by E. Cordiez, O. Lambot, J. M. Bienfait, A. Pondant and C. Van Eenaeme
Among the factors contributing to improvements in the techniques of beef production, feed is undoubtedly the most important, as it represents three quarters or more of the total cost of animal production. To obtain high levels of productivity through superior feed conversion efficiency, it is essential to provide an adequate, well-balanced diet; otherwise a large part of the feed consumed will be devoted to meeting maintenance needs only.
Of the various types of feeds that may be provided, energy feeds are most important, irrespective of whether they are utilized for beef production (with steers slaughtered at 15 to 18 months of age at live weights ranging from 470 to 530 kg) or for milk production. While feed constitutes the principal component of the total cost of animal production, the cost of energy feeds exceeds that of all other nutrients. The energy content of the diet, i.e. the amount of energy supplied per unit of weight, may therefore be regarded as a prerequisite to success in animal production. The accurate assessment of the energy content of feeds and a thorough knowledge of the factors influencing their use are thus essential to ensure efficient utilization.
The authors are at the University of Liege, Faculty of Veterinary Medicine, Rue des Vétérinaires 45, B1070 Brussels, Belgium.
It has long been known that in fattening steers for beef production, indiscriminate substitution of one farm feed for another solely on the basis of their theoretical energy values produces undesirable results, particularly in regard to the quality of animal products. This means that in order to attain the highest efficiency, certain feeds should preferably be reserved for certain classes of animals; thus, feeds that are good for three-year-old steers are not necessarily the best for younger animals. A similar idea was expressed by P. Rintelen, Director of the Agricultural Institute of Weihenstephan: “The usual methods of assessment (based on starch units or feed units) are not always appropriate for determining the feeding value of forages or fodder crops used for fattening cattle. Moreover, while natural or cultivated grasslands provide a poor basic feed for intensive fattening, they serve as an excellent feed resource for dairy herds.”
Energy value of feeds
It is a well-established fact that the conventional method of expressing the energy value of feeds in terms of starch units or fodder units has little merit when one is dealing with high production levels. Nevertheless, the assignment of a true energy value (expressed as net energy) to a feed or diet would be a most useful contribution to progress in animal production.
A certain differentiation of net energy values has been achieved for the different animal species, but within species individual animals exhibit considerable variation depending on whether they are in the maintenance or production phase.
Blaxter and his co-workers have shown that the conversation of digested energy into net energy of production is not the same for the two major categories of feed (coarse and concentrated feeds), nor is it the same for maintenance and production requirements. In order to cover maintenance requirements, the efficiency of conversion of digestible energy into net energy of production is practically the same for both coarse and concentrate feeds; but insofar as production requirements (lactation, gestation, fattening, etc.) are concerned, the conversion of concentrates is more efficient. This has been confirmed by the work of Lofgreen and Garrett (1968) on the energy requirements for maintenance, growth and fattening of beef cattle. They showed that the net energy value of a feed varies with the use to which it is put, the net energy value for maintenance being vastly different from that for production (Table 1).
It should be noted that some feeds, e.g. hay, may suffice to cover maintenance requirements, but their value is greatly reduced if they are used to meet production needs. On the other hand, high-energy feeds such as grains in general, oil cake and dried sugar beet pulp have an efficiency for production purposes that is 60 to 100 percent of their energy value for maintenance.
Table 1 shows that dried sugar beet pulp has a net energy value practically identical to that of barley, whether fed for production or for maintenance purposes. Cordiez et al. (1963) arrived at the same conclusion on the basis of trials conducted with young beef steers fed a diet containing up to 70 percent dried beet pulp. In more recent experiments where beet pulp was used to supplement diets based on maize silage, the equivalence of the feed value of pulp and barley was fully confirmed.
Our research was carried out both at the farm and at the experiment station with the support of grants from the Agricultural Research Department of the Ministry of Agriculture, and from the Institute for the Promotion of Scientific Research in Industry and Agriculture. Since we were principally concerned with obtaining practical results that would have general application, the objective of these studies was to determine the relative roles of farm-produced and commercial feeds as components of the diets of young bulls during the growing-fattening phases at a weight range of 250 to 350 kg initial weight and 475 to 525 kg slaughter weight. The trials at the experiment station involved the study of volatile fatty acids and ammonia in the rumen fluid.
Our work was therefore not concerned with the production of “baby beef”, which involves the feeding of animals from a very young age to a slaughter weight of about 450 kg on high-energy rations containing a large proportion of grains, resulting in the production of the so-called “barley beef.” Our experiments were concerned with trying to reduce as much as possible the use of grains in beef production.
Diets based on dried beet pulp.
