% wheat-based DDGS, 10% barley silage and 5% supplement. Low grain diets had 75% barley silage, 20% wheat-based DDGS and 5% supplement. High sulfur diets contained 0.6% sulfur, and low sulfur diets contained 0.3% sulfur.
What they found
Small Pen Study: During the backgrounding phase, cattle fed wheat-based DDGS had the highest sulfur concentration in the blood (179.7 ppm), followed by corn-based DDGS (177.9 ppm). This was significantly higher than the levels found in the blood of steers fed the control diet, but no statistically significant differences existed between the wheat DDGS and corn DDGS diets in terms of blood sulfur concentration. The 50:50 blend had the lowest concentration of all the diets. The same held true for the finishing phase, although cattle fed the 50:50 wheat/corn DDGS had a higher serum sulfur level than those fed the control diet in the finishing phase.
Large Field Study: Wheat DDGS included at a rate of 22.5% of the diet negatively affected ADG, feed:gain, reduced hot carcass weight, reduced the number of AAA carcasses, and tended to increase A carcasses compared to those cattle fed no DDGS. Those cattle on a 22.5% corn DDGS diet showed an improvement in ADG and hot carcass weight, but a decrease in YG1 carcasses. No significant effects of wheat or corn DDGS on mortality or histopathological lesions were observed (steers fed wheat DDGS had a 0.49% and 0.79% numerical increase in mortality over corn DDGS and the control diet). Incidence of liver disease was significantly increased in those steers fed wheat DDGS, but no liver disease at all was observed in either the control or corn DDGS groups. No significant effects of feeding either type of DDGS on ruminitis were found, although there was a numerical increase, with eight of the corn DDGS fed animals suffering from ruminitis. The prevalence of PEM was not associated with feeding DDGS of either type, and number of liver abscesses were very similar between groups as well.
Metabolic Study: High dietary sulfur significantly reduced dry matter intake, but dry matter intake was not affected by forage:concentrate. Rumen pH was affected by both dietary sulfur levels and forage:concentrate ratio, with high grain diets reducing pH and high sulfur diets increasing pH. Heifers fed high dietary sulfur produced about 4.5 times more H2S gas than the animals fed low dietary sulfur. No signs of PEM were observed in these heifers, and there was no impact on forage:concentrate ratio on serum sulfate levels, which disagrees with the small pen study above. Heifers on the high sulfate diet excreted more than 50% more urinary sulfate than the low dietary sulfur groups. The researchers found differences in trace minerals in the rumen, blood serum, and urine attributable to the different types of diet (high grain vs. low grain, high sulfur vs. low sulfur), but they had not yet finished the trace mineral composition of the diet, so these results should be interpreted with caution.
High sulfur diets inhibited absorption of acetate, propionate and butyrate. Significant increases in total thiamine were found in the brain of heifers consuming high dietary sulfur, indicating increased demand for thiamine. As thiamine treatment sometimes reduces the symptoms of PEM, thiamine and thiamine phosphate esters were analyzed from five brains of sulfur-induced PEM feedlot steers. The PEM affected animals had significantly higher levels of free thiamine and total thiamine in their brain tissue than the heifers fed differing levels of dietary sulfur.
What it means
The results from the small pen study revealed that high grain diets may have an effect upon sulfur metabolism, given that sulfate concentration in the blood was much higher during the backgrounding phase, when sulfur content of the diet was much lower than during the finishing phase. This could indicate that high grain diets affect the population of sulfur reducing bacteria, or that sulfide absorption is reduced. It is worth noting that each type of DDGS (wheat, corn, 50:50 wheat/corn mixture) were sourced from different ethanol plants, and each plant may have slightly different processing methods which affect the amount of sulfur present in the DDGS.
The large field trial demonstrated that feeding either wheat or corn DDGS at 22.5% of the diet did not have an effect upon animal health, in terms of morbidity, mortality, or rumen function. However, some feedlot performance measures and carcass attributes were negatively affected with the inclusion of DDGS in the diet. This is contrary to some other findings regarding feedlot performance when either wheat or corn DDGS is included in the diet. Again, because the sources of DDGS were different for all three types, the nutrient content likely varied as well, causing the differences in performance. Cost-effectiveness of using DDGS as a ration component will depend on pricing relative to barley grain.
The metabolic study demonstrated that ruminal H2S, ruminal S2, and serum and urinary sulfate mirrored dietary sulfur intake. In fact, heifers on the high sulfate diet excreted over 50% more urinary sulfate than the low dietary sulfate groups, which may indicate an ability to avoid sulfur toxicity through urine excretion (to a point). In addition, animals afflicted with PEM had significantly higher levels of free thiamine and total thiamine, but decreased levels of TPP (another form of thiamine) in their brain tissue than the heifers fed differing levels of dietary sulfur, indicating that TPP synthesis from free thiamine may be inhibited in PEM affected animals. This could cause a depletion of energy in the brain, possibly resulting in neuron cell death. In this study, increased levels of dietary sulfur did not cause an increased incidence of PEM.
