1878
Degradation ruminal kinetics of organic matter, neutral detergent fiber and crude protein of sorghum wet distiller grain without solubles in comparison to the original sorghum grain
A study was conducted to characterize ruminal crude protein (CP) and energy supply of sorghum wet distillers grains (SWDG; 31.4±0.7% CP and 70.2±2.2 % neutral detergent fiber –NDF, 11.0±0.7 % fat, dry basis) from an ethanol plant in Uruguay in comparison to the original sorghum grain (SG). In situ technique was conducted to determine ruminal organic matter (OM),NDF and CP degradation kinetics, their respective effective degradability (considering passage rate of 2% h-1, ED) and the relationship between rumen available Nitrogen (N) and fermentable OM (N:OM ratio) from 3 batches of SWDG and SG. Duplicate samples (5 g of 2 –mm ground) of each feed were incubated in the rumen of 2 lactating dairy cows for 0, 2, 4, 8, 12, 24, 48 and 72 hours. Data were fitted to the nonlinear model D(t)=a+b(1-e-kd(t-t0)) with PROC NLIN of SAS program to determine degradation parameters, where D is percentage disappearance of OM, NDF or CP at the time t, (a) soluble fraction, (b) slowly degradable fraction, (c) degradation rate, and t0 is lag time. Parameters were analyzed with PROC GLM in a completely randomized design and compared by Tukey test. There were not differences for any degradation parameters between batches, neither in SWDG nor in SG. Comparing degradation parameters of SWDG with SG the results were: fractions (a) and (b) of OM were lower (8.1 vs. 22.7% , 54.5 vs. 73.9 %; P<0.05) but (c) was greater (4.8 vs. 3.5 % h-1; P<0.05); (t0) was only present in SWDG (3.1 h); (c) of NDF was greater (6.3 vs. 3.5 % h-1, P<0.05) but (c) of CP was lower (1.1 vs. 1.9 % h-1; P<0.05); fraction (b) of NDF was lower (69.5 vs. 79.3 %, P<0.05) and fraction (b) of CP did not differ (71 vs. 71.7%); fraction (a) of NDF and (t0) were only present in SWDG (5.6 % and 2.7 h), and fraction (a) of CP was lower (0.0 vs. 18.2%). The ED of OM and CP were lower in SWDG compared to SG (44.3 vs. 69.8; 25.5 vs. 52.8 %, respectively; P<0.05) but the ED of NDF was greater (58.3 vs. 50.6%; P<0.05). The N:OM ratio for microbial growth was better in SWDG than in SG (29.4 vs. 8.4 g of N effectively degraded /kg OM effectively degraded). The SWDG seems to be a good supply of ruminal PC and energy in ruminants’ diets.
Keywords:
Sorghum, ethanol by-product, in situ