Raw Rock Phosphate as a Phosphorus Supplement for Growing Pullets and Layers

Abstract

Duplicate groups of Leghorn-type strain-cross chicks were reared on four diets with 0, .6, 1.2, and 1.8% of raw rock phosphate replacing appropriate quantities of dicalcium phosphate and corn. The fluorine levels added by the rock phosphate were 0, 216, 432, and 648 ppm for the four diets, respectively.The four groups were kept on the same levels of raw rock phosphate through starting, growing, and laying. After the first year of production, the hens were force molted and kept for another year on the same diets.The initial phases of the experiment were repeated and samples of pullets were kept in individual cages until their sexual maturity was determined.The fluorine content of the diet had no significant (P<.05) effect on body weights of the starting chicks. No apparent differences were noticed in feed consumption, feed conversion, and mortality of the chicks. However, growth depression and reduced feed efficiency were noticed among birds on the highest dietary fluorine (648 ppm) at 20 weeks of age. Mortality was not related to the level of fluorine in the diet. Inclusion of 1.8% raw rock phosphate in the diet resulted in 7 to 11 days delay in sexual maturity of the pullets. First year egg production was 77.4% for the basal group and 72.3, 71.3, and 68.8 % with increasing levels of rock phosphate. The basal group was significantly better than the others.Egg weight, interior quality of the egg, shell quality, fertility and hatchability, and performance of the progeny were not affected by the different levels of dietary fluorine.Hens receiving raw rock phosphate produced eggs containing up to .48 ppm and .66 ppm fluorine in the albumin and yolk, respectively, compared with the controls (.23 ppm fluorine in the albumin and .27 ppm fluorine in the yolk). The levels of fluorine added to many community water supplies range from .8 to 1.2 ppm fluorine.