Abstract:
Proc. Aust, Soc. Anim. Prod. Vol. 18 R.J. MOSS*, W.EHRLICH*, I.K. BUCHANAN* and P. MARTIN** Recycled paper pulp residue was evaluated as a potential component in feed for cattle. Four mature rumen fistulated Hereford steers were fed a mixture of paper pulp and lucerne hay for two months. Initially 4 kg pulp mixed with 4 kg lucerne chaff (dry matter) were fed, and over 5 weeks the pulp component was increased to 6 kg DM/day. At greater than 6 kg feed rejects increased. Paper pulp was high in cell wall, lignin and ash. Protein content (2-4%) and digestibility in sacco (31%) were low. Levels of 20 ppm lead and 60 ppm copper in the pulp may be a concern with prolonged feeding. INTRODUCTION Pulp residues from paper and cardboard manufacture can present a waste disposal problem for paper mills. Most pulp and paper making residues have undergone partial delignification, which would increase the accessibility of wood carbohydrate for digestion by rumen micro-organisms (Millet et-al. 1973), and . digestibility of some paper products can be quite high (Coombe and Briggs 1974). Waste paper is being recycled and extended with wood chip pulp for cardboard manufacture (APM:Petrie). Residue material from this process was examined for its potential food value by laboratory tests and a feeding experiment with Hereford steers. MXLXRIALSANDMETHODS The experiment was conducted at Mutdapilly Research Station 80 km south west of Brisbane (lat. 27O46'S; long- 152�40'E), Digestibility of paper pulp residue was examined in sacco using four mature rumen fistulated Hereford steers (500 kg live weight). These animals were fed 8 kg lucerne hay/head/day for six weeks (April - May 1988) (Period 1) and had access to a small area of heavily grazed Pioneer Rhodes grass, but this contributed little to the animals diet at this time. Thereafter animals were fed a ration of paper pulp residue and lucerne chaff for two months from June to August 1988 (Period 2). Pulp was a mixture of recycled paper and soft-wood chip pulp which had been through a pulping process at the start of paper making (APWPetrie). Fine fibre washed through the drying belts during this process is pressed and stored for recycling. This material was examined in the laboratory and fed in this trial. Two batches of paper pulp were received for the feeding experiment. The first pulp was unsieved (maximum diameter 45 mm) and was used in the first nylon bag digestion experiment. It was fed for the first 14 days of the feeding experiment. Animals were able to separate and reject the larger particles of this pulp and a second batch of paper pulp residue, sieved to a maximum diameter of 15 mm was fed for the remainder of the trial. Two nylon bag digestion trials (Kempton 1980) were conducted to determine the rumen digestibility of the pulp residue and to assess the effects of pulp feeding on rumen breakdown of paper pulp, lucerne hay and two reference concentrates - maize grain and cottonseed meal (CSM). Unsieved pulp (Pulp 1) was used in the first in sacco digestion trial with animals fed lucerne hay and sieved pulp (Pulp 2) in the second trial with animals fed paper pulp plus -lucerne chaff. Nylon bags containing about 5 g (DM) of each individual * ** Qld Dept Primary Industries, Mutdapilly Research Station, MS 825, Ipswich, Qld. 4305, Qld Dept Primary Industries, ARI, Yeerongpilly, Qld. 4001. 316 Proc. Aust. Soc. Anim. Prod, Vdl. 18 substrate were incubated in the four rumen fistulated steers and serially removed over 72 hours. Paper pulp was examined as fed, lucerne hay was oven dried (80�C for 24 hours) and milled through a 2 mm laboratory screen, maize was passed through an agricultural roller mill and cottonseed meal was as obtained. The first digestion experiment was conducted after animals were fed 8 kg lucerne hay plus Rhodes grass for six weeks and the second after two months of feeding pulp plus lucerne chaff. Feed solubility, digestibility and rate and extent of digestion of the feeds were determined in sacco in nylon bags (Kempton 1980)- Pulp dry matter, in vitro dry matter digestibility (IVDMD) (Minson and McLeod 1972), total and digestible cell wall (Moir 1974), and crude protein, lignin and ash contents of pulp and lucerne and mineral and heavy metal content of the pulp were measured (AOAC 1975). RESULTS For the first four weeks animals were fed 4 kg paper pulp plus 4 kg lucerne chaff (dry matter basis). After adaptation animals consumed all feed within 6 hours. To assess voluntary intake of pulp this was increased to 6 kg DM/head/day with 4 kg lucerne in week 5. Paper pulp was increased to 