A study recently completed at the Agriculture Canada Lethbridge Research Centre has shown that triticale dried distillers grain with solubles (DDGS) can replace a portion of the barley grain as well as part or all of the barley silage in finishing rations without having adverse effects on animal performance or carcass quality.
Most of the work to date in Canada investigating the properties of DDGS as a livestock feed has focused on the inclusion of wheat DDGS to replace a portion of the grain in cattle diets. The research has shown that wheat DDGS contains more fermentable fibre than barley grain, but the fermentation rate of this fibre is slower than that of the barley starch, resulting in a slower rate of feed digestion in the rumen. As a result, the rate of acid production in the rumen is also slowed and in turn, reduces the risk of acidosis.
Previous research has determined that performance of feedlot cattle is enhanced when DDGS is substituted for a portion of the grain up to 20 per cent of dry matter (DM) of the ration. The premise of this study was that the initial replacement of the dry-rolled barley grain with triticale DDGS would reduce the starch content of the mixed diet and thereby reduce the amount of forage required to maintain rumen health, and that further substituting triticale DDGS for barley silage would improve growth performance as a result of the increased energy content in the diet.
The study confirmed that there is an adequate level of fermentable fibre in triticale DDGS to maintain rumen function when this alternate ingredient replaces all or part of the barley silage in finishing diets.
The trial investigated the potential of triticale DDGS rather than wheat DDGS to replace silage because triticale is an excellent alternative to wheat for ethanol plants. Both grains contain about 65 per cent starch in the kernels, says Tim McAllister, ruminant nutrition research scientist at Lethbridge Research Centre. Ethanol plants can have difficulty sourcing wheat when there is a high demand for its use as human food. Furthermore, supplies of wheat may become more limited in the future as the ethanol industry continues to expand. Triticale is a high-yielding, drought and disease-resistant cereal crop that is well adapted to production in Western Canada. The market for triticale as a livestock feed or food for humans is very limited, therefore, it doesn’t compete with traditional feed and food grains in the commodity market.
McAllister says that the triticale DDGS findings could be applied to wheat DDGS because they are similar in composition and studies have shown that the fermentation characteristics of triticale DDGS in the rumen are similar to those of wheat DDGS. He doesn’t know whether the same response could be expected from corn DDGS, though it is quite possible because corn DDGS contain higher levels of oil than wheat DDGS. Oil is a component that can further modulate rumen fermentation.
The feed value of DDGS does vary depending upon differences in ethanol production process. As a percentage of the DM, the triticale DDGS fed in this trial contained 36.7 per cent crude protein (CP), 32.6 per cent neutral detergent fibre (NDF), 5.9 per cent starch, and 11.4 per cent acid detergent insoluble nitrogen (ADIN).
McAllister suggests that substituting wheat or triticale DDGS for silage may be a way to conserve your silage supply during times of shortages or high prices. The general recommendation is to gradually introduce DDGS through a two-week period as it is substituted for a portion or all of the silage in the finishing diet.
DDGS could be substituted for silage in a backgrounding diet, however, if DDGS exceed more than 30 per cent of the diet, you’ll end up with a finishing diet as opposed to backgrounding diet, he adds.
Graduate student Kris Wierenga headed up the project. On a DM basis, the four trial diets included: a conventional ration with 85 per cent dry-rolled barley (DRB) and 10 per cent barley silage; 65 per cent DRB, 20 per cent triticale DDGS and 10 per cent barley silage identified as D-10S; 65 per cent DRB, 25 per cent triticale DDGS and five per cent barley silage; and 65 per cent DRB with 30 per cent triticale DDGS and no barley silage. Supplement was included at five per cent of DM in all diets.
The trial involved 160 crossbred yearling steers, 16 of which were fitted with ruminal cannulas. This trial was unique in that the cannulated animals were placed with the others and allowed to roam freely within their assigned feedlot pens rather than being housed in individual stalls. Two cannulated steers along with eight other intact steers were placed into each of eight pens equipped with an automated system to measure the intake and feeding behaviour of each individual. The remainder of the intact steers were placed in groups of 10 into standard feedlot pens.
All of the steers were weighed every 28 days, but the cannulated steers were not included in the performance and carcass results. Intact steers from the standard pens were shipped to the abattoir after 92 days on feed, while the remainder from the intake-monitored pens were shipped after 112 days on feed.
