Nutrient requirements of beef cattle

Starch is the major energy component of grains. Wheat contains 77% of DM as starch, corn and sorghum contain 72%, and barley and oats contain 57 to 58%. In vitro systems have provided valuable data on kinetic aspects of starch digestion. Molecular biological techniques have provided a clearer picture of the ruminal microbial milieu. Proportions of starch fermented in the rumen can be predicted satisfactorily for a variety of grains and processing methods. Compared with dry rolling, steam processing (flaking or rolling) increases ruminal digestibility of starch (percentage of intake) from 52 to 78% for sorghum, from 75 to 85% for corn, and six percentage units or less for other grains. Recent research provides new insight into pancreatic function and intestinal glucose transport systems. The capacity to digest starch in the intestine ranges from 45 to 85% of starch entering the duodenum, with that capacity apparently limited by the supply of pancreatic amylase. There is evidence that amylase secretion may be enhanced by increasing duodenal entry of protein. Capacity for active transport of glucose across of gut wall does not seem to limit the amount of starch digested that is absorbed as glucose. For ruminants eating medium- to high-concentrate diets, about 30% of their total glucose need comes from glucose absorption, 50% from organic acid absorption (substrates for hepatic gluconeogenesis), and 20% from other sources. When glucose absorption from the gut increases, ruminants generally adjust (decrease) gluconeogenesis to meet their need; that need is directly linked to DE intake. In terms of overall ME yield, grain starch is best used when it is fermented in the rumen. However, close coordination of protein and starch supply to the duodenum may improve capture of starch in the form of glucose.

Starch utilization by ruminants: from basics to the bunk.

The ethanol industry is expanding rap- idly. This expansion in production of renewable energy also increases production of by-products. These by- products, primarily distillers grains plus solubles (DGS), are utilized very efficiently by ruminants. When the starch in corn is fermented to produce ethanol, the remaining nutrients (protein, fat, fiber) are concen- trated about 3-fold. Whereas DGS is an excellent pro- tein source for ruminants, the large supply and the price relative to corn make DGS an attractive energy source as well. This is especially important with re- duced availability and higher price of corn because of demand by the ethanol industry. A meta-analysis of 9 experiments, where various levels of wet DGS were fed to feedlot cattle, shows that wet DGS produced higher ADG and G:F compared with cattle fed corn-based diets

/pdf/board-invited-review-use-of-distillers-by-products-in-the-174bma6zwn.pdf

BOARD-INVITED REVIEW: Use of distillers by-products in the beef cattle feeding industry.

Ruminant animals have two metabolic systems that differ in their nutrient requirements: microbial metabolism in the rumen and mammalian metabolism in the tissues. Maximizing or optimizing ruminant productivity involves meeting requirements in proper amounts and balance for both metabolic systems. Ruminant nutritionists formulate diets with an intention of providing the animal with optimal levels of nutrients to achieve the optimal or maximal level of performance. Ideally, most of the dietary constituents should be digested, absorbed and utilized by the tissues as completely as possible. However, in reality, feed components are digested incompletely, more so with feedstuffs fed to ruminants than to non-ruminants. In ruminants, nutrient inputs are subjected first to fermentative digestion by microorganisms and then to glandular digestion by the host. Fermentative digestion is advantageous for substrates that cannot be digested by the host enzymes but is inefficient for digesting proteins, amino acids and sugars, because of losses in energy and nitrogen. Therefore, a proper balance between fermentative and glandular digestion needs to be achieved for optimal productivity.

Manipulation of ruminal fermentation

Five trials investigated the feeding value of wet and dried corn distillers byproducts as a source of protein and energy for growing and finishing cattle and investigated the effect of heat damage on the feeding value of dried distillers byproducts. In a calf growth trial, no differences in rate of gain or protein efficiency were observed among calves fed wet distillers byproducts (wet distillers grains + thin stillage; WDB) or one of three composites of dried distillers grains + solubles (DDGS) having a low, medium, or high concentration of ADIN. A finishing trial compared the energy value of dry-rolled corn (DRC) with WDB or the three DDGS composites, fed at 40% of the diet DM replacing DRC. Cattle consuming WDB or DDGS gained faster ( P .lo). In a lamb finishing trial, the addition of 5 or 10% ethanol did not affect (P > .lo) daily gain, DMI, or feed efficiency. In two metabolism trials with steers, grain byproducts (wet distillers grains, dry distillers grains plus solubles, wet corn gluten feed, dry corn gluten feed, hominy feed) and DRC had similar effects on ruminal pH and total VFA. Feeding thin stillage or condensed solubles reduced (P < .lo) ruminal pH and tended to reduce acetate:propionate. Wet corn distillers byproducts, fed at 40% of the diet DM, contain more NE, than did DRC and drying WDB reduces its NE, content. Acid detergent insoluble N is a poor indicator of protein and energy value in distillers grains.

http://www.ddgs.umn.edu/sites/biodieselfeeds.cfans.umn.edu/files/cfans_asset_416532.pdf

Wet corn distillers byproducts compared with dried corn distillers grains with solubles as a source of protein and energy for ruminants.

