Abstract: The aim of the present study was to characterize the changes occurring in amino acids profile of camel milk protein during the 1st month of lactation and seek to justify such dynamics of change in relation to the specific needs of growing neonates. Milk samples were collected from camels at varying stages of lactation from the 1st day till 30 day of parturition. Daily samples were tested for fat, protein, lactose, ash and total solids %. The respective mean values at parturition were 0.50±0.06, 12.99±0.20, 2.75±0.40, 0.96±0.037, 20.25±2.50, while at the 30 day the respective mean values were 3.78±0.68, 3.30±0.25, 5.85±0.43. 0.70±0.040, 15.06±1.45. The mean of different amino acid values at the 1st day were significantly increased then sharply decreased in the 3rd day and continuously decreased till reach to the 5th day after that slightly decreased in the 7th day. So, we noticed a non significant decreased in the reminder time, 10, 15, 21 and 30 day, respectively. While there is a significant increase in the level of serum insulin growth factor-1 at zero time and then began to decrease till 30 days. At the same time, concentrations of triiodothyronine and thyroxin were very high at birth and then decreased to relatively low concentrations on day 30. This study demonstrates that camel milk during the 1st month of lactation have important effects on clinical, metabolic and endocrine traits.
INTRODUCTION
Camel's milk is a major source of protein and energy for desert inhabitants especially for those in the Middle East. Recently camel´s milk has been introduced in local markets in countries of Gulf region. Few investigations have focused on studying the chemical composition and nutritional quality of camel´s milk, Farah (1993) and Zheng et al. (2005). Proteins of camel milk contain all essential amino acids and in its fats there are unsaturated aliphatic acids. The amino acid composition of milk declines as lactation advances. The contents of methionine, valine, phenylalanine, arginine and leucine are greater than in cow milk. The nitrogen content of camel milk was found to be 15.6 g/100 g. The following amino acids are present: Alanine 3.05; arginine 3.15; asparagine 7.65; glycine 1.57; glutamine 23.4; histidine 2.5; isoleucine 6.4; leucine 10.4; lysine 7.6; methionine 3.5; phenylalanine 5.7; proline 13.3; serine 5.9; threonine 6.9; tyrosine 5.8; valine 7.4; ammonia 1.72 (Zafar and Shahan, 2004).
Camel colostrum is rich in IgG (Immunoglobulin G) and serum albumin. The main protein in camel colostrum serum is serum albumin while that of bovine colostrum whey islactoglobulin individual camel colostrums (Ibrahim, 1989; Zafar and Shahan, 2004). Colostrum is the exclusive nutrient source for the neonate and the most abundant and well-characterized growth factors in colostrum are probably
Amino acids and insulin like growth factors I and II (Blum and Baumrucker, 2002). Amino acids are an important source of energy for the growing fetus as well as regulators of embryo development and viability (Bell et al., 1989). Furthermore, glutamine plays a major role in fetal nitrogen and carbon metabolism. The vital roles of amino acids in fetal nutrition and metabolism are consistent with our recent findings of the predominance of glutamine in fetal plasma and amniotic fluid and the unusual abundance of arginine and ornithine in the allantoic fluid, Wu et al. (1996). Insulin like growth factor-I (IGF-I) is a major form in colostrums and is biologically more potent than IGF-II. IGF-I has a strong anabolic effect on muscle tissue and it is associated with regulatory feed back of growth hormone. IGF-I can mimic most but probably not all effect of growth hormone (Hammon and Blum, 1998; Daughaday and Rotwein, 1989). This hypothesis is supported by the finding that dietary cow colostrum has been shown to increase blood IGF-I concentration in calves. Endocrine factors such as insulin like growth factor and thyroid hormones (Triiodothyronone (T3) and Thyroxine (T4) can also influence the time point of gut closure for protein and peptide absorption (Hadron et al., 1997; Blum and Hammon, 2000).
The objective of this study was to characterize the changes occurring in amino acids of Camel milk protein and determine the dynamic relation ships among IGF-I, T3 and T4 during the 1st month of lactation and seek to justify such dynamics of change in relation to the specific needs of the growing neonates.
MATERIALS AND METHODS
Milk Samples
Milk samples were collected from camels in Marsa Matrouh Farm (Animal Production
Institute-Dokki-Egypt) at varying stages of lactation, samples were collected
in the morning during winter. Samples (350 mL from each camel) were collected
in polyethelyne bottles and kept on ice during transportation to the laboratory
where they were stored at 30°C until analyzed.
All camels milk taken during the first 7 day of lactation were considered as colostrums, the reminder (10-30 day) considered as mature milk.
All samples were taken with supervision by manual expression and were collected in sterile containers without preservatives.
