Ignculhirc^ hibuvai Hrts Mjjgcitnaloigg The Nutritive Value of Dried Citrus Pulp for Dairy Cattle By H. A. Keener, N. F. Colovos, and R. B. Eckberg Station Bulletin 438 Agricultural Experiment Station University of New Hampshire Durham, New Hampshire January 1957 The Nutritive Value of Dried Citrus Pulp for Dairy Cattle By H. A. KEENER, N. F. COLOVOS, AND R. B. ECKBERG* DURING recent years there has been much interest in New England in the use of dried citrus pulp as a supplemental concentrate feed for dairy cattle. Its use has become widespread due to its increasing availa- bility, favorable price relationships, and apparent high nutritive value. Because the citrus industry is still expanding very rapidly, increasing quantities of dried citrus pulp will become available during the next few years. For this reason it appeared that citrus pulp might be used econom- ically in larger quantities under New Hamphire conditions in the place of other concentrates, if the nutritive value of the ration was not lowered. As fresh citrus fruit production began to exceed the demand at about the time of World War I, the canning industry started to process juice and hearts. Disposal of the waste peel, rag, seeds, and cull fruit became a problem. Studies of by-product utilization were undertaken and about 1920 some attempts were made to feed such materials to livestock. It was found by the California and Florida experiment stations that cattle could readily utilize the fresh waste and such a practice became common in the citrus regions. The extent of this outlet was limited by the bulk and spoilage of the fresh citrus waste. Occasionally dried citrus by-products were left over from other uses and were fed to cattle with satisfactory results. The Florida Station then conducted some feeding trials and determined that dried citrus pulp had much the same use in cattle feeding as beet pulp. In 1938 Archibald of Massachusetts reported that dried citrus pulp could replace dried beet pulp in feeding dairy cows. Around 1940 it was discovered that because of the high sugar content of the press juice from the pulp, it could be made into a citrus molasses. When cane molasses came into short supply during World War II, citrus molasses found wide use in the mixed feed industry as a partial replacement for it. Now it is often mixed back with the pulp after drying. Currently the process for making the dried citrus pulp involves the addition of hydrated lime to aid the removal of bound water from the fresh pulp. The pulp is pressed to remove about half the moisture and then dried with artificial heat to a low moisture content. The press juice is concentrated to make citrus molasses which is either added to the dried pulp to make cake or is utilized separately. Such a procedure gives a wide variation in composition to the dried citrus pulp. Because almost all of the fat is contained in the seed, the fat content of the finished product is affected markedly when the seeds are removed in the processing of the * Dr. Keener is Dairy Husbandman, Mr. Colovos is Animal Nutritionist, and Mr. Eckberg is a former graduate research assistant, all in the New Hampshire Agricul- tural Experiment Station. pulp. The type of fruit processed, i. e., grapefruit, oranges, tangerines, lemons or seedless navels, affects the composition. The growing season as well as the variety of fruit also affects the product. For these reasons the analysis on the bag tag is an important consideration in feeding dried citrus pulp. While the dried citrus pulp is quite palatable to cows, its use is limited in that its composition is somewhat like that of a concentrated carbohydrate feed such as corn. That is, it is high in carbohydrate and total digestible nutrients, but low in protein. Many feeding experiments and a lot of practical experience have shown that dried citrus pulp is a satisfactory feed for dairy cattle. About the only work to determine the digestibility of citrus pulp by cattle appears to have been carried out at the Florida Station by Neal and associates. The work reported here was carried out for that purpose as well as to determine its value as an ingredient in the concentrate mixture. Digestion and Utilization Study Experimental Procedure The dried citrus pulp was evaluated in digestion and utilization studies carried out in the Animal Metabolism Laboratory of the Department of Dairy Husbandry of the New Hampshire Agricultural Experiment Sta- tion. Four 18-24 month old dairy heifers were used as experimental sub- jects. In order to evaluate dried citrus pulp under typical