Effects of irradiation and high-pressure steam sterilization on nutrients of rabbit breeding feeds
DING Li1, LIU Jian-gao1, LIU Jian-qi1, WU Bi-zhen1, ZUO Jia-xin1, CHEN Dong-yang1,#br# LIU Xian-jun1, LI Bang-rui1, ZHOU Li-ping1, YI Min2, FENG Jia-li1, ZENG Dong1
1. Hunan Provincial Center for Disease Control and Prevention, Changsha, Hunan 410008, China;
2. Hunan SJA Laboratory Animal Co., Ltd., Changsha,Hunan 400125, China
Abstract:Objective To study the effects of irradiation and high-pressure steam sterilization on formula feeds for laboratory animals and their effects on nutrients, and to explore the optimal sterilization conditions for irradiation and high-pressure steam sterilization.Methods Sterilization of rabbit breeding feeds was carried out by high-pressure steam (121℃, 0.14 MPa) at different time points (10, 15, 20, 30 and 40 min) and 60Co-γ ray irradiation at different doses(10, 15, 25, 30 and 40 kGy). We detected the colony count, coliforms, mold and yeast, pathogenic bacteria, the conventional nutrients (including moisture, crude protein, crude fat, crude fiber, ash, calcium and total phosphorus), vitamins (including vitamin A, vitamin D, vitamin E, vitamin B1, vitamin B2, vitamin B6 and niacin), amino acids (including lysine, arginine, histidine, phenylalanine+tyrosine, threonine, leucine, isoleucine and valine) and minerals (including magnesium, potassium, sodium, iron, manganese, copper, zinc, iodine and selenium) in the unsterilized feed and the sterilized feed. The effects of two sterilization methods on feed nutrients were compared and analyzed, and the optimal sterilization conditions were obtained according to the sterilization effect and the influence on the nutrients.Results The detection results of hygienic microbiological indicators showed that the sterilization effect could meet the requirements of GB 14924.2-2001 only when the time of high-pressure steam sterilization reached 20 minutes and the irradiation sterilization dose 25 kGy. Compared with the control group, high-pressure steam sterilization resulted in 12%-27% loss of crude protein, 45%-54% loss of vitamin D, 35%-46% loss of vitamin B1, 26%-32% loss of vitamin B6, 15%-25% loss of vitamin A and 15%-24% loss of vitamin B2, and led to a decrease in lysine, arginine, histidine, phenylalanine+tyrosine, threonine and leucine, of which the loss of arginine, lysine and phenylalanine+tyrosine was 19%-30%, 23%-32% and 3.5%-8.4% respectively (all P<0.05). Prolonged sterilization time could increase the loss of vitamin A, D, B1, B2, B6, arginine, lysine and phenylalanine+tyrosine, with statistically significant difference (all P<0.05). Irradiation sterilization caused a decrease in lysine content and vitamin content (all P<0.05), of which the loss of vitamin B1 and vitamin D was 25%-27% and 12%-13% respectively. The loss of vitamin B1 increased with the increment of irradiation dose (P<0.05). No statistically significant differences were found in the effects of high-pressure steam sterilization and irradiation sterilization on other nutrients (all P>0.05).Conclusions We can obtain good sterilization effect on the formula feeds for laboratory animals under the condition of sterilization with high-pressure steam at 121℃ and 0.14 Mpa for 20 minutes and irradiation sterilization at a radiation dose of 25 kGy, with preservation of most of the nutrients. Compared with the high-pressure steam sterilization, irradiation sterilization has less loss and damage to nutrients, more convenient sterilization operation and better sterilization effect.