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Brief mention has already been made of the use of a number of NPN compounds other than urea in the nutrition of ruminants. These compounds included ammonium acetate, bicarbonate, carbamate and lactate, biuret and dicyanodiamide. Although amino acids have also been used, they are generally too expensive for practical use in diets of ruminants. Other NPN compounds studied include various ammonium salts, biuret, urea phosphate, and others listed in Table 2 on page 14.


Biuret is a condensation product of urea. Berry, Riggs and Kunkel (1956) reported that biuret was not toxic for sheep and cattle. They found, however, that it depressed the appetite and reduced the gains of both species and that these effects could be overcome by feeding more urea or vegetable protein. Using an in vitro fermentation procedure for evaluating various nitrogen sources, Belasco (1954) found that biuret supported only 7 percent as much cellulose digestion as an equal amount of nitrogen from urea, and he suggested that biuret was not a useful nitrogen source for rumen micro-organisms.

Other workers have presented data which suggest that biuret is a useful nitrogen source for ruminants. Meiske et al. (1955) found that urea, biuret and soybean meal as supplements to a ration of wheat straw, maize, alfalfa and molasses gave equal growth responses for growing-fattening lambs. Repp, Hale and Burroughs (1955) observed that NPN-containing rations improved in value after an adaptation period of 2 to 3 weeks. Ewan, Hatfield and Garrigus (1958) reported that a urea-supplemented diet gave higher apparent digestibility of nitrogen and dry matter and higher retention of nitrogen than biuret in initial studies. The reverse was true, however, after the lambs were given inoculations of rumen ingesta and maintained on the biuret diets for periods up to 20 months. In studies by Anderson et al. (1959) biuret was utilized about as well as urea, especially following an adaptation period of several weeks. Iwata (1959) suggested that biuret was a useful source of nitrogen for milking cows. Campbell et al. (1963) found that biuret promoted slightly, but not significantly, lower growth and feed efficiency with dairy heifers than urea. Biuret also gave slightly lower nitrogen retention with bull calves and appeared to be slightly inferior to urea for lactating cows but the differences were very small. Both nitrogen sources gave better responses after an adaptation period of 2 to 5 weeks.

Biuret is not available commercially so that its utilization has no practical significance at present. It has no nutritional advantage over urea except that it is much less toxic at usual intake levels. Mixtures of urea and biuret might prove more practical than either one alone.

Use of ammoniated feeds

One of the problems in using urea as a replacement for protein is its rapid breakdown to ammonia in the rumen. Any ammonia not utilized by the bacteria is absorbed through the rumen wall into the bloodstream and on high N intakes tends to be lost to the animal by excretion in the urine as urea. This loss is thought to explain the low value of urea in some studies as well as its toxic effects. Among the various attempts to overcome this loss of nitrogen has been the reacting of ammonia with feeds low in protein and high in carbohydrates so that the product provides a desirable combination of nitrogen and energy which are available simultaneously for bacterial growth.

Millar (1942) and Stiles (1952) have developed methods of impregnating certain products with ammonia to form compounds which may release ammonia nitrogen at a slower rate than urea and might avoid toxicity and improve nitrogen synthesis. Several groups of workers have studied these products.

McCall and Graham (1953) reported favorable responses from ammoniated furfural residues derived from maize cobs. Davis et al. (1955b) studied experimental ammoniated residues from the manufacture of furfural. The original materials used in the process included maize cobs, oat hulls, cottonseed hulls and other fibrous materials. In vitro fermentation tests and nitrogen balance studies with steers showed that the nitrogen, in the ammoniated products tested, was appreciably less available than nitrogen from vegetable proteins. Tillman et al. (1957) found that the nitrogen of ammoniated furfural residue was not well utilized by steers fed fattening rations. Using in vitro fermentation procedures Hershberger, Bentley and Moxon (1959) demonstrated that only the “free” ammonia in ammoniated furfural residue, maize cobs, sugarcane bagasse, and molasses was utilized by rumen bacteria. The “bound” nitrogen was not utilized but it was not toxic to the bacteria. Because of low utilization values these ammoniated industrial products have not found any important practical use as feeds for ruminants in the United States.

