Research scientists at Ag Canada’s Lethbridge Research Centre have put wheat to the test every which way and found that it could replace all the barley in feedlot finishing rations with no measurable negative effects on growth or carcass quality.
In a nutshell, there’s a tendency toward lower feed intake and improved feed efficiency with wheat versus barley grain. However, wheat’s reputation as a hot, highly fermentable feed, which can cause acidosis opening the door to liver abscesses, and concerns about gluten reducing rumen motility have kept it from becoming widely accepted as a cattle feed. The general recommendation has been to limit it to 50 per cent or less of the grain portion of a ration.
“Wheat may become attractive to replace a portion of barley or corn in cattle rations at times when it can be competitively priced against other grains because of high wheat stocks or adverse growing or harvesting conditions that make it unsuitable for human consumption,” says beef nutrition scientist Wenzhu Yang.
“As with other cereal grains, wheat is primarily a source of energy in the form of carbohydrates with digestible energy similar to corn and higher than other cereals. It can also be used as a protein source when protein prices are high and wheat is relatively cheap compared to other protein sources.”
Yang suggests the first step when thinking about substituting wheat for barley is to test it because there’s as much variation in feed quality of wheat as any other grain depending on variety, agronomic practices and growing conditions.
Generally, wheat offers the highest crude protein level of all feed grains. The average is 15.9 per cent, but it can be as high as 19 in durum or as low as 10 in red winter wheat, compared to 12.7 for barley, 10.3 for corn, 15.7 for triticale and 11.6 for oats.
Typically, as total protein content in wheat increases, so do the natural gluten proteins.
The average starch content is 70.9 per cent, which falls about midway between barley at 64.3 per cent and corn at 75.7. Neutral detergent fibre is as low as corn averaging 10 per cent, compared with barley at 21 per cent and oats at 35 per cent.
Wheat starch does break down rapidly in the rumen, more so when the kernels are rolled, which Yang says is a must for effective digestion. However, results from the first in a series of recent trials comparing wheat to barley found no measurable negative effect on rumen function or feed digestibility when wheat replaced some or all of the barley in a finishing diet of 90 per cent grain and 10 per cent silage.
Rumen pH levels followed a very similar curve whether the grain portion was all barley, 60 per cent barley/30 per cent wheat, 60 per cent wheat/30 per cent barley, or all wheat. Rumen pH was above 6.0 at feeding and dropped to 5.8 within two hours of feeding, and to 5.5 within the next two hours. It dipped lower for the next four hours and then rose to 5.5 by hours 13 through 16 and above 5.8 by hours 16 through 20.
In all, rumen pH was below 5.8 for 13.8 to 15.7 hours and below 5.5 for 10.4 to 12.6 hours during the 24-hour period. The longest duration below 5.8 and 5.5 was for the all-wheat grain ration and the shortest was for the all-barley grain ration.
The danger zone for ruminal acidosis starts at a pH of 5.8, which indicates acids are starting to build up faster than can be buffered by saliva and fibre. Ruminal acidosis is confirmed when pH drops below 5.5 and the longer it stays low, the greater the chance of damage to the rumen.
Given these limits Yang recommends feeding wheat-based rations twice a day rather than once to reduce the swings in rumen pH and lessen the amount of time it spends below 5.8.
Yang says they also found measurable but not significant differences in fermentation patterns. The acetate-to-propionate (A:P) ratio was the lowest at 1.12 for the 30 barley/60 wheat ration; 1.31 for the all-wheat grain ration and 1.32 for all-barley grain ration.
A lower A:P ratio is beneficial because it indicates a greater proportion of propionate volatile fatty acid, which is more energy dense than acetate.
Intake was highest for the all-barley grain ration at 12.6 kg/day and dropped by 0.2 kg/day as the percentage of wheat increased.
Crude protein digestibility was lowest for the all-wheat grain ration at 59.1 per cent compared to 63.9 per cent for the all-barley grain ration. However, dry-matter (DM) digestibility was highest for the all-wheat grain ration at 73.0 per cent compared to 70.0 per cent for the all-barley diet.
Processing index matters
The PI indicates the degree of processing and is calculated by dividing the bulk density of the processed grain by the bulk density of the whole grain multiplied by 100. For example, if a barley sample had a bushel weight of 50 pounds before processing and 35 pounds after processing, the PI would be 70 per cent (35/50×100). The tighter the rollers, the lower the index.
The PI in samples of processed barley from 10 feedlots in the Lethbridge area ranged from 60 to 90 per cent, and averaged 78 per cent, which is in line with the recommended PI of 75 to 80 for barley.
A PI of 85 is recommended for wheat. This should break the kernels into two or three pieces without creating fines that contribute to acidosis.
However, as the next feedlot study showed, the optimum PI depends on starch content of the wheat as well.
Wheat with a low starch content of 46 per cent and barley with similar starch content were processed to PIs of either 85 or 75 per cent to evaluate the effect of PI on wheat versus barley.
