Effects of Dietary Conjugated Linoleic Acid on the Productivity of Laying Hens and Egg Quality During Refrigerated Storage

Abstract

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.

Effect of storage temperature on the quality of eggs from conjugated linoleic acid-fed laying hens

“…The increase in yolk weight of eggs from hens fed CLA was much higher than the control group . A recent study showed that dietary CLA increased yolk water content linearly (Shang et al, 2004). Similarly, in the present study, when eggs from CLA-fed laying hens were stored at 4 °C for 30 days, there was a significant increase in the proportions of yolk weight and a decrease in the proportions of albumen compared to the control group.…”

“…colour defects and abnormal pH changes in yolk and albumen of eggs) of the eggs stored at 4 °C. As the level of CLA was increased in the diet, yolk pH increased and albumen pH decreased in the eggs stored at 4 °C (Shang et al, 2004). Similar adverse effects were observed in the eggs from laying hens fed cyclopropene fatty acids .…”

“…CLA eggs had higher iron, calcium and zinc concentrations and lower magnesium, sodium and chloride concentrations in albumen relative to those from laying hens fed the control diet (Aydin et al, 2001). Recently, Shang et al (2004) showed that there was a linear increase in the levels of sodium, potassium, and magnesium of the yolk of the eggs stored at 4 °C for 28 days. Interestingly, the colour changes seen in yolk and albumen were only associated with cold storage temperatures.…”

“…In a previous study, it was shown that eggs from CLA-fed hens (stored at 4 °C for 10 weeks) had higher iron, calcium and zinc concentrations and lower magnesium, sodium and chloride concentrations in albumen relative to those from laying hens fed maize oil (Aydin et al, 2001). A recent study showed that sodium, potassium and magnesium concentration of the egg yolk increased as the CLA levels increased in a diet (Shang et al, 2004). The textural changes in the eggs from CLA-fed laying hens could be related to an increase of yolk water content, the movement of ions between yolk and albumen or change of egg yolk pH during cold storage .…”

Effect of dietary conjugated linoleic acid on laying hen performance, egg yolk fatty acid composition and egg quality during refrigerated storage

“…No mortality of hens occurred during the experiment. Ahn et al (1999) and Shang et al (2004) reported that with increasing dietary CLA supply, feed intake and the rate of egg production decreased linearly. Although initially no significant differences were observed between groups with respect to percentage of egg yolk at one day of storage, there were significant differences between percentage increases of egg yolks at the end of the storage period (Table 3).…”