Abstract: This study was carried out to evaluate the procedures and management practices and their effect on milk microbiological quality in 15 cross dairy goat farms that distributed in Khartoum State. The areas of study include Kuku, Alhatana, Aldroshab, Alkadrow, Shambat and Ombada. The information were collected through field visits and questionnaire, moreover seventy five raw bulk milk samples were collected from those farms. One duplicate sample per month from each farm were collected and examined for total bacterial counts, coliform counts, yeast and mould counts, milk acidity and freezing point. The questionnaire showed that the dominant breed for crossing was Saanen breed (100%) with blood percentage which vary from 50-90% and it was observed that the well designed housing was dominant in the studied farms and there was a high level of education for the goat owners, since more than 50% awarded a university degree. The laboratory examination of the milk samples revealed that the total bacterial counts were 762x106±2.14, 1423x106 and 702x105 cfu mL-1 for mean±standard deviation, maximum and minimum values, respectively. The coliform bacteria counts revealed 636x105±1.66, 1204x106 and 652x105 cfu mL-1, respectively. Similarly the average yeast and mould counts were 51x105±3.63, 160x105 and 30x104 cfu mL-1. Acidity was found to be 0.231±.0026, 0.279 and 0.185%, while the freezing point were -0.484±0.032, -0.443 and 0.576°C, respectively. The present result also showed that there were significant (p<0.01) positive correlations between total bacterial counts and each of coliform counts (r = 0.470) and acidity (r = 0.808). Similarly significant positive (p<0.01) correlation between coliform counts and acidity (r = 0.613) and significant (p<0.05) correlation between yeast and mould counts and freezing point (r = 0.283) were estimated.
Introduction
One of the first animals to be domesticated by man was the goat, through the century the goat has remained a popular animal serving the needs of man and goat is known as poor man cow over all the world (Harbans et al., 1982). Goat is one of milk sources that characterized by the economic important, since goat can utilize feed roughages and crops residues by products undesirable for human consumption and convert them into desirable food (Devendra and Mcleroy, 1982). Moreover goats are found in all type of environments from arid to humid zones and they do very well in the drier tropics, beside their ability to withstand dehydration and their browsing habit enable them to survive where cattle and sheep can not (Steele, 1996).
Goat milk has a medical important especially for children who suffer allergy from the milk of cows (Klinger and Rosenthal, 1997; Jandal, 2001). Also goat plays role in the treatment of metabolic diseases, beside its uses to treat intestinal disturbances, mal absorption and renal stone and cardiac diseases (Jandal, 2001). Moreover, when goat milk lactoperoxidase was purified, it was found to have high antifungal and antibacterial activity (Benoy et al., 2000).
Since milk represent highest importance, for human as source of nutrition, it must therefore be protected from contamination or deterioration from sites of production (farms) to the table of the consumer (Giovannini, 1998). Milk is a favorable physical environment for the multiplication of microorganism, which leads at the end to degradation of the quality of milk and milk products or they create some health hazards (IDF, 1994).
The total number of bacteria from a normal animal may range from few hundreds to few thousands (Murphy and Boor, 2000). Undesirable organism may get into milk either through the body of the animal or some from external sources after the milk has been drawn from the animals, which are ill or carriers of infectious diseases (Murphy and Boor, 2000). Contamination of goat milk usually is in the form of hair, insect part, particles of dust, feed or manure, or bacteria associated with these contaminants plus unclean utensils (Loewenstein and Speck, 1992). However, Droke et al. (1993) reported that goat milk escape tuberculosis as they seldom affected. Hence goat milk considered safe as reported by Harbans et al. (1982).
The microbiological content of raw milk affects quality, shelf life and safety of the processed milk and other dairy products (Gunasekera et al., 2000). The implementation of hygienic practices at the time of milking is therefore one of the first and most important step in clean milk production (Sinha, 2000). Regular tests and frequent inspections of milking animals coordinated with a definite plan for holding the milk from suspected animal until confirmation tests can be completed are a must (Loewenstein and Speck, 1992). Total bacterial counts which carried out with Standard Plate Count (SPC) gives an indication of total number of aerobic bacteria present in the milk at the time of pick up from the farm (Murphy and Boor, 2000).
