Looking toward a future of dwindling corn supplies: feeding North American dairy cattle

Distillers grains (DG) are raising questions and concerns on North American dairy farms as corn grain prices continue to increase. Corn grain has three major alternatives for expanded or continued use (Lyons, 2006):

• Food for human consumption or human products
• Fuel as a source of stable and renewable ethanol
• Feed for livestock use

Monogastric animals will have greater challenges until technology allows great inclusion of DG in swine and poultry rations. Ruminant animals have the ability to convert forages and fibrous by-products such as DG to energy and protein resources. In 2005, nearly 13% of the US grain crop was committed to ethanol production. USDA estimated that 20% of the 10.53 billion bushel 2006 US corn crop will be used for ethanol production with July 2007 settling at $4.14 a bushel and soybeans at $7.43 a bushel (Levitt, 2007).

One key question is the amount of soybean acreage that will be switched to corn acreage by grain producers. In central Illinois, the cost to raise one acre of corn in 2007 was projected at $416, yielding 180 bushels of corn, and resulting in a profit margin of $118 to $271 per acre. Soybean projections were $301 per acre with a 55 bushel yield and a potential profit of $5 to $94 per acre (Schaumburg, 2007; Schingoethe, 2006). Prices and profit vary depending on corn-on-corn systems compared to rotation systems and fuel and chemical costs.

Other factors affecting corn prices include oil prices, soybean yields and prices in South America, government taxing subsidy of ethanol at the fuel pump, the future role of cellulose (fiber) as a carbon source for ethanol production, and the continued tariff on foreign ethanol of $0.54 per gallon. This paper will focus on dairy farm strategies with high price corn and the role of DG.


Dairy manager’s dilemma: high corn prices

As corn prices passed $3.50 per bushel, feed cost increased over $0.80 per 45 kg (100 lb) while milk price slowly increased. In 2007, milk price will need to increase $1.00 per 45 kg (100 lb) to cover higher corn grain and silage costs.

Dairy nutritionists recommend 24-26% total starch in the ration dry matter with a range from 18 to 32% reported in the field. Starch or rumen fermentable carbohydrate is critical to optimize rumen microbial fermentation, maintain microbial amino acid production (can supply over 60% of amino acid needs), and produce over 80% of energy for high producing cows. Several strategies can be considered by dairy managers when corn grain prices are high.


STRATEGY 1. REDUCE STARCH LEVEL

If the target level is 25% starch for high producing cows, can starch levels be lowered by 1 to 5 percentage points while maintaining performance? The key factor is to evaluate the level and rate of fermentable carbohydrate that is currently available including forage quality, dry matter intake, digestibility of neutral detergent fiber (NDF), availability of starch for rumen fermentation and lower gut enzymatic digestion, rate of passage, use of monensin (an ionophore), and complementary aspects of other feed ingredients.

Each herd may have a different starch optimal level that can be lowered. If a dairy nutritionist decides to lower starch levels, the signs of ‘cheating’ starch levels (too low) are listed below.

• Decline in peak milk production
• Lower milk yield in the herd in general, especially early lactation cows
• Drop in milk protein test and yield (drop in microbial amino acid yield)
• Lower milk fat test (less rumen volatile fatty acids)
• Increase in milk urea nitrogen (MUN) by more than 3 mg/dL from the herd’s normal baseline value
• Increase in manure scores over 3.5 (stiffer manure)
• Decline in dry matter intake
• Thinner cows (less energy available)
• Lack of response to bovine somatotropin (BST)

STRATEGY 2. INCREASE CURRENT STARCH AVAILABILITY IN THE RUMEN

Plant processing of corn silage can reduce the passage of partial or whole kernels of corn allowing for improved rumen fermentation of starch. The corn is also reduced in particle size increasing surface area for microbial fermentation of fiber. Guidelines for plant processing are chopping at 18 cm (0.75 in) theoretical length of chop with 2-3 mm openings between rollers. The processed corn silage should have 10-15% on the top box of the Penn State Particle Size Box, over 50% in the second box, and less than 35% in the bottom two boxes (all values expressed on a wet or as-is basis).