Ammoniated beet pulp and citrus pulp

Ferguson and Reeves (1943), Millar (1944), and Connell et al. (1944) found that ammoniated dried sugar beet pulp enhanced its nitrogen value, but there was a question as to whether the nitrogen was as useful as that in vegetable proteins.

Davis, Kirk and Crowder (1952) prepared ammoniated citrus pulp by treating the dried pulp with liquid ammonia. Acceptability of the product varied with the age of the animals. Older cattle consumed up to 30 percent of the crude protein requirements and 50 percent of the energy needs. Ammoniated citrus pulp containing 12 percent crude protein produced satisfactory growth in young cattle (Kirk, Davis and Peacock, 1954).

Volcani and Roderig (1953) found that dried and ensiled orange peel that had been enriched with ammonium sulfate was a safe feed for cattle and sheep. Broster et al. (1960) reported that ammoniated sugar beet pulp increased milk production and solids-not-fat content when added to a low-protein ration. In nitrogen balance studies, only 11 percent of the nitrogen from the ammoniated sugar beet pulp was utilized compared to 44 percent for groundnut meal fed as a supplement to the same ration.

Although the published research supports the view that there is some utilization of the nitrogen of ammoniated dried beet pulp and citrus pulp, there are no critical studies to compare these products with supplements containing urea, with legume forages or with such bulky feeds as dried brewers' or distillers' grains. Thus the general economic evaluation of these ammoniated feeds is not possible at present and there may be wide differences in various areas.

The subject of the first investigations initiated in Poland in 1957 at the Institute of Animal Physiology and Nutrition was dried ammoniated sugar beet pulp. Originally it was obtained by soaking the ordinary dried pulp with an ammonia solution under laboratory conditions. Later it was produced in larger amounts in a pilot plant by treatment with gaseous ammonia under atmospheric pressure. Both chemical and nutritional tests showed no difference between these two products. The nitrogen content of the ammoniated air-dry (about 89 percent dry matter) pulp amounted to approximately 2.6 percent as compared to approximately 1.2 percent in the untreated pulp: no losses of nitrogen were observed after drying at 105°C, or during one year of storage under farm conditions. The smell of ammonia, detectable after treatment, disappeared entirely after a short aeration (Chomyszyn, Ziolecka and Bielinski, 1959; Pujszo, 1960, 1961). Good quality silage was produced by adding 0.5 to 1.0 percent ammonium sulfate to fresh sugar beet pulp (Sobczak, 1961c).

Experiments with wethers fed high rations of ammoniated pulp providing up to 27 grams of NH3 daily per head, and 0.54 gram per kilogram live weight showed no adverse effects on the health of animals (Chomyszyn and Bielinski, 1959). It has been repeatedly observed that sheep and cattle ate the ammoniated pulp even more readily than the untreated pulp.

In further experiments the digestibility of nutrients, the nitrogen balance, and the levels of various nitrogen fractions in the rumen fluid, blood serum and urine were examined. As a rule the apparent digestibility coefficients of nitrogen were higher for the ammoniated pulp than for the untreated one (Chomyszyn et al., 1960; Chomyszyn, Bielinski and Slabon, 1960b; Seidler et al., 1962; Sobczak, 1962a), and in some cases a higher digestibility of crude fiber (62.5 versus 68.6, and 58.0 versus 66.9) was observed (Chomyszyn et al., 1960, Chomyszyn, Bielinski and Slabon, 1960). In experiments with wethers fed the ammoniated pulp as the only feed, the following coefficients of apparent digestibility were obtained (average of 8 animals): organic matter, 82.0; crude protein (total N × 6.25), 71.6; crude fiber, 84.4; and N-free extract, 88.5. The computed nutritive value of 1 kilogram of ammoniated pulp (89 percent dry matter) amounted to 0.546 kilogram of starch value, or 0.722 kilogram of total digestible nutrients (TDN); the content of the “digestible protein” (digestible N × 6.25) was 118 grams (Chomyszyn et al., 1963).