Yearling and calf finishing trials (replicated over 2 yr) evaluated the feeding value of wet distillers byproducts (wet distillers grains and thin stillage). An additional trial estimated the amount of thin stillage bypassing the rumen when consumed by drinking. Yearlings were 5, 10, and 20% more efficient (linear, P < .01; quadratic, P = .05), whereas calves were 2, 6, and 14% more efficient (linear, P < .01) when fed 5.2, 12.6, and 40.0% (DM basis) wet distillers byproducts, respectively, compared with cattle fed a 79% dry-rolled corn diet. Cattle fed 5.2 or 12.6% wet distillers byproducts, or the dry-rolled corn diet, received similar amounts of protein (crude or metabolizable), which exceeded the metabolizable protein requirement of all cattle. Therefore, differences in efficiency were attributed to differences in energy utilization of the diets. Wet distillers byproducts fed at 5.2, 12.6 and 40.0% contributed 80, 62, and 47% more net energy for gain than corn when fed to yearlings and 17, 33, and 29% more net energy for gain than corn when fed to calves, respectively. Wet distillers byproducts averaged 169% the energy value of corn (2.53 Mcal of NEg/kg) when fed to yearlings and 128% the energy value of corn (1.96 Mcal of NEg/kg) when fed to calves. The increased energy values cannot be explained by increased digestibility, but they may be due to a combination of factors (reduced acidosis, increased energy utilization, yeast end products, etc.) that increase the net energy content of distillers byproducts. Approximately 50% of the thin stillage consumed by drinking bypassed ruminal fermentation.(ABSTRACT TRUNCATED AT 250 WORDS)

https://www.biofuelscoproducts.umn.edu/sites/biodieselfeeds.cfans.umn.edu/files/cfans_asset_413508.pdf

Feeding value of wet distillers byproducts for finishing ruminants.

A trial involving four commercial feedlots and an individual feeding trial evaluated the effect of monensin and monensin/tylosin on intake variation and deaths from digestive disorders. Four commercial feedlots in Texas and Colorado fed 2,904 yearling crossbred steers (340 kg) high-grain diets containing approximately 82% grain, 8% silage and alfalfa hay, 4% fat, and 6% supplement (DM basis). Steers were allotted randomly to one of three monensin/tylosin levels: 1) no monensin or tylosin (control); 2) 22 mg/kg of monensin and 11 mg/kg of tylosin; or 3) 33 mg/kg of monensin and 11 mg/kg of tylosin. Monensin/tylosin reduced DMI (P < .05) and improved ADG (P < .05) and feed efficiency (P < .01). Intake variation associated with dry matter offered per pen was not different among treatments. In the individual feeding trial, feeding 27 mg/kg of monensin reduced (P < .10) DMI variation during grain adaptation and during d 57 to 70 and d 97 to 110 compared with the control (no monensin) diet. The magnitude of intake variance was 5 to 10 times greater with individually fed steers than with steers fed in the commercial feedlot pens. When the DMI of the individually fed steers were averaged and treated as a pen of steers, DMI variance was reduced drastically and was not different between treatments. We interpret these data to indicate that monensin and monensin/tylosin reduce feed intake variation among individual steers within a pen of steers. Pen means mask individual animal variation to the point that it is difficult to detect treatment differences.

Effect of monensin and monensin and tylosin combination on feed intake variation of feedlot steers.

Three trials were conducted to evaluate the energy value of hominy feed in finishing diets for ruminants. Hominy feed contained 56.9% starch, 25.2% NDF, 11.1% CP, and 5.3% fat (DM basis). In all trials, hominy feed replaced dry-rolled corn. As the level of hominy feed or ground corn increased in a lamb digestion trial, DM digestibility decreased (P < .01); however, starch digestibility increased (P = .09). Hominy feed and ground corn interacted (linear, P = .08) with respect to NDF digestibility. As the level of ground corn increased, NDF digestibility decreased (linear, P = .10). In a finishing trial, yearling heifers were fed either hominy feed with or without fat added to hominy feed at 0, 13.3 (.67% added fat), 26.7 (1.33% added fat), and 40.0% (2.0% added fat) of diet DM. Fat addition did not interact with hominy feed level. Heifers fed 13.3 or 26.7% hominy feed or hominy feed + fat consumed more DM (P = .10) than heifers fed the 0 or 40.0% diets; however, gain and feed efficiency were similar. In a second finishing trial, steers fed 40% (diet DM) hominy feed consumed more (P = .05) DM, but daily gain and feed efficiency were similar to those of cattle fed dry-rolled corn. Steers fed all-concentrate diets were more efficient (P < .01) than cattle fed 7.5% forage. Results indicated that expeller-extracted hominy feed contained 1.35 Mcal of NEg/kg, or 87% of the energy of corn, when included at levels up to 40% of cattle finishing diets, despite its containing 20% less starch than corn.

E. M. Larson

Papers

Wet corn distillers byproducts compared with dried corn distillers grains with solubles as a source of protein and energy for ruminants.

Feeding value of wet distillers byproducts for finishing ruminants.

Effect of monensin and monensin and tylosin combination on feed intake variation of feedlot steers.

Energy value of hominy feed for finishing ruminants.