8 kg/head/day for a short period in week 6 but animals began refusing feed and the level of 6 kg was maintained through the rest of the experiment. This was totally consumed. The unsieved (Pulp 1) and sieved (Pulp 2) -paper pulps differed in composition, with the unsieved pulp having a higher ash content and lower IVDMD (Table 1). Pulp 1 contained 58.2% lignin and Pulp 2 62.9% lignin in the organic matter. Crude protein content and digestibility of both pulps were very low (Table 1). Digestion of paper pulp residues in sacco was low. Rate and extent of digestion of the sieved pulp in the second trial were higher than for the unsieved pulp, but disappearance (rumen digestibility) after 24 hours was similar for both pulps (Table 2). Estimated ME content of paper pulp based on 24 hour digestion in sacco was 4.7 MJ ME/kg DM (MAFF 1975). Digestibilities of lucerne, maize and cottonseed meal after 24 hours were lower on pulp/lucerne than on the lucerne/grass diet, but extent of digestion after 72 hours was similar for both diets (Table 2). Table 1 Chemical composition and i n vitro digestibility lucerne, maize grain or cottonseed meal of paper pulp, The steers lost an average of 12 kg (range 5-15 kg) live weight during the experiment. Most of this weight loss occurred in the first month.- Rumen contents were extremely fluid, lacking the dorsal layer of solid material normally present when grazing. Faecal consistency in all animals was normal and no adverse effects on animal health were apparent during or after the feeding experiment. 317 Proc. Aust. Soc. Anim. Prod. Vol. 18 Table 2 Effect of diet on digestion of feeds from nylon bags in the rumen Sodium and copper content of the paper pulp residue were high but other minerals were not excessive (Table 3). Heavy metal analysis indicated that mercury and cadmium were very low, but both pulps contained a significant level of lead. 'Table 3 Chemical and mineral content of paper pulp residue (Pulp 1) DISCUSSION Crude protein and digestibility estimates on both pulps were very low, consistent with values for wood chip pulp (Baker 1973) and newsprint pulp (Dinius and Oltjen (1972). Lignin content was higher, and rumen digestibility much lower than measured by Millet et al. (1973) in paper pulp residues in USA. Our results would indicate a high content of wood chip and newsprint in this pulp residue. Laboratory analyses and estimates of metabolizable energy eontent indicate that this recycled paper pulp residue could only be-regarded as a low quality roughage source for ruminants. Digestibility of paper pulp may have increased with adaptation to the diet and might have been improved by the availability of nitrogen from the lucerne component of the diet. Digestion of lucerne and the reference concentrates of maize and cottonseed meal were 318 Proc. Aust. Soc. Anim. Prod. Vol. 18 reduced, This reduction may have been due to the lower quality diet (Kempton 1980) or to mineral imbalances in the paper pulp. This paper pulp contained levels of copper and lead which may have been sufficient to be toxic to rumen micro-organisms (Mertens and Van Soest 1971) or the animal (Millet et al, 19731, but in our study no obvious signs of toxicity were recorded after 8 weeks of feeding. The low energy content of this paper pulp would limit its potential to use as a minor component to provide fibre in productive rations. The contents of copper and lead may be of concern and should be investigated in longer term experiments, ACKN-EKKNTS Australian paper mills, Petrie supplied the pulp used and Agdale provided financial support for the project. ALS Laboratories Brisbane conducted mineral analysis of the paper pulp. K. McGuigan, DPI Yeerongpilly carried out analyses of heavy metals. REFERENCES ASSOCIATION OFFICIAL AGRICULTURAL CHEMISTS (1975). 'Methods of Analysis.' 11th Ed. (Association of Official Agricultural Chemists: Washington D-C.). BAKER, A-J. (1973). J. Anim. Sci. 36: 768. COOMBE, J.B. and BRIGGS, A.L.(1974). Aust. J. Exp. Agric. Anim. Hush. 14:292. DINIUS, D.A. and OLTJEN, R.R. (1972). J. Anim. Sci. 34: 127. KEMPTON, T.J. (1980). In 'Recent Advances in Animal Nutrition 1980', p-28, editor D.J. Farrell (U.N.E. Armidale, N.S.W.). MAFF (1975). Tech. Bull. 33. 'Energy Allowances and Feeding Systems for Ruminants'. MERTENS, D-W. and VAN SOEST, P.J. (1971). J. Anim. Sci. 33: 293. MILLETT, M-A., BAKER, A-J., SATTER, L-D,, MCGOVERN, J.N. and DINIUS, D.A. (1973). J. Anim. Sci. 37: 599. MINSON, D.J. and McLEOD, M.N. (1972). CSIRO: Div. Trap. Past. Tech. Paper No 8, Australia 1972. MOIR, K-W. (1974). 3. Agric. Sci., Camb. 83: 295.