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:
The progress reported here relates to research Objective 1. Through the course of this project, a number of methods have been developed or evaluated to provide improved methods of feed analysis for commercial application and research. Two advances occurred in the area of neutral detergent fiber digestibility (NDFD) by ruminal microbes. 1) A novel in vitro fermentation system was developed that gives values similar to the most commonly used system. This system can be used with less handling of samples in fermentations where low-speed centrifugation of samples can be performed without sample transfer. 2) A ring test provided definitive information on within- and between-lab variation, which stimulated a key industry group to monitor NDFD values in its check sample system. Additionally, the impact of sample processing methods before measurement of NDFD was characterized. An improved laboratory procedure for measuring rumen protein degradability was developed that accurately reflected differences between protein sources that were provided to lactating cows. Work progressed on development of near infrared reflectance spectroscopy calibrations for rapid analysis of undried and unground feed samples, which will improve the on-farm utility of feed analyses. A robust reference method for starch in animal feeds has been developed and will be tested in a collaborative study through the Association of Official Analytical Chemists (AOAC) to become an official method (appropriate for regulatory purposes). The technology of this method has already been transferred to, and is widely used by commercial feed analysis laboratories serving the livestock, feed, and forage grower industries in the U.S. This new method for starch analysis more accurately reflects available energy to dairy cattle. It has given nutritionists and dairy farmers a better tool to fine-tune rations with optimal energy levels that help dairy cows remain healthy and productive. Methods of sugar analysis were evaluated. A nutritionally relevant carbohydrate fraction for dairy cows was identified. Work continues with the AOAC as it strives to identify methods to measure monosaccharides, sucrose, lactose, and maltose in feeds fed to multiple livestock species.