For these trials over 300 bulls on six farms were used in two years. The animals were divided into homogeneous groups of 8 to 10 head each and were fed on experimental rations from the age of 8 to 10 months. In order to facilitate between-diet comparisons, the results of all trials are expressed here in relation to the weight range that was common to all of them, i.e. 280 to 519 kg.
Dried beet pulp, the basic ingredient of the ration, was fed ad libitum in order to allow maximum consumption. Supplementary compound feeds were provided at three levels (0.65, 0.75 and 1 percent) in fixed proportion to the live weight of the animals; these correspond to the intake levels shown in Table 2. The protein supplied was consistent with generally accepted norms; the crude protein content of the supplement diminished as fattening progressed so that the total amount of protein consumed was kept at a fairly constant level.
The dried beet pulp was usually provided to the animals once every 24 hours or placed in feed troughs within their reach. The incidence of bloat was less than two per thousand because the animals were able to consume 0.5 to 1.0 kg straw per day from the bedding provided and had access to all the water they wanted; they were also allowed a period of three to four weeks to adjust to the dried beet pulp, which was gradually increased during this period.
As shown in Table 2, the average daily gains were fairly similar for all three treatments and were only slightly influenced by the proportion of beet pulp and grain in the rations. When the level of supplementation declined from 1 to 0.65 percent of live weight, the animals compensated for the decrease in grain consumption by an almost proportionate increase in the intake of dried pulp. From these observations it would appear that the total consumption of dry feed per kg live weight gain was virtually the same for all three diets (6.8 to 6.94 kg). They demonstrate the equivalence in energy value of all three diets and show that dried beet pulp has a nutrient value very close to that of grain.
Assuming that the gain in carcass weight represents 63 percent of the increase in live weight, the quantities of dried beet pulp and grains consumed per kg of carcass weight produced may be estimated to be as follows:
Reducing the supplementation of compound feeds from 1 to 0.65 percent resulted in a saving of grain of 1.81 kg per kg of carcass weight. In the nine EEC countries, the area devoted to sugar beet cultivation is about 1 500 000 ha; with an average crop of 42 tons of sugar beet per ha and 52 kg of dried beet pulp per ton of beet, the potential production of dried pulp is about 3 276 000 tons. If all this pulp were used for beef production, 423 000 tons of carcass weight would be produced at the 0.65 percent level of supplementation, with a saving of 765 000 tons of grain as compared with the 1 percent level.
Rolled barley versus dried beet pulp
As dietary staples. In a 190-day trial conducted at the experiment station using young steers for fattening, the diet consisted of rolled barley or dried beet pulp fed ad libitum as the staple feed and a 33 percent crude protein supplement to cover standard protein, mineral and vitamin requirements. Between the two staples, practically no difference was observed in average daily weight gain (1.29 kg and 1.31 kg respectively) and in feed intake per kg increase in live weight (5.8 kg rolled barley and 5.6 kg dried beet pulp).
In a trial conducted on the farm, one diet consisted of 81.7 percent rolled barley and 18.3 percent protein supplement while a second consisted of 65 percent dried beet pulp, 16.2 percent rolled barley and 18.8 percent protein supplement. The protein supplement contained 74 percent oil cake (soybean and groundnut), 7 percent alfalfa meal, 10 percent molasses, 3 percent dicalcium phosphate, 2 percent limestone and 4 percent of a vitamin-enriched mineral supplement. The average daily gains of the young bulls fed these diets at weights ranging from 250 to 500 kg were similar, i.e. 1.27 kg for the first diet and 1.24 kg for the second. Feed intakes per kg of carcass weight were 8.40 kg barley and 1.88 kg compound feed for the diet based on barley, and 6.68 kg beet pulp, 1.67 kg barley and 1.93 kg compound feed for that based on beet pulp. Thus, barley consumption per kg of carcass weight was 6.73 kg less for the diet based on sugar beet pulp than on the barley-based diet, and by supplementing the beet pulp with compound feed equivalent to 0.65 percent of the live weight of the animals, the saving on barley would have amounted to 7.24 kg per kg carcass weight. If all the beet pulp that could be produced in the nine EEC countries were used at the 0.65 percent level, this would lead to a consumption of 1 256 000 tons of barley to produce 423 000 tons carcass weight. On the other hand, with a diet based on barley for the production of “barley beef,” the same carcass yield would require 3 062 000 tons of barley, i.e. an additional consumption of 1 806 000 tons.
