Abstract:
SODIUM HYDROXIDE TREATMENT AND UREA SUPPLEMENTATION OF CHAFFED OATEN HAY G.E. ROBARDS and G.A. WILLIAMS SUMMARY The intake and digestibility of oaten hay by Merino wethers was increased by both urea supplementation and treatment with sodium hydroxide. The combination of treatments resulted in higher intakes and digestibility coefficients than for either treatment alone. INTRODUCTION There have been few experiments in which the intake and in V<VO digestibility of low quality roughage treated with sodium hydroxide have been examined when the treated roughage was consumed as a sole ration by sheep (Jackson 1977). More commonly, sodium hydroxide treatment has been applied as a means of improving the digestibility of ground low quality roughage prior to including it in a mixed ration to be used for production feeding of livestock (Palmer 1976). In Australia where a large proportion of ruminants obtain their nutrient requirements by grazing, there is only limited potential for economic adoption of techniques involving chemical treatment of roughages. However, during the regular seasonal dry periods and particularly those which are abnormally long and develop into droughts, there may be value in treating mature pasture residues orcrop stubbles to change them into rations of at least maintenance quality for livestock. Such modification may also change the utilization of specific nutrients, particularly nitrogen, in the rumen (Donefer 1968). The present experiments were conducted with oaten hay centre of the cereal belt of New South Wales, near Parkes. bility by sheep were examined before and after spraying the hydroxide. In each case the effect of urea supplementation digestibility,parameters was also examined. MATERIALS AND METHODS Experiment 1 Twenty medium peppin Merino wethers with a mean liveweight of 39 kg were placed in metabolism cages and their ration of chaffed oaten hay progressively increased over one week until all sheep were being offered 1300 g (air dry) per day. Half of these wethers were randomly allocated to the treatment group and had 15 ml of a solution containing 100 g urea in 150 ml of water sprayed onto their ration each day. The other ten wethers each had 15 ml of . water sprayed onto their daily ration. After one preliminary week of feeding the chaffed oaten hay with and without urea supplement the dry matter intake of Additionally, over the last 'four days each wether was recorded for nine days.. of the measurement period the daily faecal and urine outputs were collected from five urea-supplemented and five control wethers. produced in the Intake and digestihay with sodium on the intake and N.S.W. Department of Agriculture, Drought Research Unit, Veterinary Research Station, Glenfield, N.S.W. 2167. 261 ' Animal production in Australia Experiment 2 The twenty wethers remained in the metabolism cages and were offered the same oaten hay as that used in experiment 1, but after treatment with sodium hydroxide. The amount offered was adjusted each day in an attempt to ensure that each sheep had a refusal of 200 g. From the beginning of a seven day preliminary period and subsequently throughout a nine day measurement period the same wethers as in experiment 1 had urea sprayed onto their daily ration and the other ten wethers again had their ration sprayed with an'equivalent volume of water. The concentration and volume of urea solution was the same as in experiment 1, and once again during the last four days of the measurement period the daily faecal and urine outputs were collected from five of the ten wethers. The oaten hay offered during this experiment had been chaffed as for experiment 1. Twenty kg batches were then sprayed with 10 1 of a 10% solution of sodium hydroxide. This gave a sodium hydroxide concentration in the feed offered of 5.1 per cent of dry matter or 3.3 per cent on an as-offered basis. Organic matter and nitrogen analyses of feed, faeces and urine were conducted by standard laboratory procedures. Acid detergent fibre and lignin . analyses of feed and faeces were conducted using the methods of Van Soest (1963) and Van Soest and Wine (1968). Analysis of variance was used to determine the significance of differences in digestibility of ration components due to the addition of urea and to treatment with sodium hydroxide. The statistical significance of the effects of these treatments on dry matter intakes was also examined by analysis of variance. RESULTS Components of the chaffed oaten hay as offered to the sheep in experiments 1 and 2 are given in Table 1. TABLE 1 Components of low quality oaten hay as offered to sheep in experiment 1 without treatment and in experiment 2 following spraying with NaOH (each as per cent of dry matter) When the untreated 'Experiment 1 no effects on dry matter, organic digestibility coefficients (Table calculated nitrogen digestibility urea in the nitrogen intake value. oaten hay was supplemented with urea there were matter, acid detergent fibre and lignin 2). The only difference (P<O.O5) was in estimated by including the nitrogen supplied as . 