Effect of garlic oil added to feed and water of laying hens on table egg quality

Transcription

1 Effect of garlic oil added to feed and water of laying hens on table egg quality K. POŁTOWICZ* and S. WĘśYK Department of Animal Genetics and Breeding, National Research Institute of Animal Production, Balice, Poland. *Corresponding author: The effect of supplementing layer diets with garlic oil on table egg quality was investigated. The study involved 135 general-purpose Rosa 1 hens assigned to three groups of 45 hens each. Birds were kept on litter and fed ad libitum with the same complete diet. Group 1 (control) received this feed throughout a -day experiment, while layers from the experimental groups received twice a week an aqueous solution of pressed garlic oil in feed (group 2) or in drinking water (group 3). At 1, 14, 28 and days of the experiment, 10 eggs were randomly chosen from each group to analyse their quality traits. In addition, 6 yolks were randomly chosen from each group of analysed eggs to determine total, HDL and LDL cholesterol. The results obtained were subjected to analysis of variance and significant differences were determined using Duncan s test. The garlic preparation had no effect on laying rate and weight of eggs laid by generalpurpose Rosa 1 hens. No differences were found in majority of egg and egg shell quality traits. The use of garlic oil as a feed supplement for laying hens significantly decreased the level of total cholesterol in egg yolk. Hens given water with the garlic oil laid eggs with reduced cholesterol in yolk, although this effect was slightly smaller than in hens given the garlic oil in feed. As the level of total cholesterol decreased, LDL cholesterol in the egg yolks from the experimental groups decreased and HDL cholesterol slightly increased. The present results show that garlic oil used in layer nutrition lowers the level of cholesterol in egg yolk, but is more effective when supplemented in feed. Key words: garlic oil; yolk cholesterol; egg quality Introduction The abundance of natural, readily available amino acids, fatty acids, minerals and vitamins make hen eggs an important part of the human diet. However, limited egg consumption was recommended for many years due to the considerable yolk cholesterol content. Today, many consumers reduce or avoid the consumption of eggs for health reasons. To improve the dietetic value of eggs, efforts have been made to modify the composition of eggs, in particular to alter the proportion of particular fatty acids (Sirri et al., 1995; Koreleski et al., 1998; Scheideler et al., 1998; Rizzi et al., 2003; Alvarez et al. 2005). Many studies attempted to reduce egg yolk cholesterol levels. Although it is very difficult to reduce the egg cholesterol level, there are some ways of modifying the composition of yolk to reduce it. Good results are achieved by feeding laying hens with a diet containing special mixtures of herbs, oilseeds or plant oils, as well as garlic and onion (El Habbak et al., 1989; Ryś et al., 1996; Narahari and Sujatha, 2003). In recent years, garlic (Allium sativum) has been popular as a strong natural antiatherosclerotic, bactericidal, cholagogic and hypotensive agent that reduces the cholesterol level. It is also used for intestinal disorders and respiratory infections (Kendler, 1987; Lau, 1989; Strzelecka and Kowalski, 2000; Abbott, 2006). Garlic is also used in poultry nutrition (Carrijo et al., 2005). Taken prophylactically, it enhances birds natural immunity and helps to improve health and reduce mortality. The possibility of using garlic as

