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Animal Science 4332

Ruminant Nutrition

By-product feedstuffs

Feed costs represent the greatest proportion of a beef cattle enterprise. Producers must strive to efficiently utilize available resources while optimizing animal performance and minimizing cost. When cattle graze marginal to low quality forages, supplemental protein and/or energy is required to enhance either the utilization of forage or animal performance. By-products have an opportunity to reduce the cost of supplementation while maintaining or improving animal performance. The following co-products have been effective as feed ingredients in a number of situations. These by-products have been developed as a result of processing a traditional feed ingredient to generate another product.

Corn gluten feed- is a by-product of corn wet milling which produces high fructose corn syrup. A kernel of corn has 5 primary constituents: starch, gluten, hull, water, and germ. Corn gluten feed is that portion of the corn kernel that remains after extraction of starch, gluten and germ. The major constituent in CGF is the hull or bran, along with the gluten, protein.

Dried distillers grains- Dried distillers grains (DDG) are by-products of the distilling industry, in which grains are fermented into alcohol. The spend grains are dried and sold as feedstuffs primarily used in ruminant diets. Solubles remaining from fermentation usually are added to the grains before drying resulting in a product called distillers dried grains with solubles. Distillers' grains are identified from the type of grain from which they are made (corn distillers, milo distillers etc.) distillers' grains contain 25 to 30 5 CP and 10 to 12 % fat.

Soybean hulls-soyhulls are generated from the rolled or cracking of soybeans into small pieces so that hulls can be removed. Soyhulls are separated from the cracked seeds by an air stream, and seeds are extracted with hexane to remove oil, leaving high protein bean meal (48 %). Next, the soyhulls pass through a toaster to destroy the unease activity. Finally, the hulls are ground to the desired particle size and stored to be added back to the $ bean meal or shipped as soyhulls. Soyhulls contain approximately 12 to 14 % CP. They are an excellent energy source in the form of digestible fiber.

Wheat Midds-Approximately 25 % of total wheat milled is left as a byproduct, and termed wheat middlings or mill feed. This by-product feed has been used in ruminant diets and is widely used in commercial supplements as a protein and energy source. Wheat midds tends to vary in nutrient composition due to the varying amount of flour starch. The CP content of wheat midds is 15 to 19 % and energy is in the form of fiber and starch.

By-products are being used as energy and protein supplements for growing cattle as well as cows. In these situations, supplemented to moderate to low quality forage or where forage availability is limiting.

Advantages include:

Excellent energy and protein source

Less risk of digestive upset due to over consumption

Need to look at mineral differences

Disadvantages:

Storage and handling can be a problem. Producer must take these in bulk form, semi-trailer delivery, and must have storage and handling facilities.

Product variability

Season product

Thiamin deficiency in the rumen with wet corn gluten feed due to high sulfur content.

The nutrient composition of these by-products (% of DM)

Feed

CP

RDP

NDF

Fat

Corn

10

35

-

4

CGF

25

70-80

51

5

DDG

25

40-60

33

11

SH

12

-

73

2

WM

18

60-80

37

3

The composition of the by-products suggests that the protein is more degradable than corn, while the NDF in these by-products is also higher than corn. The DDG is the best source of fat. One must take the nutrients into consideration when balancing a diet with these co-products.

Performance of steers receiving fescue hay supplemented with corn, SH, or wheat midds

Item

Control

Corn

SH

WM

Hay DM intake (%BW)

2.1

1.8

1.9

1.8

Sup. DM intake (% BW)

0

.7

.7

.7

ADG, lbs

.66

1.3

1.5

1.5

Feed cost/lb gain

$.42

$.31

$.28

$.28

Crawford and Garner, 1993, J.An.Sci. 71 suppl.1, p. 185

Fescue hay valued at $45 per ton, corn, SH and WM valued at $80 per ton

The use of the by-products as a source of energy for steers fed fescue hay revealed that they are better than corn as replacement for energy. One must keep in mind that SH and WM also have more degradable CP than corn. In terms of cost per unit of gain, all three supplements have better cost of gains than no supplement but the by-products are also cheaper than corn.

The addition of by-product feeds, like soyhulls or corn gluten feed, have advantages as a supplement to high roughage, low energy diets as compared to using corn grain. When comparing Wet and Dry corn gluten feed for beef cattle in grass hay, the supplement did not depress hay intake or reduce fiber digestibility. The protein quality of corn gluten feed has been compared to soybean meal and found that it is almost equivalent to soybean meal as a protein source for growing cattle. Wet corn gluten feed was superior to dry corn gluten feed in a corn silage based diet. Wet corn gluten feed was superior to dry corn gluten feed when diets contained less than 70 % corn silage. Digestibility of DM and NDF are 5-10 percent higher in diets containing wet corn gluten feed as compared to dry corn gluten feed. Explanation may be: Particle size differences; effect of particle size on fiber digestion in the rumen; Particle size of wet corn gluten feed is larger than dry corn gluten feed. Generally particles smaller than about 1 mm are not retained in the rumen.

Energy value relative corn

 

Level of corn silage

WCGF

DCGF

Low silage diet

10%

95% of C

86% of C

Medium silage diet

40%

95% of C

92% of C

High silage diet

70%

102% of C

102% of C

As corn silage in diet increases, the energy value of CGF relative to corn increases. This may be attributed to the negative associative effects of corn on fiber digestibility.

A similar relationship has been established for brome hay diets with supplemental soyhulls and corn. Addition of soyhulls improved ruminal and total tract digestibility. The addition of .21 % BW corn with .42 % BW SH further increased ruminal digestibility. Feeding .63 % BW corn decreased ruminal digestibility.

Substituting corn at .2 % BW for soybean hull for energy had no negative effects on forage utilization. Thus the inclusion of soyhulls at low inclusion rates in high forage diet (> 50 % forage) for beef cattle resulted in similar energy value to that of corn.

The inclusion of soyhulls in high concentrate diets resulted in a feeding value of 74 to 80 of that of corn. The use of soyhulls at a level of > 20 5 diet dry matter in concentrate based diets will be dictated by the cost of soyhulls relative to cereal grains. The criteria utilized to evaluate the relative feed value will be gain, intake, and feed efficiency.

Distillers' grains in diets for beef cattle are a good source of protein, energy, and phosphorus. They have the potential for meeting a major portion of beef cattle requirements for these nutrients. They contain, however, less than the required amounts of calcium and potassium. Based on considerable research studies, wet distillers' corn grains alone or in combination with urea are equal in value to soybean meal or corn gluten meal in supplying total supplemental protein requirements for growing and finishing beef cattle. The only exception to this relationship was the results for sorghum stillage in which it was inferior to soybean meal. In summary of several studies, the addition of 50 % wet distillers' grains in a finishing for 680 lb steers resulted in 10 % improvement in gain and feed efficiency of steers as compared to those fed a corn diet. These studies suggested that wet distillers' grains could replace half of the corn or milo in finishing diets.