Effect of storage time on the characteristics of corn and efficiency of its utilization in broiler chickens.

Corn is one of the staple food and feed ingredients in China, therefore its storage is of particular importance. Corn is typically stored for 2 or more years in national barns before it is sold as a food or feed ingredient. However, the effects of stored corn in national barns on the animal performance and nutrient utilization have not been investigated thus far. This study attempted to determine the effects of storage time on the chemical and physical characteristics of corn and its nutritional value, broiler growth performance, and meat quality. Corn grains used in the present study were stored for 4 different periods, from 2 to 5 yr, under the same conditions in a building at the Beijing National Grain Storage Facility. A total of 240 birds in Exp. 1 and 90 birds in Exp. 2 were used to compare the effects of storage time on the utilization of nutrients of corn, the performance, and meat quality of broilers. The content of starch, crude protein, amino acids, fatty acids, and test weight generally decreased with increasing storage time. Corn stored for over 4 yr showed decreased catalase (CAT) and peroxidase (POD) activities and increased fat acidity. Body weight gain (BWG) and European production index (EPI) of broilers from 0 to 3 wk tended to decrease linearly with storage time (0.05 <  P  < 0.10), and the BWG and EPI of broilers from 4 to 6 wk decreased quadratically ( P  < 0.05), whereas feed conversion ratio (FCR) increased with storage time ( P  < 0.05). The FCR, performance, and EPI of broilers positively correlated with CAT activity ( P  < 0.05), and negatively correlated with fat acidity ( P  < 0.05). Drip loss of breast muscle increased linearly with corn storage time ( P  < 0.001); however, pH decreased linearly with corn storage time. Drip loss had a strong negative correlation with POD ( P  < 0.05). There were no significant differences of the storage length on metabolizable energy (ME), digestibility of crude protein, and starch ( P  > 0.05). The digestibility of histidine and arginine, and C18:2 and C18:3 changed quadratically with storage time ( P  < 0.05). Collectively, the results suggest that the use of corn stored for 4 yr in animal feed decreased the performance and meat quality of broilers. Fat acidity, CAT, and POD activities can be used as indexes for evaluating the storage quality of corn.