Predicting ruminal nutrient degradation from physicochemical traits and in vitro gas production of corn grain from contrasting origins

Corn grain texture varies with corn hybrid and growing conditions, affecting its ruminal digestion, microbial rumen-degradable protein ( RDP ) demand, and, ultimately, cattle performance. However, ruminal digestibility assessment is laborious. Therefore, practical alternative tests are warranted as proxies for the aforementioned purpose. Twenty-five Argentinian ( AR ) and eleven North American ( US ) whole-shelled corn samples were collected to (a) evaluate the corn origin effect on color and physicochemical hardness traits, in vitro gas production ( IVGP ), and in situ dry matter ( ISDMD ), starch ( ISSTD ), and crude protein ( ISCPD ) ruminal disappearance; (b) test hardness traits and IVGP measurements to predict nutrient degradability. Kinetics of IVGP was described using an automated system, for which 1 mm-ground samples were 48-h incubated, in duplicate, thrice. To measure ISDMD, ISSTD, and ISCPD, corn samples were 6.25 mm-ground, 22-h incubated in triplicate, using two rumen-cannulated steers, twice. Color coordinates and physicochemical properties differed (P≤0.029) between origins, indicating light-yellow and softness-related attributes for US corn and orange-reddish, hardness-associated attributes for AR corn. The rate of IVGP, ISDMD, ISSTD, and ISCPD were 22, 23, 20, and 10% higher (P<0.001) in US compared with AR corn samples. Corn from AR has higher (P<0.001) crude protein (+28%) and RDP (+17%) concentration compared with US corn. The ISDMD, ISSTD, and ISCPD could be predicted from physicochemical traits and 12- and/or 24-h IVGP with Adj-R 2 ranging from 0.59 to 0.87. This work provides equations for rapid and economical estimations of corn grain nutrients degradability and may aid in balancing nutrient supply with microbial demands in high corn-containing diets.