Processing corn grain to an optimal particle size, heat treatment, or high moisture content can increase rumen fermentation and availability. Table 1 lists the energy values of corn with different processed corn grain (NRC, 1989). Table 2 illustrates the impact of three different particle sizes of corn grain on milk performance and rumen parameters (Hutjens and Dann, 2000). Finely processed corn (1100 μm), stream flaking, and high moisture corn (over 25% moisture) can increase energy content and rumen fermentation.










Optimizing rumen fermentation can improve total starch and ration digestibility. Favorable rumen pH (over 5.8), microbial volatile fatty acids (VFA) pattern (over 2.2 parts rumen acetate to 1 part propionate), and low levels of lactic acid can improve microbial yield and cow performance. Use of rumen buffers (0.75% sodium bicarbonate), yeast culture, direct fed microbials, mycotoxin binders, and ionophores can be beneficial.


STRATEGY 3. REDUCE FECAL STARCH LOSSES

Starch levels in manure can vary from 5 to 20% of dietary starch. Fecal starch losses could occur for two general factors.

Factor 1 could be the physical presence of corn starch in fecal droppings due to improper processing of corn grain or corn silage. Proper plant processing of corn silage, ensiling at the proper dry matter level (28-33% for bunker silos, piles, or bags; 33-36% percent for tower silos, and 35-40% for oxygen limiting structures), and selection of softer textured corn grain can be considered.

Factor 2 could be the chemical presence of starch related to poor rumen fermentation. Adjusting rate of passage to allow adequate time for rumen fermentation and optimal rumen fermentation environment, and avoiding rumen acidosis could improve this aspect of chemical starch loss.

Data in Table 3 were collected from early lactation cows (less than 60 days in milk) fed the same ration and in the same environmental onditions at the University of Illinois. Free manure samples were sent to a lab to determine pH and starch content. Fecal starch levels were not statistically related to dry matter intake, milk yield, or days in milk. Multiple samples over three weeks did not indicate cow changes as cows progressed in early lactation. Rumen pH and starch were correlated. While the results were interesting, analyzing fecal starch content remains variable and is not routinely used in the field.






STRATEGY 4. CONSIDER STARCH ALTERNATIVES

As corn prices increase, other feed ingredients can be economically attractive in replacing corn grain. Table 4 lists typical starch and sugar content of feed ingredients. Sugar can replace starch, but dairy managers must consider the rate of fermentation and limit the total level of sugar to 4-6%. Nutritionists recommend 24-26% starch and 4-6% sugar (without substituting sugar for starch).






The take-home points when evaluating the strategies with higher price corn or starch with high producing cows are outlined below.

• Cows can convert 1 lb (0.45 kg) of dry matter (valued at $0.07-$0.08 per 0.45 kg or 1 lb) to 1 kg (2-2.5 lb) of milk valued at $0.28 to $0.35.
• Feed additives such as buffers, yeast culture, direct-fed microbes, mycotoxin binders, and ionophores that can improve rumen health and environment will enhance nutrients derived from microbial fermentation.
• Never reduce rumen fermentation below optimal levels.

Dairy manager’s dilemma: corn distillers grains

Corn DG continues to increase in availability while prices depend on competition in the area, alternative feeds, wet vs. dry corn distillers, and the price of corn grain. Several guidelines should be considered when adding DG to the feeding program.

• Corn DG is a protein source for dairy cattle, not corn grain.
• The recommended levels are 10-20% of the total ration dry matter for high producing cows (Table 5). Distillers grains are a source of rumen undegraded protein (RUP) and should be positioned to replace other protein sources in the ration. One approach is to blend 50% soybean meal and 50% DG. For older heifers, dry cows, and low producing cows, DG could be the only source of supplemental protein.
  
