Title:

Development of a Ninhydrin Assay to Quantify Methionine Loss from Commercial Rumen Protected Amino Acid Products

Amino acids (AAs) are an important aspect of dairy cattle nutrition, and they are often limited by diet which makes supplementation valuable for producers. These products are typically coated with a pH-sensitive polymer, fats, or other compounds that help the AAs avoid degradation in the rumen for maximum absorption in the small intestine. Little is known about the quality of these coating techniques or their effect on AA bioavailability. Ninhydrin (NH) is a widely used chemical reagent in quantification of AAs. The objectives of this study were to calculate a standard curve of Methionine (Met) then quantify the amount of AA loss in rumen-protected products to determine quality of the coating. A 1% NH solution was used. To develop the standard curve, Met was weighed in 5mg increments from 0-50mg and dissolved with 3mL of hot distilled water. 100µL of NH was added, samples were vortexed, then incubated at 39°C for 30 minutes. The absorbance of each solution was measured at 570nm. The product testing portion included four commercial rumen-protected methionine products. Tubes were prepared in duplicate with 1g of product in 3mL distilled water and were incubated for either 1, 2, 3, 6, or 9 hours. The liquid portion of these samples were pipetted into cryovials and stored at -80°C for further analysis post development of the standard curve. A total of 17 complete standard runs were used for the final analysis of the standard curve. The results showed that a quadratic model was the best fit, indicating a non-constant rate of change. Preliminary results of the coating quality analysis showed that each treatment released Met at different rates. After the 1-hour incubation, product A had released 36.0 mg Met, product B had released 18.9 mg Met, and product C released 3.3 mg Met. If this product is being degraded over time in this trend, it may result in some products being less bio-available to the animal, which is an important aspect of feed efficiency and milk production.

Name

Comment*

Comments are viewable only by submitter

Captcha*