Pigmentation potency of turf Bermuda grass with analysis of carotenoids in egg yolks

Abstract

Four experiments were performed to evaluate the potential of using turf Bermuda grass as a pigmenting agent for laying hens. In experiment 1, the carotene and xanthophyll changes during growth of turf Bermuda grass (Cynodon dactylon) were monitored every three days for a total of 18 days. The carotene and xanthophyll concentrations were not proportional to age or length of the grass clippings. Several methods of processing raw turf Bermuda grass to feed-grade materials were also evaluated. Freeze-drying was by far the best method to maintain the maximum carotene and xanthophyll concentrations. Field drying resulted in considerable losses of both carotene and xanthophyll concentrations. In experiment 2, the effect of diets containing various levels of dehydrated turf Bermuda grass on egg production, feed utilization, yolk color and egg weight was studied. Milo-soybean meal diets were formulated into 4 treatments containing 0, 3, 6 and 9% dried turf Bermuda grass. After 4 weeks the average Roche color score was 1.3, 4.9, 7.0 and 8.7 for treatments 1 through 4, respectively. The maximum egg production and minimum feed consumption were observed in diets containing 3% turf Bermuda grass meal. There was no significant difference of egg weight between control and grass-fed treatments. In experiment 3, the deposition of xanthophylls in egg yolks from laying hens fed 9% turf Bermuda grass meal was studied. The various carotenoids present in egg yolks were analyzed by open-column, thin-layer and high-performance liquid chromatography (HPLC). Chromatographic analyses suggest that the yolk color was due mainly to the presence of free lutein and zeaxanthin at a ratio of 79:21 respectively. In experiment 4, a simple, rapid HPLC method was developed to separate and quantify the major carotenoids present in turf Bermuda grasses with minimum isomerization and oxidation. A reversed-phase isocratic solvent system of water-acetonitrile-chloroform (2:83:15) provided a clear separation of neoxanthin, violaxanthin, lutein and β-carotene. Separation occurred within 10 min with detection at 470 nm and a sensitivity at 0.01 a.u.f.s. This method was found to be very reproducible with coefficients of variation less than 3% in 5 sample analyses.