Vitamin E level okay with oxidized DDGS

Vitamin E level okay with oxidized DDGS

*John H. Goihl is president of Agri-Nutrition Services Inc., Shakopee, Minn. To expedite answers to questions concerning this article, please direct inquiries to Feedstuffs, Bottom Line of Nutrition, 5810 W. 78th St., Suite 200, Bloomington, Minn. 55439, or email [email protected]

THE use of corn dried distillers grains with solubles (DDGS) in swine diets has increased in recent years because of its cost competiveness compared to other ingredients, its availability and the better understanding of its nutrient composition.

There have been numerous swine research trials to evaluate the effects of DDGS on pig performance and carcass quality.

Some trials have reported reduced growth performance and carcass quality when swine are fed DDGS at higher inclusion levels (i.e., more than 30%).

There are many potential reasons for this, including anti-nutritional factors, mycotoxins, lower amino acid availability, lower energy content, peroxidized lipids, different ethanol processing procedures or a combination of these.

The issue of peroxidized lipids is of interest because corn DDGS contains approximately 7-10% corn oil, which contains a high concentration of polyunsaturated fatty acids. These are particularly high in linoleic acid, which is vulnerable to lipid peroxidation. Lipid peroxidation is a free radical chain reaction that produces oxidized lipids and a series of toxic aldehydes.

In ethanol production, the drying temperatures and length of drying time used vary from facility to facility. Higher temperatures and longer drying times may accelerate lipid peroxidation by oxidizing unsaturated lipids in DDGS.

Previous research has found that oxidative damage of lipids in animal feed negatively affects pig health and growth performance.

The total sulfur content of DDGS can vary from 0.30% to 0.95% on an as-fed basis because of the variable amount of sulfuric acid used for pH adjustment and clearing of fermenters in the ethanol process.

Sulfur is an essential component in many physiological functions and is incorporated into many amino acids and enzymes.

The effects of feeding DDGS that contains higher levels of sulfur on pig performance and health have not been well documented.

It has been hypothesized that antioxidants may be needed and/or higher levels of vitamin E may need to be supplemented in swine diets containing DDGS to minimize the negative effects of lipid peroxidation.

Researchers R. Song, C. Chen, L. Wang, L.J. Johnston and G.C. Shurson at the University of Minnesota and B.J. Kerr and T.E. Weber of the U.S. Department of Agriculture's Agricultural Research Service conducted a study to evaluate the effects of feeding DDGS with a high content of oxidized lipids on pig growth performance and metabolic oxidation status and also to determine if any of the negative effects could be overcome by increasing the dietary concentrations of vitamin E.

The highly oxidized DDGS source used in this study was selected from among 31 corn DDGS sources. This source contained the greatest thiobarbituric acid reactive substances (TBARS) value of 5.2 ng/mg of oil, a peroxide value of 84.1 mEq/kg of oil and a total sulfur content of 0.95%. The other 30 DDGS sources had mean values of 1.8 ng/mg of oil for TBARS, 11.5 mEq/kg of oil for peroxide value and 0.50% sulfur.

The experiment used 54 weanling pigs with an average initial weight of approximately 7 kg for the eight-week study. After eight weeks, all pigs were transferred to individual metabolism crates for a five-day adaptation period, followed by a three-day total collection of feces and urine and one-time collection of blood samples one hour after the 7 a.m. feeding.

The pigs were assigned randomly to one of six dietary treatments (Table 1), with four pens per treatment and two or three pigs per pen for a total of nine pigs per treatment. All treatments were based on fortified corn/soybean meal diets except that fish meal and whole whey were incorporated into the phase I (7-11 kg) diet and lactose was added to the phase II (11-25 kg) diet. All diets met or exceeded National Research Council nutrient requirements for the various weight ranges.

Pigs were allowed ad libitum access to feed and water during the first eight weeks, and when put into metabolism crates, the pigs were fed at 4% of their bodyweight.

Table 2 summarizes the growth performance data for the eight-week nursery period. The researchers provided the following interpretations of these results:

* No interactions between DDGS and vitamin E were observed for any of the growth performance responses.

* Vitamin E did not affect any of the growth performance criteria.

* Pigs fed DDGS had lower final weights, but overall average daily gain, average daily feed intake and gain:feed were not affected in pigs fed DDGS compared to pigs fed no DDGS.

