The objective of this study was to determine the comparative changes in the monthly blood urea nitrogen (BUN) concentration, total protein (TP) concentration in blood serum and the body condition score of Nguni cows and heifers raised on sweetveld. Twenty-four clinically healthy animals in different parities, namely Parity 1 (n = 5), Parity 2 (n = 5), Parity 3-6 (n = 9) and heifers (n = 5), were randomly selected for the study. BUN concentration, TP concentration and body condition scores of the animals were measured over 12 months. Blood samples were collected from the coccygeal vein, while body condition score was assessed once a month during weighing. Cows in Parity 1 maintained a significantly higher body condition score (2.6 ± 0.01) than all the other animals in the trial. All the cows and heifers maintained higher levels of BUN concentration (7.5 ± 0.03 mmol/L) in November, while a lower value (1.9 ± 0.03 mmol/L) was recorded in January. The TP concentration was lowest in August at 70.8 ± 2.65 g/L, before it improved to reach a peak value of 92.3 ± 2.66 g/L in March. The Nguni cows and heifers had variations in the levels of BUN and TP concentrations in the various months while maintaining a steady body condition score throughout the trial.