Protein and energy availability of sorghum wet distiller grains without solubles in comparison to the parental grain

Tuesday, July 22, 2014
Exhibit Hall AB (Kansas City Convention Center)
Marķa de los Angeles Bruni , Facultad de Agronomia Universidad de la Republica, Paysandu, Uruguay
Ana Ines Trujillo , Facultad de Agronomia, Universidad de la Republica, Montevideo, Uruguay
Abstract Text:

Sorghum can be an alternative for ethanol industry in Uruguay and its by-product (SWDG) can be used as animal feed. An accurate characterization of protein fractions and energy is required for ruminant diets formulation. The chemical profile (in % ± standard deviation) of SWDG presented high values of moisture (66.7 ± 2.6), crude protein (CP, 31.4 ± 0.7), fat (11.0 ± 0.7) and neutral detergent fiber (70.2 ± 2.2).The objective of this study was to characterize the protein fractions and estimate energy digestible (ED) content of three batches of SWDG and its parental grain (SG). In addition, intestinal digestible protein (IDP) of SWDG was measured. Protein fractions were assessed according to the Cornell Net Carbohydrate and Protein System (rapidly protein degradable: A+B1; intermediate degradability: B2; slowly degradable: B3 and undegradable fraction: C, as percentage of CP). The rumen undegradable protein (RUP) was evaluated by in situ assay. Pepsin-pancreatin digestion of rumen pre-incubated (12 h) samples was used to estimate IDP. Digestible energy content was estimated using summative equation computed from digestibility’s nutrients by chemical (NRC, 2001) or in situ (using 48 h of nutrient disappearance) approach. Data was analyzed with PROC GLM in a completely randomized design and compared with Tukey test. No differences were found between batches, neither in SWDG nor in SG. The SWDG presented lower (P<0.005) values of A+B1 and B2 fractions than SG (2.3 vs. 4.2 % and 36.3 vs. 60.5 %) respectively; however B3 and C fractions were greater (P<0.018) than SG (27.7 vs. 13.2% and 33.7 vs. 22.1%). The SWDG presented greater (P<0.05) RUP (estimated using passage rate = 2%/h) compared with SG (75.5 vs. 42.2 % CP). The IDP of the SWDG was 51.1 ± 4.5%RUP providing an average value of total digestible protein of 63.6%. Digestible energy estimations of SDWG were lower (P<0.003) than SG (3.16 vs. 3.7 and 2.5 vs.3.7 Mcal/kg DM for chemical or in situ approach, respectively). The greatest difference between the two approaches was observed in SWDG which could be probably explained by estimation of truly digestible CP and NDF fractions. The potential supply of protein fractions of the SWDG was modified by the industrial process increasing slowly degradable and undegradable fractions. The potential of absorbable protein of SWDG was around half of a soybean meal while its ED content represent 70-80% of energetic value of SG.

Keywords: Distillers grain, nutritive value, intestinal digestibility