Both the type of grain and the PI made a difference in dry-matter intake and feed-to-gain (F:G) ratio. At PI 85, barley consumption was 10.6 kg/head/day and wheat was 10.3 kg. When the grains were further processed to PI 75, barley consumption dropped only slightly, whereas wheat consumption dropped to 9.9 kg/head/day. The drop in consumption and steady rate of gain translated into a significant improvement in the F:G ratio from 7.35 at PI 85, down to 7.09 at PI 75. The F:G ratio for barley also improved from 7.81 down to 7.30.
Carcass traits were affected by the PI as well. Although there wasn’t a difference in warm carcass weight, the steers on PI 75 grains had slightly less back-fat thickness and larger rib-eye areas and the percentage of salable meat was slightly higher than for steers fed PI 85 grains. Nearly all of the steers fed PI 75 grains graded AAA (100 per cent on barley and 95 per cent on wheat) compared to 88 and 86 per cent respectively on the PI 85 grain diets.
The percentages of total liver abscesses and severe liver abscesses were the same whether the steers received barley or wheat when the PI was 75 per cent.
The type of grain was a deciding factor when PI 85 grains were fed. For barley, the percentage of animals with abscesses stayed around 70 per cent regardless of PI, however, the percentage with severe abscesses dropped from 44.7 per cent on PI 75 barley to 17.5 per cent on PI 85 barley.
Processing had the opposite effect for the wheat-based rations. The percentage of animals with severe abscesses jumped from 45.8 on PI 75 wheat to 56.4 on PI 85 wheat and the overall percentage of animals with liver abscesses also rose from 71.8 per cent to 91.7.
Yang says the increase in liver abscesses in cattle fed the higher PI wheat was apparently related to greater dry-matter intake.
Monensin and wheat type
Using cannulated heifers the researchers found daily average rumen pH was highest for the barley diet at 5.91 compared to 5.55 for the wheat diets. The length of time the pH stayed below 5.8 or 5.5. was shortest for barley (9.9 or 4.3 hours) than for wheat (17.3 or 11.5 hours), indicating that the incidence of ruminal acidosis was higher for the wheat diets than the barley diet.
The average rumen pH and the duration of pH below 5.8 or 5.5 didn’t differ for the type of wheat. Similarly, increasing the monensin rate didn’t increase the daily average rumen pH, therefore, had limited effect on alleviating ruminal acidosis.
The type of wheat didn’t make as much difference to dry-matter intake as the kind of grain (barley versus wheat) and upping the monensin level. Monensin at the higher rate with both types of wheat decreased dry-matter intake by as much as 1.0 kg/head/day compared to the rations with monensin at the lower rate.
Monensin lowered the A:P ratio, most notably at the 44-mg rate for both types of wheat. The A:P ratio for soft wheat at 1.09 and for hard wheat at 1.13 was significantly lower than the A:P ratio of 1.45 for barley.
Overall, the organic matter digestibility of both types of wheat was higher than that for barley and was improved by increasing the monensin rate.
Fibre digestibility of barley was 60.6 per cent compared to 46 per cent for both types of wheat with monensin at the low rate. Increasing the monensin level did improve the digestibility of fibre in the wheat kernels.
The digestibility of starch in both wheats at both monensin rates was higher than that for barley.
Type of wheat did come into play when they analyzed carcass traits for the 200 crossbred beef steers in the feedlot part of the trial. The hard wheat/low monensin group finished with the most back fat at 21.7 mm versus the barley group at 19.9 mm. The steers fed the soft wheat/high monensin ration finished with the lowest back fat at 17.5 mm.
Consequently, meat yield was highest at 52.8 per cent for the soft wheat/high monensin group and lowest at 48.9 per cent for the hard wheat/low monensin group. It was near 51 per cent for the two other groups.
While 79.5 per cent of steers fed barley graded Canada AAA, over 87 per cent of those fed wheat graded Canada AAA. The exception was the soft wheat/high monensin group finishing with 77 per cent grading AAA.
Abscessed livers were least prevalent at 33.3 per cent in the barley-fed group, compared to 51.3 per cent in the soft-wheat group and 52.5 per cent in the hard-wheat group. Monensin at the 44-mg rate slightly reduced the occurrence of abscesses to 46.2 per cent of the steers in the soft-white group, but abscesses increased to 67.5 per cent for the hard-wheat group. Severe abscesses ranged from 20 to 23 per cent of steers across all treatments groups.
“So we can say if you feed a higher level of monensin you have potential to increase feed efficiency, but in our case we didn’t find the higher level reduced rumen acidosis,” Yang sums up. “Increasing monensin may be beneficial to improve feed efficiency in the short term, but seems not beneficial to growth performance and carcass quality for the entire finishing period.”
Even though the trial results indicate that wheat could replace barley at levels greater than the current recommended maximum of 50 per cent in feedlot rations without negatively affecting performance or carcass quality, he cautions producers that these were small studies with long adaptation periods of four weeks. While a longer adaptation period when introducing wheat would be a beneficial management practice, he realizes this isn’t the usual practice because of cost in commercial feedlots.
Yang’s presentation on this topic including all of the tables and graphs is available on the Feed Coalition website at feedcoalition.com, or he can be reached at 403-317-3427.