Table 1. Net energy value of selected feeds
|Feeds||For maintenance (NEm)||For production (NEg)||NEg as % of NEm|
|kcal/kg||in % of barley||kcal/kg||in % of barley|
|Dry roughages (90% dry matter)|
|Alfalfa hay 21% fibre||1 230||64||700||55||56.9|
|29% fibre||1 010||52||300||24||29.7|
|Timothy hay before bloom||1 230||64||700||55||56.9|
|late bloom||1 030||53||380||30||36.9|
|Concentrates (90% dry matter)|
|Barley grain||1 930||100||1 270||100||65.8|
|Maize grain||2 030||105||1 320||104||65.0|
|Beet pulp, molasses, dried||1 830||95||1 210||95||66.1|
|Soybean oil meal|
|Expeller||1 850||95||1 230||97||66.5|
|Solvent||1 720||89||1 150||91||66.8|
SOURCE: Lofgreen and Garrett, 1968.
Table 2. Results obtained with diets based on dried beet pulp for young bulls1
|Supplementation level as percentage of live weight|
up to 300 kg [live weight]
from 300 to 400 kg
from 400 kg to slaughter weight
|Average daily gain||1.24||1.21||1.26|
Dried beet pulp
Dried beet pulp
1 Initial weight, 280 kg; final weight, 519 kg.
As supplements. Trials conducted at the experiment station showed that digestibility of organic matter remained practically the same (at close to 67 percent) when dried beet pulp replaced rolled barley in a ration based on a mixture of maize (i.e. the aerial part of the plant dehydrated in the dough stage, ground and pelleted) and barley; the ration also contained a 35 percent crude protein supplement.
Another trial conducted on the farm compared the effects of using dried beet pulp and rolled barley, respectively, as supplements to maize silage containing 30 percent dry matter. The rations were fed at levels up to 0.75 percent of the live weight of the animals. They included a compound feed containing 38 percent crude protein that was fed at the rate of 1.5 kg per animal per day. The compound feed consisted of 81 percent oil cake (groundnut, cottonseed and soybean meal in equal parts), 9.5 percent molasses and 9.5 percent of a premix providing the required supplementary minerals, trace elements and vitamins. Table 3 presents the results obtained from two groups of over 110 animals each that had identical daily feed intakes when offered rations based on rolled barley and dried sugar beet pulp respectively. They show that the kind of energy supplement used exerted no influence on the average live weight gain. Intakes of feed per kg increase in live weight gain in the two groups were identical: 11.6 kg maize silage, 1.25 kg protein supplement and 1.45 kg of either dried beet pulp or rolled barley. The saving per kg of carcass produced, with dressing percentages of about 60 percent, amounted to 3 kg when beet pulp was used as the supplement instead of barley, i.e. 364 kg per animal.
Table 3. Results obtained from feeding barley and dried beet pulp to young bulls as a supplement to maize silage
|Rolled barley||Dried beet pulp|
|Number of animals||114||115|
|Average daily gain||kg||1.19||1.20|
|Dried beet pulp||-||1.75|
Young bull raised for meat production on dried sugar beet pulp
Our experiments have demonstrated that in diets fed to young steers for fattening, the feeding value of dried beet pulp is identical to that of rolled barley, irrespective of whether it is used as a staple food or as a supplement. These observations confirm the findings of Lofgreen and Garrett (1968) and are in agreement with the net energy values of these feeds (Table 1).
Bhattacharya and Sleiman (1971), working with wether lambs, determined the nutrient digestibility and energy utilization of rations containing 60 percent of a staple food and 40 percent of a mixture of wheat bran, groundnut oil cake, alfalfa hay, salt, limestone and bone meal; the staple food consisted of maize meal and dried beet pulp in proportions that varied inversely from 0 to 100 percent; thus, the four experimental rations contained 0, 30, 45 and 60 percent beet pulp. With average digestibility coefficients of 76.7 percent for dry matter and 76.9 percent for energy, there were no significant differences due to rations.
Beet pulp may therefore be considered as an energy source having the same value as maize grain, even when it comprises 60 percent of the ration. The digestibility of the crude fibre increases with the pulp content of the ration. This was attributed to the high digestibility of the sugar beet pulp fibre due to its low lignification. However, with diets of high grain content Kesler and Spahr (1964) considered that the lower digestibility of fibre was due to the disappearance of bacteria and protozoa that live on cellulose in the rumen, while McCullough and Smart (1970), studying the digestibility of cellulose in vitro, observed a faster and greater disappearance of cellulose when the ferment utilized consisted of rumen fluid taken from bulls on a diet with a high beet pulp rather than maize grain content.