2 an alternative to commercial growth promoter for broiler chicken has been already investigated by many authors (Mottaghitalab, 2000). Due to the rapid development of alternative animal management systems and the promotion of safe natural foods, this natural feed additive may play a considerable role in poultry nutrition in the future (Griggas and Jacob, 2005). Unfortunately, there are very few reporting results concerning effect of garlic supplement in poultry nutrition on the eating quality of poultry products. Therefore, this study was aimed to determine the effect of an aqueous solution of pressed garlic oil as a feed or water additive for laying hens on table egg quality. Materials and methods A total of 135 general-purpose Rosa 1 hens were randomly assigned to three groups of 45 hens per group. Birds were kept on litter and fed ad libitum with the same DJ1 feed. Hens from group 1 (control) received this feed for the entire -day period of the study, while layers from the experimental groups received, twice a week, an aqueous solution of pressed garlic oil (ALLIVET) in feed (1 ml per 2 kg of feed; group 2) or in drinking water (1 ml per 2 l of water; group 3). During the experiment, the number and weight of eggs laid were recorded daily. Based on the results obtained, the mean percentage of egg production and mean egg weight were calculated at weekly intervals for each group. At 1, 14, 28 and days of the experiment, 10 eggs were randomly selected from each group to evaluate the internal egg and eggshell quality. The following quality traits were determined using an electronic egg evaluation equipment (Technical Service & Supplies): egg weight (g), shell colour (%), height of dense albumen (mm), Haugh units, yolk colour intensity using the Roche colour fan (pts), as well as shell weight (g), shell thickness (µm) and shell density (mg/cm 2 ). Shell strength (N) was determined using an egg crusher. In addition, 6 yolks were randomly chosen from each group of analysed eggs to determine total, HDL and LDL cholesterol. The yolk cholesterol level was determined based on the method of Allain et al. as modified by Roeschlau, following extraction using the Washburn and Nix method. Cholesterol concentration in the analysed sample was read using EPOLL 20 equipment at a wavelength of 500 nm. The results obtained were subjected to analysis of variance and significance of differences was determined using Duncan s test. Results and discussion The use of garlic oil as a layer diet supplement significantly reduced the level of total cholesterol in egg yolk (Table 1). At days of the experiment, hens from group 2 laid eggs in which the level of total cholesterol was mg lower (P 0.01) than in the control group. The same trend, which persisted throughout the experiment, was found in the level of total cholesterol in 1 g of yolk, with a significant difference already confirmed at 28 days of the experiment. All the groups were characterized by a tendency towards lower levels of total cholesterol as hens grew older. In the control group, this decrease was 0.14 and 0.17 mg/g at 28 and days of the experiment, respectively. The greatest differences in cholesterol level at the start and at the end of the study occurred in group mg/g (P 0.01) and 1.04 mg/g (P 0.05) at 28 and days of the experiment, respectively. Similar results were obtained in earlier studies by Połtowicz et al. (2005) using commercial Hy-Line Brown layers. However, the findings of Reddy et al. (1991) failed to confirm the effect of garlic oil on reducing the level of total cholesterol in egg yolk. In their studies, both hens receiving the control diet and those receiving a diet with a 0.02% additive laid eggs with a similar yolk cholesterol content. In the present study, hens receiving water supplemented with a garlic extract laid eggs with a lower yolk cholesterol level, although this effect was smaller compared to the diet supplemented with the garlic extract. At days of the experiment, the total cholesterol level in terms of 1 g yolk decreased by 0.82 mg in relation to the level found on day 1 of the experiment, and in the end of the study was lower by 0.67 mg compared to the control group. According to Codony et al. (1995) and Griffin (1993), a significant decrease in the yolk cholesterol level is difficult to attain. The level of cholesterol can be successfully reduced only by modifying cholesterol biosynthesis (Griffin, 1992). In hens,

