The Effect of Gamma Irradiation of Corn Seeds on Performance and Fermentation Parameters of Corn Forage and Silage

The use of radiation has become a way of life in most countries around the globe. The utilization of nuclear techniques in the area of agriculture, defense, and power generation has increased over the last few decades. Radiation technology is widely used to produce changes in product characteristics leading to the development of new products. Radiation-mediated morphological, structural and/or functional changes in a plant are governed by the intensity and duration of the gamma irradiation. Gamma irradiation was found to increase plant productivity. Gamma rays represent one of the important physical agents used to improve the characters and productivity of many plants (e.g. rice, maize, bean, cowpea, and potato). Gamma irradiation also has been found to be very useful for both sterilization and for the preservation of food and cereal grain in nutrition and agriculture. Gamma rays were also found to cause modulation in protein patterns by inducing the appearance and/or disappearance of some protein bands. It has been shown that large DNA strands were broken into small strands at low irradiation doses but small and large DNA strands were broken at higher irradiation doses. Also it has reported that germination of seeds can be influenced in both positive and negative directions by gamma radiation exposure as a result of mutation inductions depending on cellular abnormalities or stimulatory modifications triggered by radiation doses. In several studies, lethal and stimulatory effects of gamma irradiation on germination percentage, emergence, and survival of seedlings of different plant species have been reported. The present work has been intended to investigate the response of corn seeds exposed to gamma irradiation (25 Gys) in terms of the nutritional performance of its forage and silage compared with control non-exposed seeds. Corn seeds were obtained from the Vegetable Crop Seed Production and Technology section, Ghezlagh Farm, College of Abouraihan, university of Tehran, Iran. Four kg corn seeds (single cross 704) were divided into 2 groups. The first group did not have any treatment to serve as a control, while the second group was irradiated with Gamma rays (25 Gray) using Gamma cell – cobalt- 60 instruction and with the rate of 0.55 Gr/ min at the Nuclear Agricultural Research School, Nuclear Science and Technology Research Institute, Karaj, Iran. Field experiments were conducted during the summer seasons at Ghezlal farm Research Station located at the southwest of Tehran province, Varamin, to study the effect of gamma irradiation (25 Gray) on the performance of corn forage and silage. After irradiation, control and irradiated seeds were cultivated in 2000 m2. Agricultural practices such as: irrigation, weeding, fertilization, and pest control were carried out as recommended. Samples of corn plants were obtained at the late stage of growth and amounts of proline, soluble carbohydrate, and protein were determined. Performance chrematistics of experimental groups were also recorded. After harvesting, the corn forage was chopped and transferred to an experimental silo made of polyethylene pipe. DM, ash, CP, NDF, and ADF of experimental silages were determined according to standards procedures. The pH of silage also was determined using pH meters. For the determination of gas production parameters, 200 mg of dry samples were incubated at gas production environment and the amount and rate of gas production were recorded at a different time of incubation (0, 2, 4, 6, 8, 12, 24, 48, 72 and 96 h). Using gas production parameters, the amount of OM digestibility, ME, NEL, and SCFA were also determined. Data were analyzed using the t-student test of SAS software (ver. 9.1). Duncan’s multiple range test was used to detect statistical significance between treatments using a significance level of 0.05. Irradiation of corn seeds increased corn performance (wet and dry weight of seed and forage), amount of soluble carbohydrates and protein, and concentration of proline (P<0.05). The exposed treatment showed the highest increase in seed weight, seed number, and weight of 1000 seeds as compared to the control (P < 0.05). Amount of gas, and b and c fractions of gas production, the concentration of short-chain fatty acids (SCFAs), metabolizable (ME) and net energy for lactation (NEL), and organic matter digestibility (OMD) were higher for treated corn forage and silage compared to the control group (P < 0.05). Also, exposed corn silage had a lower level of pH and higher amount of dry matter (DM) and crude protein (CP) than control (P < 0.05). The results of this study show that exposing irradiation of corn seeds to 25 gray gamma-ray improves fermentation parameters and nutrition values of corn forage and silage.