Feeding trials with dairy cows showed that, depending on the level of milk production, 20 to 35 percent of the nitrogen requirement could be covered with the ammonia nitrogen of the ammoniated pulp, with no adverse effect on the milk yield or the live weight of the animals (Burzynski, 1963; Felinski, 1962). In experiments lasting three months with cows yielding about 20 kilograms of milk per day, up to 35 percent of the nitrogen requirement could be covered by equal parts of the nitrogen of urea, and ammonia nitrogen of the ammoniated pulp (Chomyszyn, Bielinski and Slabon, 1962). In one experiment, however, the cows responded with a gradual decrease of milk production, when the proportion of ammonia nitrogen of the pulp was raised from 12 to 23 percent of the requirement (Burzynski, 1963). It seems possible that the utilization of the ammonia nitrogen of the pulp depends partly on the composition of the entire ration, and more evidence upon this question is needed.

Numerous feeding trials with growing-fattening cattle and sheep indicated that up to 30–35 percent of the nitrogen of feeds might be substituted by ammonia nitrogen of the pulp (Abgarowicz et al., 1962; Bielinski, 1963; Bielinski and Chomyszyn, 1962; Chomyszyn et al., 1959; Kielanowski et al., 1962).

Ammoniated straw and silage

In addition to ammoniating the sugar beet pulp, studies on the treatment of straw with ammonia (Chomyszyn et al., 1964b), maize silage (Abgarowicz et al., 1962) and potato-malt distillers' slop (Centr. Lab. Przemyslu Rolnego PGR, 1962) were conducted. The nitrogen content of ammoniated straw was double that of nonammoniated straw (0.7 versus 1.5 percent). The addition of ammonia solution to maize silage decreased the level of lactic acid, analogically to an addition of urea or ammonium sulfate, but in all cases the quality of the silage was good. The quantity of ammonia which could be fixed in the distillery slop depended mainly on its acid content, which could be increased by lactic acid fermentation.

Experiments on feeds treated with ammonia solutions were reported in the U.S.S.R. in 1950 (Bezuhlyi). The ammonia treatment of feeds, however, has not gained any great importance, and has been applied occasionally on a farm scale only.

Most common is the ammonia treatment of straw. According to a method elaborated by Zafren (1959), straw is treated with ammonia solution (approximately 12 liters of a 20 to 25 percent solution per 100 kilograms of straw), kept tightly covered for five days and, after a day of aeration, fed to animals. Bondarev and Gurtykh (1962) found that during the treatment ammonium acetate was formed in the straw. Laguta (1961) reported an increase in the digestibility of straw dry matter from 59 to 64 percent following the treatment. Trials with growing cattle (Ivanov and Plotnikova, 1961) and with dairy cows (Popov, Ievcishevich and Popova, 1962) fed ammoniated straw indicated that the ammonia nitrogen was utilized by the animals. Experiments on supplementing maize silage (Zafren and Vetshera, 1961) and fresh or ensiled sugar beet pulp (Fleishman, 1963) with ammonia solution were also reported.

In Romania, feeding trials with maize silage treated with ammonia solution were carried out (Baia, Ariesanu and Iliescu, 1962). The silage, prepared in the usual way, was treated for 30 minutes with a 20 percent ammonia solution and then immediately given to animals which, after a short period of adaptation, ate it even more readily than the untreated silage. The authors ascribed the improved acceptance to the less acid taste of the ammoniated silage, resulting from the neutralization of organic acids (especially acetic acid), and recommended ammonia treatment as a method of improving poor quality silages. Positive results were obtained in trials with growing cattle and dairy cows fed rations containing about 30 percent of the nitrogen in the form of ammonia contained in the silage.

Results of investigations into the chemical fixation of ammonia by feeds showed that ammonium salts were formed, suggesting that acid groups played an important role in the process of fixation. In straw, all the bound nitrogen was present in the soluble-N fraction. In the ammoniated sugar beet pulp, however, a considerable part of the nitrogen appeared in the insoluble nitrogen fraction, bound by the pectic substances (Pujszo, 1961, 1963). Most probably this part becomes only slowly and gradually available for bacterial decomposition. In the United States studies cited earlier, bound nitrogen in ammoniated industrial products was not utilized by bacteria. The main reason why the ammoniated pulp gives no toxic effects is probably because such bulky feeds are consumed only slowly and the ammonia dosage is spread over several hours. Preliminary experiments have been conducted on the utilization of ammonia, derived from the ammoniated feeds, by the rumen flora (Ziolecki, 1960).

