Abstract:
A study conducted at Haramaya University dairy farm aimed to evaluate the levels of macro and micro minerals in the feed, serum, and milk of lactating dairy cows. The 6 feed samples were collected from dairy farms and 22 milk and blood samples from cows selected based on parity (three to four) and stages of lactation (4 post-partum, 6 early, 6 mid, and 6 late). The analysis included measuring Calcium (Ca), Phosphorus (P), Potassium (K), Sodium (N), Magnesium (Mg), Zinc (Zn), and Iron (Fe) in the milk and feed samples, and Ca, P, K, and Na in the serum samples. Various instruments such as Ultraviolet–visible spectrophotometer (for P), flame emission photometer (for Na and K), atomic absorption spectrometer (for Ca, Mg, Zn, and Fe), and a Cobas 311 (for serum Ca, P, K, and Na) were used for analysis. Data were analyzed using the General Linear Model (GLM) procedure of SAS version 9.4, and correlations between minerals in milk and serum were assessed using bivariate analysis. The overall concentrations of Ca, P, K, Na, Mg, Zn, and Fe in the feed samples were 0.15±0.03%, 0.2±0.04%, 0.6±0.025%, 0.25±0.012%, 0.27±0.01%, 9.2±1.2ppm, and 20.7±2.1ppm, respectively. In the milk samples, the overall concentrations of Ca, P, Na, K, Mg, Zn, and Fe were 76±0.02g/L, 0.46±0.02g/L, 0.5±0.02g/L, 1±0.02g/L, 0.15±0.008g/L, 3.33±0.28mg/L, and 13±0.3mg/L, respectively. The serum samples had overall concentrations of Ca, P, Na, and K as 3.41±0.07mg/dl, 4.43±0.26mg/dl, 124.6±4.6mmol/L, and 3.7±0.14mmol/L, respectively. Significant concentration differences (p<0.05) were observed among serum minerals at different lactation stages and early lactation stage indicate a high value of mineral concentration. Only the concentration of K showed significant differences (p<0.05) based on both parity and the interaction between parity and stage of lactation. Significant correlations (p<0.05) were found between Ca and K, K and Mg, K and Fe, and Na and Zn among the analyzed minerals in the milk samples. Likewise, significant correlations (p<0.05) were observed among all analyzed minerals in the serum samples. In summary, the study revealed deficiencies in several minerals in the feed, milk, and serum samples. These deficiencies are likely due to the provision of low-quality feed, seasonal, and temperature fluctuation. Further research should be conducted to address these deficiencies by supplementing the diets for dairy animals, including, heifers, pregnant cows, and calves, with appropriate mineral sources
