B. C. Allison and M.H. Poore

Agricultural processing yields many byproducts that have significant feeding value for livestock. Because of their increasing market value as feed ingredients, many producers of such materials now consider them to be "coproducts" rather than "byprod ucts." Agricultural coproducts that are sometimes available at attractive prices in North Carolina include soyhulls, wheat midds, whole cottonseed, wet and dry corn gluten feed, wet and dried brewers grains, dried distillers' grains, poultry litter and many others. The value of these coproducts is generally calculated relative to the value of corn and soybean meal assum ing that feed intake and gain will be the same if they were included in balanced diets.

Previous feeding studies at NCSU have shown that soyhulls and wheat midds have about the same value as corn and soybean meal in both hay and silage-based diets. In a study with silage-based diets, however, both corn gluten feed and whole cottonseed depressed feed intake and gain, indicating that they may not be worth as much as their nutrient content would indi cate. The project reported here was designed to evaluate whole cottonseed, dried distillers' grains, and corn gluten feed, relative to corn and soybean meal in corn silage-based diets for stocker cattle.

Materials and Methods
Ninety head of mixed breeding M-1 steer calves (400-500 lb), were purchased from North Carolina Graded Feeder Calf Sales in September of 1992. The calves were processed within 12 hours after arrival at the Mountain Research Station in Waynesville, North Carolina and were preconditioned on pasture until the start of the trial.

On December 1st, 80 uniform steers were selected and assigned by breed to 8 groups (10 head per group.) Two groups were randomly assigned to each treatment, and cattle were housed in an open sided barn with concrete floor and outside lots. Calves were fed a total mixed ration each morning, and adequate feed bunk space was available in each pen for all animals to eat at one time. Gains were calculated from shrunk weights. Ingredient prices used were 26, 223, 121, 125, 178, and 148 $/ton for corn silage, soybean meal, corn, corn gluten feed, distillers grains and whole cottonseed, respectively. All diets con tained 76% silage and 24% concentrate (dry basis) and provided at least 200 mg lasalocid/head/day.

Results and Discussion
The four experimental diets fed in this trial had a similar nutrient composition, and varied only in the source of dietary concentrate. Despite this, both the performance of the calves and economic return were influenced. Dry matter feed intake was lower when diets contained distillers grains (14.8 lb/d) or cotton seed (14.5 lb/d) than when they contained corn and soybean meal (15.7 lb/d). Intake of the diet contain ing corn gluten feed was intermediate (15.1 lb/d). Daily gain was lower for all three alternative concen trates than for corn and soybean meal. Gains were about .4 lb/day lower for corn gluten feed, and about .2 lb/d lower for distillers grains and cottonseed than for the control.

Total feed cost was lower for the three alternative concentrate diets than for the corn and soybean meal. Feed cost per unit of gain was also lower for distillers grains and cottonseed than for the corn and soybean meal. However, due to the markedly reduced perfor mance on the corn gluten feed diet, feed cost per unit of gain was higher than for corn and soybean meal. Fixed costs were figured at $28/calf over the feeding period. This includes the costs for equipment, death loss, labor, and other miscellaneous costs, and is a reasonable figure for a large stocker operation. It is important to include this in the economic analysis because fixed cost per unit of gain decreases as gains increase.

For the economic analysis, purchase price of the cattle was calculated to be $92.30/lb. This was calculated from the purchase price of the 4 cwt cattle plus all the costs of preconditioning divided by the starting weight. Sale price was calculated as the total price per head divided by the finishing weight ($83.20/cwt). Because the groups on byproduct feeds finished the trial somewhat lighter than the corn and soybean meal group a 2 $/cwt slide was used to determine value of each treatment group.

Net return after all costs on the cattle was similar for the corn and soybean meal, cottonseed and distillers' grains diets, but was lower for the corn gluten feed diet. Using a price slide greatly increased the net return on the corn gluten diet because the steers were 53 lb lighter than the control steers at the end of the trial. Based on the crude protein and energy values, the corn gluten feed, distillers grains and whole cottonseed should have been worth 148.00, 169.58 and 149.81 $/ton, respectively. Based on the net returns, the realized value, or the price we could have paid for the byproducts and still made as much profit as with corn and soybean meal, would have been 35.52, 138.69 and 134.60 $/ton for corn gluten feed, distillers grains and whole cottonseed, respectively.

This trial demonstrates that byproduct commodi ties can not always be purchased based on their protein and energy values alone. Effects on feed intake and performance can have dramatic effects on net returns. Based on the feed costs used in this trial, corn and soybean meal was the most profitable source of concentrate.

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