| Popis: |
IN RECENT years several ingredients have been reported to contain one or more unidentified factors necessary for maximum hatchability of eggs and maximum growth of chicks and poults. These findings give rise to the question of the need for such unidentified factors for egg production. Beneficial effects of unidentified factors on egg production have been reported by Wiese et al. (1948), Petersen et al. (1948), Schlamb and Winter (1948), Couch et al. (1950), Patterson and Blaylock (1953), Kurnick et al. (1955), Jensen and McGinnis (1957) and others. However, most of these were hatchability experiments with breeding hens, in many cases using heavy breeds. Skinner et al. (1951) showed that animal protein factor and fish meal increased egg production in caged White Leghorn hens. The need for zinc and molybdenum in poultry diets has received considerable attention in the work of Dannenburg et al. (1955), Morrison et al. (1955), Reid et … |
