Information from Greg Stewart

Index

• Dealing with low test weight corn
• Feeding value of low test weight corn for pigs
• Swine feeding results using 1992 low test weight corn

Dealing With Low Test Weight Corn

Greg Stewart, OMAFRA Corn Specialist

The 2000 growing season has resulted in the potential for significant amounts of low test weight corn.  1992 research trials indicated that this corn had significant energy content and relatively little additional corn was required to arrive at feeding values equivalent to normal test weight corn (see Table 1).  Using these values, dockage for low test weight corn can be calculated.  The resulting potential dockage is generally lower than traditional discounts applied to low test weight corn (Table 2).  These adjusted values should be considered when seeking to set a fair value on low test weight corn in 2000.  It should be noted, however, that these calculations are based on 1992 corn and OMAFRA staff are attempting validate these findings with samples from the 2000 harvest in the near future.

Table 1.  Feed weight adjustments for low test weight corn.   

Source:  Gwen McBride, OMAFRA.  Based on analysis of corn samples from 1992 growing season.

Table 2.  Grain corn test weights and potential dockage based on feeding value.

Feeding Value of Low Test Weight Corn for Pigs

Janice Murphy, OMAFRA Swine Nutritionist

Based on current knowledge, corn test weight does not significantly affect pig growth until it drops below 45 lbs/bu. As test weight declines below 45 lbs/bu, digestible energy decreases by 5-6 % and as a result, feed efficiency and growth rate will also suffer (3-10%) because of reduced energy intake. Research has shown that adding 2-3% oil or fat to diets made with very low test weight corn (below 45 lbs/bu) will help improve performance, but it will not return it to the level achieved with normal test weight corn

Feed companies adjust their product ingredient formulas to compensate in bad years when corn has a lower nutritive value. On farm feed mixers must adjust their own rations to compensate as well.

To deal with low test weight corn, producers should:

1. Test corn for moisture and protein.
2. Determine bushel weight of corn at 15% moisture.
3. Balance rations to account for differences in protein, energy and moisture.
4. Recalibrate volumetric mix mills to compensate for lower bushel weights.

Table 1 provides an estimate of the weight of low grade corn needed to provide the same energy as 1 kg of 56 lbs/bu corn. These guidelines can be used to reformulate rations.

Table 1: Feed weight adjustments for low grade corn.

Example calculation

Reformulate mix of 800 kg corn (56 lbs/bu) + 200 kg soybean meal (SBM) with 50 lbs/bu corn.

Calculate amount of corn needed to provide identical amount of energy: 800 kg x 1.026 = 820.8 kg .

Reformulate mix = 820.8 kg corn + 200 kg SBM = 1020.8 kg mix

On a 1000-kg basis, new mix would contain: 820.8/1020.8 x 1000 = 804 kg corn, and 200/1020.8 x 1000 = 196 kg SBM

Swine Feeding Results Using 1992 Low Test Weight Corn

Greg Stewart, OMAFRA Corn Specialist, and Janice Murphy, OMAFRA Swine Nutritionist

Concerns over feeding low test weight corn produced in 2000 have prompted a re-examination of feeding trials conducted using low test weight corn from the 1992 corn crop.

One study conducted by Jim Morris, University of Guelph, Ridgetown College examined the effect of feeding various test weight corn to swine.  The animals in this study had initial weights of approximately 32 kg and at the end of the study weighed, on average, 75 kg.  Results indicated that animal performance as measured by average daily gain and by feed:gain ratios was virtually unaffected by the test weight/quality of the corn in the diet.  Table 1 provides a brief overview of the experimental results.

Table 1. The effect of feeding corn of various test weights to growing swine.

(J. Morris, 1993, University of Guelph, Ridgetown College)

A, 1992 Corn, Kent County

B, 1992 Corn, Kent County

C, 1992 Corn, Huron County Slow dried (No Carmelization)

D, 1992 Corn Huron County, Carmelized.

A second study conducted by R. Patterson, J. Tuitoek and L. Young (University of Guelph, Department of Animal and Poultry Science) fed various test weight corn to younger pigs.  Animals in this second study had initial weights of approximately 8.4 kg and were fed diets consisting of corn with test weights ranging from 43.0 to 58.7 lbs/bushel.  This study also concluded that bushel weight was not a good indicator of the feeding value of corn.  Table 2 indicates that average daily gains and feed:gain ratios for diets comprised of low test weight corn harvested in 1992 in Ontario were similar to results from diets consisting of high test weight corn from Ontario (1991 harvest) and Indiana (1992 harvest).