The effect of season and agro-ecology on physicochemical properties of cow's raw milk in Central and North-Western Zone of Tigray, Ethiopia.

Milk at a normal state has unique physical, chemical, and biological characteristics that are used as quality indicators. The quality of milk is influenced by many factors and the components of milk are very sensitive indicators for milk production practices. Season and agro-ecologies have influences on physicochemical properties of cow milk. Therefore, this research aimed to investigate the effect of season and agro-ecology on the physicochemical properties of cow's raw milk in Central and North-Western Zone of Tigray. The study was conducted in Aksum, Shire-Indaselassie, and Sheraro administrative towns. A two-stage sampling method was used to select both the study area and respondents. All towns in the Central and North-Western zones of Tigray were categorized into three agro-ecologies, and sample towns were purposively selected from each category based on accessibility and milk production potential. Sample respondents were then randomly selected from each agro-ecology. Agro-ecology categorization was based on altitude, temperature, and feeding practices, while seasons were classified according to rainfall and temperature. A total of 210 samples, comprising 35 samples from dairy farms and 35 samples from cafeterias within each agro-ecology, were analyzed to assess the physicochemical properties of cow milk across two different seasons. Physicochemical analysis including determination of fat, crude protein, solids not fat, density, lactose, salt, water added and freezing point was conducted in the laboratory of Mekelle University using Lacto scan, Bulgaria. The overall mean values of milk fat, solids-not-fat (SNF), protein, and lactose were 3.72 ± 0.12 %, 6.72 ± 0.17 %, 2.6 ± 0.08 %, and 3.72 ± 0.09 %, respectively. Specific gravity, salt content, water added, and freezing point exhibited mean values of 1.026 ± 0.001 g/ml, 0.53 ± 0.01 %, 19.33 ± 1.8 %, and -0.42 ± 0.01C, respectively. Significant differences (p < 0.05) were observed in protein, solids-not-fat, lactose, and salt content among agro-ecologies, seasons, and sources of milk. Correlation analysis revealed positive correlations between specific gravity and solids-not-fat, protein, lactose, and total salt, while negative correlations were observed with water added and freezing point (p ≤ 0.01). In conclusion, the physical and chemical properties of cow's raw milk are influenced by agro-ecology, season, and the source of milk. Notably, milk adulteration, particularly with the addition of water, was more prevalent among cafeteria owners. Given the absence of established milk quality standards in Ethiopian conditions, it is imperative for the government to introduce quality standard measures, rules, and regulations to effectively control milk quality.