Titratable acidity is valuable for measuring the extent of growth of acid producing bacteria in dairy products (Harding, 1999). The acidity of cross Saanen goats averaged 12.96±3.64 °D in Brazil (Chornobai et al., 1999). Abd El Gadir and El Zubeir (2005) found that the acidity and freezing point of milk of crossbred SaanenxNubian goat under Sudan condition were to range from 0.3 to 0.13% and -0.468 to -0.722°C. Harding (1999) stated that the freezing point of goats is slightly lower than cow's milk. The freezing point of Saanen goat’s milk in south eastern of Brazil is found to be -0.575° H (Prata et al., 1998).
The objectives of the present study are aimed to compare the effect of management procedures of the different goat’s breeds at dairy goat farms in Khartoum State and evaluation of the hygienic quality of cross goat milk.
Materials and Methods
The Farms
The present study was conducted on farms of cross bred dairy goats that
established in Khartoum State, Sudan. This study was done during the period
of October 2003-February 2004.
Questionnaire and Data Collection
Field visits and a questionnaire, which was designed for data collection
from 15 dairy cross bred goat farms in Khartoum State, were tried. The questionnaire
consisted of ten main part that include general information, housing of the
farm, herd structure, production performance, level of cross breeding, labours,
nutrition, sources of fodder, amount of fodder and water, breeding, kids rearing,
milk production, types of records and problems and constrains which faced the
farms.
Sources and Numbers of Milk Samples
A total of 75 raw bulk milk samples were collected from the 15 cross bred
dairy goat farms that are located at six areas in Khartoum State. The areas
include Kuku, Alhatana, Alkadrow, Ombada, Aldroshab and Shambat. Five bulk tank
milk samples were collected from each farm at monthly intervals.
Collection of Milk Samples
Milk samples were collected in the morning under aseptic conditions in labeled
sterilized bottles and kept under refrigerated conditions (kept in ice box at
0-4°C). They were brought to the laboratory of the Department of Dairy Production,
Faculty of Animal Production, University of Khartoum for analysis. Each milk
sample was examined for total bacterial count, coliform counts, yeast and mould
counts, freezing point and acidity.
Microbiological Examinations
Preparation of the samples, sterilization, serial dilutions, plating and
counting were done according to Harrigan and MaCance (1976). Plate count agar
was used to determine standard plate counts, MacConkey agar medium was used
to determine the coliform counts and Yeast extract medium was used to determine
yeast and mould counts (Barrow and Feltham, 1993).
Determination of Physiochemical Properties of Goat Milk|
The freezing point was measured by means of a thermistor Cryoscope, FISKE
(USA) as described by Harding (1999). The acidity of milk was determined according
to Foley et al. (1974).
Statistical Analysis
Social Science Statistical Package (SPSS 9.5) was used for data analysis
of the present study. T-test was used for comparison. Also personal correlation's
was done between some of the measurements.
Results
Management Procedures and Practices in Dairy Cross Goat Farms
The present study was done to assess the hygiene and quality of raw milk
produce by 15 cross dairy goat farms in Khartoum State. General information
and procedures of management practices in those farms were collected through
the filed visits and questionnaire.
General Information
The educational levels of the owner of those farms were found as follows:
13.3% primary, 33.3% secondary, 46.7% university and 6.7% post graduate as shown
in Table 1. There was a non significant positive correlation
between education level with each of coliform counts (r = 0.024), yeast and
mould counts (r = 0.525) and acidity (r = 0.093) as shown in Table
3.
Comparison of Management Practices and Procedures in Cross Dairy Goat Farms
The filed visits and questionnaire conducted during the present study revealed
that a well housing design was among 60% of farms compared to 40% of the random
traditional housing (Table 1). The dominant breed of goat
in the studied farms was Saanen. It was found either as pure cross of Saanen
(33.3%) or mixed with Damascus (60%) and Damascus and Anglo Nubian (6.7%). The
labours running the farm showed significant variations (p<0.05) and they
were either the owner them selves (53.3%) or rent labours (46.7%) as shown in
Table 1. The type of breeding was either natural (66.5%) or
artificial breeding (33.5%). Most of the farms obtained their fodder from market
(86.6%), while only 13.4% were found to cultivate the fodder in their farms
(Table 1). Moreover 79.9% of the farms used nutritional program
through out the year and only 20.1% used different regime due to the seasonal
variations. Twice a day milking was found as the common practice of milking
(73.2%) compared to once a day milking (26.8%) as shown in the Table
2. The same table showed that gradual drying of the milking goat (79.9%)
was more than the sudden drying (20.1%) of the milking animal. The absence of
records and mastitis infection (66.5%) were higher in the studied dairy goat
farms (Table 2).