262 Animal production in Australia TABLE 2 Digestibility of ration components and nitrogen balance of sheep when offered untreated and NaOH-treated oaten hay with and without a urea supplement. The addition of urea significantly increased dry matter intake of the oaten straw by 10 per cent (Table 3). There were also significant differences in the average dry matter intake on different days but these were common to both supplemented and unsupplemented groups. When the oaten hay was treated with sodium hydroxide and offered Experiment 2 with and without urea supplement the values recorded for the digestibility of dry matter, organic matter, acid detergent fibre and lignin were markedly higher than had been recorded for the hay before treatment (Table 2). Although the effect of urea on these digestibility values was greater than it had been for the untreated straw the differences were not significant (P>O.O5). There were significant differences (PcO.01) in favour of the urea supplemented group for both apparent nitrogen digestibility and nitrogen balance (Table 2). There was a mentation of the in intake due to 33.9 per cent for TABLE 3 28 NaOH NaOH the per cent increase in dry matter intake due to urea suppletreated oaten hay. These values represented an increase treatment of 14.8 per cent for the unsupplemented group and group supplemented with urea. The effect of urea on the intake by sheep (g D.M./day + SD.) of untreated oaten hay (experiment 1) or the same hay sprayed with NaOH (experiment 2) 263 Animal production in Australia DISCUSSION The large differences in digestibility values and levels of intake reported here demonstrate the value of sodium hydroxide treatment and urea supplementation of chaffed cereal roughage fed to sheep as a sole ration. The values obtained in the two experiments must be considered with the restriction that they were obtained at different times. However, the animals remained in the same treatment group and the experimental periods were conducted only three weeks apart under the same conditions. With an organic matter digestibility of 55.8 per cent, of which 60 per cent probably occurred in the rumen (Hogan and Weston 1969), the associated nitrogen intake would have been barely sufficient to provide for potential incorporation into microbial protein of 3.1 g nitrogen other than ammonia per 100 g of organic matter digested in the rumen (Hogan and Weston 1967). Thus the nitrogen provided as urea was at least partly utilized in increasing the intake and digestibility of the untreated oaten hay. The intake response to urea supplementation was even greater after digestibility of the fibre and other components of the oaten hay had been increased by sodium hydroxide. The increase of 15 per cent in dry matter intake following sodium hydroxide treatment reflects the-observed increase in organic matter digestibility. When the next limiting factor to intake was removed by supplying readily available ' nitrogen, a further response of 28 per cent in dry matter intake was observed. Even higher intake of the oaten hay may have been possible with an increase in sodium hydroxide concentration to further increase organic matter digestibility. However, this is unlikely to be feasiblein a simple system in which the sodium hydroxide is not neutralized, as higher intake of alkaline material may have a deleterious effect on rumen function or animal health. The other alternative is that the sheep may have responded further in intake if the urea supplement had also contained other minerals which may not be present in mature roughage in the quantities required for optimum microbial growth in the rumen. REFERENCES DONEFER, E. HOGAN, J-P., HOGAN, J.P.,, JACKSON, M.G PAL&ER, F-G. VAN SOEST, P VAN SOEST, P (196 8). Proc. Wld. Conf. Anim. Prod. c: 446. and, WESTON, R.H. (1967). Aust. J. Ag'ic. Res. == 973. 18: 20: and. WESTON, R-H. (1969). Aust. J. Agric. Res. == 347. 977) . Anim. Feed Sci. Technol. &: 73. 22: (19 176). ADAS Q.R. == 247. .J. (1963). J. Assoc. Off. Agric. Chem. 46: 829. == .J., and WINE, R-H. (1968). J. Assoc. Off. Anal 8. Chem . == 51: l (1 780. * 264