Research on the Factors Affecting Cholesterol Content and Some Other Characteristics of Eggs in Laying Hens* The effects of genotype and rearing system

The effects of the age of the hen, genotype, rearing system and dietary structure on egg and serum cholesterol content and some other characteristics of eggs were investigated in laying hens. However, only the findings related to genotype and rearing system are given. A total of 840 hens, 21weeks of age and consisting of 400 white layers (Babcock-300) and 440 brown layers (IsaBrown) were used. The 2 genotypes had been housed in different rearing systems, floor pens and cages. Ten different feed groups consisting of controls (I and II), 2% and 4% fiber increment (III, IV, V and VI), 2% and 4% fiber increment + 250 mg/kg vitamin C (VII, VIII, IX and X) formed the feed material of the trial. Energy shortfalls in the diets were made good by soybean oil in one half, and by animal fat (beef tallow) in the other. Genotype and rearing system significantly affected egg and serum cholesterol content. The serum and egg yolk cholesterol contents of white layers were lower than those of brown layers. The effect of genotype on shell ratio and thickness was not significant. Differences between rearing systems were nonsignificant for egg weight, and shell weight and thickness. White layers were better than browns layers, and cage rearing was better than floor pen rearing for egg production, feed consumption and feed conversion. There were positive and significant correlations (P < 0.05) among egg cholesterol content and egg weight, and yolk weight, and also between serum cholesterol and egg production for each genotype. The correlations between serum and egg yolk cholesterol Ozet: Bu cal›flmada yafl, genotip, yetifltirme sistemi ve rasyon yap›s›n›n yumurta tavuklar›nda yumurta ve serum kolesterol icerii ile yumurtan›n dier baz› ozelliklerine etkileri araflt›r›lm›flt›r. Ancak bu makelede sadece genotip ve yetifltirme tipi ile ilgili araflt›rma bulgular› verilmifltir. Cal›flmada 400 adet Beyaz (Babcock-300) ve 440 adet Kahverengi (IsaBrown) olmak uzere 21 haftal›k toplam 840 adet tavuk kullan›lm›fl ve her iki genotipteki hayvanlar yer ve kafes olmak uzere iki farkl› yetifltirme sistemlerinde bar›nd›r›lm›fllard›r. Araflt›rman›n yem materyalini, Kontrol (I ve II), % 2 ve 4 selluloz art›r›m› (III, IV, V ve VI) ve % 2 ve 4 selluloz art›r›m› + 250 mg/kg Vitamin C art›r›m› (VII, VIII, IX ve X) olmak uzere 10 farkl› yem grubu oluflturmufltur. Oluflturulan deneme karmalar›n›n yar›s›nda enerji ac›¤› soya ya¤› dier yar›s›nda ise hayvansal ya¤ (s›¤›r don ya¤›) ile kapat›lm›flt›r. Genotip ve yetifltirme sistemi yumurta ve serum kolesterol iceriini onemli duzeyde etkilemifltir. Serum ve yumurta kolesterol icerii Beyaz yumurta tavuklar›nda, Kahverengi yumurta tavuklar›na gore, daha dufluk saptanm›flt›r. Genotipin kabuk oran› ve kal›nl›¤› uzerindeki etkisi onemli bulunmam›flt›r. Yetifltirme sistemi farkl›l›¤› yumurta a¤›rl›¤›, kabuk a¤›rl›¤› ve kal›nl›¤›n› onemli duzeyde etkilememifltir. Yumurta verimi, yem tuketimi ve yemden yararlanma bak›m›ndan genotipler aras›nda Beyaz yumurta tavuklar›, yetifltirme tipleri aras›nda da kafeste yetifltirme daha iyi sonuc vermifltir. Her iki genotip icin yumurta kolesterol icerii (mg/yumurta) ile yumurta ve sar› a¤›rl›¤›; serum kolesterol icerii ile yumurta verimi aras›nda pozitif ve onemli korrelasyonlar bulunmufltur. Serum ve yumurta kolesterol icerii (mg/g ve mg/yumurta) aras›ndaki korrelasyon ise negatif bulunmufl olup bu iliflki Beyaz yumurta tavuklar›nda onemli c›km›flt›r.