Milk Analysis
| • | Milk samples were analyzed for total protein, fat, lactose, total solids and ash as described by AOAC (1995), while lactose content was measured according International Dairy Federation (IDF) (1974). |
| • | Amino acid was analyzed by precipitating of casein from skimmed milk with 0.01 mol L-1 acetic acid at pH 4.5-4.6. The precipitate was washed three times with water and freeze dried. Twenty to thirty milligram of this acid casein were hydrolyzed with 6 mol L-1 HCl for 24 h at 110°C under vacuum. The hydrolyze was analyzed on a model liquimat III amino acid analyzer (Kontron Instruments AG, Zurich) according to the procedure of Amado et al. (1983). |
Blood Samples
Blood samples were individually collected from camels (calves and mature)
per treatment and serum samples were separated and kept at a refrigerator until
used for analysis.
Hormone Analysis of Serum
Both T3 and T4 concentration were estimated with commercially
available solid-phase single antibody kits (ImmuChemTM Triiodo thyronine
and ImmuChemTM thyroxine, ICN Biomedicals, Irvine, CA). As previously
described by Kinsbergen et al. (1994). Insulin-like growth factor-I were
estimated with radioimmunoassay as previously described by Hammon and Blum (1997).
Statistical Analysis
The results were reported as the mean±Standard Error (SE). Significance
of the observed differences was tested at p≤0.05 probability level. One way
ANOVA was performed the least significant of differences among treatments according
to the procedure reported by Perrie and Watson (1999).
RESULTS AND DISCUSSION
Gross Composition
Changes in gross composition (protein, lactose, fat, ash and TS) of camel
colostrum and milk during the 1st month of lactation period are shown in Table
1. Colostrum is produced for the first week, after which the secretion is
considered regular milk (Gorban and Izzeldin, 1997). There was a sharp decline
in protein content from 12.99±0.20 in the 1st day, It continued decreasing
gradually to reach 5.12±0.65% on day 2 of lactation, stabilized between
day 3 to 6 and further decreased to 3.95±0.67, 3.85±0.34 and 3.30±0.25%
at day 7, 10 and 30, respectively. A similar trend was observed in Alxa bactrian
camel milk, Zheng et al. (2005) and Najdi camel colostrum (Abu-Lehia,
1989), where the protein content decreased from 13.00 to 5.12% within the first
24 h and further decreased to 4.02% on day 10 of lactation. Ohri and Joshi (1961)
also reported a protein content decreased from 14.49% at the first milking day
to 3.95% on day 6 of lactation in Indian camel colostrum. In contrast, Kazakhstan
camel colostrum exhibited higher protein content (19.4%) at parturition and
then decreased quickly to 3.6% within 2 day (Bestuzheva, 1958). Moreover, the
mean protein contents in pooled colostrum (1 to 7 day PP) and regular milk (10
to 240 day PP) of dromedary camels in Saudi Arabia were 5.82 and 3.27%, respectively
(Gorban and Izzeldin, 1997), which were almost similar to those of our results.
This result may be due to a greater protein accretion in the intestine probably
because of Ig absorption and protein synthesis in visceral organs, brain, lung
and muscle.
The lactose content was 2.75±0.40% in the 1st day and increased gradually
to 4.24±0.15% in the 2nd day and remained relatively stable from 5th
day 5.20±0.44% till the 30 day 5.85±0.43 during the study period.
The values of the lactose content of Alxa camel milk ranged from 4.24 to 4.44%,
whereas for dromedary camel milk, the values ranged from 2.56 to 5.80% (Mehaia
et al., 1995; Gordan and Izzeldin, 1997). It is well known that bovine
colostrum is also rich in most of its components such as protein, fat, serum
proteins and ash, the only component that is low in bovine colostrum in the
first days after parturition and increases subsequently is lactose (Merin et
al., 2001).
| Table 1: | Major components of camel colostrum and mature milk |
| ***: Highly significant; **: Moderate significant | |
The same was reported for camel milk (Yagil and Etzion, 1980; Abu-Lehia, 1991), but was not confirmed in the study by Merin et al. (2001), possibly due to the determination of lactose by difference.
The fat content of camel colostrum at 1st day after parturition was as low as 0.50%, which was similar to Kazakhstan camel (Bestuzheva, 1958) and Najdi camel (Abu-Lehia et al., 1989). Its content significantly increased to 1.27% within the first 48 h, peaked at 3.78% after 1 month. A similar trend was noted for dromedary camel milk as reported by Merin et al. (2001), where the fat content of colostrum initially was low, then reached its highest levels after about a week and then decreased to its average value thereafter. This pattern was in contrast to those of the bovine, sheep and goat colostrum (Abu-Lehia et al., 1989). It can be theorized that in camels the low fat content of colostrums immediately after parturition is due to the camel ability of physiological fluctuations of body temperature by 6°C, reducing the need in calories immediately after birth (Yagil, 1985). In addition, the suckling of camels takes place every half an hour, so the caloric requirements are met in total (Merin et al., 2001).
