Virginia Tech researchers have found that dietary phosphorus requirements are independent of calcium requirements. In other words, as long as the diet meets the individual requirements for each mineral, you don't have to worry about matching up phosphorus and calcium in a particular ratio.
In a follow-up e-mail exchange with the editors of Nutritionist e-Network, lead researcher Katharine Knowlton said there's a substantial body of work (beyond the Virginia Tech paper in JDS) that documents this. One experiment showed no ill effects in varying the calcium-to-phosphorus ratio all the way from 1:1 to 7:1, she said. And, being free of the ratio can help to avoid the over-feeding of phosphorus, which means less excretion of phosphorus into the environment. Nutritionists don't have to worry about adding extra phosphorus to balance high-calcium ingredients — they can absolutely get out of that practice, Knowlton says. In monogastric animals, the calcium-to-phosphorus ratio seems to be important, but in ruminants, it isn't, she adds.