feeding condi- tions four different rations were fed. During the course of the experiment each ration was evaluated with each animal. The rations studied were hay alone, hay plus dried citrus pulp (50-50), hay plus a 14 percent pro- tein concentrate mixture (50-50). and hay plus 20 percent protein con- centrate mixture and dried citrus pulp (50-25-25). The citrus pulp was fed with the 20 percent protein grain mixture because the protein content of the mixture would be approximately the same as that of the 14 percent mixture. The hay fed was grass hay of average quality. The citrus pulp was a blend of pulps produced by members of the Citrus Processors Associa- tion. The concentrate mixtures are given in Table 1. The chemical com- position of the various feeds used is given in Table 2. Table 1. Poonds of Concentrate Mixtures Used Crude Protein in Mixture 14% 20% Ground corn 600 Crimped oats SCO Wheat bran 500 Soybean oil meal 200 150.0 Molasses 200 Dicakium phosphate 20 1.5 Trace mineralized salt 20 1.5 14% protein mixture 600.0 Table 2. Chemical Composition of Feeds Citrus Grair 1 Mixture Grain Mixture Hay Pulp 147^ Protein 20% Protein Protein % 6.39 5.81 15.63 20.86 Ether extract % 1.16 4.34 3.55 3.05 Crude fiber % 32.76 12.63 6.52 6.46 Nitrogen-free e.xtract % 46.53 63.69 58.31 53.79 Ash % 4.79 5.68 5.39 5.70 Moisture % 8.37 7.85 10.60 10.14 Each animal was given free choice of trace minerahzed salt. They were watered and fed twice daily. The rate of feeding was adjusted to the amount that each animal would clean up. The general plan of the ex- periment is given in Table 3. Table 3. General Plan of Experiment Animal Number Period 1 Period 2 Period 3 Period 4 Guernsey 4 Hay, 20% grain. Hay, 14% grain Hay, citrus pulp Hay citrus pulp Guernsey 5 Hay Hay, 20% grain. Hay, 14%. grain Hay, citrus citrus pulp pulp Holstein35 Hay, 147o grain Hav, citrus pulp Hay Hay, 20%) grain, citrus pulp Holstein 36 Hay, citrus pulp Hay Hay, 20% grain. Hay, 14%) grain citrus pulp The methods generally used in the laboratory were followed. These consist of a 10-14 day preliminary period during which the animal becomes adjusted to the kind and amount of feed to be evaluated. This is followed by a 14-day collection period during which the feed eaten and the urine and feces voided are carefully weighed, sampled, and analyzed. At the end of each collection period each animal is placed in the respiration chamber for two consecutive 12-hour periods during which heat and methane production are measured. From such studies results on both digestibility and utilization are obtained. Results and Discussion The average digestion coefficients for the various rations are given in Table 4. The "digestibility of the energy" of the ration which contained citrus pulp and grain was not significantly dififerent from that which con- tained the 14 percent protein grain. The difference in digestibility of pro- tein, however, was significant at the 5 percent level. The difference be- tween the digestibility of the energy of the citrus pulp-hay ration and that of the 14 percent grain-hay ration was significant at better than the 5 percent level and the difference between that of the citrus pulp-hay ration and the citrus-grain-hay ration was significant at the 1 percent level. The differences between the digestibility of the protein of the citrus pulp-hay ration and the two rations which contained grain were significant at the 1 percent level. Table 4. Average Digestion Coefficients for Various Rations Energy Protein Ether Extract Crude Fiber Nitrogen-free Extract % % % % % Hav 48.4 34.3 29.5 58.5 60.9 Hav, 14% grain 60.5 65.4 68.9 49.6 71.6 Hav, citrus pulp SS.4 37.1 74.6 45.1 71.7 Hav, 20% grain, citrus pulp 62.7 59.0 11.1 56.7 74.0 Using the values for the chemical composition of the various feeds and the digestion coefficients for the entire rations, the digestion coefficients for the grain mixture and citrus pulp were calculated by difference. Because citrus pulp was fed in two different rations, values for each were calculated. These values are given in Table 5. Table 5. Digestion Coefficients for 14 percent Grain and Citrus Pulp Calculated by Difference 1-nergv Crude Ether Protein Extract Nitrogen- Crude free Fiber Extract % Grain 14% 72.6 Citrus pulp fed with hay 62.4 Citrus pulp fed with hay and grain 81.4 % % % % 96.5 108.3 40.7 82.3 39.9 119.4 31.8 82.4 70.9 121.5 69.1 91.9 Digestible crude protein, total digestible nutrients, and "digestible energy" values for the entire rations and values calculated by difference for the individual ingredients