At 2 h after parturition, the ash content of camel colostrum was 0.96%. This was higher than that of Jordanian (0.57%) and similar to Najdi (0.99%) camels and lower than that of Indian (2.6%) and Kazakhstan (3.8%) camel colostrum as reported by Yagil and Etzion (1980), Abu-Lehia et al. (1989), Ohri and Joshi (1961) and Bestuzheva (1964), respectively. The ash content decreased significantly to 0.96% in the first 12 h and then fluctuated slightly thereafter with percentages ranging from 0.85 to 0.70%. In contrast, a steady decrease in ash content of colostrum was reported for the Najdi camel, Abu-Lehia (1989). Ash content ranged from 0.6 to 1.0% for dromedary camels (Mehaia et al., 1995; Gordban and Izzeldin, 1997; Guliye et al., 2000), suggesting that camel milk may provide a satisfactory level of minerals for consumers (El-Amin and Wilcox, 1992).
The TS content of colostrum showed a rapid decrease from 20.25 to 13.95% during the first 12 h, likely attributed to the sharp decrease in the protein content over the same period. The TS content remained relatively stable (13.95 in the 2nd day to 13.90% in the 7th day), however, slightly increased from 14.22% on day10th till 15.06% in the 30 days of lactation. Bestuzheva (1964) and Abu-Lehia (1989) also reported a sharp decrease in TS content in colostrum during the 1st days of lactation for Kazakhstan and Najdi camels. According to Mehaia et al. (1995), the TS content ranged from 10.0 to 14.4% in dromedary camel milk. This decrease in the TS content may be attributed mainly to the decrease in the protein content over the same period. This increase in TS was obviously may be due to the gradual increase in the content of lactose and fat.
The contents of protein, lactose, fat, ash and TS of camel milk at 30 day PP were 3.30, 5.85, 3.78, 0.70 and 15.06, respectively (Table 2). Under the same conditions, the chemical composition of camel milk varies from species to species (Mehaia et al., 1995; Gaili et al., 2000) and the largest variations during lactation were in TS and fat contents. Gaili et al. (2000) showed that the stage of lactation did not significantly affect the constituents in regular camel milk. According to Alhadrami (2003), the composition of camel milk is similar to bovine milk and the average values of protein, lactose, fat, ash and TS contents of camel milk were 3.4, 3.7, 4.1, 0.7 and 13.1%, respectively.
Regarding to the differences between mature Camel, Cow and Goat milk, Table
3, which revealed a non significant changes between the various species
in the fat, protein, lactose and ash content except in TS there are a significant
difference between the three animals, it was 15.06, 11.95 and 8.90% in camel,
cow, goat, respectively.
| Table 2: | Comparison between mature camel, cow and goat milk |
| ***: Highly significant; ns: Not Significant | |
| Table 3: | Amino Acids composition of camel colostrum and mature milk |
| ***: Highly significant between times | |
The results agree with Gaili et al. (2000), They revealed that the chemical composition of camel milk varies from species and the largest variations during lactation were in total solid and fat contents. But, Alhadrami (2003), show that a composition of camel milk is similar to bovine milk and the average value of protein, lactose, fat, ash and TS continuity of camel milk were 3.4, 3.7, 4.1,0.7 and 13.1%, respectively.
Amino Acid Composition
Table 3, show the amino acid composition of camel milk
through different times. The mean of different amino acid values at the 1st
day were significantly increased then sharply decreased in the 3rd day and continuously
decreased till reach to the 7th day. So, we noticed a non significant change
in the reminder time, 10th, 15th, 21 and 30 day, respectively, this result may
be due to the sharp decline in the mean value of protein content where the total
milk protein yield was defined as a function of individual amino acid supply
(Doepel et al., 2004). Ontsouka et al. (2003) show that protein
in colostrums is utilized by the neonate for protein synthesis in addition to
the absorption of Ig and stimulation of protein metabolism after calving requires
large amounts of amino acids. Also, Newborn that were fed colostrums had greater
amino acids accretion in the intestine (probably because of Ig absorbtion) and
protein synthesis in visceral organs, brain, lung and muscle (Farah and Ruegg,
1989). Glutamic acid is increased in neonate because it play a major role in
fetal nitrogen and carbon metabolism and help in development of placenta and
fetal growth (Korhonen et al., 2002).
