ENERGY: PROTEIN RELATIONSHIPS IN THE DIETS OF GROWING MINK

Abstract

The apparent digestibility coefficients for energy and protein and the growth responses from weaning to the age of 28 weeks were studied in male and female standard dark mink receiving diets varying in crude protein and gross energy content. Diets containing 16% of crude protein and gross energy at levels of 4.5, 5.6, and 6.7 Cal/g of dry matter were inadequate for survival and growth of weanling mink of either sex. The protein of diets containing either 22% or 28% of crude protein was digested better by males than by females; the digestibility of protein from these rations by males was greater at 21 weeks than at 11 weeks of age, but no such effect of age was found with females. Mature body weights and body lengths of male mink increased as the ratio of apparent digestible energy (A.D.E.) to apparent digestible protein (A.D.P.) was reduced from 34 to 12 (Cal per 100 g/percent protein), the major effect occurring prior to the age of 16 weeks. The A.D.E.:A.D.P. ratios affected the performances of female mink to a lesser degree than those of male mink. Diets containing gross energy at levels below 4.9 Cal/g of dry matter did not support optimum growth of males, but gross energy levels at least as low as 4.5 Cal/g of dry matter appeared to be satisfactory for the growth of females.