Table 3 summarizes the effect of DDGS and vitamin E supplementation on TBARS, alpha-tocopherol and sulfur-containing antioxidants. The researchers provided the following interpretations of those results:

* There were no effects of DDGS, vitamin E supplementation or their interaction on TBARS values in serum.

* The interaction between DDGS and vitamin E resulted in a higher serum alpha-tocopherol concentration, but at the highest supplemental vitamin E levels, the serum alpha-tocopherol levels were similar for pigs fed no DDGS and for pigs fed 30% DDGS.

* No effects of DDGS or vitamin E concentration were detected for any of the measured sulfur-containing antioxidants.

* No effect of vitamin E supplementation level was observed for serum sulfur amino acid concentrations.

* The liver glutathione concentration was greater in pigs fed 30% DDGS than in pigs fed no DDGS. Vitamin E supplementation increased liver glutathione concentrations.

* Daily sulfur excretion in the feces and urine was greater, and more sulfur was absorbed and retained in pigs fed DDGS compared to pigs fed no DDGS.

* There was no effect of vitamin E supplementation or any interaction between DDGS and vitamin E level on daily sulfur balance.

The researchers indicated that using peroxide values as the only indicator of lipid peroxidation may not be accurate or sufficient because it is only a measurement of hydroperoxides. Hydroperoxides that are generated by lipid peroxidation begin to decompose as soon as they are formed, which yields a variety of smaller molecular weight compounds. Therefore, a low peroxide value could be due to either minimal oxidation or decomposition of hydroperoxides that has already begun.

Previous research results concluded that a high sulfur content in swine diets containing DDGS may not be the cause of the observed reduced growth performance. However, the elevated concentrations of sulfur-containing antioxidants in vivo may protect pigs against oxidative stress when feeding highly oxidized DDGS.

Therefore, the increased sulfur content in DDGS may be beneficial, and increasing the concentrations of vitamin E in diets may not be necessary to protect pigs against metabolic oxidative stress when feeding high-sulfur/highly peroxidized DDGS.

 

The Bottom Line

The results of this study demonstrated that it may not be necessary to increase vitamin E levels over National Research Council-recommended levels to protect pigs against oxidative stress when feeding highly oxidized lipids and high sulfur DDGS.

Also, the increased sulfur content of DDGS wasn't detrimental to growth performance but may be beneficial against oxidative stress.

 

Reference

J. Anim. Sci. Vol. 91, No. 6.

 

1. Composition of treatment diets

 

 

-Vitamin E, IU/kg-

Treatment

DDGS, %

Phase I (7-11 kg)

Phases II, III (11-50 kg)

1

0

0

2

13.2

11.0

3

132

110

4

30

0

0

5

30

13.2

11.0

6

30

132

110

 

2. Growth performance data

 

-Treatment-

Criteria

1

2

3

4

5

6

Initial bodyweight, kg

6.9

6.9

6.9

7.0

6.9

7.0

Final bodyweight, kg

42.0

41.3

43.8

39.9

39.9

40.0

Avg. daily gain, kg

0.56

0.57

0.59

0.54

0.54

0.54

Avg. daily feed intake, kg

0.99

1.10

1.16

1.07

1.05

1.11

Gain:feed

0.57

0.52

0.51

0.50

0.51

0.49

 

3. Summary of DDGS and vitamin E supplementation on TBARS, alpha-tocopherol and sulfur-containing antioxidants

 

-Treatment-

Criteria

1

2

3

4

5

6

TBARS, microM

3.69

3.54

3.68

3.72

3.63

3.56

Alpha-tocopherol, micrograms/mL

0.42

0.95

3.32

1.60

1.61

3.54

Liver glutathione, mmol/g

35.3

44.6

45.7

50.2

56.4

62.3

Sulfur balance, g/day

 

 

 

 

 

 

Intake

3.13

2.90

3.19

5.57

5.64

5.95

Feces

0.50

0.46

0.48

0.70

0.79

0.76

Urine

0.65

0.40

0.09

1.97

1.95

1.88

Absorbed

2.63

2.44

2.70

4.86

4.84

5.19

Retained

1.90

1.89

2.42

2.78

2.84

3.20

 

Volume:85 Issue:29

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