The Effects of High Fat Diets on Laying Hens

The objectives of this study were: (1) To determine the effects of feeding a corn-soybean type diet containing 25.0 percent stabilized yellow grease to Single Comb White Leghorn hens. (2) To determine the effects of such a diet when the protein, total vitamin and mineral contents of the diet were varied. In a six month study, four groups of 144 hens each were fed four experimental diets. Diet 1 represented a normal corn-soybean type laying mash. Diets 2, 3 and 4 each contained 25.0 percent stabilized yellow grease but varied in their protein, total vitamin and mineral contents. The experimental factors measured were: rate of egg production, feed consumption, feed conversion, egg weight, interior egg quality, egg fertility and hatchability, hen body weight, hen mortality, incidence of apparent fatty livers and blood serum and egg yolk .cholesterol concentrations. The addition of 25.0 percent stabilized yellow grease to the diet significantly lowered the rate of egg production and feed consumption. The feed conversion values were not significantly different between dietary treatment groups. The addition of 25.0 percent stabilized yellow grease to the diet had no significant effect on either egg weight, interior egg quality, egg fertility, hatchability or incidences of apparent fatty livers. The largest body weight gains were observed with hens consuming a ration containing 25.0 percent stabilized yellow grease, 24.5 percent protein and an increased vitamin and mineral content. In comparison to the control group, the rate of hen mortality increased when fat was added to the diet without a corresponding increase in the protein, total vitamin and mineral content. Egg yolk and blood serum cholesterol levels were not affected when a diet containing 25.0 percent stabilized yellow grease was fed to White Leghorn hens for a period of six months