3 cholesterol synthesis takes place mainly in the liver, with the greatest amounts deposited in yolk (Ryś et al., 1996). The increased consumption of cholesterol during bile acid synthesis in the liver reduces the proportion of cholesterol in cells (Murray et al., 1995). As the level of total cholesterol decreased, LDL cholesterol in the egg yolks of hens from the experimental groups decreased and HDL cholesterol slightly increased. However, there are few studies on the proportion of particular lipoprotein fractions in egg yolk. The possible reason for this is the belief that total yolk cholesterol rather than its lipoprotein fractions in the human diet plays a role in the coronary heart disease. The level of HDL cholesterol may be important during the production of hatching eggs. The findings of Michalska and Stępińska (1996) showed a positive correlation between the level of HDL cholesterol and fertility as well as hatchability in Japanese quail. These authors also found a significant (P 0.05) correlation between yolk HDL concentration and yolk cholesterol concentration. Table 1. Level of egg yolk cholesterol Day of Group experiment Weight of yolk ± ±1.53 x 19.02±1.28 (g) ± ±1.66 x 18.30± x 19.44±1.68 Y 21.34± ±0.98 Yy 21.54±2.10 Y 20.96±0.93 y 21.02±1.44 Total 1 x ±23.21 x ± ±11.22 cholesterol ± ± ±7.45 (mg) ±15.05 Y ± ±6.09 AYy ±16.44 BYy ±9.35 Y ±13.44 Cholesterol ±0.41 x 14.14± ±0. in 1 g of yolk ±0.32 x 13.56± ±0.51 (mg/g) 28 A 14.06±0.59 BaYy 12.64±0.52 b 13.68±0.55 a 14.03±0.67 by 13.10± ±0.39 HDL ± ± ±0.11 cholesterol ± ± ±0.15 (mg/g) ± ± ± ± ± ±0.12 LDL ± ± ±0.52 cholesterol ±0. a 10.02±0.76 bx 11.18±1.87 (mg/g) 28 A 10.54±0.50 BY 9.34±0.45 y 10.08±0.51 a 10.74±0.57 b 9.66±0.27 y 9.90±0.43 Values in rows marked with different letters a, b differ at P 0.05; A, B at P 0.01 Values in columns marked with different letters x, y differ at P 0.05;, Y at P 0.01 The use of garlic oil in the feeding of laying hens did not affect most of the egg content (Table 2) or egg shell traits (Table 3). The yolk of eggs laid by the control and experimental hens was characterized by similar colour. No differences were found in shell thickness, density or strength. However, giving the garlic extract to hens in feed and water was detrimental to the quality of dense albumen. The greatest differences between albumen traits of eggs laid by the control and experimental hens occurred on day 28 of the experiment, and the lower height of dense albumen and the lower value of Haugh units in groups 2 and 3 were confirmed statistically at P 0.01.

4 Table 2. Results of egg quality evaluation Day of Group experiment Weight of egg ± ± ±4.27 (g) ± ± ± ± ± ± ± ±3.70 Y 69.84±4.43 Weight of yolk 1 x 19.05±1.36 a 19.19±0.96 b 18.03±1.59 (g) 14 x 19.13± ± ± ± ±1.31 Y 20.58±1.16 y 20.39±1.83 Y 20.83±1.26 Y 20.86±1.49 Yolk colour ± ± ± Y 14.67±0.49 Yy 14.75±0.45 Yy 14.67± ±0.78 x 13.75±0.87 x 13.67±0.78 Y 14.58±0.79 Y 14.00±1.04 x 13.58±1.00 Height of dense ± ± ±0.66 albumen ± ± ±0.98 (mm) 28 A 10.19±1.05 BYy 8.90±1.16 BY 8.64± ±0.71 x 9.95± ±1.87 Haugh units ± ± ± ± ± ± A 98.33±4.74 BYy 91.83±6.12 BY 90.92± ±3.27 y 96.83± ±11.43 For explanations see Table 1. Table 3. Results of shell quality evaluation Day of Group experiment Weight of egg ± ± ±4.27 (g) ± ± ± ± ± ± ± ±3.70 Y 69.84±4.43 Shape index ± ± ±4.03 (%) ± ± ± ± ± ± ± ± ±2.66 Shell colour 1 x 55.50±5. 54.±6.53 x 55.92± x 54.75± ± ± ± ± ±5.37 y 50.00± ±6.14 y 49.83±3.83 Shell ± ± ±11.13 strength ± ± ±14.72 (N) ±13.84 x 35.12± ± ±14.36 y 23.06± ±12.48 Weight of shell ± ± ±0.51 (g) ±0.49 b 5.89± ± ± ± ±0. a 5.55± ±0.44 b 6.10±0.51 Shell thickness ± ± ±19.61 (µm) 14 x ± ± ± ± ± ±25. y ± ± ±24.45 Shell density ± ± ±4.77 (mg/cm 2 ) ± ± ± ± ± ± ± ± ±4.78 For explanations see Table 1. The garlic oil supplemented to feed or water did not affect the rate of egg production (Figure 1) or the egg weight (Figure 2) of general-purpose Rosa 1 hens. Similar results were obtained by Reddy et al. (1991) for 26-week-old White Leghorn hens.

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