THE EFFECT OF VARIOUS PLANES OF NUTRITION IN THE LAYING TYPE OF HENS ON CHOLESTEROL CONTENT IN EGG-YOLK

The objective of trials was determine and compare cholesterol content in 1 kg of yolk and in whole yolk and yolk weight as depending upon va rious planes of nutrition mostly in the laying type of hens Shaver Sta rcross 288, Shaver Starcross 579 and in the Hampshire breed with dual- purpose efficiency. Cholesterol content was determined by a Bio-La tes t (Lachema Brno) modified for the purposes of egg yolk analysis. A com parison of the cholesterol content in egg yolk in the Shaver Starcross 288 layers showed the statistically confirmed higher values in the Sh aver Starcross 588 layers at the same plane of nutrition (Tab. I, grou p K). The eggs of Hampshire layers raised on a small farm, on which it was not possible to specify the diet accurately had the statistically significantly higher cholesterol content in yolk than the laying type s of hens Shaver Starcross 288 and 579 (Fig. 1). Partial or full repla cement of wheat by the triticale ingredient in feed mash for the Shave r Starcross 288 layers did not bring about any differences in choleste rol content in the yolk of their eggs (Fig. 2). A decrease in the amou nt of dietary soybean meal to 10% and addition of 5% rapeseed cake wit h higher fat content coming from cold extraction during bio-oil produc tion did not influence cholesterol content in the egg yolk of the Shav er Starcross 288 layers. A decrease in the amount of soybean meal to 5 % and addition of 10% rapeseed cake feed mash increased the cholestero l content in yolk statistically significantly (Tab. 1, Fig. 3). The ad ministration of low-protein feed mashes enriched with supplements of 1 %, 3% and 5% waste fat with oil at a ratio of 3 : 1, that means with t he contents of metabolizable energy 10.93, 11.50 and 11.92 MJ/kg, grad ually the cholesterol content in egg yolk statistically significantly as results of feeding mashes with 3 and 5% supplements of fat mixture (Tab. II. Fig. 4). Cholesterol content in whole yolk decreased after a dministration of low-protein fat-enriched mash fortified with methioni ne, choline and vitamin B2 up to the maximum standardized requirement at the layer age of 24 and 61 weeks and fortified with methionine up t o the maximum standardized amount and with choline and vitamin B2 20% above the standardized requirement and/or with choline and vitamin B2 20% above the standardized requirement at the layer age of 24, 38 and 61 weeks. The same trend was observed during the investigation of chol esterol content per 1 kg yolk, except the layer age of 61 weeks, when cholesterol content per 1 kg yolk, except the layer age of 61 weeks, w hen the cholesterol content was higher after administration of low-pro tein fat-enriched mash fortified with choline 20% above the standardiz ed requirement and with vitamin B2 UP to the maximum standardized requ irement. Those diets did not influence the cholesterol content in egg yolk at the layer age of 28 and 56 weeks (Tab. III, Fig. 5). Chemical hydrolysis of com used as a mash ingredient lead to an increase in cho lesterol content in yolk (Fig. 6). Fortification of non-fat-enriched m ash (Tab. I, group K) with the probiotic premix Lactiferm L-5 for the Shaver Starcross 288 layers decreased the cholesterol content in egg y olk (Fig. 7); the indicator in question was not influenced by fortific ation of low-protein fat-enriched mash with 3% waste fat (Tab. III, gr oup P-A3), except the cholesterol content in whole yolk at dic layer a ge of 61 weeks, when its increase was observed (Fig. 8).