The result of the effect of housing on milk quality showed that there is a
non significant positive correlation between housing system and total bacterial
counts (r = 0.215). Similarly non significant negative correlations were found
for the housing system and each of coliform counts (r = -0.278), yeast and mould
counts (r = -0.181), freezing point (r = -0.004) and acidity (r = -0.049). Also
non significant positive correlations between mastitis infection and each of
type of cross breed (r = 0.411) freezing point (r = 0.169) and yeast and mould
counts (r = 0.019) were obtained. Non significant negative correlations were
obtained when comparing mastitis infection with each of total bacterial counts
(r = -0.057), coliform counts (r = -0.278) and acidity (r = -0.326) as shown
in Table 3.
| Table 1: | General information on cross dairy farms in Khartoum State |
| * = Significant at p<0.05, ns = Non significant | |
| Table 2: | Management practices in cross dairy farms in Khartoum State |
| ns = Non significant | |
| Table 3: | Correlation between some milk quality measurement |
| *Correlation is significant at the (p<0.01) level, correlation is significant at the (p<0.05) level | |
| Table 4: | Level of the hygienic quality of cross dairy goats milk |
| *SD = Standard Deviation | |
| Fig. 1: | The average log total bacterial counts of milk of cross dairy goats in the different areas of Khartoum State |
Microbiological Examination of Cross Bred Dairy Goat Milk
Total Bacterial Counts
The average total bacterial count of cross dairy goat milk was 762x106±2.14
cfu mL-1, the maximum was 1423x106 cfu mL-1
and the minimum was 702x105 cfu mL-1 (Table
4). There were variations of the average log total bacterial counts of cross
dairy goat in the different areas in Khartoum State as shown in Fig.
1.
A significant (p<0.05) correlation was estimated for the total bacterial counts when it was compared with yeast and mould counts (r = -0.259). Moreover highly significant (p<0.01) correlations were estimated for the total bacterial counts with each of coliform counts (r = 0.470), freezing point (r = -0.677) and acidity (r = 0.801) as shown in Table 3.
Coliform Counts
The average coliform count of cross dairy goat milk was 652x106±1.66
cfu mL-1, the maximum was 1204x106 cfu mL-1
and the minimum was 636x105 cfu mL-1 (Table
4). Variations of the average log coliform counts in cross dairy goat farms
in the different areas in Khartoum State were shown in Fig. 2.
| Fig. 2: | The average log coliform counts of cross goats milk from different areas of Khartoum State |
| Fig. 3: | The average log yeast and mould counts of cross goats milk from different areas of Khartoum State |
A non significant positive correlation was estimated for the coliform counts and education level (r = 0.024). However highly significant (p<0.01) positive correlation was estimated for the coliform counts when compared with acidity (r = 0.613) and negative correlation with freezing point (r = -0.494) as shown in Table 3. Also significant (p<0.01) negative correlation was found for coliform counts and yeast and mould counts (r = -0.283).
Yeast and Mould Counts
The average of yeast and mould count of cross dairy bred goat was 51x105±3.63
cfu mL-1, the maximum was 160x105 and the minimum was
30x104 (Table 4). Higher variations between the
farms for average log yeast and mould counts in milk of cross dairy goat farms
in the different areas of Khartoum State were recorded (Fig. 3).
There is a positive correlation between yeast and mould counts with education
level (r = 0.525). Significant (p<0.05) positive correlation was estimated
for the yeast and mould counts when compared with freezing point (r = 0.283)
as shown in Table 3. Moreover highly significant (p<0.01)
negative correlation was found when yeast and mould counts were compared to
acidity of the cross goat milk (r = -0.392).
| Fig. 4: | The average freezing point of cross goats milk from different areas of Khartoum State |
| Fig. 5: | The average lactic acid% of cross goats milk from different areas of Khartoum State |
Physio-chemical Properties of Milk
Freezing Point
The average of freezing point of milk of cross dairy goat was found to be
-0.484±0.032°C, the maximum freezing point was -0.443°C and the
minimum freezing point was -0.575°C (Table 4). The average
freezing point of milk of cross dairy goat farms in the different areas of Khartoum
State revealed more or less similar values (Fig. 4).
A positive correlation was estimated for the freezing point with mastitis infection (r = 0.169). Significant (p<0.05) positive correlation was estimated for the freezing point and yeast and mould counts (r = 0.283) as shown in Table 3. Moreover the same table revealed highly significant (p<0.01) negative correlation between freezing point and acidity of milk (r = -0.808).