Feeding Behaviour, Performance and Carcass Traits
Wierenga observed that the steers ate less frequently and consumed the ration more quickly as the proportion of DDGS replacing silage increased. This was attributed to the particle size of DDGS being smaller than that of barley silage.
Steers on the conventional ration had 50 per cent more variation in daily dry-matter intake (DMI) than steers fed the D-10S ration.
The DMI for steers receiving the D-10S diet tended to be greater than that of the steers on the conventional ration. The cannulated steers on the D-10S diet consumed 1.1 kilograms more per day than the steers fed the conventional finishing diet.
Though DMI increased in steers fed the D-10S ration, the average daily gain and gain-to-feed ratio (G:F) was similar to that of the steers on the conventional ration. The DMI tended to decrease and G:F tended to increase as the amount of DDGS was increased to replace more than 10 per cent of the silage.
Though the DMI of the steers on the D-10S ration was higher, the estimated starch intake per day was lower than that for the conventional group due to the differing starch contents in the two diets. Some of the responses may have arisen from differences in CP content of the diets, however, most were attributed to changes in amount of physically effective fibre (peNDF) in the diet as triticale DDGS replaced barley silage.
Carcass evaluations showed that steers that received the D-10S ration tended to have greater backfat thickness, lower dressing percentage, smaller rib-eye area and lower meat yield than steers finished on the conventional ration.
Previous studies have shown that increasing supplemental protein in feedlot diets increases fat deposition rather than lean muscle and that feeding triticale DDGS in place of barley grain may increase carcass fat content. Further increasing the percentage of triticale DDGS in the ration did not have a compounding effect on carcass quality.
Rumen pH, Acidosis and Liver Abscess
Previous studies suggest rumen pH less than 5.5 for a duration of 12 hours or more is a reflection of an increase in the occurrence of subacute acidosis, whereas rumen pH less than 5.2 for six hours or more per day may be indicative of acute acidosis. These were the parameters Wierenga used to define bouts of subacute and acute acidosis in this trial as well.
Rumen pH was measured with electrodes inserted through the cannulas into the rumen for four, seven-day periods. Though mean daily rumen pH didn’t differ between the steers on the conventional ration and those fed the D-10S ration, there was less variation in the mean hourly rumen pH when steers received the D-10S ration.
The mean rumen pH decreased as the DDGS portion of the ration was increased to replace more than 10 per cent of the barley silage. Researchers also observed a corresponding increase in the length of time that the rumen pH stayed below 5.5, as well as an increase in the occurrence of bouts of acidosis.
The steers fed the conventional ration experienced 21 bouts of subacute acidosis. This compares with 12 bouts for the steers fed the D-10S diet, 30 bouts for those fed the ration with five per cent barley silage, and 44 bouts for the steers fed the diet with no silage. A similar pattern was observed for bouts of acute acidosis with 18, 14, 28, and 35, respectively.
The lower incidence of acidosis in steers fed D-10S may have contributed to their higher DMI compared with the steers on the conventional ration. The increase in incidence of subacute acidosis as the amount of DDGS increased to replace barley silage in the ration, may be attributed to the decline in effective fibre content of the diet. Previous research has shown that lowering the fibre content of the diet reduces chewing and salivation, and the buffering effect of saliva on rumen pH.
The results of this study were in line with previous studies indicating that substituting dry-rolled barley grain with triticale DDGS at 20 per cent of the DM in finishing diets decreased the prevalence of subacute acidosis, but increased the incidence of liver abscesses. Even though the rumen pH of the steers on the D-10S diet was higher, the prevalence and severity of liver abscesses were much greater than that in steers with lower rumen pH on the conventional ration.
Wierenga suggests that one factor may have been that a dietary antimicrobial was not included in any of the rations. Previous studies have reported that feeding corn or wheat DDGS in place of cereal grains did not affect the prevalence of liver abscesses, however, those studies included a liver abscess preventive in the diet. Recent research at the University of Saskatchewan showed that the number of severe liver abscesses in steers fed wheat DDGS rations without an antimicrobial was higher than in steers fed a barley grain-based diet (with no wheat DDGS).
This study concluded that even though the mean rumen pH decreased and the incidence of acidosis increased as barley silage was replaced with triticale DDGS, the trend toward improved growth suggests that the lowered rumen pH did not affect animal performance. It may be that feed intake is not adversely affected until a certain pH threshold is reached. They do, however, recommend including an antimicrobial in the diet to reduce liver abscesses when substituting DDGS for barley silage in a ration.