الفهرس 
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Abstract
Buffalo milk is produced in several countries including Egypt, Bangladesh, China, Philippines, Brazil, Pakistan and India.
The different aspects of cow milk including its chemical and physical properties aspects have been intensively searched and reviewed, but buffalo milk gained much less attention owing to infertility of buffaloes.
This study consists of two parts, these parts are:-
The first part was directed to study the effect of stage of lactation (from the begging to the end of lactation period) on the chemical composition of milk from five different farmers (one buffalo from each), from different towns in Assiut Governorate.
The second part was directed to study the chemical composition of:-
1- Weekly sample was taken from the milk comes for manufacturing of dairy products in the factory of the Dairy Department, Faculty of Agriculture, Assiut University.
2- Three random samples were taken weekly from three different farmers, 10 times from each.
3- Weekly samples were collected from two milk vendors in Assiut city.
I- Effect of stage of lactation on the chemical composition
The results obtained showed that:-
1-The physical properties:-
* Specific gravity:-
Specific gravity at the first day colostrum after parturition ranged from 1.038 to 1.052 gm/cm3, with an average of 1.043 gm/cm3, after 10 days of parturition the corresponding values were 1.032 to 1.039 gm/cm3 with an average of 1.035 gm/cm3, at the end of the lactation period these values decreased to 1.029-1.035 gm/cm3 with an average of 1.031 gm/cm3.
2-Chemicial composition:-
A- Titratable acidity:-
The titratable acidity at the first day colostrum after parturition ranged from 0.280 to 0.405 % with an average of 0.349 %. The Titratable acidity decreased gradually to 0.180-0.195 % with an average of 0.190 % at the 10th day after parturition, then gradually decreased over the lactation period reaching minimum values ranged from 0.090 to 0.160% with an average value of 0.135% at the begging of mid-lactation, thereafter, the percentage of titratable acidity gradually increased up to the end of lactation, reaching percentage ranged from 0.135 to 0.195% with an average 0.159%.
B- Lactose content:-
The lowest lactose contents, ranged from 1.500 to 2.500 g/L (average 1.926 g/L) was found at the first day colostrum after parturition however big difference in lactose content during the first 10 days of lactation between each individual buffalo was observed. A gradual increase in the percentage of lactose was observed from the 2nd until the 10th days after parturition. After the 10th day of parturition increased by slower rate comparing by the rate of increase during the first days after parturition, reaching a maximum at the mid lactation, then it fluctuated with a narrow limits at mid- lactation after that it decreased until the end of lactation period.
C-Total solids:-
The obtained results showed that the total solids content ranged from 23.100 to 29.361% (average 25.871%) at the first day colostrum after parturition, these values decreased to 16.327 to 19.121% (average 18.044%) at the second day colostrum after parturition. After which, the total solids content decreased by slower rate up to the 8th day after parturition. Decrease in the total solids content continued at the begging of lactation period from percentage of 23.100 to 29.361% (average 25.871), at the first day colostrums, reaching range from 16.327 to 19.121% (average of 18.044%), and range from 12.755 to 16.016% (average of 14.27%) and range from 12.181 to 14.800% (average of 13.453%) after 1, 2, 8 days and 7 weeks respectively. The total solid of milk started to increase again until the end of lactation.
D-Solids not fat:-
The higher solids not fat content was found at the first day colostrum after parturition, ranged from 13.100 to 16.361% by an average of 14.267%, these values decreased to 8.701-14.700% (average of 12.083%) at the second day colostrum after parturition, then it decreased up to the 10th day after parturition and then flocculated until the end of the lactation period.
E-Fat content:-
The obtained result indicated that there was big difference in fat content, the highest value ranged from 9.6 to 13% with an average of 11.52% in the first day colostrums after parturition, which the fat percentage gradually flocculated during the next few days and up to the end of colostrum period .
Comparing the obtained results for the percentage of fat in each individual animal from the begging to the end of lactation period, it can be seen that these values were different from each animal to other, and from day to day, where it increased at the end of lactation period.
F-Total nitrogen:-
The higher percentage of total nitrogen was found in the first day colostrum as compared to any other samples during the lactation period. The percentage of T.N. in the first day colostrum after parturition ranged from 1.500 to 2.000% with an average of 1.765%, then decreased gradually reaching a range of 0.254 to 0.791% with an average 0.656% after 9 days of parturition, after that the percentage of total nitrogen remained fairly constant with little decrease or increase from early lactation up to the end of lactation period.
G-Soluble nitrogen and non- protein nitrogen:-
The percentage of soluble nitrogen in the first day colostrum was extremely higher comparing with the contents of all samples then it gradually decreased up to the end of lactation period. Percentage of non protein nitrogen showed the highest value ranged from 0.042 to 0.168 % with an average of 0.107% in the first day colostrum. Starting from the second days after parturition up to the 5th day, there was gradual decrease in the percentage content of NPN. However, some increase in the percentage of NPN during early lactation was observed.
On the other hand, the percentage content in NPN decreased during mid- and late-lactation.
H- Ash contents:-
The ash contents of colostrum obtained 1st day after parturition had the highest value (ranged from 0.500 to 1.155 gm/100gm with an average of (1.014 gm/100gm). These values gradually decreased reaching a range from 0.586 to 0.977 gm/100gm with a mean value of 0.777 gm/100gm after 7 days of parturition.
