The fatty acid profile and physical quality were assessed for the eggs of six varieties of chicken and duck viz. Desi, Kamrupa, Vanaraja, Pati, Nageswari, and Chara-Chemballi collected from various places of Kamrup district of Assam. After collection, the eggs were sent to Veterinary College and Research Institute, Namakkal for estimation of various fatty acid contents of the eggs. The per cent of total saturated fatty acid (SFA), mono unsaturated fatty acid (MUFA) and poly unsaturated fatty acid (PUFA) content ranged from 45.49 to 49.21, 31.30 to 45.00 and 7.89 to 19.19 respectively in different varieties of poultry. MUFA content was highest in Chara-Chemballi duck followed by Nageswari duck and lowest in Kamrupa chicken. On the contrary, PUFA content was highest in Kamrupa chicken followed by Vanaraja and lowest in Chara-Chemballi duck. Among all SFAs, Palmitic acid (C16:0) content was the highest in all species. Oleic acid (C18:1) and Linoleic acid (C18:2) were the major MUFA and PUFA respectively in all the varieties. Eggs of Vanaraja chicken contained highest Linoleic acid (C18:2). Higher levels of Linolenic acid (C18:3), Ecosapentaenoic acid (C20:5) and Docosahexaenoic acid (C22:6) were found in Kamrupa chicken eggs. The most favourable omega-6: omega-3 PUFA ratio in Desi chicken eggs indicated its superiority over other eggs in reducing cardiovascular risks.
Egg is the cheapest and best source of protein and is consumed by almost all section of people. In general, consumers like to eat eggs of Desi chicken and duck than other eggs because of their taste and hence paid a premium prices for them. Presently, the consumption of eggs has been increasing day by day with increasing awareness in quality. Now-a-days consumers are much concerned about quality of the egg, particularly cholesterol and omega-3- fatty acid content of eggs. The compositions of fatty acids in egg lipids have been highly concerned to human health such as saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA). The cholesterol content of the egg yolk is controversial as it is related to the risk of cardiovascular disease. However the results of numerous studies clearly indicate that cholesterol does not cause atherosclerosis (Trziszka and Przetwórstwo, 2000). The role of PUFAs becomes more important as they are not synthesized in human organism and have to be delivered with food. From the human health point of view, it is important to know the fatty acid profile of eggs of different varieties of poultry and the information on fatty acid composition are also scanty; hence the present study was undertaken to determine the fatty acid profile and physical qualities of different varieties of chicken and duck eggs.
Materials and Methods
Freshly laid eggs with an age not more than one week were collected randomly from different places of Kamrup district to determine the physical qualities and fatty acid profile. Twenty numbers of eggs from each varieties of chicken viz. Desi, Kamrupa and Vanaraja and twenty from each of the duck varieties viz. Pati, Nageswari and Chara-Chemballi were used for the present study. Thus, a total of one hundred and twenty numbers of eggs from which, sixty numbers of eggs were sent to Veterinary College and Research Institute, Namakkal, Tamil Nadu, with suitable packing to prevent breakage for analysis of fatty acid profile by using the methods as per Folch et al., 1957 using methylene chloride and methanol (2:1). The remaining eggs were utilized to determine various physical qualities like egg weight, shape index (Shultz, 1953), air cell height, albumen index (Heiman and Laver, 1936), Yolk index (Funk, 1948), Haugh unit Score and shell thickness as per standard procedures. Yolk colour was measured with the help of Roche Colour Fan. The data were analyzed as per standard statistical methods (Snedecor and Cochran, 1994).
Results and Discussion
The data on different fatty acid profiles of chicken and duck eggs presented in the Table 1 indicated that saturated fatty acid (SFA) was almost similar in both chicken and duck eggs. However, myristic, palmitic, behenic and arachidonic acid contents were comparatively higher in duck eggs than in chicken eggs. The stearic acid content was comparatively higher in chicken eggs than duck eggs. The mono-unsaturated fatty acid (MUFA) content was also higher in duck eggs than chicken eggs. Chara-Chemballi duck recorded the highest and Kamrupa chicken recorded the lowest MUFA content. The total MUFA contents of chicken and duck eggs ranged from 31.30 to 33.72 and 37.88 to 45.00 per cent respectively.