Ammoniated molasses

Culbertson et al. (1950) found that, when ammoniated cane molasses replaced one half of the linseed meal, the performance of beef cattle was better than with linseed meal as the sole protein supplement. Knodt, Williams and Brumbaugh (1950, 1951) reported that ammoniated cane molasses could be used at 10 percent of the ration of dairy calves, 14 to 16 weeks of age, to replace part of the vegetable protein in a grain mixture.

Tillman and Kidwell (1951) reported that ammoniated condensed distillers' molasses solubles could satisfactorily replace cane molasses and some of the cottonseed meal in rations for growing beef cattle. The material tested was a by-product of the manufacture of alcohol from the fermentation of molasses. It contained approximately 13 percent crude protein after ammoniated treatment. The original material contained 4 to 5 percent crude protein, 28 to 30 percent carbohydrates, 15 to 17 percent ash, and 39 to 40 percent water. Slightly faster gains were obtained when the ammoniated condensed distillers' molasses solubles replaced only 25 percent than when it replaced 50 percent of the cane molasses.

McCall and Graham (1953) reported almost identical weight gains of fattening steers fed rations in which one fifth to one sixth of the protein supplement was replaced by ammoniated cane molasses, ammoniated dried citrus pulp or ammoniated furfural residue. There was no negative control group in any of the tests and it seems entirely likely that the cattle might have gained as rapidly without any of the supplements. Clearly at such a low level of substitution it is difficult to make a critical evaluation of the usefulness of a feed.

Barrentine and Darnell (1954) found that ammoniated molasses was not a satisfactory protein source for beef calves. Richardson et al. (1954) observed that liberal intakes of ammoniated cane molasses caused nervous symptoms in cattle and they considered it an unsafe feed.

In tests at the Oklahoma station (Pope et al., (1954) fattening steer calves were full-fed with a basal ration of rolled milo grain and limited amounts of sorghum silage; they gained faster on a supplement consisting of ammoniated cane molasses, cottonseed meal and chopped alfalfa hay than on cottonseed meal as the sole supplement or on cottonseed meal plus alfalfa hay. Dairy heifers in Louisiana (Parkam et al., 1953–54) fed a basal ration of maize-soybean silage plus chopped grass hay made similar gains on supplements of ammoniated molasses or urea as with cottonseed meal. Heifers fed cottonseed meal required less feed per unit of gain than those fed nonprotein nitrogen.

King, O'Dell and Roderick (1957) reported that dairy heifers fed 20.5 kilograms of maize silage, 0.9 of cottonseed meal and 1.5 of cane molasses per day gained 0.78 kilogram compared to 0.65 kilogram when 5 percent urea was added to the molasses to replace half of the cottonseed meal. Balance studies revealed lower apparent digestibility and retention of nitrogen on the ammoniated molasses than on cottonseed meal or molasses plus urea. Wintering beef heifers fed sorghum silage and milo grain made slightly lower, but satisfactory, gains on ammoniated maize molasses (hydrol) than on soybean meal (Richardson, Baker and Cox, 1955). No undesirable effects on the cattle were noted.

Tillman et al. (1957) found that the nitrogen in ammoniated cane molasses was not well utilized on the basis of evidence from fattening trials with beef cattle. Wintering growth trials and digestion and balance studies gave evidence both for and against efficient utilization of the nitrogen. Cattle fed ammoniated cane molasses (32 percent crude protein equivalent) showed abnormal behavior within 5 to 6 days so that they began running into and jumping fences in a violent manner.

In studies with sheep (Tillman et al., 1957) the apparent digestibility of the nitrogen of ammoniated cane molasses (33 percent crude protein equivalent), calculated by difference, was 50 and 42 percent on basal rations with low- and medium-protein content. Feeding high levels of ammoniated cane molasses produced both mild and extreme types of stimulation or excitement similar to that observed in cattle. In a fattening ration for lambs, ammoniated cane molasses gave unfavorable results and caused endocardial hemorrhages.

