NUTRITIONAL VALUE AND ENVIRONMENTAL

IMPLICATIONS OF DEGERMED, DEHULLED CORN FOR SWINE

 

A.J. Moeser, I.B. Kim, E. van Heugten, and T. van Kempen

 

Summary

Three experiments were designed to assess the feeding value and potential environmental benefits of feeding a low fiber by-product originating from the corn dry milling process, degermed, dehulled corn, to pigs.  Results from these trials suggest that corn processed to remove poorly digestible fiber fractions provides more digestible nutrients than corn grain.  As a result, degermed, dehulled corn improves feed efficiency and reduces fecal and N excretion.

 

Introduction

Dietary fiber negatively impacts energy and nutrient utilization by swine and as a consequence, increases waste production and nutrient excretion (Shi and Noblet., 1994; Davidson and McDonald, 1998; Canh et. al., 1998).  Although the fiber content in a standard U.S. corn-soybean meal diet is considered to be relatively low (approximately 9% NDF), any means to further reduce this fiber would improve the overall nutritional value of the diet.  Corn, due to its high inclusion level in swine diets, contributes approximately 70% of the dietary fiber content in a typical corn-soybean meal diet.  The fiber in the corn kernel, as with most other cereal grains, is predominantly located in the hull and germ fractions of the kernel.  The hull fraction makes up approximately 5% of the total kernel weight and contributes 51% of the total kernel fiber while the germ fraction makes up 11% of the kernel weight and contributes 16% of the total kernel fiber (Watson, 1987).  Therefore, removal of these fiber-rich corn fractions should have a significant impact on the nutrient composition of corn and potentially enhance the nutritional value of corn. 

 

Degermed, dehulled corn is a product of the corn dry milling processes in which the germ and hull fraction of the kernel have been removed thus yielding a potential low-fiber swine feed ingredient.  The objectives of this research were to assess the nutritional value of degermed, dehulled corn and its impact on environmental pollution.

 

Materials and Methods

Experiment 1: Twelve crossbred barrows with an initial average body weight of 27± 8 kg were used to determine the apparent fecal digestibility and balance of energy and nitrogen (N) in degermed, dehulled corn compared to corn grain.  Two diets were formulated to contain either 96.4% corn grain (control) or degermed, dehulled corn and 3.4% vitamins and minerals (Table 1).  Vitamins and minerals were supplied to meet or exceed requirements for 20-40 kg pigs (NRC, 1998). Pigs were fed experimental diets twice daily (0800 and 1500) in mash form at a feeding level equal to 90 g/kg body weight^.75.  The metabolism study consisted of two 9-day periods, each including a 5-day dietary adaptation period followed by a 4-day quantitative collection of feces and urine.  Feces were collected twice daily, weighed, and pooled for individual pig and stored at -20° C until subsequent sample preparation for chemical analysis.  Urine was collected daily in plastic buckets to which 10 mL of sulfuric acid was added.  Urine volume was measured daily, composited and stored at -20° C until subsequent chemical analyses.

 

Experiment 2: Eight crossbred barrows with an initial average body weight of 75 kg, surgically fitted with simple-T ileal cannulae, were used to measure the ileal digestibility of DM, energy, and amino acids in degermed, dehulled corn compared to corn grain. Diets and feeding procedures were identical to those described in Experiment 1 except that .3% chromic oxide was added as an inert digestibility marker.  The experiment was conducted according to a cross-over design that consisted of two 7-day periods each with a 5-day dietary adaptation period followed by a 2-day collection period.

 

Table 1. Ingredients used in Experiments 1 and 2 (g/kg).

 

Ingredient	Diet
	Corn grain control	Degermed, dehulled corn
Corn grain	964	-
Degermed, dehulled corn	-	964
Dicalcium phosphate	25.0	25.0
Calcium carbonate	5.0	5.0
Salt	3.5	3.5
Vitamin/mineral premixa	2.5	2.5
aContributed the following nutrients per kg of diet: 0.3 mg selenium as sodium selenite, 110 mg zinc as zinc oxide, 1,875 IU vitamin A as vitamin A acetate in gelatin, 1,375 IU Vitamin D3, 22 IU Vitamin E as menadione sodium bisulfate, 0.25 mg calcium as calcium carbonate, 22 mg copper as copper sulfate, 110 mg iron as iron sulfate, 110 mg zinc as zinc oxide, 55 mg manganese as manganous oxide, 0.3 mg iodine as ethylendiamine dyhydroiodide, 165 mg choline as choline chloride, 22 mg niacin, 17.6 mg pantothenic acid as d-calcium pantothenate, .02 mg vitamin B12, 4.4 mg riboflavin.

 

Experiment 3:  Ninety six nursery pigs (48 barrows and 48 gilts) of approximately 8.8 ± .001 kg were used to evaluate the impact of dietary inclusion of degermed, dehulled corn in nursery pig diets on growth performance. Diets were formulated to contain either degermed, dehulled corn or corn grain as the major grain source equal to 56.2 and 58.5% of the diet, respectively.  Diets were formulated to contain identical ME and  ileal digestibility values for degermed, dehulled corn measured in Experiments 1 and 2  (Table 2).  Body weight and feed disappearance were measured on days 7, 14, 21, and 28 of the 4-week growth performance trial.

