E ARLIER studies conducted in this laboratory have dealt with energy, protein and vitamin requirements of ducklings (Scott and Heuser, 1951, 1952;and Scott et al., 1959); little information is available on mineral requirements. Since rickets is uncommon in commercial ducks, it appears likely that the calcium and phosphorus levels used in commercial diets are adequate. These levels usually have been set somewhat higher than the 1.0% Ca and 0.45% available P which are the recommended levels for chickens. In view of the possible detrimental effects of excessive calcium and phosphorus levels, or improper ratios of calcium to phosphorus, not only upon the occurrence of rickets but also as etiological factors in leg weaknesses, it was considered desirable to determine the calcium requirement of young ducklings. The results of four experiments on the calcium requirement, conducted during the past four years, are presented in this report.
EXPERIMENTALWhite Pekin ducklings were distributed at one day of age into pens with wire floors in an enclosed building equipped with forced-air heating. In experiments 1 and 2 which continued until the ducklings were 56 days of age, the ducklings were moved at 28 days to an unheated shed type building, open to the south where they were al-