Tests by Bartlett and Broster (1958) confirmed that 9.45 kilograms per day of ammoniated invert molasses, containing 5.6 percent total nitrogen, were toxic for yearling dairy cattle. When acidified with acetic acid there were no toxic effects but the ammoniated molasses was inferior to a protein-deficient ration as far as supporting weight gains in young cattle.

Results in the United States with cattle and sheep fed ammoniated molasses and molasses products have been variable. In some tests when these products were fed at low levels, performance has appeared satisfactory, but there is uncertainty as to whether critical evaluation of the materials is practicable at such low levels. Intermediate intakes have often given less satisfactory results than mixtures of urea and molasses or vegetable proteins. In some tests, but not all, high levels of intake of ammoniated molasses have caused violent excitement in the animals and the feed was considered to be unsafe.

Ammoniated sugarcane bagasse

Sugarcane bagasse and pith, the residue remaining after the syrup is pressed from sugarcane, has been ammoniated as a feed for ruminants. Up to 2.0 percent nitrogen was absorbed when anhydrous ammonia was added to bagasse (Temple and Wiggins, 1956; Bourne, 1956). The ammonia reacted with lignin and also with the sugars to give pyrazine and imidazole compounds. The product was palatable and nontoxic for cattle.

Davis et al. (1957) found ammoniated sugarcane bagasse acceptable as a replacement for all other roughage for fattening cattle two years of age or older, but less satisfactory for younger animals. The nitrogen was somewhat less available than urea nitrogen in replacing protein.

Ammonium salts

In the U.S.S.R. experiments on the utilization of several ammonium salts by ruminants were reported. Ammonium acetate was studied by Bondarenko, Bielova and Slesarev (1959) and Bondarenko and Slesarev (1962). In long-term experiments the authors administered 250 grams of ammonium acetate per head daily to Jersey and Holstein-Friesian cows, and analyzed blood, milk and rumen fluid. No adverse effects on the health of the animals were observed, and the fat content in milk increased. The increase was greater in Jersey (0.75 to 0.95 percent) than in Holstein-Friesian cows (0.26 to 0.37 percent) and it was greater at early than at later stages of lactation.

In experiments conducted by Fremel, Losiakova and Shishkova (1960) and Shunkova and Slesarev (1961) ammonium lactate was obtained by the neutralization of lactic acid, produced by the fermentation of distillers' slop. The fermented slop neutralized with ammonia solution was added to the rations of dairy cows and growing cattle. About 40 percent of the nitrogen requirement of dairy cows could be covered by the nitrogen contained in the treated slop, out of which about 16 percent of the requirement was provided by ammonia nitrogen. Growing cattle fed 10 kilograms and dairy cows fed 18 kilograms of the distillers' slop per head daily showed no health disturbances and seemed to utilize the ammonia nitrogen.

Hulyi (1955) and Veresenko (1958) added ammonium sulfate or ammonium sulfate together with ammonium chloride at about 1 kilogram of nitrogen per ton of ensiled maize, sunflower and clover. Both authors found that the addition of ammonium salts not only prevented the breakdown of the proteins in the ensiled forages, but also caused formation of organic nitrogen compounds.

According to Modianov (1962), the addition of 9 to 13 kilograms of ammonium bicarbonate to the ensiled maize caused an increase of pH up to 4–4.3, as compared with 3.5 in the untreated silage. The quality of the experimental silage, however, was satisfactory, and the enrichment of the maize silage by the addition of ammonium bicarbonate was recommended for practical application.

The few experiments on inorganic ammonium salts so far reported in Poland were conducted mainly at the College of Agriculture in Wroclaw (Pres and Sobczak, 1962; Sobczak, 1961a, 1961b, 1961c, 1962b, 1963; Sobczak, Skrzypek and Detkens, 1962). From the ammonium salts studied (chloride, nitrate, oxalate and sulfate) only ammonium sulfate has come into wider use. Experiments were carried out with sheep, dairy cows and fattening cattle, rations were supplemented with ammonium sulfate alone or in combination with urea. In agreement with experiments with other nonprotein compounds, nitrogen of the ammonium sulfate replaced 20 to 30 percent of the nitrogen of the control ration. No disturbances in the health of animals were observed. Feeding ammonium sulfate as a substitute for oil cakes did not decrease the milk yield (Sobczak, Skrzypek and Detkens, 1962).

