| Abstrakt: |
In studies of the iodine requirements of poultry a simple type of goitrogenic ration has been used at this Station. This has consisted essentially of ground yellow corn, dried brewers' yeast residuals, soybean oil meal, steamed bone meal, salt and vitamin D oil. This has supported fairly good growth and feathering and has allowed the production of severe goiter when feedstuffs selected for low iodine content were used. The goitrogenic effect has been readily overcome by the addition of iodine to the ration. However, it was found that both production and reproduction on this ration were poor, even when sufficient iodine was present to prevent goiter.In order to study the iodine requirements of laying birds, it was necessary to correct this difficulty. Experience had shown that the replacement of part of the soybean oil meal with casein in the type of ration just mentioned would permit excellent growth. Accordingly, a number of single-comb White Leghorn pullets, reared on the goitrogenic type of ration, were divided into 3 pens at time of sexual maturity and were fed rations containing different proportions of casein and soybean oil meal. The protein, vitamin, calcium and phosphorus content of these rations were approximately the same. Oat groats were also added at the 15% level in pens 2 and 3. Pertinent data are given in Table I.It is obvious from the data in Table I that reproductive performance in period A improved as the soybean oil meal was replaced with casein and oat groats. Nevertheless the results were not satisfactory. Hence in period B the amount of soybean oil meal was reduced to 6% in pens 1 and 2. Pen 3 was retained as control on the same level of soybean oil meal as in period A. |