 

Table 2. Performance of pigs fed diets containing corn grain or degermed, dehulled corn in Experiment 3

 

 

Results and Discussion

Digestibility and Retention of Dietary Nutrients: Fecal digestibility of DM and energy was greater by 6 and 7% respectively, in degermed, dehulled corn compared to corn grain (Figure 1).  Improvements in the digestibility (by 29%) and retention (by 24%) of N was observed in degermed, dehulled corn compared to corn grain (P <.001).  It is noteworthy that the retention values were surprisingly high in both of the corn grain and degermed, dehulled corn diets given that each diet contained 96.4% of either corn or degermed, dehulled corn and therefore were not formulated to meet the essential amino acid requirements of grower pigs.  These high retention values may well be a result of excessive N loss during the collection of urine.  Nevertheless, retention values for corn grain are similar to data presented by Adeola and Bajjalieh (1997) and indicate that the utilization of N in degermed, dehulled corn is superior compared to corn grain.

Figure 1. Total tract digestibility of nutrients in degermed, dehulled corn

 

In line with our data on apparent fecal digestibility, ileal digestibility of DM and energy digestibility were 11 and 13% greater (P < .01), respectively, in degermed, dehulled corn compared to corn grain (Figure 2).  A 7% improvement in ileal crude protein digestibility of degermed, dehulled corn compared to corn grain was observed (P < .01).  True ileal digestibility of essential amino acids was greater in degermed, dehulled corn compared to corn grain (P < .05).  The greatest improvement was in the first limiting amino acid for swine, lysine, in which a 10% improvement in the true ileal digestibility of degermed, dehulled corn over corn grain was observed.  However, the net result was that degermed, dehulled corn and corn grain yielded approximately 1.5 and 2.1 grams of available lysine per kg of DM intake, respectively (data not shown).  Practically, this implies that additional lysine will have to be supplied to overcome this difference when formulating degermed, dehulled corn into swine diets.

 

The Effects of Degermed, Dehulled Corn on Animal Performance: Inclusion of degermed, dehulled corn as the major grain source in nursery pig diets had no effect on average daily gain (Table 2).  However, pigs fed the degermed, dehulled corn diet tended to consume less feed than pigs fed the control (P = .09) resulting in a 4% improvement in gain to feed (P < .05). 

 

Figure 2. True ileal digestibility of nutrients in degermed, dehulled corn in experiment 2

 

Degermed, Dehulled Corn and Environment Pollution: In Experiment 1, feeding degermed, dehulled corn to pigs resulted in a 67% reduction in fecal production compared to feeding corn grain (P < .001).  Also, a 29% reduction in N excretion (as % of N intake) was observed in pigs fed degermed, dehulled corn compared to corn grain (P < .001).  Feeding degermed, dehulled corn to pigs may also have a beneficial effect on odor production.  Data on ileal digestibility (Figure 2) suggests that pigs fed degermed, dehulled corn will have 45% less DM material entering into the cecum and large intestine of the pig.  Given that the production of malodorous compounds in swine feces is predominantly a result of the fermentation of undigested feed residues in the large intestine (Mackie et al., 1998), these data suggests that feeding degermed, dehulled corn to pigs has the potential to reduce odor emissions.

 

Implications

Results from this study suggest that processing corn to remove poorly digestible fiber fractions significantly improves the digestibility and retention of energy and nitrogen.  In addition, reductions in dietary fiber content via addition of degermed, dehulled corn to pig nursery diets improves feed efficiency by 4%.  The use of degermed, dehulled corn in pig diets has potential to greatly reduce fecal and nitrogen excretion thus providing a novel approach to reduce the negative environmental impacts of intensive pig production.

 

References

Adeola, O., and N.L. Bajjalieh. 1997. Energy concentration of high-oil corn varieties for pigs. J. Anim. Sci. 75: 430-436.

Canh, T.T., A.L. Sutton, A.J.A. Aarnink, M.W.A. Verstegen, J.W. Schrama, and G.C.M. Bakker. 1998. Dietary carbohydrates alter the fecal composition and pH and the ammonia emission from slurry of growing pigs. J. Anim. Sci. 76: 1887-1895.

Davidson, M.H., and A. McDonald. 1998. Fiber: Forms and functions. Nutr. Res. 18:617-624.

Watson, S.A. 1987. Chapter 3. Structure and Composition. In: S.A. Watson and P.E. Ramstad (Eds.). Corn: Chemistry and Technology. pp. 53-82. American Association of Cereal Chemists, Inc. St. Paul, MN.

National Research.Council. 1998. Nutrient Requirements of Swine (9^th Ed.). National Academy Press, Washington, D.C.

Mackie, R.I., P.G. Stroot, and V.H. Varel. 1998. Biochemical identification and biological origin of key odor components in livestock waste. J. Anim. Sci. 76:1331-1342.