1a. Objectives (from AD-416)
The objectives of this research are to: 1) Improve accuracy, reproducibility, and ease of measuring/estimating feed digestibility for fiber and protein for use in developing feeding strategies for improving animal performance; 2) Develop rapid methods for measuring feed qualities to improve on-farm precision of feeding; and 3) Establish methods to measure feed characteristics of nutritional relevance in dairy cattle diets.
1b. Approach (from AD-416)
The approaches for the diverse projects in this research will also be diverse. They will include evaluation of feed evaluation equipment and methods used on the farm and in the laboratory to measure specific feed components or their digestibility. We will compare the results of the experimental approaches to values for the feed components measured with standard measurement systems, or to digestibility data from studies with dairy cattle.
3. Progress Report
1.A1. Develop rapid methods for defining and quantifying indigestible residue. One of the project scientists left ARS, and so efforts were redirected toward evaluation of in vitro methodology to insure that maximal digestion of feeds is achieved. 1.A3. Improve in vitro fermentation systems used to evaluate in vitro fiber digestibility. Initial experiments indicated the need for a manifold capable of purging of fermentation tubes with carbon dioxide while allowing individual handling of those tubes. The manifold is being constructed. 1.B. In vitro methods for assessment of ruminal degradability of dietary proteins. Our studies involved comparing the kinetics of proteolysis of several common feed proteins using mixed organisms obtained from the rumen and Streptomyces griseus protease, a commercially available enzyme source commonly used to assess feed protein degradability. This commercial enzyme is widely applied in feed analysis labs, but does not yield rates of degradation that reflect the rates at which rumen microbes break down protein. We modified an analytical assay for total amino acids so that small peptides (molecules containing 2 to about 8 amino acids) can also be detected. This assay is now being used to compare how rumen microbes and Streptomyces griseus protease degrade standard feed proteins. 2.A. Use diode arrays for spectral analysis of undried, unground feeds & 2.B. Develop hardware and software systems to automate the on-farm collection, analysis and transfer of feed composition information. For the progress report on the near infrared reflectance milestone, see 421 report for project 3655-31000-021-02S. 3.A. Establish a reference method for starch analysis of animal feedstuffs. An unexpected requirement for the study arose: a need to establish a starch definition that is analytically accurate. One of the principal ARS investigators has been leading discussions with chemists and nutritionists nationally and internationally to arrive at the needed definition. 3.C. Establish analytical methods for measuring dietary sugar content in feedstuffs. Sample selection and high performance liquid chromatography (HPLC) analysis of 80% and 50% ethanol extracts for specific sugars was completed. Additional evaluation of extraction conditions (time extracted, amount of sample) to enhance recovery of sugars was performed. These activities relate to the development of techniques to evaluate the nutritional value of forages and feeds for use in diet formulation. Such techniques will allow improved diet formulation to increase the conversion of forage to milk production in support of the NP101 Action Plan, Component 2.
5. Significant Activities that Support Special Target Populations
Hristov, A.N., Mcallister, T.A., Ouellet, D.R., Broderick, G.A. 2005. Comparison of purines and nitrogen-15 as microbial flow markers in beef heifers fed barley- or corn-based diets. Canadian Journal of Animal Science. 85:211-222.