Ruminal disappearance of barley sources using in vitro techniques

Open Access
Author:
De Feo, Mary Elizabeth
Area of Honors:
Animal Sciences
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Tara L. Felix, Thesis Supervisor
  • William Burton Staniar, Honors Advisor
Keywords:
  • rumen
  • barley
  • cattle
  • feedlot
  • hulless
  • in vitro
  • digestibility
Abstract:
Even though barley is often used in animal feed, processing of the grain is necessary to break the tough outer hull and expose the nutritious endosperm. Because processing is expensive, a hulless variety of barley was developed. Not much research has been done comparing the digestibility of hulless barley to traditional processed barley, especially in beef cattle. Therefore, the objectives of this study were to compare in vitro disappearance of dry matter (DM), neutral detergent fiber (NDF), and starch of traditional unprocessed barley, rolled barley, and hulless barley. Each barley source was ground through a 1mm Wiley screen, and subsamples were weighed into F57 filter bags. The samples were incubated in ruminal fluid taken from 2 Angus steers in the DAISY II Incubator for 3, 6, 12, 24, 48, and 72 hours. Residual contents were analyzed to determine in vitro disappearance of DM, NDF, and starch. Data were analyzed using MIXED procedures of SAS (9.4 SAS Inst., Cary, NC) with repeated measures. There was a barley by time interaction for dry matter disappearance. Dry matter disappearance was greatest (P<0.05) for hulless, and was similar (P>0.05) between unprocessed barley and rolled barley, at all time points except for hour 3. Similarly, there was an interaction with time for NDF disappearance where it was also greatest (P<0.05) for hulless barley at all time points when compared to unprocessed barley and rolled barley except for hour 3. NDF disappearance differed (P<0.05) between rolled and unprocessed barley at hours 6 and 48, but rolled barley and unprocessed barley did not differ (P>0.05) in NDF disappearance at 3, 12, 24, and 72 hours post incubation. There was a barley by time interaction for starch disappearance, as well. Starch disappearance was greatest (P<0.05) for hulless barley at 6 hours post incubation when compared to rolled and unprocessed barley. Hulless barley had the greatest (P<0.05) disappearance of both DM and NDF. While unprocessed and rolled barley were not different in DM disappearance, NDF disappearance of unprocessed barley was least (P<0.05) and NDF disappearance of rolled barley was intermediate and different (P<0.05) than both unprocessed and hulless barley. Mean starch disappearance was comparable (P=0.60) between the barley sources. Of the 3 grains tested, hulless barley had the greatest DM and NDF disappearance in vitro. Hulless barley grain also contained 35% less NDF than unprocessed and rolled barley. At 6 hours post incubation, hulless barley had greater starch disappearance than either rolled and unprocessed barley, by 53% and 23% respectively. Based on these results, hulless barley appears to be an acceptable substitute for both whole and processed barley, but more research should be performed on total tract digestibility before making this conclusion.