Table 1: Fatty acid profile of different chicken and duck eggs
|Myristic acid (C14:0)||0.27||0.60||0.24||0.39||0.48||0.81|
|Palmitic acid (C16:0)||28.28||25.84||25.70||29.83||33.31||30.56|
|Stearic acid (C18:0)||14.68||14.26||14.21||9.80||7.01||7.50|
|Behenic acid (C22:0)||5.82||5.49||6.07||8.38||6.84||6.25|
|Arachidic acid (C20:0)||0.16||0.24||0.20||0.43||0.26||0.37|
|Oleic acid (C18:1)||31.61||34.25||29.41||35.80||38.79||41.78|
|Palmitoleic acid (C16:1)||2.11||2.60||1.89||2.08||3.85||3.22|
|Linoleic acid (C18:2)||12.06||13.39||11.65||8.34||2.46||5.78|
|Linolenic acid (C18:3)||0.20||0.22||0.33||0.27||0.24||0.38|
|Ecosapentaenoic acid (C20:5)||0.13||0.61||3.30||0.18||2.51||0.24|
|Docosahexaenoic acid (C22:6)||2.17||1.23||3.91||1.78||2.68||1.52|
|ώ 6: ώ 3 PUFA||4.82||6.50||1.55||5.22||0.45||2.70|
However, Polat et al. (2013) reported higher total MUFA as 39.1 in chickens and 52.5 per cent in duck eggs. The oleic acid content of chicken and duck eggs ranged from 29.41 to 34.25 and 35.80 to 41.78 per cent respectively in the present study. The results of the present study were in accordance with the results of Polat et al. (2013), who reported similar palmitic (21.1-26.3%) and linoleic (10.7-28.5%) acid content in chicken eggs. In contrast to present findings, Polat et al. (2013) recorded higher content of oleic (33.9- 48.3%), palmitoleic (2.6-6.5%) and arachidonic (0.7 to 2.2%) acid but lower stearic (4.3-8.1%) acid in chicken eggs. The poly-unsaturated fatty acid (PUFA) contents were higher in chicken eggs than the duck eggs. The SFA: PUFA ratio in Desi chicken and duck eggs were recorded as 3.38 and 4.62 respectively. Among chicken varieties, highest total PUFA was found in Kamrupa and lowest was recorded in Desi chicken. Further Pati duck egg contained highest and Chara- Chemballi contained the lowest total PUFA among duck varieties. The linoleic acid was recorded as the major PUFA in both chicken and duck eggs. Among other PUFAs, Ecosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA) contents were highest in Kamrupa among chicken varieties and in Nageswari among duck varieties. The determination of ώ 6: ώ 3 PUFA was most important from human health point of view. In the present study, the ration was most favourable in Desi chicken and Pati duck eggs which indicated that the consumption of Desi eggs was better for human health. The variations in the fatty acid profile might be due to the differences in species and varieties (Mustonen et al., 2009), different feeding habits (Krimpen et al., 2011) and level of dietary oils (Bean and Leeson, 2003). The cholesterol content was found to be higher in duck eggs than chicken eggs. This finding was similar with the findings of Sarma et al. (2013). Vanaraja and Chara-Chemballi eggs contained the highest level of cholesterol among chicken and ducks respectively.
The mean egg weight of Desi (39.67±0.75g) chicken was significantly (P<0.05) lower than the egg weight of Vanaraja (54.71±0.87g) and Kamrupa (52.65±0.93g) chickens; however there was no significant (P<0.05) difference between Vanaraja and Kamrupa eggs (Table 2). Kalita et al. (2016) also reported similar egg weight in Kamrupa birds under free range system as 52.54±1.72g. In contrast to the present findings, Kalita et al. (2011) recorded much lower average egg weight in case of indigenous and Vanaraja chicken as 33 and 38 g respectively. Among ducks, egg weight was significantly (P<0.05) higher in Chara-Chemballi (66.23 g) followed by Nageswari (60.24±0.93 g) and Pati (57.83±0.87 g).
The mean shape indices recorded for Desi, Vanaraja and Kamrupa as 75.03±1.13, 74.27±1.31 and 75.11±1.06 respectively and there were no any significant differences among them (Table 2). The present findings corroborated the findings of Kalita et al. (2016) and Niranjan et al. (2008) in case of Kamrupa and Vanaraja respectively. The mean shape index of Nageswari duck was found to be significantly (P<0.05) higher than other two varieties of duck. Mahanta et al. (1998) also reported higher egg weight in Chara (69.69 g) and Chemballi (68.08 g) ducks of Kerala.
The mean values for air cell height ranged from 2.07±0.003 to 2.54±0.004 and 2.07±0.004 to 3.02±0.004 in case of chicken and duck egg respectively and were almost within the normal ranges; however the value was significantly (P<0.05) higher in Chara-Chemballi duck eggs (Table 2). Sarma et al. (2013) also reported higher air cell height in case of Chara-Chemballi duck eggs as 3.08±0.005. There were no significant differences in the mean values of shell thickness among chicken varieties and also among the duck varieties; however there was significant difference between chicken and duck.
