The use of various combinations of urea and water treatment to improve the nutrient content and in sacco disappearance of Rhodes grass hay (Chloris gayana cv. Callide)

Abstract

Animal Production in Australia 1998 Vol. 22 THE USE OF VARIOUS COMBINATIONS OF UREA AND WATER TREATMENT TO IMPROVE THE NUTRIENT CONTENT AND IN SACCO DISAPPEARANCE OF RHODES GRASS HAY (Chloris gayana cv. Callide) B.C. GRANZINAB, G. McL. DRYDENA and A.S. CHAUDHRY A B A Dept of Animal Production, The University of Queensland Gatton, Lawes, Qld 4343 Present address: NSW Agriculture, Wollongbar Agricultural Institute, Wollongbar, NSW 2477 Urea or ammonia treatment of low-quality temperate forages and crop residues is widely used to increase their intake and digestibility (Fahey et al. 1993). Given that the low intake and digestibility of tropical grasses can limit meat and milk production, it would be advantageous if the benefits of urea or ammonia treatment could be obtained with tropical grasses. The improvement in nutrient content and digestibility of forages treated with ammonia or urea depends on the dry matter content of the feedstuff being treated (Sundstol et al. 1978, Dryden and Leng 1986). No observations could be found in the literature concerning optimum combinations of urea and water required to maximise the nutrient content and digestibility of tropical grasses. In a factorial experiment replicated three times, 500 g DM samples of chaffed Rhodes grass hay were treated with five levels of urea (0, 20, 40, 60, and 80 grams of urea/kg DM) and three levels of added water (250, 500 and 750 grams of water/kg DM). The treatments were made by adding the urea/water solution to Rhodes grass chaff preweighed into plastic bags. After mixing, the samples were stored at 22oC for 28 days. Significant interactions between urea and water, and significant main effects of urea and water on nutrient content and in sacco digestibilities are shown in Table 1. Responses to urea are similar to those reported for temperate low-quality roughages treated with urea or ammonia. The effects of water should be further examined. Urea treatment should improve the nutritional value of conserved tropical grasses for ruminants provided that optimum urea/water combinations are defined. Table 1. Interactions between urea (X1; g/kg DM) and water (X2; g/kg DM), and significant main effects of urea and water on the variables (Y; g/kg DM) of nutrient content and 48 hour in sacco digestibilities Variable Protein Neutral detergent fibre Regression Y = 97.6 + 2.84 X - 0.00240 X X 1 1 2 1 2 2 P 2 R 2 s.e. a 0.0001 0.92 15.8 Y = 747 - 1.77 X - 0.254 X + 0.00579 (X ) + 000211(X ) + 0.00292 (X X ) 1 -3.05*10 (X X ) In sacco dry matter digestibility Main effect - urea Acid detergent fibre Acid detergent lignin Main effect - water Acid detergent fibre Acid detergent lignin a -8 2 2 2 1 2 Y = 684.4 + 0.0012 X X 1 1 1 2 0.0001 2 2 0.80 0.52 0.55 0.25 0.10 0.08 0.37 9.4 20.3 21.2 10.6 5.4 11.7 4.5 0.0001 0.0001 0.0009 0.0024 0.0427 0.0001 In sacco organic matter digestibility Y = 685.6 + 0.0013 X X Y = 358 - 0.211 X Y = 40 - 0.062 X 1 1 Y = 342 + 0.067 X Y = 29 + 0.017 X 2 2 Standard error of regression DRYDEN, G.McL. and LENG, R.A. (1986). Anim. Feed. Sci. Technol. 14, 41-54. FAHEY, G.C. JR, BOURQUIN, L.D., TITGEMEYER, E.C. and ATWELL, D.G. (1993). In Forage Cell Wall Structure and Digestibility (Eds H.G. Jung, D.R. Buxton, R.D. Hatfield and J. Ralph) p. 715. (American Society of Agronomy:Wisconsin). SUNDSTOL, F., COXWORTH, E. and MOWAT, D.N. (1978). World Animal Review 26, 13-21. 385