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Evaluation of individual amino acids (AA) and factors that affect the AA profile in corn silage over a 2-year period.

X. Huang



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Evaluation of individual amino acids (AA) and factors that affect the AA profile in corn silage over a 2-year period.
X. Huang*1, P. Yoder2, R. Ward1. 1Cumberland Valley Analytical Services Waynesboro, PA, 2Perdue AgriBusiness LLC Salisbury, MD.

Balancing diets for essential AAs has both environmental and economic benefits for the dairy industry, and this approach requires accurate AA profiles of feedstuffs. The objectives of this study were to assess NIR measurements for individual AAs and factors that may affect the EAA profile of corn silage. The fermentation results and nutrient components data were collected from 1,243 corn silage samples across 2 years (2018 and 2019). Around 13% outliers were removed using the 3-step method published by Yoder et al. (2014). Analysis methods (NIR vs chemistry fermentation) had no effect on nutrient composition (P > 0.05). The sampling year had a significant effect on nutrient composition, with higher CP, starch, ammonia and dry matter concentrations but lower NDF for 2019 corn silage compared with 2018 (P < 0.05). Averaged AA content in corn silage was 1.65 � 0.11, 4.75 � 0.23, 3.14 � 0.12, 8.59 � 0.55, 4.76 � 0.34, 1.56 � 0.22, 2.59 � 0.31, 1.75 � 0.44, 3.37 � 0.21% of CP for Met, Val, Ile, Leu, Phe, His, Lys, Arg and Thr respectively, which was similar to CNCPS and NRC 2001 library values. All EAAs except for Met, Val, Arg and Thr were affected by sampling year. The Leu, Ile, Phe and His as a % of CP were higher in 2019 corn silage, while Lys as % of CP was higher in 2018 corn silage, which was likely associated with ammonia and starch contents. For example, Leu was positively correlated (0.74) with starch while Lys and Arg were negatively associated with ammonia (−0.71 correlation for both AA). The EAA profile likely is related to corn kernel content versus plant content in corn silage considering the different EAA profile present in these 2 parts of corn silage (12.0 vs. 8.5 Leu as % of CP for corn grain vs. corn silage (CNCPS, v6.5)). Regression models were derived and for some EAA, nutrient components could be used to predict the variation observed in EAA as a percent of CP. In summary, the amount of starch (i.e., corn grain vs. plant material) and ammonia concentration affected individual EAA profile of corn silage protein. Consideration for this variation present maybe warranted for improving our ability to balance diets for EAA.

Keywords: AA profile, corn silage, NIR.