Silages of good quality were produced from maize (Abgarowicz, Swietlikowska and Truszynski, 1963) with an addition of 0.5 to 1.0 percent ammonium sulfate.

Experiments with ammonium lactate were initiated by Chomyszyn et al. (1964). It was fed in the form of a preparation manufactured in the following way (patented in Poland): in diluted molasses, lactic acid was produced by fermentation and gradually neutralized by ammonia solution up to pH 6.5. The product, which was afterward condensed, formed a thick (specific gravity 1.26) dark brown syrup of a slightly acid taste containing 82 grams of nitrogen per kilogram, out of which about 68 grams were ammonium nitrogen, mainly as ammonium lactate. This preparation was mixed with the ration immediately before feeding, or premixed in a factory with dried sugar beet pulp (total nitrogen content in mixture was about 3.7 percent). Positive nitrogen balances were found in wethers fed rations in which 26 to 38 percent of the nitrogen came from ammonium lactate; the nitrogen excretion in the urine and the blood level of urea were equal in experimental and control animals. No negative effects of intakes up to 200 grams of ammonium lactate per head daily were observed. Preliminary experiments with the same preparation fed as a supplement to the rations of dairy cows (Chomyszyn et al., personal communication) showed very promising results.

Studies in Michigan (Lassiter, Brown and Keyser, 1962) have shown that diammonium phosphate is as useful as urea in rations for growing dairy heifers and for milking cows. At levels higher than 2 percent of the concentrate, palatability was a problem. Phosphorus would be a useful addition for some low-protein rations. In balance studies (Russell, Hale and Hubbert, 1962) diammonium phosphate and urea gave equal N retention. Urea was considerably more toxic than diammonium phosphate when administered to lambs by stomach tube.

Ammoniated rice hulls

Rice hulls are fed to livestock in many countries, often as an adulterant of fine rice bran, but also as a substitute for roughage. Eng (1964) reported that treatment of ground rice hulls, in the presence of catalysts with heat and pressure in an atmosphere of ammonia, gave a product containing 10 to 11 percent crude protein and 45 percent crude fiber. When fed at 10 to 20 percent of the ration of steers, the ammoniated rice hulls gave good results but, when fed at the 30 percent level, they depressed the rate of gain. The question as to whether it is economically feasible to produce and transport ammoniated rice hulls has still to be resolved.

Other nonprotein nitrogen compounds

All the NPN compounds shown in Table 2 (page 6) have given relatively satisfactory results in feeding tests with ruminants, but none of them was better than urea while most were more expensive.

Diammonium phosphate has proved satisfactory in a number of trials (Schaadt, Johnson and McClure, 1966) and it has the advantage that it supplies phosphorus, which is often a limiting nutrient in low-protein, poor quality rations. Perez, Warner and Loosli (1967) reported that urea-phosphate was a source of NPN which was utilized as well as urea and a supply of phosphorus which was used as efficiently as was dicalcium phosphate when fed to lambs and calves.

Kay et al. (1967) reported that ammonium acetate in the drinking water of early weaned calves, to replace part of the protein in fish meal, reduced the rate of gain. Replacing 13.9 percent of fish meal in the dry diet with 3.0 percent urea also lowered the rate of gain and efficiency of feed utilization. Stobo et al (1967) also found that young calves made less satisfactory growth when urea furnished one third of the dietary nitrogen than when fed with fish meal. Cyanuric acid (approximately 32 percent N) was nontoxic to sheep in rumen fistula doses of up to 96 grams or in oral doses of up to 120 grams of acid plus 400 milliters of water (Altona and Mackenzie, 1964). In a feeding trial, cyanuric acid reduced the weight loss of sheep.

Sewage sludge

Sewage sludge, the residue removed from sewage clarification plants, has shown some value as a source of nitrogen for ruminant animals. More than one half of its nitrogen content is in the form of NPN.

