Effect of Different Stages of the Lactation Period on Physicochemical Properties of Camel, Goat and Cow Milk

Abstract

This research was conducted to study the effect of different stages of the lactation period on physicochemical properties of three species, dromedary camel, saanen goat and cow milk during different lactation stages. The lactation period of each species was divided into three stages after calving, early, mid and late stages. Milk samples for each species were collected at different intervals during each stage and thus covering the whole lactation period. The samples were then subjected to laboratory analysis, which include compositional properties (Fat, Protein, Moisture, Lactose, Ash, Total solids and Solids not fat calcium, phosphorus, iron) and physical properties (pH, titratable acidity, electrical conductivity, specific gravity and freezing point).The obtained results indicated the following: The mean fat % of camel, goat and cow milk obtained in early stage of lactation period was 3.807±0.098, 2.933±0.126 and 4.407±0.263 respectively. The statistical analysis revealed a high significant difference (P≤0.01) between the averages of the fat content of the different animals. In mid stage, means of 3.367±0.073, 5.020±0.149 and 3.787±0.356 for camel, goat and cow milk were detected and were also highly significant difference (P≤0.01). For late stage of lactation, average fat % of 2.300±0.072, 3.580±0.047 and 4.367±0.352 was found in camel, goat and cow milk respectively. Similarly, high significant difference was noticed herby (P≤ 0.01). The protein content (%) of milk in early stage for camel, goat and cow was 3.087±0.092, 3.633 ±0.039 and 3.400±0.072 respectively. Values obtained were highly significant difference (P≤0.01). In mid stage were 3.333±0.055, 3.267±0.089 and 3.540±0.065 for camel, goat and iv cow milk respectively. A significant difference (P≤0.05) was noticed in this case. Average values detected in late stage were 3.393±0.055, 3.513±0.045 and 3.280±0.034 for camel, goat and cow milk respectively, and showed a significant difference (P≤0.05). The average moisture content (%) of camel, goat and cow milk in early stage was 88.159±0.171, 87.974±0.175 and 87.957±0.159 respectively, and no significant (P≥0.05) was revealed between the averages. In mid stage mean values of 88.254±0.155, 87.714±0.133 and 87.802±0.045 were obtained for camel, goat and cow milk respectively and there were highly significant difference (P≤0.01). In late stage mean values of 88.817±0.34, 87.569±0.106 and 87.802±0.045 were obtained for moisture content of camel, goat and cow respectively, with a high significant difference between the means (P≤0.01). Average total solids (TS) % for camel, goat and cow milk obtained in early stage was 11.841±0.171, 12.026±0.175 and 12.043±0.159 respectively. No significant difference was found herby (P≥0.05). In mid stage was 11.746±0.155, 12.286±0.132 and 12.671±0.132 were obtained and also highly significant differences were obtained (P≤0.01). In late stage mean values of 11.183±0.034, 12.431±0.106 and 12.198±0.045 were reached and a high significant difference (P≤0.01) was noticed. The average lactose % of camel, goat and cow milk found in early stage was 4.093±0.113, 4.651±0.071 and 3.491±0.071; in mid stage 4.271±0.074, 3.356±0.088 and 4.603±0.097 and in late stage 4.673±0.041, 4.557±0.097 and 3.807±0.097 respectively. A high significant difference (P≤0.01) was noticed between the average percentages of lactose for the three stages of the lactation period. v Mean values of ash % found in early stage was 0.745±0.008, 0.755±0.007 and 0.740±0.007 in camel, goat and cow respectively, with significant difference (P≤0.05). In mid stage mean value of 0.743±0.008, 0.756±0.005 and 0.747±0.007, in late stage was 0.745±0.008, 0.755±0.007 and 0.740±0.007 for ash % were reached for camel, goat and cow milk respectively. No significant difference (P≥0.05) was detected between the average ash % in both mid and late stages of the lactation period. However, the calcium content (mg/100g) of camel, goat and cow milk was highly significant difference (P≤0.01) in early, mid and late stages of the lactation period. Same was applicable for the phosphorus and iron contents. Mean values of the solid non fat (SNF) in early stage in camel milk 8.035±0.174, in goat milk 9.092±0.080 and in cow milk 7.656±0.115. In mid stage was 8.379±0.104, 7.266±0.156 and 8.891±0.092, in late stage were 8.889±0.071, 8.851±0.093 and 7.831±0.104 for camel, goat and cow milk were recorded, a high significant difference (P≤0.01) was recorded between the means of the SNF throughout the three stages of the lactation period. Concerning physical properties; average pH values of camel, goat and cow milk in early stage obtained were: 6.584±0.019, 6.727±0.018 and 6.440±0.042 respectively. A high significant difference (P≤0.01) was detected. In mid stage was 6.477±0.024, 6.573±0.042 and 6.600±0.041, in late stage were 6.486±0.042, 6.591±0.027 and 6.583±0.009 for camel, goat and cow milk respectively. The statistical analysis revealed a significant difference (P≤0.05) between the means of pH in both mid and late lactation stages. Average titratable acidity (as lactic acid) % obtained in early stage, was 0.161±0.003, 0.140±0.002 and 0.141±0.002 for camel, goat and cow milk respectively, and showed a high significant difference (P≤0.01). For mid stage were 0.166±0.004, 0.154±0.004 and 0.169±0.003 respectively, indicating a significant difference (p≤0.05). In late stage were 0.150±0.005, 0.175±0.002 and 0.156±0.005 for camel, goat and cow milk respectively, with a high significant difference (P≤0.01). Mean values of electrical conductivity (mS) in early stage, 6.553±0.124, 5.767±0.147 and 4.487±0.034, in mid stage was 7.989±0.135, 5.798±0.073 and 5.453±0.091, and for late stage was 7.965±0.086, 6.234±0.122 and 5.427±0.109 for camel, goat and cow milk respectively. The statistical analysis showed a high significant difference (P≤0.01) between the means values during the three stages of lactation period. The specific gravity showed means of 1.0324±0.0003, 1.0322±0.0003 and 1.0327±0.0003 for early stage; for mid stage, 1.0318±0.0005, 1.0324±0.0005 and 1.0325±0.0004 and late stage, 1.0326±0.0004, 1.0318±0.0004 and 1.0320±0.0004 for camel, goat and cow milk respectively, and no significant difference (P≥0.05) was noticed throughout the three stages of the lactation period. Freezing point (̊C) showed an average of -0.543± 0.002, -0.472±0.073 and -0.549±0.001 in early stage, in mid stage was -0.546±0.002, -0.545±0.002 and -0.546±0.002. In late stage was -0.576±0.002, -0.576±0.002 and -0.576±0.002, with no significant difference (P≥0.05) throughout the three stages of the lactation period.