Adding calcium oxide directly to a feed mix at a rate of 0.8-1.6% made the distiller grains less acidic, more digestible and more nutritious, leading to better growth performance in beef cattle, the Purdue University researchers found.
Distiller grains - a relatively inexpensive and plentiful bi-product of ethanol production - are used as an alternative energy and protein source to corn in cattle diets. However, to maintain optimal performance, distiller grains are typically limited to inclusion rates of less than 30% of the diet.
Previous research has demonstrated that that acidity of distiller grains, from the sulphuric acid used to control the starch fermentation during ethanol production, may play a primary role in reducing intake and growth rates when inclusion exceeds 30%. Therefore, if this acidity can be neutralized, it might become feasible to increase thier inclusion in beef cattle diets.
“We hypothesized that increasing dietary calcium oxide inclusion would decrease feed acidity and consequently increase ruminal pH, thus improving nutrient digestibility, ruminal fermentation and performance of beef cattle fed diets containing 60% dried distiller grains,” wrote the researchers in the Journal of Animal Science.
Two experiments were conducted to determine the effect of increasing dietary calcium oxide on ruminal fermentation, diet digestibility, performance and carcass characteristics.
In the first experiment, 112 cows were divided into four groups and given feed containing 60% distillers grains, dry rolled corn, a vitamin and mineral
supplement and calcium oxide at 0%, 0.8%, 1.6% or 2.4% of total dry matter.
The second experiment was a digestibility study with four animals. Each animal was given each of the four diets for four different periods, rumen pH was measured and urine and fecal samples were analyzed to establish digestibility.
0.8-1.6% calcium oxide is optimal
The groups that were fed distiller grains with 0.8 and 1.6% calcium oxide performed better than the other test cattle, consuming less feed while maintaining a steady 5% increase in body weight.
“Increasing concentrations of calcium oxide added to the diet stabilizes ruminal pH, improves fiber digestibility and improves metabolic acid-base balance of cattle fed 60% distiller grains,” they said.
They did, however, point out that feeding calcium oxide at higher concentrations may decrease palatability and reduce intake, resulting in no improvement in average daily gain.
Interestingly, these results had less to do with the calcium oxide bringing about an increase in ruminal pH and more to do with its effect on the pattern of pH change.
“Calcium oxide slows down the decrease in pH, which increases fiber digestibility, making the energy more available. That is why they gain better,” explained Purdue University scientist Jon Schoonmaker.
He told FeedNavigator the team was investigating other ways of changing the pH of distiller grains, for example through the addition of fiber ingredients such as soya bean hulls, or with other alkalines, such as calcium hydroxide.
Source: Journal of Animal Science
Date: September 2014 vol. 92 no. 9 3954-3965, doi:10.2527/jas.2013-S7501J
Title: Effect of calcium oxide inclusion in beef feedlot diets containing 60% dried distiller grains with solubles on ruminal fermentation, diet digestibility, performance, and carcass characteristics.
Authors: AJC Nunez, TL Felix, RP Lemenager, JP Schoonmaker