Effect of dietary lipid saturation on layer production and egg quality

[摘要] English: A study was conducted to investigate the effects of dietary lipid saturation on nutrientdigestibility, egg production and egg quality characteristics of laying hens during peakproduction (�?42 weeks of age). Five isoenergetic (12.6 MJ AME/kg DM) andisonitrogenous (170 g CP/kg DM) diets were formulated with a 30 g/kg lipid inclusion level,using a blend (50 / 50) of fish- and linseed oil (control n-3), pure fish oil (polyunsaturated n-3), sunflower oil (polyunsaturated n-6), high oleic acid (HO) sunflower oil (monounsaturatedn-9) and tallow (saturated fatty acid treatment). The blend of fish- and linseed oil blend wereused to increase the α-linolenic acid content of the control n-3 diet, while fish oil was used inthe polyunsaturated n-3 diet to increase the concentration of eicosopentaenoic- (EPA) anddocosahexanoic acid (DHA) fatty acids primarily. Sunflower oil and HO sunflower oil wasused to increase the linoleic- and oleic acid in the polyunsaturated n-6 and monounsaturatedn-9 diets respectively, whereas tallow was used to increase palmitic- and stearic acid levels inthe saturated fatty acid (SFA) treatment. Two hundred, individually caged Hy-Line SilverBrown hens (20 weeks of age) were randomly allocated to the five dietary treatments (n = 40replicates/treatment) and received the respective experimental diets. During 24, 28, 32, 36and 40 weeks of age, all eggs produced were recorded, individually weighed and used foranalysis of internal and external egg qualities. While feed intake of hens was measuredweekly, body weights were determined monthly. Data for the respective collection weekswere pooled for calculation of parameter means during statistical analysis. During thementioned weeks eggs were evaluated for shell quality and internal egg quality. During week30 of age, 12 eggs per treatment were also randomly selected for analyses of fatty acidmethyl esters (FAME), thiobarbituric acid reactive substances (TBARS) and peroxide value(PV) while another 12 eggs were stored at 4oC for analyses after 28 days. At the end of thestudy (42 weeks of age) six birds per treatment were used to determine the effects of dietarylipid saturation on nutrient digestibility.Dietary lipid saturation had no effect (P > 0.05) on feed intake as well as most of the nutrientdigestibility coefficients, except in the case of crude protein (P < 0.05) and fat (P < 0.0001),whereby the monounsaturated n-9 diet resulted in the highest (P < 0.05) CP digestibilitywhich differs statistically only with that of the polyunsaturated n-6 diet, but not with any ofthe other dietary treatments. Therefore, no clear influence of dietary lipid saturation on apparent digestibility of CP could be detected. Furthermore, all poly- and monounsaturateddiets had a higher fat digestibility (94.2 to 95.6%) than the SFA diet (90.4%). Although boththe polyunsaturated n-6 and control n-3 treatments had the lowest (P < 0.01) apparentmetabolisable energy (AME) and AME corrected for nitrogen (AMEn) values, no clear trendregarding dietary lipid saturation on nutrient digestibility could be established. Similarly tonutrient digestibility results, dietary lipid saturation resulted in a limited significant responseon production parameters tested without any recognisable trends. The SFA treatment resultedin the lowest (P < 0.015) percentage sellable eggs, while feed efficiency (P < 0.001) andpercentage eggshell (P < 0.05) was the lowest for the monounsaturated n-9 andpolyunsaturated n-6 treatments respectively. Evaluating internal egg qualities, the control n-3and polyunsaturated n-3 treatments had the lowest (P < 0.0001) egg yolk colour compared tothat of the SFA which resulted in the highest colour score. Additionally, the FAME of eggyolk was successfully altered to represent that of the particular dietary treatment without anydetrimental effects on the total fat content (P = 0.24), fat free dry matter (P = 0.17) ormoisture (P = 0.66) content of egg yolk. The polyunsaturated n-3 treatment was highlyeffective (P < 0.0001) in increasing the EPA and DHA concentration of egg yolk, whereas ageneral increase in the dietary n-3 content resulted in a decreased (P < 0.0001) ratio of n-6 /n-3 for both the control n-3 and polyunsaturated n-3 diets. Both the SFA andmonounsaturated n-9 treatments resulted in the lowest (P < 0.0001) TBARS for both timeperiods, whereas the polyunsaturated n-3 treatment resulted in the highest (P < 0.001)TBARS for both fresh and stored eggs (0.27 mg malonaldehyde / kg yolk during both timeperiods).From the results of the current study it can be concluded that although fat digestion was lowerfor the SFA treatment, AME values did not differ between treatments. With the exception ofthe SFA treatment that resulted in less sellable eggs, no influence of lipid saturation on eggproduction and external egg shell qualities could be detected. The results showed that PUFAn-3 diets could be successfully used to enrich the essential n-3 fatty acids of eggs. However,lipid oxidation stability as well as yolk colour was negatively influenced by an increase inPUFA n-3 type fatty acids.

[发布机构] University of the Free State