Adams et al. (1955) found that yearling steers would accept up to 0.5 kilogram per day of dried sewage sludge in place of soybean meal in a normal ration. Weight gains were only slightly lower, and the apparent digestibility of the nitrogen in the sewage sludge was 64.5 percent as compared with 73.5 for the soybean meal ration. In further studies (Hackler, Neumann and Johnson, 1957), the nitrogen of sewage sludge was shown to have an apparent digestibility of 52 percent and a biological value of 51 when measured with experimental rats. Using sheep, the apparent digestibility of the nitrogen was 55 percent and the biological value 69 compared with 66 and 60 percent respectively for a soybean meal ration. Amino-acid analysis by microbiological methods revealed a composition more nearly approaching bacterial protein than the protein of soybean meal. Nitrogen retention was approximately the same on rations containing soybean meal, urea, or sewage sludge. The sludge used in these tests contained about 30 percent crude protein (N × 6.25) and 40 percent mineral matter.

While sewage sludge has value in ruminant feeds, it is difficult to handle and it presents serious palatability problems which have not yet been resolved.

Poultry litter

Poultry litter, consisting of the droppings and bedding used to absorb moisture, is high in nitrogen content. This material shows promise as a feed for ruminant animals. Noland, Ford and Ray (1955) reported that ewes performed as well on a ration containing chicken litter as a supplemental nitrogen source as when fed soybean meal and better than when fed ammoniated molasses. The chicken litter contained 4.85 percent nitrogen (30.3 percent crude protein), 19.2 percent of which was uric acid. Oat straw and groundnut hulls had been used as the litter base to absorb moisture. Fattening steers fed a concentrate consisting of 24 percent chicken litter, 62 percent maize, 11 percent cane molasses and 1 percent of each dicalcium phosphate and a trace of mineralized salt mixture, along with prairie hay, did not gain as rapidly as others fed cottonseed meal as the source of nitrogen, and more feed was required per unit of live weight gain with the chicken litter ration. There was no palatability problem with the feed.

Southwell, Hale and McCormick (1958) found that fattening steers gained as well on a ration containing 15 or 30 percent poultry litter, having a base of ground maize cobs, as on cottonseed meal, but that more feed was required per unit of gain on the 30 percent litter level.

Bhattacharya and Fontenot (1965) and Fontenot et al. (1963) have made extensive studies of poultry litter as feed for sheep and cattle. The chemical composition of the poultry litters having groundnut hulls or wood shavings as a base is shown in Table 3.

Steers made equal gains on rations containing 25 percent of either groundnut hull litter or of soybean meal. In balance studies with sheep, apparent digestibility of nitrogen was depressed as the dietary nitrogen, supplied by the litter, was increased to 50 and 100 percent of a purified diet. Less nitrogen was retained on the highest level of feeding than on the lower intakes or on soybean protein. The authors concluded that poultry litter was efficiently utilized by cattle and sheep at levels of up to 50 percent of the dietary nitrogen.

Brugman et al. (1964) also reported favorable results with beef cattle on the following ration: poultry litter 500 kilograms, dried potato pulp 200 kilograms, and dicalcium phosphate (18.5 percent P) 6.7 kilograms, and vitamin A supplement (10,000 IU per gram) 440 grams. The analysis of the litter was 19.5 percent moisture, 14.4 percent protein, 0.8 percent ether extract, 16.2 percent crude fiber, 6.1 percent calcium and 1.8 percent phosphorus, and 3.6 kcal per gram and 2.41 percent crude protein equivalent in the form of nonprotein nitrogen. These authors pointed out the need:

  1. to pass the litter over a magnet to remove nails, wire, etc., so as to make it a safe feed;

  2. to add vitamin A and phosphorus.

Table 3. - Composition of poultry litter

 Litter base
 Groundnut hullsWood shavings
Dry matter85.588.9
Crude protein32.630.6
Crude fiber13.114.6
Ether extract3.02.8
NitrogenPercent of total N
True protein46.244.4
Uric acid30.528.8

No residues derived from coccidiostats or other additives were found in the litter used in these tests.

Considering the large quantities of poultry litter being produced by the present-day poultry industry and the expensive problem of its disposal even as a fertilizer, the prospect of converting it into a useful livestock feed offers a challenging prospect.

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