  

• Several factors will determine the risk of feeding too much DG as dairy managers report drops in milk fat test of 0.3 point or more (for example from 3.8 to 3.5%). A lack of functional or total fiber, too much starch, high levels of unsaturated fatty acids, and/or ionophores can lead to lower fat tests (Schingoethe, 2006).
• Quality of DG is critical. Risks that must be managed include the presence of mycotoxins in the original corn used, level of solubles added back, color of the DG (indication of heat damage), and storage of wet DG.
• Nutrient variation of DG can be large, as corn nutrient content will be reflected in DG, amount of solubles added back, and processing effects.

With continued efforts to market DG, ethanol plant managers are refining their methods by extracting more starch for ethanol production. Another approach is to determine if more value can be derived from DG while providing feeds that can fit in modern dairy rations at higher levels. A new process in ethanol plants can result in several new corn by-products and does not use supplemental sulfur dioxide (can affect feed palatability and cause corrosion). Table 6 lists several potential new products including corn germ, corn bran, modified corn gluten meal, and modified distillers dried grains (DDG) compared to ‘typical DDG’, listed for comparison.






Corn germ could be a premium product that may be sold to corn oil processors. It contains a significant amount of phosphorus. Biodiesel could be an alternative use for the corn oil.

Corn bran is a feed that ruminants could ferment and digest (similar to citrus or beet pulp). For dairy producers, this product could be used to replace lower quality forages, soy hulls, and/or dilute starch found in corn silage-based dairy rations.

Modified corn gluten meal is more applicable as swine and poultry feed (source of pigmentation). The energy content is similar to high protein soybean meal, but it is not high in fiber, which is important for swine and poultry rations.

Modified DDG would be similar to typical DDG, but lower in oil that can cause rumen fermentation challenges and lower milk fat test. For dairy managers, this product may allow for higher levels of inclusion compared to typical DDG.

As modified ethanol production plants come on-line, dairy and beef managers must carefully consider which corn by-products are available, the break-even prices of each product, and the strategy needed to balance rations with each corn product used. New corn co-products will be valuable tools for dairy nutritionists and managers for the following reasons:

• Lower levels of oil will allow higher inclusion levels.
• Less phosphorus may allow higher manure application rates avoiding high soil levels of phosphorus.
• New co-products contain digestible fiber that is lower in protein compared to typical DDG.

Summary

DG levels while controlling feed costs and increasing nutrient availability. Additives such as yeast culture that can enhance starch fermentation in the rumen and stabilize the rumen environment would be strategically important. Increasing fiber digestion using enzymes and/or direct fed microbes would increase rumen VFA yields while not increasing starch levels. Dairy ration formulation in the future will focus on high digestible forage/fiber sources in diets while optimizing milk yield, milk components, and cow health.


References

Hutjens, M.F. and H.M. Dann. 2000. Grain processing: is it too coarse or too fine? http://www.livestocktrail.uiuc.edu/dairynet/paperDisplay.cfm?ContentID=588.

Kalscheur, K.F. 2005. Impact of feeding distillers grains on milk fat, protein, and yield. Proc. Distillers Grain Tech Council, 9th Annual Symp., May18-19, Louisville, KY, USA.

Levitt, A. 2007. Major milk move. Daily Dairy Report 11(8), Jan 12, http:// www.dailydairyreport.com.

Lohrmann, T. 2006. Rethinking ethanol co-products. Distillers Grain Quarterly. Fourth Quarter, p. 23.

Lyons, T.P. 2006. The grain and sugar devouring ethanol industry: the competition for food, feed, and fuel. Distillers Grain Forum Conference Proc., Oct 23, Nicholasville, KY, USA, p. 1.

Meier, B.J., M. Hutjens, H.M. Dann and R.D. Shanks. 2004. Manure evaluation field study. Illinois Dairy Report, pp. 24-25.

National Research Council. 1989. Nutrient Requirements for Dairy Cattle. 6th rev. ed Natl. Acad. Sci. Washington, DC.

Schaumburg, B. 2007. Midwest express: corn is king. Farm Futures, p. 11.

Schingoethe, D.J. 2006. Can we feed more distillers grain? Tri-State Dairy Nutrition Conf. Proc., April 25-26, Fort Wayne, IN, USA, p. 71.