In a lactation trial with eight Holstein-Friesian dairy cows, Bhattacharya and Sleiman (1971) compared a control ration containing 57 percent barley with an experimental ration containing 55 percent beet pulp; no significant difference was observed in either changes in live weight or fatcorrected milk production. In a series of three experiments, Bhattacharya and Lubbadah (1971) studied the effeet of replacing maize with dried sugar beet pulp in high-concentrate dairy cow rations. The control diet contained 73 percent maize, while in the experimental rations 50, 75 and 100 percent respectively of the maize was replaced by beet pulp. No significant differences were observed among rations in live weight gain, milk yield and composition, digestibility of dry matter and energy. Castle (1972) made similar observations during experiments lasting up to 18 weeks with diets in which the concentrate ration contained 80 percent dried beet pulp instead of barley; he concluded that an energy value equivalent to that of barley can be attributed to beet pulp. This was confirmed by the findings of energy balance sheets drawn up by van Es et al. (1971).
Kosar et al. (1974) used dried beet pulp (to which molasses had been added) to replace 75 percent of the concentrate in rations based on maize silage for dairy cows and found no significant differences in milk production.
In a recent experiment, Bhattacharya et al. (1975) studied the replacement of maize by dried beet pulp in highenergy rations fed to sheep and young bulls during the growing-finishing period. The rations contained 90 percent maize grain or 90 percent dried beet pulp, or a mixture of the two in equal proportions (45 percent each); the rest of the ration consisted of 5 percent molasses, 1 percent urea and 4 percent of a mineral mixture fortified with vitamins. These diets were fed to sheep weighing from 34.5 to 55 kg. When the diet contained beet pulp there was a higher average daily weight gain, a better feed conversion efficiency and improved carcass quality. The same was true for dry matter digestibility as measured in young bulls: the digestibilities were 78.1 percent for the pulp plus maize ration as compared to 76.0 percent for the ration containing 90 percent maize. Our own results have confirmed these findings; the dry matter digestibility in our trials with young bulls was 77.9 percent on a diet consisting of 62 percent dried beet pulp, 14 percent flaked maize, 5 percent hay (to ensure proper functioning of the rumen) and 19 percent of a supplement that had a 35 percent crude protein content and provided the necessary minerals and vitamins.
All the results reported here show that beet pulp is an excellent source of energy for ruminants during the growing-finishing period and during lactation. In compounding high-energy rations, beet pulp may be used as the sole source of energy or as a replacement for some of the grain, whether it be barley or maize. Levels of beet pulp as high as 90 percent of the ration have no detrimental effects on animal performance.
In feeding for beef production, dried sugar beet pulp may therefore be used as an energy source to replace a substantial part of the grain component of the ration. In practice, the ration will be fed at a level equivalent to 0.65 percent of the live weight of the animal. The quantities of supplements that should be fed to animals of different weights and the average intake of dried pulp fed ad libitum are shown in Table 2.
The capacity of young bovines to utilize dried beet pulp with remarkable efficiency makes it possible to conserve a considerable portion of the grain crop for direct use by humans and thus helps to reduce the competition between man and animals in meeting energy requirements.
Sectional view of ninth rib of a young bull raised on a beet pulp-based ration
Bhattacharya, A.N. & Lubbadah, W.F. 1971. Feeding high levels of beet pulp in high concentrate dairy rations. J. Dairy Sci., 54:95.
Bhattacharya, A.N. & Sleiman, F.T. 1971. Beet pulp as a grain replacement for dairy cows and sheep. J. Dairy Sci., 54:89.
Bhattacharya, A.N. Khan, T.M. & Uwayjan, M. 1975. Dried beet pulp as a sole source of energy in beef and sheep rations. J. Anim. Sci., 41:616.
Castle, M.E. 1972. A comparative study of the feeding value of dried sugar-beet pulp for milk production. J. Agric. Sci., Camb, 78:371.
Cordiez, E., Bienfait, J.M. & Lambot, O. 1963. Production de viande. Engraissement de jeunes bovins. Paris, Ministère de l'agriculture, Administration de la recherche agronomique. Groupe de travail pour l'étude de l'alimentation du bétail.
Kesler, E.M. & Spahr, S.L. 1964. Physiological effects of high level concentrate feeding. J. Dairy Sci., 47:1122.
Kosar, J., Prokova, M., Zobal, J. & Rohlicek, J. 1974. Effect of sugar beet as the chief source of energy on milk yield of dairy cows. Nutr. Abstr. Rev., 45: 791.
Lofgreen, G.P. & Garrett, W.N. 1968. A system for expressing net energy requirements and feed values for growing and finishing beef cattle. J. Anim. Sci., 27:793.
McCullough, M.E. & Smart, W.W.G., Jr. 1970. Rumen fermentation and in vivo and in vitro digestibility of all-in-one rations. J. Dairy Sci., 53:1560.
van Es, A.J.H., Nijkamp, K.J. & Vogt, J.E. 1971. The net energy content of dried sugar-beet pulp and sucrose when fed to lactating cows. Neth. J. agric. Sci., 19:48.