Milk Acidity
The average of milk acidity of cross dairy goat (lactic acid%) was 0.231±0.026%,
the maximum was 0.279% and the minimum was 0.185% (Table 4).
The average of milk acidity in the different areas of Khartoum State revealed
higher variations (Fig. 5).
There is a positive correlation for the milk acidity with education level (r = 0.093). Moreover highly significant (p<0.01) correlations were estimated for the milk acidity with each of total bacterial counts (r = 0.801), coliform counts (r = 0.613), yeast and mould counts (r = -0.392) and freezing point (r = -0.808) as shown in Table 3.
Discussion
The present study was done to evaluate the procedure and management practices and their effect on microbiological quality of raw milk produced by cross dairy goat farms in Khartoum State.
The field visits and the questionnaire showed that in some cross dairy goat farms milkiers' practiced bad habits during milking process such as talking, singing, snuffing and introducing of hands into the milk as mean for udder massage. Those habits could lead to contamination of milk as represent by the high bacterial counts (Table 4). Also those bad management practices might be due to lower labours skills in hygienic principles for milk production and handling. Moreover the differences in the education levels between the owners of these farms might be the reason for those management and practices which led to increase number of bacterial colony especially coliforms bacteria. As the enhance growth of bacteria in the milk result in degradation of milk quality (IDF, 1994).
The influence of health problem showed increase in the reading of freezing point especially in the farms, which has mastitis infection. This might be due to the fact that increased bacteria will lead to decrease the freezing point of the milk (Marshall and Richardson, 1992).
The influence of housing system on milk quality revealed an increase in the number of bacterial colony especially in the random designed housing. The lack of environmental sanitation during milking was found to lead to contamination of milk (Murphy and Boor, 2000). Moreover, Dirar (1975) reported that under tropical condition like Sudan, the high temperature enhances the growth and multiplication of bacteria.
The laboratory examination for milk samples during the present study showed that the average total bacterial count of milk (762x106±21.4 cfu mL-1) was higher than that reported by Muehlherr et al. (2001) who reported log 4.69 cfu mL-1 for bulk milk tank samples of dairy goat farms. Similarly, it was higher than Foschino et al. (2002) who found 5.0x104 cfu mL-1 for bulk milk tank samples from dairy goat farms.
The total bacterial count in the present study was high for tropical grading as reported by Chandra and Hedrick (1979). They stated that the milk was graded as good when it has total bacteria count (TBC) of 500x105 cfu mL-1 or less, satisfactory when it ranged between 50x105 and 50x106 cfu mL-1 and bad when TBC was more than 50x106 cfu mL-1.
The average of the coliform counts in the present study (636x105±16.6 cfu mL-1) was higher than that reported by Foschino et al. (2002) for bulk milk tank samples from dairy goat farms (91x102 cfu mL-1). This milk is considered to lack sanitation during milking according to Murphy and Boor (2000) who reported that the coliforms counts above 50 cfu mL-1 indicated poor milking hygiene.
The average of yeast and mould counts in the present study (51x105±36.3 cfu mL-1) was smaller than that reported by Foschino et al. (2002). Since they reported 2.5x102 cfu mL-1 for bulk milk tank samples from dairy goat farms.
The freezing point obtained during the present study (-0.484±0.032°C) was more or less similar to those reported by Prata et al. (1998) and Abd El Gadir and El Zubeir (2005). They reported -0.574 and -0.561°C, respectively.
The average acidity (lactic acid%) in the present study (0.231%) was more or less similar to those reported by Chornobi et al. (1999) for cross Saanen. They found the acidity was 12.96° D and 0.203%, respectively. This might indicate that milk produced by the studied farms is not adulterated by addition of water.
The present study concluded that the management practices influence the quality of milk. However, some conditions like Sudan local environmental conditions, which affect milk quality, must be eliminating by implementation of good management practices. Hence it is recommended that improvement of milk hygiene by introduction of simple hygienic principles for milk production and handling. Also improvement of the management practices and extension programs to the owners and establishing of standards and grades of raw milk to ensure good quality should be initiated. Establishment and encouragement of specialized farms of dairy goat in order to ensure food security especially in rural areas will fill the gap of domestic production of milk supply. Future research is needed to estimate and evaluate the keeping quality and nutritional aspects of goat milk.
Acknowledgements
The fund received from the Islamic Development Bank is acknowledged with thanks. Also the author would like to thank the dairy goat farmers who participate during the present study.