Study area
The study was conducted in Gadarif State (Baladia Locality) situated between latitude 12-17◦ North and longitude 34-36◦ East, geographically it has a wide variety as well as heavy rains, which range between 600- 900 mm during the year. The livestock is the most important renewable resource in the state and some of the state's population depend on it, and comes secondly after agriculture. The state is very rich in livestock, which is estimated to 7% of the total census of livestock in Sudan. The number of livestock in Gadarif State is approximately five million heads of different species, this increase to seven million heads in the rainy season as the result of movement of animals from the traditional pastoral system in the prevailing system. According to the Ministry of Animal Resources and Fishery of Gadarif State (MARF 2011), the total number of animals is estimated to be 3.896.134 head. Sheep herds comprise about 48% of the total animal number followed by goats (24%), cattle (24%) and camels are about 4%.
Source of milk samples
Eighty milk samples were collected randomly from Gadarif locality from different sources; 33 samples of raw milk were collected from dairy farms; 31 samples of raw milk was collected directly from sale points and 16 samples of raw milk were collected from groceries.
Collection of milk samples
Raw bulk milk samples were collected in the afternoon during May to June 2018. After collection, the milk samples were kept in ice box till the next morning, and then they were taken to the laboratory of the Faculty of Agricultural and Environmental Sciences for the detection of aflatoxin.
Laboratory examination of milk samples
The raw milk samples were subjected to analysis and detection of aflatoxin.
Test for aflatoxin M1 detection
The Aflasensor kit 041 and its associated accessories (Heatsensor, negative and positive standards, deionized water) that were used in the present study were produced by the Unisensor Company (Liege, Belgium). It is a rapid (10 minutes at 40°C) test that use for the quantification of aflatoxin M1 (AFM1) in raw milk samples. The limit of quantification (LOQ) of the aflsensor is 20 ppt with a range of quantification up to 150 ppt. Aflsensor test requires the use of microwells that containing a predetermined amount of antibody lined to gold particles and a dipstick made up of a set of membranes with specific capture.
The lines for a valid test include the upper red (control line) that should be visible after second incubation time (7 minutes). The test was done by suspending 200 μ1 of milk sample with the reagent from microwell. A specific antibodie will bind the analyses; if present; during the first incubation time (3 minutes). When the dipstick is dipped into the sample, the liquid starts running vertically on the dipstick and passes through capture zones.
The development of a color at the test line indicates that the sample is free of aflatoxin M1. On the opposite, the presence of aflatoxin M1 in the sample will not cause the appearance of the colored signal at the test capture line. The concentration of aflatoxin M1 present in the milk sample will be based on the intensity of the line color that should be started from the bottom line of aflatoxin M1. The results were directly interpreted by visual observation. When the test line was darker in color like the control line, the result was negative, which means that at the given sensitivity of the test, the milk samples contain no aflatoxin M1 or aflatoxin M1 at a lower level than the value stated in the enclosed aflatoxin M1 limit of detection. When the line was as the same intensity or lighter in color than the control line, the result is considered positive (+) and the sample should contain higher concentration than 100 ppt. When there was no test line at all, the milk sample should contain higher concentrations of aflatoxin M1 residues and considered as full positive (++) as was described by UNISENSOR (2013). Figure 1 showed some valid results.
Statistical analysis
The analysis has carried out after obtaining results using a percentage basis for the presentation of the results.