W.P. Weiss*, D.L. Frobose+, and M.E. Koch*
*Department of Animal Sciences and
+Wood County Extension
Wet tomato pomace is a byproduct of the tomato canning industry. Because the product is wet (25% dry matter), storage is difficult. Tomato pomace contains moderate amounts of protein, and high concentrations of fat and fiber. A mixture of tomato pomace and whole corn plants (400 pounds of pomace/wet ton of corn) was ensiled and compared to untreated corn silage. The tomato pomace and corn mixture fermented well. When fed in a balanced diet with 40% concentrate, cows fed the tomato and corn silage produced similar amounts of milk (77 pounds/day). The tomato and corn silage did not affect milk composition or dry matter intake. Based on typical feed prices, wet tomato pomace is worth about $23/wet ton.
The production of juice and other products from tomatoes is a major industry in certain areas of Ohio. After the juice is extracted, a residue primarily consisting of tomato seeds and peels is left (tomato pomace). In the past, this byproduct often has been discarded. Increased landfill costs and societal concerns about solid waste have generated interest in finding an economical outlet for this byproduct. As with many food byproducts, tomato pomace can be fed to livestock.
Based on previous research, dried tomato pomace is an acceptable feed for ruminants. The equipment and energy needed to dry the pomace are expensive, which is why most pomace currently is discarded. The production of tomato pomace is seasonal; most of the product is available in late summer (September). This corresponds to the time when corn is harvested for silage in Ohio. An experiment was conducted to determine if wet tomato pomace could be added to corn silage at the time of ensiling and to determine the feeding value of a mixture of corn silage and wet tomato pomace.
Corn plants (half-milk line) from a single field were chopped in late September (theoretical length of chop = 3/8 inch) and placed into two identical concrete stave silos. Corn in one silo was untreated, and approximately 400 pounds of wet tomato pomace (donated by Hirzel Food Systems, Ottawa, OH) was added to 1 ton of wet corn silage (12% of dry matter) in the other silo. Each wagon load of corn was weighed after chopping, and an appropriate amount of wet tomato pomace was added to the top of the load prior to silo filling. Both silos were filled during a single day, covered with plastic after filling, and left sealed for approximately 3 months. Nutrient composition of the silages and tomato pomace is in Table 1.
| Table 1. Nutrient composition of tomato pomace, untreated corn silage, and corn-tomato silage (dry matter basis). | |||
|---|---|---|---|
| Item | Tomato Pomace | Corn Silage | Corn + Tomato Silage |
| DM, % | 24.7 | 37.5 | 33.8 |
| CP, % | 19.3 | 9.3 | 10.7 |
| NDF, % | 61.0 | 37.0 | 37.9 |
| NEL Mcal/kg | 1.54 | 1.63 | 1.61 |
| Calcium, % | 0.23 | 0.29 | 0.34 |
| Phosphorous, % | 0.40 | 0.28 | 0.27 |
Two diets were formulated using untreated or corn + tomato silage and fed to 14 midlactation Holstein cows (7/treatment) for 60 days. Diet composition met or exceeded NRC recommendations (Table 2). Daily milk production and dry matter (DM) intake were measured. Milk was sampled and analyzed every 2 weeks for protein and fat. No adaptation period was used.
| Table 2.Ingredient and nutrient composition of diets (DM basis) | ||
|---|---|---|
| Item | Control | Corn + tomato |
| Corn Silage, % | 60.0 | 52.8 |
| Tomato pomace, % | - | 7.2 |
| Corn Grain, % | 17.1 | 18.8 |
| Soybean meal - 44%, % | 13.2 | 11.4 |
| Alfalfa meal, % | 3.9 | 3.9 |
| Distillers grains, % | 2.0 | 2.0 |
| Molasses, % | 0.8 | 0.8 |
| Urea, % | 0.5 | 0.5 |
| Minerals/vitamins, % | 2.5 | 2.6 |
| CP, % | 16.0 | 16.0 |
| NDF, % | 30.0 | 30.6 |
| Ca, % | 0.72 | 0.75 |
| P, % | 0.39 | 0.39 |
The tomato pomace was high in neutral detergent fiber (NDF), and contained a moderate amount of crude protein (CP) and a large amount of water (Table 1). Estimated net energy was similar to that of corn silage. Adding the pomace to the top of each wagon load resulted in a well mixed silage. The corn + tomato silage had about 1.5 percentage units more CP than did untreated silage; NDF concentration was about 1 percentage unit higher in the corn + tomato silage. The mixed silage had less DM than control silage, but DM was within the range for a normal fermentation. The corn + tomato silage fermented normally and was not greatly different in lactic and acetic acid concentrations and ammonia (data not shown).
Milk production, composition, and DM intake was not affected by treatment (Table 3). Even though no adaptation period was used, cows accepted the corn-tomato silage, and overall DM intake was normal (3.75% of bodyweight vs. 3.71% for control cows). Milk production averaged 77 pounds/day across treatments. Milk fat percent was lower than herd average for both treatments but was not different between treatments. Milk protein percent was similar to the herd average for both groups.
| Table 3. Milk yield, milk composition, and dry matter intake of cows. | |||
|---|---|---|---|
| Item | Control | Corn + tomato | Stat. signif.1 |
| Body weight, pound | 1390 | 1300 | 0.18 |
| DM intake, pound/day | 51.5 | 48.4 | 0.40 |
| Milk, pound/day | 78.5 | 77.4 | 0.86 |
| 4% Fat-corrected milk, pound/day | 72.2 | 68.2 | 0.49 |
| Milk fat, % | 3.47 | 3.2 | 0.34 |
| Milk protein, % | 3.16 | 3.17 | 0.89 |
| Probability that treatment difference is caused by chance | |||
The economic value of tomato pomace was estimated by using average prices for corn silage, soybean meal, and corn grain. Both diets resulted in similar production by the cows, so diets were assumed to be of equal nutritional value. Prices used were: corn silage, $0.03/pound of DM ($23/ton of wet silage); soybean meal-44%, $0.12/pound of DM ($210/ton, as fed); corn grain, $0.05/pound of DM ($2.50/bu, as fed). Based on these prices and average DM intake of the cows in this experiment, tomato pomace is worth approximately $0.05/pound of DM (DM or $23/wet ton having 25% DM). Costs for hauling, labor necessary to add the pomace, and the cost of the material would have to be less than $23/wet ton to justify the use of this product.
The corn silage + tomato pomace mixture fermented well and was an acceptable feed for dairy cows. The corn + tomato silage had a higher concentration of CP than did control silage; therefore, less supplemental CP (soybean meal) could be fed. Based on milk production, the energy value for corn + tomato silage was similar to that of untreated corn silage. Mixing wet tomato pomace with corn silage at the time of filling and feeding the mixture to dairy cows is a viable alternative to discarding the residue. The economic value of the pomace including transportation costs, the labor necessary to add the pomace to the silage, and the actual price of the pomace is equal to approximately $23/wet ton (25% DM).