The mean shell thickness recorded for Desi, Vanaraja and Kamrupa was as 0.32±0.002, 0.34±0.001 and 0.32±0.005 respectively and no significant difference was found among the mean values. However, Kalita et al. (2016) reported lower mean values for shell thickness in case of Kamrupa as 0.292±0.006 in free range system. The higher shell thickness in the present study might be due to the higher access to minerals of scavenged chicken. Similarly there was also no significant difference among the mean values of shell thickness of duck varieties. However, shells of Nageswari duck eggs were thicker than Pati and Chara-Chemballi eggs. Sachdev et al. (2011) reported that the shell thickness was affected by environmental temperature, age of the bird and its genetic constituent. Lowest mean values for albumen index were recorded in Kamrupa (0.09±0.002) and Pati (0.08±0.002) among chicken and duck varieties respectively (Table 2). The present findings were contradicted with the findings of Kalita et al. (2011), who reported the values as 0.09±0.01 and 0.16±0.01 in case of indigenous and Vanaraja chicken. The differences in the findings of the present study might be due to duration in storage of the eggs. The mean value in case of Pati was significantly lower than other two duck varieties. However, there was no significant difference in the mean values among chicken varieties.
Table 2: Physical qualities of different chicken and duck species
|Egg weight (g)||39.67±0.75a||54.71±0.87b||52.65±0.93b||57.83±0.87c||60.24±0.93d||66.23±1.09e|
|Air cell height (mm)||2.07±0.003a||2.11±0.006a||2.54±0.004b||2.07±0.004a||2.78±0.002c||3.02±0.004d|
|Shell thickness (mm)||0.32±0.002a||0.34±0.001a||0.32±0.005a||0.37±0.003b||0.38±0.004b||0.36±0.004b|
|Haugh Unit Score||70.27±1.12a||76.29±0.95b||73.26±0.84ab||80.28±0.97c||84.74±1.23d||87.23±1.04d|
|Yolk colour||7.23±0.23a||8.44±0.31b||8.65±0.13b||9.04±0.16 c||10.34±0.22c||8.69±0.33b|
Figures with Different Superscripts in a Row Differ Significantly (P<0.05)
The mean values of yolk index for Kamrupa (0.41±0.005) were significantly (P<0.05) higher than other chicken varieties (Table 2). The present findings were in accordance with the findings of Kalita et al. (2016) in Kamrupa under free range system. In another study, Kalita et al. (2011) recorded much higher values both in case of indigenous and Vanaraja chicken under intensive system of management in Assam. There was no significant difference among the mean values of duck varieties.
The mean values of Haugh unit recorded as 70.27±1.12, 76.29±0.95 and 73.26±0.84 for Desi, Vanaraja and Kamrupa respectively were significantly (P<0.05) lower than the duck varieties. This might be due to higher weights of duck eggs than chicken. However, Kalita et al. (2016) reported much higher values in case Kamrupa. Sarma et al. (2013) also reported the similar trends of mean values in duck eggs. The differences in mean values might be due to differences in genetic constituents of birds. The yolk weight differed significantly (P<0.05) among the two groups of birds (Table 2). The Vanaraja and Chara-Chemballi eggs recorded the largest yolk among the chicken and duck varieties respectively. The eggs of Chara-Chemballi recorded the heaviest yolk followed by those of Nageswari and Pati. The results of the present findings corroborated the findings of Sarma et al. (2013) in case of Pati and Chara-Chemballi duck eggs. Yolk colour was significantly higher (P<0.05) in Nageswari ducks followed by eggs of Pati, Chara- Chemballi , Kamrupa, Vanaraja and Desi birds.
As the egg is thought to be the most unadulterated food in the world hence assessment of the physical qualities along with fatty acid profiles of chicken and ducks eggs is of paramount importance. Therefore the present study was undertaken to determine the physical as well as fatty acid profiles of eggs of different species of poultry. The Vanaraja and Chara-Chemballi eggs were found to be better in respect of physical quality among chicken and duck group respectively. Further it may be concluded that lower the SFA to PUFA ratio indicated higher proportion of omega-6 fatty acid. The most favourable omega-6: omega-3 PUFA ratio in Desi chicken eggs indicated its preference over other eggs in reducing cardiovascular risks.
The authors are highly thankful to the Directorate of Research, (Vety.), Assam Agricultural University, Khanapara, Guwahati for their assistance and technical guidance for carrying out the research.