are given in Table 6. Table 6. Digestible Crude Protein, Totol Digestible Nutrients, and Digestible Energy in Entire Rations and in Individual Ingredients Digestible Total Digestible Digestible Crude Protein Nutrients Energy % % Therms/100 lb. Hay 9 -7 50.4 89.0 Hay, 14% grain 7.2 58.1 111.4 Hay, citrus pulp 2.3 56.6 101.2 Hay, 20% grain, citrus pulp 5.8 60.7 114.5 Grain \^% 15.1 65.8 133.8 Citrus pulp fed with hay 2.3 62.8 113.4 Citrus pulp fed with hay and grain 4.1 76.1 146.2 The amount of each ration fed and the amount of protein and energy gained by the animal body is given in Table 7. The amount of protein and energy stored from the hay, citrus pulp, and grain ration was not sig- nificantly different from that stored on the hay and grain ration. The storage of protein and energy from the hay, citrus, and grain ration was greater than that on the hay and citrus ration with the difference for pro- tein being significant at the 1 percent level and the difference for energy I)eing significant at the 5 percent level. Table 7. Average Daily Feed Intake and Gain in Protein and Energy on Each Ration Averag Daily Wt. Fed Protein Energy Hav Hay, Hay, Hay, 14% grain citrus pulp 20% grain, citrus pulp lb. 12.1 16.0 13.3 15.0 g- 4.52* 157.43 37.99 180.64 Cal. 2238 6984 3376 6015 * Represents a loss The chemical analyses indicate that dried citrus pulp is relatively low in crude protein, higher than grain in ether extract, intermediate in crude fiber, and high in nitrogen-free extract. This would indicate that it might be a good source of energy. The digestion coefficients for the entire rations indicate that when the hay-dried citrus pulp ration was fed, the mixture was digested more efficiently than hay with respect to energ}^, ether extract and nitrogen-free extract, about the same with respect to protein and more poorly with respect to crude fiber. When grain was added to the hay-citrus pulp ration, however, this ration was digested just as efficiently as the hay-grain mixture with respect to all constituents except crude protein. This indicates a supplementing effect between the energy constituents of grain and citrus pulp. The calculated digestibility values for grain and citrus pulp actually credit all the differences due to the supplementing effect to the value of the grain or the citrus pulp. While this is not correct, there is no satis- factory method of getting around this problem. The digestion coefficients for citrus pulp fed with grain make it appear to be superior to grain with respect to energy, ether extract, crude fiber, and nitrogen-free extract. This is probably not the case. The truth of the situation probably is that grain, citrus pulp, and hay when combined are all digested more efficiently than when fed in the other mixtures. It is interesting to note that the calculated value of 76.1 percent total digestible nutrients for dried citrus pulp is very close to the value of 76.0 percent for dried grapefruit as obtained by Neal and co-workers. Digestible protein values obtained in this experi- ment, however, were somewhat higher than those reported by the Florida workers. Feeding Experiment with Lactating Cows Experimental Procedure This phase of the evahiation of citrus pulp was carried out on a privately owned herd of purebred Guernsey cattle. The purpose was to see if dried citrus pulp could be used successfully to replace half of the grain. The herd was managed and fed in the customary manner except for the use of citrus pulp. Early-cut grass hay and grass silage were fed during the winter months and high quality pasture during the summer months. A commercial grain mixture containing 16 percent crude protein was fed at a rate of 1 lb. for each 3^2 lb. milk during most of the year, but the ratio was widened some when the cows were on pasture. A record was kept of milk production, grain, and citrus i)ulp consumption and breeding dates. The body weight of each cow. estimated by means of a tape, and a condition rating were determined at monthly intervals. This study was divided into two parts. The first part was a reversal experiment which was carried out with six pairs of cows. These animals were paired as well as possible on the basis of freshening date, age, and previous production rate. Beginning at parturition one member of each pair was fed in the usual manner. The other member of the pair was given dried citrus pulp as the concentrate at one feeding and the same weight of the usual grain mixture at the other. Thirty days after parturi- i 50 o Q. § « g 30 a Z 20 < o UJ I »0 O GRAIN X CITRUS PULP an