Shang X G, Wang F L, Li D F, Yin J D, Li J Y
Animal Science and Technology College, China Agricultural University, Beijing, China.
Poult Sci. 2004 Oct;83(10):1688-95. doi: 10.1093/ps/83.10.1688.
Five hundred and four 40-wk-old Brown Dwarf hens (1.51 +/- 0.08 kg BW) were fed corn-soybean meal diets containing 0, 1, 2, 3, 4, 5, or 6% conjugated linoleic acid (CLA) for 56 d to measure the effects of dietary CLA on laying hen productivity and egg quality during refrigerated storage. Four hens were placed in 1 cage, and 3 cages were grouped as 1 replicate resulting in 6 replicates per treatment. After feeding the experimental diets for 11 d, eggs were collected to determine the fatty acid composition of egg yolks. From d 12 to 18, eggs from hens fed diets containing 0, 2, 4, and 6% CLA diets were stored at 4 degrees C for up to 28 d. At designated times (1, 14, or 28 d), eggs were taken, broken, and shelled to evaluate water content, pH, and ion concentration. Firmness of hard-cooked egg yolk was also determined. With increased dietary CLA, feed intake, BW gain, rate of egg production, egg weight, and feed efficiency all decreased linearly (P < 0.01). The weight of the yolk, albumen, and shell decreased linearly (P < 0.01) with increasing dietary CLA. Concentration of CLA in the yolk lipids increased quadratically (P < 0.01), with increasing dietary CLA. Concurrent increases (P < 0.01) in the concentration of myristic, palmitic, and stearic acids and decreases (P < 0.01) in oleic, linoleic, linolenic, and archidonic acids in egg yolk lipids were observed. Days of storage and CLA (P < 0.01) increased yolk firmness. Egg yolk water content and pH increased with storage and CLA content (P < 0.01). Corresponding decreases were observed in albumen pH. Regardless of dietary treatment, the concentrations of Na, K, and Mg in egg yolks increased with longer storage time. At 28 d of storage, there was a linear (P < 0.01) increase in Na, K, and Mg content in egg yolks as dietary CLA increased. In contrast to the egg yolk, the concentrations of Na, K, and Mg in egg albumen decreased with storage time. On d 28, there was a linear decrease (P < 0.01) in the Na content of albumen with increasing CLA. This study suggests that the greater firmness of CLA-fed eggs might be related to the change of pH, water content, and ion concentrations during refrigerated storage.
选用504只40周龄的褐壳蛋鸡（体重1.51±0.08千克），饲喂含0%、1%、2%、3%、4%、5%或6%共轭亚油酸（CLA）的玉米-豆粕型日粮，为期56天，以测定日粮CLA对蛋鸡产蛋性能及冷藏期间蛋品质的影响。每笼饲养4只母鸡，每3个笼子作为1个重复，每个处理设6个重复。饲喂试验日粮11天后，收集鸡蛋测定蛋黄脂肪酸组成。从第12天至第18天，将饲喂含0%、2%、4%和6%CLA日粮母鸡所产鸡蛋在4℃下储存长达28天。在指定时间（1天、14天或28天），取出鸡蛋，打破并去壳，以评估水分含量、pH值和离子浓度。同时还测定了煮熟蛋黄的硬度。随着日粮CLA含量增加，采食量、体重增加、产蛋率、蛋重和饲料效率均呈线性下降（P<0.01）。随着日粮CLA含量增加，蛋黄、蛋白和蛋壳重量呈线性下降（P<0.01）。随着日粮CLA含量增加，蛋黄脂质中CLA浓度呈二次曲线增加（P<0.01）。同时观察到蛋黄脂质中肉豆蔻酸、棕榈酸和硬脂酸浓度增加（P<0.01），而油酸、亚油酸、亚麻酸和花生四烯酸浓度下降（P<0.01）。储存天数和CLA（P<0.01）增加了蛋黄硬度。蛋黄水分含量和pH值随储存时间和CLA含量增加而增加（P<0.01）。蛋白pH值则相应下降。无论日粮处理如何，蛋黄中钠、钾和镁的浓度随储存时间延长而增加。在储存28天时，随着日粮CLA含量增加，蛋黄中钠、钾和镁含量呈线性增加（P<0.01）。与蛋黄相反，蛋白中钠、钾和镁的浓度随储存时间下降。在第28天，随着CLA含量增加，蛋白中钠含量呈线性下降（P<0.01）。本研究表明，饲喂CLA的鸡蛋硬度增加可能与冷藏期间pH值、水分含量和离子浓度的变化有关。