The obtained results indicated that stage of lactation had no effect in ash content as it was fluctuated within a narrow limit.
I- Iron and Cupper contents:-
Fe was found at the highest levels in colostrum obtained in the 1st day after parturition (ranged from 0.323 to 0.860 mg/100gm, mean value 0.722 mg/100gm). Then decreased from the 2nd day after parturition until the mid lactation, where it was ranged from 0.085 to 0.824 mg/100gm with mean value of 0.389 mg/100gm. During mid lactation the iron content fluctuated , then gradually increased up to the end of lactation period.
The higher content of Cu was obtained in colostrum obtained in the 1st day after parturition, ranged from 0.250 to 1.060 mg/100gm, with mean value of 0.955 mg/100gm, after which it was gradually decreased up to the mid-lactation, after reaching a minimum values, Cu contents fluctuated within a narrow limits up to the late lactation where it was again gradually increased up to the end of lactation period.
J- Zinc, Calcium and Magnesium contents:-
The highest level of Zn was recorded in the 1st day after parturition, ranged from 0.017 to 0.177 gm/100gm, with mean value of 0.122 gm/100gm. During the next 10 days there was gradual decrease in Zn content reaching a value ranged from 0.031 to 0.070 gm/100gm with a mean value of 0.051 gm/100gm. Average milk content of Zn fluctuated during mid-lactation, up to the late lactation were it started to decrease gradually up to the end of lactation period.
The first day colostrum contain the lowest level of Ca, ranged from 0.042 to 0.100 gm/100gm with mean value of 0.060 gm/100gm after which it was started to gradually increase up to the end of lactation period.
The highest levels of magnesium, ranged from 0.019 to 0.193 mg/100gm with mean value 0.095 mg/100gm, in the first day colostrum after which it was gradually decreased up to mid-lactation, however, during the late lactation it was gradually increased.
K- Potassium, Sodium and Phosphorus contents:-
The first day of colostrum contain the highest level of K ranged from 0.200 to 0.299 with an average of 0.293 gm/100gm During the next few days it was gradually decreased, then fluctuated up to the end of lactation period.
The highest of Sodium values ranged from 0.119 to 0.387 gm/100gm with mean value of 0.300 gm/100gm in the first day of colostrum. During the next few days there was gradually decrease in sodium level in milk. During mid- and late lactation the sodium level fluctuated up to the end of lactation period.
The highest phosphorus content was obtained in the first day colostrum which ranged from 0.082 to 0.266 gm/100gm with mean values of 0.201 gm/100gm, this value decreased in the second day of colostrum where it ranged from 0.090 to 0.257 with an average 0.178 then it increased from 3rd day to the 5th day, after that it fluctuated until the end of lactation.
L- Milk fat constants:-
Tabulated results shows that the initial iodine value in the first day colostrum ranged from 22.080 to 42.300 gm/100gm with a mean value of 33.158 gm/100gm. Iodine value fluctuated over the lactation period.
In the first day colostrum the saponification number ranged from 221.034 to 245.166 with mean value 233.432. The corresponding values at the end of lactation period, saponification number was fluctuated more or less either in day to day sample from the same animal, or between the samples obtained from different animals.
The lower values for Reichert meisel and Polenske number were obtained in the first day after parturition, the Reichert meisel ranged from 26. 510 to 31.350 with mean values 29.104, and Polenske number ranged from 0.5 to 1.1 with a mean value 0.860.
Starting from the second day colostrum and up to the end of lactation period, The Reichert meisel and polenske number fluctuated
II- Chemical composition of milk in Assiut city:-
The study was carried out to evaluate the chemical composition and minerals content of buffaloes milk collected from individual animals and vendors bulk milk in Assiut city. Samples were collected and analysed each 10 days from three individual farmers (one buffalo from each), and three milk vendors during the period between December (2010) to February (2011). The obtained results showed that the main milk constitutes were found to be at higher levels in the individual samples. Values of total solids, fat, total nitrogen and lactose, ranged between 14.430 to 16.550%, and 5.4 to 7.2% and 0.665 to 0.940% and 3.828 to 5.500% for the individual milk, respectively. In bulk milk samples Values of total solids, fat, total Nitrogen and lactose, ranged between 14.604 to 15.293% and5.5 to 6.5% and 0.562 to 0.676% and 3.620 to 4.933% respectively. The specific gravity of individual milk was slightly higher than that of bulk milk samples 1.030 to 1.035 and 1.029 to 1.033 gm/cm3 respectively. Concerning milk fat constants, the iodine number was mostly lower while Polenske and Reichert- meisel number were higher in the individual samples comparing with that for the bulk samples. However no big difference was found in the saponification number for individual and bulk samples. The results of ash contents showed that bulk buffaloes milk samples showed higher contents ranged from (4.696 to 6.626) mg/kg as compared to individual samples (4.023-5.553) (mg/kg). Metals, i.e. iron, calcium, sodium and phosphorus were found in higher levels in bulk samples. However magnesium was found in the same levels in bulk and individual samples. Samples available in Assiut markets may suspect to be adulterated by vendors with adding water, or removing cream. The overall picture of buffalo’s milk quality in Assiut markets as measured by chemical composition evaluation appears to indicate a need for emphasis on quality roles within milk vendors. There is a need to the activate regulations of the standard limits to control the quality of buffalo milk collected from vendors.