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Brown Dwarf hens and White Leghorn hens were fed corn- and soybean meal-based diets containing 0, 2.5, or 5.0% conjugated linoleic acid (CLA) for 56 d to explore the effects of dietary CLA on the fatty acid profile and cholesterol content of egg yolks from laying hens of different breeds. 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 the egg yolks. From d 54 to 56, eggs were collected to measure the cholesterol content of yolks, and on d 56, a hen was selected randomly from each replicate and bled to determine the cholesterol content in plasma. There was a significant effect of layer breed on layer performance and egg composition. Concentrations of stearic, arachidonic, and docosahexaenoic acids were higher in the yolks of Brown Dwarf hens than in those of White Leghorn hens. Enrichment of cis-11, trans-13 was higher in the yolks of White Leghorns, but cis-10, cis-12 was higher in those of Brown Dwarf hens. In contrast, feed intake and egg weight, as well as yolk weight and its ratio to egg, were decreased by the 5% dietary CLA treatment. Egg production and feed efficiency were not affected by dietary CLA. Concentrations of total CLA and CLA isomers in the yolk lipids increased (P < 0.01) with increasing dietary CLA. Furthermore, yolk cholesterol was increased with increasing dietary CLA (P < 0.01), but this was significantly decreased in Brown Dwarf hens (P < 0.01) by feeding 2.5% CLA. There was no apparent correlation between yolk cholesterol content and serum cholesterol content. In conclusion, Brown Dwarf layers had the breed-specific characteristics of enrichment of CLA isomers and fatty acids in yolk lipids in response to dietary CLA. [ABSTRACT FROM AUTHOR]

A total of 216 Brown Dwarf laying hens (1.62 ± 0.06 kg BW and 60 wk old) were fed 1 of 3 corn-soybean meal-based diets containing 0, 2.5, or 5.0% conjugated linoleic aicd (CLA) to explore its effects on the fatty acid composition of egg yolk, plasma, and liver as well as hepatic stearoyl-coenzyme A desaturase-1 (SCD-1) activity and its mRNA gene expression. Four hens were placed in wired-floored cages (45 ⊗ 40 ⊗ 45 cm) and 3 cages were grouped as 1 replicate, resulting in 6 replicates per treatment. The experimental diets were fed for 54 d, and then eggs were collected to determine the fatty acid composition of egg yolk. Four eggs were randomly selected from the total day's production for each replicate, and the contents were pooled prior to analysis. On d 56, one randomly chosen hen from each replicate (6 hens per replicate and a total of 18 hens) was bled via heart puncture and then killed in order to collect liver samples to measure the fatty acid profile of plasma and liver tissue as well as hepatic SCD-1 activity and its mRNA abundance. Dietary supplementation of CLA resulted in a significant deposition of CLA in egg yolk, plasma, and liver lipids (P « 0.01). As the dietary level of CLA increased, the concentration of saturated fatty acids in egg yolk, plasma, and liver also increased (P « 0.05). However, the concentration of monounsaturated fatty acids in these same tissues decreased (P « 0.01). Compared with the control, the activity of SCD-1 was reduced by feeding 2.5% CLA (P « 0.05) without a change in SCD-1 mRNA gene expression. However, feeding 5% CLA reduced both SCD-1 activity and mRNA abundance (P « 0.05). These results indicate that the conversion of saturated to monounsaturated fatty acids in egg yolk, plasma, and liver might be modulated directly at hepatic mRNA gene expression levels, or may be indirectly regulated at the downstream post-transcriptional levels. [ABSTRACT FROM AUTHOR]

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°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. [ABSTRACT FROM AUTHOR]

The research studied the effects of l -methionine (l -Met) on growth performance, carcass quality, feather traits, and small intestinal morphology of Pekin ducks compared with conventional dl -methionine (dl -Met). A total of 1080, 1-day-old male Pekin ducks were randomly allotted to 9 groups with 6 replicate pens of 20 birds each. During the starter phase (1 to 14 d), ducks were fed a basal diet (Met, 0.30%) or that supplemented with dl -Met or l -Met at 0.05, 0.10, 0.15, or 0.20% of feed. During the grower phase (15 to 35 d), ducks were fed a basal diet (Met, 0.24%) or that supplemented with dl - Met or l -Met at 0.04, 0.08, 0.12, or 0.16% of feed. Compared with ducks fed the basal diet, supplementation with either dl - Met or l -Met increased the body weight (BW) of ducks at days 14 and 35, increased average daily gain (ADG) and average daily feed intake (ADFI), decreased F:G at the starter phase, and increased ADG over the whole 35-d period (P < 0.05). The efficacy of l -Met compared to dl - Met was 140.1% for 14-d BW, 137.6% for ADG and 121.0% for F:G for days 1 to 14. Ducks fed diets supplemented with l -Met had greater proportion of leg muscle, higher than in ducks provided with dl - Met (P < 0.05). The breast muscle proportion was enhanced with dl - Met rather than l - Met supplementation (P < 0.01). The back feathers score and fourth primary wing feather length were increased with dl - Met or l -Met supplementation (P < 0.01), and there was increased efficacy of l -Met relative to dl - Met for back feathers score (153.1%). Dietary dl - Met or l - Met supplementation increased villus height of ileal mucosa of ducks at days 14 and 35 (P < 0.01). Overall, dietary l -Met or dl - Met supplementation affected the growth performance of ducks during the starter phase, and improved the feather traits and small intestinal morphology. The efficacy of l -Met to dl - Met ranged from 120 to 140% for growth performance of young ducks (1 to 14 d) and was 153% for the feather traits of ducks (35 d). [ABSTRACT FROM AUTHOR]