Rumen degradabilities of some cereal grains and by-products

Abstract

Animal Production in Australia 1998 Vol. 22 RUMEN DEGRADABILITIES OF SOME CEREAL GRAINS AND BY-PRODUCTS R J MOSS, I K BUCHANAN, N D CASEY, A L MATSCHOSS and P R MARTIN Australian Tropical Dairy Institute, DPI Mutdapilly Research Station, MS 825, Peak Crossing, Qld 4306 High energy concentrates are used to increase animal production. Cereal grains provide fermentable metabolisable energy (FME) and digestible carbohydrate for rumen microbial protein synthesis, and their rate and extent of degradation in the rumen could influence feed utilisation. The in sacco technique was used with three rumen fistulated Holstein Friesian steers fed lucerne hay (20% CP), to describe rumen degradation of some cereal grains and by-products available in northern Australia. Disappearance of dry matter (DM) and protein (P) were determined and degradation constants calculated for the equation P= a+b(1-e -ct) (Orskov et al. 1980). Quickly degraded (QD), slowly (SD), effective rumen degradation (ERD) and undegraded P (UDP) (g/kg DM) fractions of metabolisable DM and P were calculated using the equation P = a + (b*c)/(c+r) assuming a rumen outflow rate r = 0.08 per hour for high production (AFRC 1993) (Table 1). Table 1. Degradabilities of dry matter (DM) and protein (P) in cereal grains and by-products Feed Dry matter Barley (2mm) Barley (rolled) Maize (2mm) Maize (rolled) Sorghum (2mm) Sorghum (rolled) Sorghum (1% HCHO) Wheat pollard Rice pollard Hominy (pellet) Protein Barley (2mm) Barley (rolled) Maize (2mm) Maize (rolled) Sorghum (2mm) Sorghum (rolled) Sorghum (1% HCHO) Wheat pollard Rice pollard Hominy (pellet) CP (%) a b c QD SD ERD (g/kg DM) 5 5 3 2 2 3 1 4 7 6 5 6 4 21 29 27 7 6 1 1 2 2 7 9 2 8 9 2 3 0 7 0 6 5 5 3 4 3 8 4 6 6 3 7 7 67 62 70 7 6 4 2 3 2 7 9 3 7 8 3 4 5 8 1 4 6 6 8 7 9 12 2 4 3 3 7 0 4 2 0 2 8 6 2 64.0 47.3 43.6 22.9 31.2 23.6 0.3 86.1 67.3 76.9 UDP ERDP (% CP) 16.9 0.0 19.1 9.8 18.0 1.0 3.1 46.5 33.1 43.1 12.0 12.8 10.7 10.9 10.4 11.8 12.3 20.4 14.1 13.7 3.6 0.0 30.0 11.1 6.2 0.0 0.0 55.8 35.7 44.7 69.4 90.6 78.2 80.4 72.2 92.8 57.6 31.2 57.1 47.0 91.0 93.7 84.9 69.7 82.2 85.8 11.0 40.1 55.4 46.6 0.234 0.123 0.073 0.040 0.045 0.051 0.006 0.165 0.087 0.109 0.157 0.081 0.015 0.016 0.035 0.031 0.031 0.245 0.106 0.178 169 0 191 98 180 10 31 465 331 431 4 0 2 2 6 0 0 4 0 1 3 1 11 5 6 2 1 5 3 6 8 0.4 62 45 44 6 1 0 3 1 8 0.4 153 85 93 Although initial DM and P solubilities were similar for the grains, other degradation characteristics differed, with only 44% of DM (ERDDM) and 31% of P (ERDP %CP) in sorghum degraded in the rumen, compared with 69% DM and 64% P for barley. Maize was intermediate with 56% DM and 44% P. By-products (hominy, wheat pollard, rice pollard) were more rapidly and completely digested than the cereals, although ERDDM and ERDP (%CP) were similar for rice pollard and barley (2mm). Sorghum potentially may provide more bypass starch and bypass protein (UDP) in ruminant rations, though the practical value of this would require study. At moderate levels of supplementation animal responses to different grains are similar, but at higher feeding levels there is greater potential for incomplete digestion of starch with sorghum. Faecal starch levels 20% of faecal DM are common for lactating dairy cows fed sorghum (Ehrlich and Davison 1997). Formaldehyde treatment (1%HCHO) of sorghum (2mm) further reduced degradability. Particle size (rolled vs fine milled 2mm) had a negative influence on all in sacco measures of rumen degradation. Finer grinding is recommended for uniformity in the in sacco evaluation and comparison of feeds. AFRC (1993). Energy and Protein Requirements of Ruminants. (CAB International: Wallingford UK). EHRLICH, W.K. and DAVISON, T.M. (1997). Aust. J. Exp. Agric. 37, 505-8. ORSKOV, E.R., HOVELL, F.D. DeB and MOULD, F. (1980). Trop. Anim. Prod. 5, 195-213. 393