| Table 4: | The difference between amino acids composition of the milk of mature camel, cow and goat |
| ns = Non significant; ***: Highly significant | |
While glycine show a high experimental efficiency of utilization and is required to tissue growth and for a number of physiologic processes such as the synthesis of nucleic acids bile acids hemoglobin and glutathione. Arginine showed the highest efficiency of utilization for maximum growth in growing faetus. Threonine, leucine, isoleucine, tyrosine and phenylalanine in particular were increased at the expense of glycine, alanine, praline, this indicates an increase in the ratio between muscle and collagen protein with faster growing animals. Increasing protein-free energy generally increased the proportion of protein deposited in the carcass, this could explain the effects of protein free energy intake on the content of aspartic and glutamic acid, glycine and isoleucine and praline (Walter et al., 1998).
Table 4 present the difference between the estimated amino acid of camel milk and the other milk such as cow and goat. This table deal that aspartic acid, glutamic acid and glycine value in camel milk in the same range like that in cow and goat, serine in camel milk significantly lower than that of cow and goat, histidine, arginine, threonine, alanine, tyrosine, valine, methionine, lysine,isoleucine, leucine, Phenylalanine significantly lower in camel than that of cow and goat milk, proline value of camel milk is the same with cow milk but lower than that of goats milk, cysteine value in camel milk was significantly higher than that of cow and goat milk but isoleucine was lower in camel milk than in goat´s milk, this result disagree with Landis (2004), who revealed that the overall amino acid composition is similar in all three and all three have satisfactory balance of essential amino acids equaling or exceeding the FAO-WHO requirements for each amino acid.
Serum Insulin Growth Factor-I Hormone
Regarding to the values of IGF-I hormone, Table 5, revealed
a significant increase in the level of serum IGF-I at zero time in the neonate
(616.881±62.520) and mother's serum animals (655.330±62.333) then
a sharp decline in the 1st day (454.820±42.802) in neonate and (550.352±52.331)
in mother's serum and a further decreased in the 5, 7, 10, 15 and 21 days and
reach to (175.790±16.720) in neonates and (203.011±18.352) in
mature she-camel after 1 month. Michanek et al. (1989) show that a more
marked rise in IGF-I levels on day 1 in calves fed colostrum instead of mature
milk may lead to the conclusion that colostrum-borne IGF-I was absorbed by our
neonatal calves. The sluggish rise of IGF-I in the 1st day of parturition and
the fall of IGF-I levels during the 30 day in this study probably mirrored increased
and decreased endogenous production. Furthermore, GH enhances IGF-I production
only slightly in the neonatal calf (Breier et al., 1988; Hammon and Blum,
1997). IGF-I poduction was possibly enhanced by nutrient factors, especially
fatty acids and amino acids which increased in colostrum.
| Table 5: | Values of Serum Insulin growth factor-I (IGF-I), Triiodothyronine (T3) and Thyroxin (T4) through the 1st month of lactation |
| ***: Highly significant decrease from 0 time till 30 day of age | |
IGF binding protein patterns, hence metabolic clearance rates of IGF-I, can be altered by nutrition in neonatal calves (Hammon and Blum, 1997).
Serum Thyroid Hormone
Table 5, shows a significant decrease in triiodothyronin
(T3) from 0 time until 1month, at 0 time, it was (500.000±48.250)
in neonate and (512.511±50.430) in mother's serum then, a sharp decline
occur to (165.250±14.523) in neonate and (170.431±15.430) in mother's
serum after 1 month. While, a significant decrease in the level of thyroxin
hormone (T4), from 0, (38.678±3.550) in neonate and (38.717±3.547)
in mother's serum and decreased relatively to (31.759±3.087) in neonate
and (30.105±2.564) in mother's serum, after 1 month. Kinsbergen et
al. (1994) and Grongnet et al. (1985) agree with present results
and conclude that thyroid hormones are important for the maturation of small
intestinal function.
CONCLUSIONS
The present study shows the composition of camel milk for 1 month following parturition. Camel colostrums is poor in lactose and fat in the first day and increased gradually till reach the maximum after 1 month. On the contrary, camel colostrums is reach in protein and total solids at 1st day and gradually decreased till reach 30 day. Study conclude that the chemical composition of camel milk varies from species and the largest variations during lactation were in total solid. There are a fluctuation in the amino acids in the first 7 days, this may be due to sharp decline in the mean value of protein content. Also, the study show differences between the composition of amino acids in camels and other animals. Serum IGF-I, T3 and T4 were increase in zero time then sharply decreased at 30 day.
Although it is well documented that early camel milk during the 1st month of lactation is important for passive immunity, this study demonstrates additionally that camel milk during the 1st month of lactation have important effects on clinical, metabolic and endocrine traits.