採卵鶏の経済寿命延長のための飼養技術　ＩＶ　　一連の飼養技術における経済性と経済的飼育期間の検討

A profit of egg production of hens reared by one of 14 feeding types were calculated by following equation (1), and compared to find the most profitable feeding program.<br>Prafit (hen/year)=egg yield1)(kg)×price of egg (kg)<br>+hen weight1)(kg)×price of hen (kg)<br>-feed intake of hen1)(kg)×price of feed (kg)<br>-cost for replacer1, 2)(\)……(1)<br>1) All the data are averages per hen per year calculated from the data during about 5 years of rotation.<br>2) Cost for replacer=stater intake1, 3)(kg)×price of starter (kg)<br>+grower intake1, 3)(kg)×price of grower (kg)<br>+No. of day-old chicks1)×price of chick (kg)<br>3) Starter is fed until 4 weeks of age, and grower until 20 weeks of age.<br>In the calculation of profit, hens were intended to replace at a certain age, which was called as all-out age, and a certain times during about 5 years. The profit obtained in these rotations during about 5 years was converted to the profit per head per hen per year for comparison among the feeding types. Calculation was done at all-out ages from 52 to 128 weeks of age with 2 weeks of interval, and also at each of 26 dates of the start of feeding in the first year with 2 weeks of interval. Thus, total 5, 772 cases of calculation was carried out by an electronic computor, FACOM 230-48.<br>Average prices of feed, eggs, day-old chicks, and culled hens of 5 years from 1973 to 1978 in Japan were used in the calculation.<br>The date on performance of hens observed in two collaborative feeding experiments for 128 weeks each, which were published previously2, 3), were applied in the calculation.<br>When hens were grown by full-feeding program, the most profitable all-out age was 79 weeks with a profit of 579 yen/head/year by 4 rotations during 5 years.<br>When hens were grown by full-feeding program, the most profitable feeding type was the type forced-molting at 56 weeks of age, and the most profitable all-out age was 93 weeks which a profit of 638 yen/head/year by 3 rotations.<br>When hens were grown by restricted-feeding program without forced-molting. the most profitable all-out age was 83 weeks with a profit of 690 yen/head/year by 4 rotations.<br>Among the hens grown by the restricted feeding program, the most profitable feeding type was the type forced-molting at 80 weeks, and the most profitable all-out age was 113 weeks with a profit of 730 yen/head/year by 2 rotations, <br>From the results of these operations research, a feeding type was recommended in which chicks are grown by restricted feeding program, and hens are forced-molted at 80 weeks of age and replaced at 113 weeks of age. The details of the restricted feeding program and of the program of forced-molting were described in the first paper of the collaborative works2).<br>By the recommended feeding program, economical span of hens life will be prolonged by 1.4 times and the profit per head per year will be increased as much as 26%, compared with those of the hens full-fed without forced-molting.