The Cd balance analysis of beef breeding system based on the optimization of forage formula

This study aimed to use linear programming method for forage formulation optimization by dry matter (DM), crude protein (CP), combined net energy (NEmf), beef energy unit (RND) of forage and beef nutritional needs in spring, summer, autumn and winter. Forage formulation optimization in spring including oats, straw, ryegrass and maize with their proportions of dry matter were 47.26%, 36.55%, 13.45% and 2.74% respectively, and Guimu 1 grassy, corn and rice straw in summer with dry matter proportions of 91.25%, 8.49% and 0.26% respectively , and Guimu 1 grassy, corn and sweet potato in autumn by proportions of 89.30%, 9.01% and 1.70% respectively, and oats, rice straw, sweet potato, ryegrass and maize in winter by proportions of 50.26%, 25.59%, 17.49%, 5.61% and 1.04% respectively. There was a state of basically flat between input and output of Cd in beef breeding system by monitoring the Cd contents in forage, drinking water, dung and beef and calculating the input and output dynamic, and the single head beef’s Cd annual input was 753.70 mg while the output was 747.02 mg. In the Cd annual input of beef breeding system, the annual total Cd accumulation contribution rate of beef’s drinking water and fodder additives were 0.05% and 4.56% respectively, while the contribution rate of beef’s forage was 95.39%. The Cd annual total output contribution rates of beef meat and beef urine were 0.46% and 0.06% respectively, while the contribution rate of beef dung was 99.48%. The main ways to reduce the Cd input and increase the Cd output in farming system were to control the Cd content of forage and regulate the Cd output of dung. The net output of Cd per beef in this beef breeding system was 226.55 mg·head-1, accounting for 30.33% of Cd total output. Therefore, the beef breeding system of “forage-beef-dung-forage” building at clean territory could achieve the purpose of forage self sufficient and beef wastes security consumptive, and it ensured the quality of beef forage and beef meat and the system operating in cycle in the low Cd level.