Abstract
About 3kg of a sample of leaf protein concentrates (LPC) extracted from a stand of ryegrass and white clover pasture in New Zealand was offered by P. DONNELLY, leader of the Protein Extraction Group, Ruakura Animal Research Station, N. Z.. Chemical composition of the sample was determined by conventional procedures of feed analysis. Nutritive value of the sample was determined by bioassay with 219 8-day-old chicks in total. In addition, pigmenting effect of the sample to egg yolk was compared with that of yellow corn and dehydrated alfalfa meal, using 70 White Leghorn hens of about 1.5 years of age in total. Yolk color of the eggs of the hens fed diets containing graded levels of total xanthophyll from one of 3 sources was evaluated by Roche Yolk Color Fan. Relative pigmentation potency of the sample was determined statistically by a slope-ratio assay, taking the potency of yellow corn as 1.00. Relative xanthophyll potency (RXP) was given as a product of total xanthophyll content and relative pigmentation potency.
Under a condition of chemical composition and price of 12 feed ingredients and nutrients requirement of laying hens given in Table 3, least-cost formula feeds were calculated by linear programming using an electronic computer. Economical value of LPC was estimated by shadow price of LPC under the various conditions given to the computer.
The sample had 44.56% of crude protein, of which gross protein value was excellent being 106 with supplemental DL-methionine at a level of 2% in crude protein of LPC. Available energy of LPC, which corresponds to metabolizable energy determined by chemical analysis of diet and excreta, was 2.89kcal/g. The samle contained 3.61% of Ca and 0.48% of P. Availability of P was 64. The sample contained 1, 560ppm of total xanthophyll, of which relative pigmentation potency was 0.70, so RXP of LPC was 1, 092ppm. The corresponding values of dehydrated alfalfa meal were 149ppm, 0.74, and 110ppm, respectivaly.
Under the economic conditions given in Table 3, in which price of soybean meal was \62.40/kgt, h e computer gave 4 kinds of shadow price. Without considering the effect and presence of xanthophyll, a shadow price of \73.38/kg was given. If dietary RXP requirement for laying hens was zero, \74.24/kg was given. The same price was given when maximum levels of milo in the feed was restricted to be 25%. Under this restriction, the computer forced to use yellow corn in least-cost feed, by which enough xanthophyll was supplied. So, xanthophyll in LPC was priceless. If a certain RXP requirement less than 22.9ppm was given, shadow price of LPC was \152.99/kg. In this case, yellow corn and milo+LPC were compared. If RXP requirement was over 22.8ppm, the price was \382.80/kg. In this case, yellow corn+alfalfa meal and yellow corn+LPC were compared.
In the model case of economic evaluation mentioned above, yellow corn and milo were representatives of cereals with and without pigment, respectively. Relationship among shadowprice of LPC (y yen/kg), price ratio of milo/corn (x1), and RXP content in LPC (x2 ppm) could be described by Equation (1),
y=74.24+1.02866(1.0215-x1)•x2……(1)
where x1=1.0215, when the price ratio was over 1.0215.
Shadow price of LPC also depends upon the contents of crude protein (x1 %) and RXP (x2 ppm). The relationthip could be described by Equation (2).
y=19.72+1.224x1+0.07202x2……(2)
